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Archive for October 2018

CLIMATEREFUGEES

atoll

 

 

The world’s first climate refugees, The Age, July 29, 2009

  1. South Pacific coral atolls like Kiribati and Vanuatu are by-products of volcanism. First a volcanic island emerges from the ocean floor. Then, corals grow all around the island to form coral reefs. Finally, the volcanic island begins to sink by subduction and goes completely under water, leaving only a ring of coral islands visible above water. Such a ring of coral islands is called a coral atoll. It’s existence implies that somewhere in the middle of the atoll is a sinking volcanic island because the atoll could not have formed otherwise. The atoll itself remains above water as long as the rate of sinking does not exceed the rate of coral growth and begins to go under water otherwise. Many Islands in the South Pacific are coral atolls.
  2. That some of these atolls are sinking and becoming inundated by seawater is a tragic but natural event having to do with geological forces beyond our control. These events are not caused by carbon dioxide and they cannot be modulated in any way by cutting CO2 emissions. In fact, these are not climate events.
  3. People who abandon sinking coral atolls for higher ground are therefore not “climate refugees” and their plight has nothing whatsoever to do with our consumption of fossil fuels. The continued attempt to link carbon dioxide with sinking atolls is inconsistent with what we know about coral atolls and with the observation that all atolls are not affected. Rising sea level does not inundate selectively.
  4. 1997, THE BBC MAKES THE CASE FOR THE KYOTO PROTOCOL:  Twenty years of hard data from meteorological stations and nature show a clear warming trend. Growth rings in Mongolian and Canadian trees are getting wider. Butterflies in California are moving to higher ground once too cold for butterflies. Stalactites in Britain are growing faster. The growing season for crops in Australia is getting longer. Permafrost in Siberia and Canada is melting. The evidence is there anywhere you look. A warming rate is one 1C per century is enough to wreak havoc. The cause is the greenhouse effect of CO2 emissions from fossil fuels as well as CFCs and HCFCs that trap heat. The effect is being compounded as deforestation simultaneously removes trees that absorb CO2. Some scientists are skeptical but the majority view is that the greenhouse effect is real and it requires urgent action. This conclusion rests on the results from sophisticated computer simulation models that give the best possible information on this topic even though they are not perfect. These models are giving us scary accounts of the future and we should be paying attention. The IPCC tell us that melting ice and thermal expansion of oceans will cause the sea level to rise one meter by 2037 and inundate low lying areas and island nations. Extreme weather events will become common. El Nino and La Nina cycles will become more extreme. There will be millions of climate refugees driven from their home by global warming. Some regions of the world will become hotter, others colder, some wetter, others drier. Entire weather systems will be dramatically altered. The Gulf Stream will switch off making Europe colder. Tropical diseases such as malaria will ravage the world as vectors migrate to higher latitudes and altitudes. Some wheat farmers may be able to grow more wheat but the net effect of global warming is overwhelmingly negative.
  5. 2001, GLOBAL WARMING NOW UNSTOPPABLE:  A 500-member IPCC led by Sir John Houghton issued the most authoritative report on global warming so far. It contains the following alarming findings: so much CO2 has already been injected into the air that global warming is “already unstoppable”; the world is warming at an accelerating rate; tens of millions of people around the world will be driven from their homes in the coming decades to become climate change refugees; governments must take urgent action to reduce carbon dioxide emissions; climate change is now so rapid that it is not possible for us to adapt to these changes; human ecosystems and biodiversity will all be affected and it will affect the world economy; the temperature rise in the next 100 years will be between 1.4C and 5.8C, significantly higher than previously thought; “there is new and stronger evidence that most of the warming observed over the past 50 years is attributable to human activities; human influences will continue to change atmospheric composition throughout the 21st century; global warming will persist for many centuries by virtue of the CO2 we have already put into the air; change caused by humans is far greater than the changes due to nature; global warming is caused by carbon dioxide trapping heat.
  6. 2008: SEA LEVEL RISE INUNDATES ATOLL AND CREATES CLIMATE REFUGEES: Climate scientists say that man-made global warming has caused a rise in the sea level sufficient to inundate an atoll in Kiribati, a chain of 33 such islands, and created climate refugees. More info: http://chaamjamal.blogspot.com/2008/06/reference-atoll-leader-asks-australia.html 
  7. 2009: BANGLADESH HIT WITH CYCLONES AND CLIMATE REFUGEES: Bangladeshis displaced by Cyclone Sidr in 2007 are “climate refugees” because they have been rendered homeless by a climate change event that was caused by carbon dioxide emissions from fossil fuels and it suggests that cyclones like Sidr will continue to ravage this poverty stricken nation unless we forge a plan in Copenhagen and do away with fossil fuels. More info: http://chaamjamal.blogspot.com/2009/10/reference-climate-refugees-add-strain.html
  8. 2009: SEA LEVEL RISE SINKING SOUTH PACIFIC ATOLLS: Our use of fossil fuels causes global warming. Global warming causes sea level rise. Sea level rise causes South Pacific atolls to become inundated. The inundation of these islands creates climate refugees. More info: http://chaamjamal.blogspot.com/2009/10/worlds-first-climate-refugees-age-july.html
  9. 2018: CLIMATE CHANGE AND ITS STAGGERING REFUGEE CRISIS: Today’s research confirms that massive migration into the millions—combined, as always, with a multitude of other effects—will be an inevitable consequence of global warming.  https://www.yesmagazine.org/issues/mental-health/climate-change-and-its-staggering-refugee-crisis-20181017
  10. 2018: A NEW U.N. CLIMATE REPORT SAYS THAT A GLOBAL CRISIS COULD OCCUR AS SOON AS 2040: Scientists concluded that the most disastrous effects of climate change could occur by 2040 if greenhouse gas emissions occur at the current rate. These effects include coastlines wiped out by sea levels, widespread drought and poverty, and hordes of displaced climate refugees. It said that 50 million people in the United States, Bangladesh, China, Egypt, India, Indonesia, Japan, the Philippines, and Vietnam will be exposed to flooding. https://www.vogue.com/article/un-climate-change-report-crisis-by-2040
  11. 2018: BILL AND MELINDA GATES FOUNDATION TO HELP CLIMATE REFUGEES: There are 800 million people in developing countries who depend on subsistence farming to make a living, and many of the 143 million people who the World Bank estimates will become climate refugees by 2050 are subsistence farmers. That is how the Bill and Melinda Gates Foundation, which does not rank among the leaders in climate-related giving, is proceeding. It sat out of the $4 billion collective philanthropic pledge but it is making grants to help farmers with small plots of land in the poorest countries like Tanzania and Niger cope with “diseases, pests and drought from a changing climate.” https://www.theweathernetwork.com/news/articles/foundations-are-making-climate-change-a-bigger-priority/115841
  12. 2018: CHANGING CLIMATE FORCES GUATEMALANS TO MIGRATE: Guatemala is consistently listed among the world’s 10 most vulnerable nations to the effects of climate change. Increasingly erratic climate patterns have produced year after year of failed harvests and dwindling work opportunities across the country, forcing more and more people like Méndez López to consider migration in a last-ditch effort to escape skyrocketing levels of food insecurity and poverty. During the past decade, an average of 24 million people each year were displaced by weather events around the world. Although it’s unclear how many of those displacements can be attributed to human-caused climate change, experts expect this number to continue to rise. https://www.nationalgeographic.com/environment/2018/10/drought-climate-change-force-guatemalans-migrate-to-us/
  13. 2018:  TYPHOON YUTU CLIMATE REFUGEES: The strongest storm recorded anywhere on the planet this year has caused “catastrophic” damage on the Northern Mariana Islands, a US commonwealth in the northern Pacific Ocean, northeast of Guam. Super Typhoon Yutu reached speeds of up to 255 km/h before it slammed into the islands of Saipan, Tinian, and Rota on Thursday creating havoc and climate change refugees.  https://www.irinnews.org/news/2018/10/26/typhoon-yutu-refugee-investment-and-climate-dragons-cheat-sheet
  14. 2018: CLIMATE REFUGEES IN THE USA: When Americans think of “climate refugees,” the source locales are likely to be low-lying island states, or desertification-prone regions of Africa, India and China; possibly portions of Bangladesh or Central America, where the monsoons are growing ominously larger. It’s time to look closer to home. A provocative package by The Guardian’s Oliver Milman makes that counterpoint  clear from the opening headline: “America’s era of climate mass migration is here.” Think of the rising sea encroaching on Miami Beach, of course, but also Virginia Beach. Think of the Alaskan communities small in size but large in number, sinking into softening permafrost or washing away with the coastline. Remember the thousands displaced from New Orleans by Hurricane Katrina, many to the Houston area, where a dozen years later Hurricane Harvey repeated the process. https://www.minnpost.com/earth-journal/2018/10/great-reads-on-algal-poison-factories-american-climate-refugees-and-more/
  15. 2018: GOVT MAY CHANGE IMMIGRATION LAWS TO TAKE CLIMATE CHANGE REFUGEES: Jacinda Ardern has revealed to Newshub she isn’t ruling out New Zealand taking climate refugees. “We’re looking at creating an immigration plan that looks to the Pacific, and what options there might be within the existing arrangements.” Climate refugees are people displaced from their homes because of the impact of climate change. The existing refugee quota is being lifted from 1000 to 1500 in 2020, an increase announced recently after public in-fighting between the Government’s coalition partners. https://www.newshub.co.nz/home/politics/2018/09/govt-may-change-immigration-settings-to-take-climate-change-refugees.html
  16. 2018: THE GLOBAL CLIMATE REFUGEE CRISIS HAS ALREADY BEGUN: When Hurricane Florence struck the shores of North and South Carolina and Virginia, more than a million evacuees fled their homes seeking shelter from the storm. For some, there will be no return home, as their homes are damaged beyond repair or beyond what they can afford to repair. All these displaced people are not simply evacuees fleeing a dangerous hurricane. They are climate refugees. There are a couple of reasons why climate change is creating a new category of refugee. First, climate change contributes to rising seas. As ocean water warms, it expands. That, along with simultaneous increased melting of the world’s mountain glaciers and the Greenland and Antarctic ice sheets, contributes to rising sea levels. Sea level rise is already one factor producing climate refugees around the world.  https://thehill.com/opinion/energy-environment/409002-the-global-climate-refugee-crisis-has-already-begun

 

 

[LIST OF POSTS AT THIS SITE]

 

 

PETM-BIOTA

 

PALEOCENE-EOCENE THERMAL MAXIMUM 55 MILLION YEARS AGO

 

 

WHAT WE KNOW FROM PALEO CLIMATOLOGY

  1. Time, duration, & data: Paleoclimate data from carbonate and organic matter deposits in terrestrial and ocean sediments show that there was a 10,000 year (or so) period of global warming about 55 to 56 million years ago where the Paleocene age ends and the Eocene age begins. The warming is found in the atmosphere, in sea surface temperature, and in the deep ocean.
  2. Global Warming: Temperatures in the deep ocean rose by 4ºC from 11ºC to 15ºC while sea surface temperature (SST), estimated from oxygen isotope excursion and Mg/Ca records, warmed by 8ºC to 10ºC with temperatures as high as 33ºC in the mid-latitudes and 23ºC in the Arctic. Global mean surface temperatures rose by 5ºC to 9ºC. Although these changes are described as “abrupt” in the long paleo context, it should be noted that a warming of 10ºC over a period of  10,000 years corresponds to a warming rate of 0.1ºC per century compared with our current warming rate of 0.5ºC/century.
  3. Carbon Isotopic excursion: The data also show that over the same period of time, there were isotopic excursions of carbon13. (An isotopic excursion is a temporary divergence from the long term average.) In the 10,000-year excursion, carbon13 levels in both oceans and atmosphere fell by 0.2% to 0.4% from the norm. It is significant that the carbon isotope excursion is found in both the atmosphere and the oceans. The excursion implies that carbon in the current carbon cycle had been combined with carbon from a distant past or geological carbon that had yet not been exposed to the atmosphere. 
  4. Oceanic oxygen depletion: Warming of deep waters was followed by oxygen deficiency in the deep ocean as seen in the extinction of 30–50% of deep‐sea benthic foraminiferal species. Oxygen depletion implies that warming was associated with oxidation of some kind.
  5. Ocean Acidification: Coincident with oceanic oxygen depletion, a rapid decline in pH and evidence of shoaling of the calcite compensation depth down to depths greater than 3km of the ocean are found in the data. The data indicate a very large global oxidation event in the ocean that generated large quantities of carbon dioxide.
  6. Increase in Atmospheric Carbon Dioxide: Atmospheric CO2 levels estimated from oxygen17 isotopic signatures in tooth enamel show a large uncertainty range from 230 to 630 ppm that is thought to have increased by more than 70% in course of the 10,000-year PETM event. The attempt to describe the observed warming in terms of the greenhouse effect of atmospheric CO2 and thereby to draw theoretical parallels with the current warming episode has not yielded useful results because it yields gross anomalies in terms of climate sensitivity and also because some of the warming events recorded came before the increase in atmospheric CO2.

 

 

WHAT WE DON’T KNOW BUT HAVE THEORIES FOR

  1. What was the large deep-ocean oxidation event that warmed the ocean, depleted its oxygen, increased its inorganic carbon concentration, injected carbon dioxide into the atmosphere? The main body of research points to methane hydrates as the source of the carbon. It is proposed that the the hydrates were dissociated into methane by unspecified heat sources possibly geothermal, that then caused the methane to oxidize thus consuming the ocean’s oxygen and generating even more heat in a chain reaction. It is clear however, that much of the methane survived into the atmosphere where their further oxidation by atmospheric oxygen continued. An alternative theory identifies the mantle as a direct source of both carbon and heat (Svenson 2004). At least one study (Kent 2003) has presented evidence that bears the signature of a comet strike that may have initiated the ocean warming, carbonification, and oxidation sequence.
  2. What was the role of the greenhouse effect of atmospheric carbon dioxide? The proposed heat trapping effect of atmospheric CO2 could not have initiated the PETM warming because the oceanic carbon enrichment and oxidation events preceded the rise in atmospheric CO2; and the rise in atmospheric CO2 is poorly quantified. Also, using the IPCC climate sensitivity range of ECS = [1.5, 4.5] in conjunction with the best guess for the rise in atmospheric CO2 concentration does not explain the amount of surface warming. It is therefore possible that other sources of heat, possibly geothermal, may have been at work.
  3. Does the rate of carbon dioxide injection into the atmosphere compare with that of the current episode of anthropogenic global warming? Paleo climatology likes to refer to it as “a massive carbon injection”  and indeed a great deal of carbon dioxide was injected into the atmosphere; but the time frame is very long as these things occurred over 10,000 to 20,000 years compared with the century of two in today’s time scale. Currently, the CO2 injection rate is around 10 GTCY (gigatonnes of carbon equivalent per year). The corresponding figures for the PETM event is somewhere between 0.2 and 0.6 GTC per year. Yet, if the total amount injected had occurred in 100 years instead of 10,000 years, the corresponding annual rate would have been 20 to 60 GTCY.
  4. Is there an analogy between AGW and PETM that will give us better insight and understanding of AGW and help us to design better climate action and climate adaptation policies? This analogy is often claimed and there may be some generalities about warming that will be useful to us but there are gross departures in the details of the two events that make it difficult to draw a parallel that can relate events in one to events in the other. The fundamental issue is that while the AGW event is thought to have been initiated in the atmosphere driven by humans digging up and burning fossil fuels in the industrial economy, the PETM event was initiated by nature in the deep ocean where inexplicably, an enormous amount of carbon was released possibly from the ocean bed either from methane hydrates or from the mantle. The oxidation of the carbon simultaneously consumed the ocean’s oxygen, caused ocean acidification, and caused atmospheric CO2 to rise. The parallel between these events and AGW often drawn by climate activists, require that these sequence of events in reverse – starting with CO2 release by humans into the atmosphere – can be understood in PETM terms.
  5. The role of the earth’s internal geological carbon and geothermal heat in climate: The current episode of climate change is understood purely in terms of solar radiation arriving at the top of the atmosphere and the proposed role of carbon dioxide emissions from the use of fossil fuels in leveraging surface temperature. There is no role in this mechanism for the earth itself either in terms of its internal geothermal heat or of natural emissions of carbon from within the earth. The PETM is a cautionary tale in this regard because there, the predominant role of the earth’s internal heat and carbon emissions is acknowledged. The possible role of the earth in the current event is discussed in three related posts [Ocean Heat Content] ,  [Unprecedented Warming of the Arctic] [Carbon Cycle Measurement Problems Solved with Circular Reasoning] .
  6. What was the impact of the PETM events on the flora and fauna? Mass extinctions of some species (benthic foraminifera) and expansion of other species (subtropical dinoflagellates) are recorded in the paleo data. The most dramatic change and the one most relevant to humans is that the PETM is credited with the rapid expansion of mammals on land and the first appearance of the modern orders of mammals. For details please see the various works of Paleontologist Philip Dean Gingerich.

 

 

PETM BIBLIOGRAPHY

 

Featured Authors

Gerald Dickens, James Zachos, Philip Gingerich, & Dennis Kent

 

  1. 1995: Dickens, Gerald R., et al. “Dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the Paleocene.” Paleoceanography and Paleoclimatology10.6 (1995): 965-971. Isotopic records across the “Latest Paleocene Thermal Maximum“ (LPTM) indicate that bottom water temperature increased by more than 4°C during a brief time interval (<104years) of the latest Paleocene (∼55.6 Ma). There also was a coeval −2 to −3‰ excursion in the δ13C of the ocean/atmosphere inorganic carbon reservoir. Given the large mass of this reservoir, a rapid δ13C shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere. However, a direct consequence of warming bottom water temperature from 11 to 15°C over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic CH4 hydrate at locations with intermediate water depths. In terms of the present‐day oceanic CH4 hydrate reservoir, thermal dissociation of oceanic CH4 hydrate during the LPTM could have released greater than 1.1 to 2.1 × 1018 g of carbon with a δ13C of approximately −60‰. The release and subsequent oxidation of this amount of carbon is sufficient to explain a −2 to −3‰ excursion in δ13C across the LPTM. Fate of CH4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the LPTM.
  2. 1997: Dickens, Gerald R., Maria M. Castillo, and James CG Walker. “A blast of gas in the latest Paleocene: Simulating first-order effects of massive dissociation of oceanic methane hydrate.” Geology 25.3 (1997): 259-262. Carbonate and organic matter deposited during the latest Paleocene thermal maximum is characterized by a remarkable −2.5‰ excursion in δ13C that occurred over ∼104 yr and returned to near initial values in an exponential pattern over ∼2 × 105 yr. It has been hypothesized that this excursion signifies transfer of 1.4 to 2.8 × 1018 g of CH4 from oceanic hydrates to the combined ocean-atmosphere inorganic carbon reservoir. A scenario with 1.12 × 1018 g of CH4 is numerically simulated here within the framework of the present-day global carbon cycle to test the plausibility of the hypothesis. We find that (1) the δ13C of the deep ocean, shallow ocean, and atmosphere decreases by −2.3‰ over 104 yr and returns to initial values in an exponential pattern over ∼2 × 105 yr; (2) the depth of the lysocline shoals by up to 400 m over 104 yr, and this rise is most pronounced in one ocean region; and (3) global surface temperature increases by ∼2 °C over 104 yr and returns to initial values over ∼2 × 106 yr. The first effect is quantitatively consistent with the geologic record; the latter two effects are qualitatively consistent with observations. Thus, significant CH4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum. This conclusion is of broad interest because the flux of CH4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present-day anthropogenic CH4 sources.
  3. 2002: Thomas, Deborah J., et al. “Warming the fuel for the fire: Evidence for the thermal dissociation of methane hydrate during the Paleocene-Eocene thermal maximum.” Geology30.12 (2002): 1067-1070.  Dramatic warming and upheaval of the carbon system at the end of the Paleocene Epoch have been linked to massive dissociation of sedimentary methane hydrate. However, testing the Paleocene-Eocene thermal maximum hydrate dissociation hypothesis has been hindered by the inability of available proxy records to resolve the initial sequence of events. The cause of the Paleocene-Eocene thermal maximum carbon isotope excursion remains speculative, primarily due to uncertainties in the timing and duration of the Paleocene-Eocene thermal maximum. We present new high-resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from Ocean Drilling Program Site 690 (Weddell Sea, Southern Ocean), demonstrating that the initial carbon isotope excursion was geologically instantaneous and was preceded by a brief period of gradual surface-water warming. Both of these findings support the thermal dissociation of methane hydrate as the cause of the Paleocene-Eocene thermal maximum carbon isotope excursion. Furthermore, the data reveal that the methane-derived carbon was mixed from the surface ocean downward, suggesting that a significant fraction of the initial dissociated hydrate methane reached the atmosphere prior to oxidation.
  4. 2001: Katz, Miriam, et al. Uncorking the bottle: What triggered the Paleocene/Eocene thermal maximum methane release?   Paleoceanography 16.6 (2001): 549-562. The Paleocene/Eocene thermal maximum (PETM) was a time of rapid global warming in both marine and continental realms that has been attributed to a massive methane (CH4) release from marine gas hydrate reservoirs. Previously proposed mechanisms for this methane release rely on a change in deepwater source region(s) to increase water temperatures rapidly enough to trigger the massive thermal dissociation of gas hydrate reservoirs beneath the seafloor. To establish constraints on thermal dissociation, we model heat flow through the sediment column and show the effect of the temperature change on the gas hydrate stability zone through time. In addition, we provide seismic evidence tied to borehole data for methane release along portions of the U.S. continental slope; the release sites are proximal to a buried Mesozoic reef front. Our model results, release site locations, published isotopic records, and ocean circulation models neither confirm nor refute thermal dissociation as the trigger for the PETM methane release. In the absence of definitive evidence to confirm thermal dissociation, we investigate an alternative hypothesis in which continental slope failure resulted in a catastrophic methane release. Seismic and isotopic evidence indicates that Antarctic source deepwater circulation and seafloor erosion caused slope retreat along the western margins of the North Atlantic in the late Paleocene. Continued erosion or seismic activity along the oversteepened continental margin may have allowed methane to escape from gas reservoirs trapped between the frozen hydrate‐bearing sediments and the underlying buried Mesozoic reef front, precipitating the Paleocene/Eocene boundary methane release. An important implication of this scenario is that the methane release caused (rather than resulted from) the transient temperature increase of the PETM. Neither thermal dissociation nor mechanical disruption of sediments can be identified unequivocally as the triggering mechanism for methane release with existing data. Further documentation with high‐resolution benthic foraminiferal isotopic records and with seismic profiles tied to borehole data is needed to clarify whether erosion, thermal dissociation, or a combination of these two was the triggering mechanism for the PETM methane release.
  5. 2002: Bralower, Timothy J. “Evidence of surface water oligotrophy during the PaleoceneEocene thermal maximum: Nannofossil assemblage data from Ocean Drilling Program Site 690, Maud Rise, Weddell Sea.” Paleoceanography 17.2 (2002): 13-1. Nannoplankton assemblages at Ocean Drilling Program Site 690 (Maud Rise, Weddell Sea) experienced an abrupt and dramatic transformation at the onset of the Paleocene‐Eocene Thermal Maximum (PETM) at ∼55 m.y. The major assemblage shift suggests a change from colder, more productive surface waters to warmer, more oligotrophic conditions. Significant restructuring of assemblages during the later part of the PETM indicates that nannoplankton communities were not stable and that surface water conditions changed, although they remained warm and oligotrophic. Combined with benthic foraminiferal assemblage data, nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean. Although the PETM was a short‐lived event, it appears to have had long‐term effects on nannoplankton, leading to the extinction of Fasciculithus, a dominant Paleocene genus. The Cretaceous and early Paleogene was a time of remarkable transformation of marine communities [e.g., Vermeij, 1977]. Some of the most dramatic evolutionary changes took place in the protistans. Groups such as the diatoms and planktic foraminifera became fundamental parts of marine food chains during this time. Other groups such as the calcareous nannoplankton and radiolarians underwent wholesale changes in species composition and assemblage structure. The underlying causes of the long‐term evolutionary changes that took place are not well understood [e.g., Roth, 1987; Leckie, 1987; Leckie et al., 2002]. Research over the last decade, however, has established that these groups were also affected by environmental changes that took place over short timescales. In particular, short‐lived (<1 m.y.) global warming events sparked significant biotic turnover in association with dramatic changes in global carbon cycling [e.g., Schlanger et al., 1987; Leckie, 1989; Elder, 1991; Kennett and Stott, 1991; Coccioni et al., 1992; Erba, 1994; Koch et al., 1995; Kelly et al., 1996; Thomas and Shackleton, 1996; Aubry, 1998; Premoli Silva and Sliter, 1999; Premoli Silva et al., 1999]. One of the most extreme and abrupt warming episodes occurred close to the Paleocene/Eocene boundary at ∼55 Ma [Kennett and Stott, 1991; Bralower et al., 1995; Thomas and Shackleton, 1996]. This event, which is known as the Paleocene‐Eocene Thermal Maximum (PETM) [e.g., Zachos et al., 1993], lasted for a period of ∼210 kyr [Norris and Röhl, 1999; Röhl et al., 2000]. The deep and surface oceans warmed by ∼5° and ∼4°–8°C, respectively, during the PETM. The carbon isotopic composition of the ocean and atmosphere decreased by 3–4‰ coeval with the warming event, suggesting a massive perturbation to the global carbon cycle [Kennett and Stott, 1991; Koch et al., 1992; Bains et al., 1999; Norris and Röhl, 1999]. The large magnitude and rate of onset of the carbon isotope excursion (CIE) are most consistent with the sudden dissociation of methane hydrates from continental shelves and slopes [Dickens et al., 1995, 1997; Katz et al., 1999]; CH4 would have immediately contributed to greenhouse warming. The PETM climatic changes affected biota on a global scale, triggering abrupt turnover of benthic and planktic organisms in the ocean [e.g., Kennett and Stott, 1991; Kelly et al., 1996; Speijer and Morsi, 2002], and the rapid radiation of mammals on land [e.g., Gingerich et al., 1980; Maas et al., 1995; Hooker, 1996; Clyde and Gingerich, 1998]. Deep‐sea environmental changes led to an abrupt extinction in benthic foraminiferal communities [e.g., Thomas, 1990; Pak and Miller, 1992; Thomas and Shackleton, 1996; Thomas, 1998]. This benthic foraminiferal extinction (BFE) event [e.g., Tjalsma and Lohmann, 1983] has been well documented in a range of different environments and latitudes [e.g., Kaiho et al., 1996; Speijer et al., 1996]. The response of surface‐dwelling marine organisms to PETM environmental changes appears to have been fundamentally different: tropical planktic foraminifers radiated dramatically during this event [Kelly et al., 1996, 1998]. There have been few high‐resolution investigations of the response of phytoplankton groups such as the calcareous nannoplankton to the PETM. Most previous investigations have considered only long‐term changes in assemblages through the late Paleocene‐early Eocene interval [e.g., Aubry, 1998]. Interpretations of geochemical and biotic investigations disagree as to whether the PETM was characterized by increased or decreased surface water productivity. Tropical plankton at Pacific Site 865 suggests increased oligotrophy [Kelly et al., 1996]; benthic foraminiferal assemblages in open ocean sites also suggest reduced food supply under oligotrophic surface water conditions, whereas assemblages in marginally marine and shelf sites are interpreted as indicating high food supply likely as a result of eutrophic conditions [Thomas and Shackleton, 1996; Speijer and Schmitz, 1998; Thomas, 1998; Thomas et al., 2000]. A widespread bloom of the dinoflagellate Apectodinium in sections deposited in coastal environments is also consistent with high productivity [Crouch et al., 2001]. Bains et al. [2000] interpreted an increase in Ba accumulation rates in the PETM at several open‐ocean sites as evidence for high productivity; these authors concluded that elevated productivity led to increased CO2 draw down, curbing a potential runaway greenhouse. To attempt to resolve the contrast between biotic and geochemical proxies of productivity and to more fully constrain the effects of the PETM on marine phytoplankton, we have carried out a detailed study of calcareous nannofossil assemblages across the PETM at Site 690 (Maud Rise, Weddell Sea; Figure 1). This site contains one of the highest‐quality deep‐sea records of the PETM event. Upper Paleocene sediments are composed of ooze representing nannofossil zone NP9, planktic foraminiferal zones AP4 and AP5, and part of magnetic polarity zone C24r [Aubry et al., 1996]. White to pale brown lithologic cycles caused by oscillations of CaCO3 and clay content appear to correspond to precessional orbital rhythms [Röhl et al., 2000]. These cycles can be used to construct a timescale for Site 690 [Cramer, 2001; D. Thomas, manuscript in preparation, 2002], allowing us to monitor paleoceanographic changes at millennial resolution.
  6. 2003: Kent, Dennis V., et al. “A case for a comet impact trigger for the Paleocene/Eocene thermal maximum and carbon isotope excursion.” Earth and Planetary Science Letters 211.1-2 (2003): 13-26. We hypothesize that the rapid onset of the carbon isotope excursion (CIE) at the Paleocene/Eocene boundary (∼55 Ma) may have resulted from the accretion of a significant amount of 12C-enriched carbon from the impact of a ∼10 km comet, an event that would also trigger greenhouse warming leading to the Paleocene/Eocene thermal maximum and, possibly, thermal dissociation of seafloor methane hydrate. Indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite-rich shelf sediments that closely coincide with the onset and nadir of the CIE at three drill sites on the Atlantic Coastal Plain. After considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron-rich nanophase material at the Cretaceous/Tertiary boundary, we suggest that the CIE occurrence was derived from an impact plume condensate. The sudden increase in kaolinite is thus thought to represent the redeposition on the marine shelf of a rapidly weathered impact ejecta dust blanket. Published reports of a small but significant iridium anomaly at or close to the Paleocene/Eocene boundary provide supportive evidence for an impact.
  7. 2003: Zachos, James C., et al. “A transient rise in tropical sea surface temperature during the Paleocene-Eocene thermal maximum.” Science 302.5650 (2003): 1551-1554. The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8° to 10°C) and in bottom water temperatures (4° to 5°C). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4° to 5°C rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO2 to levels three to four times as high as those estimated for the late Paleocene.
  8. *2004: Svensen, Henrik, et al. “Release of methane from a volcanic basin as a mechanism for initial Eocene global warming.” Nature 429.6991 (2004): 542. A 200,000-yr interval of extreme global warming marked the start of the Eocene epoch about 55 million years ago. Negative carbon- and oxygen-isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid (10,000 yr) input of isotopically depleted carbon1,2. It has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source3,4 and has caused the global climate change. Large-scale hydrate melting, however, requires a hitherto unknown triggering mechanism. Here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the Vøring and Møre basins in the Norwegian Sea. We propose that intrusion of voluminous mantle-derived melts in carbon-rich sedimentary strata in the northeast Atlantic may have caused an explosive release of methane—transported to the ocean or atmosphere through the vent complexes—close to the Palaeocene/Eocene boundary. Similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the Siberian Traps (250 million years ago) and the Karoo Igneous Province (183 million years ago).
  9. 2004: Bowen, Gabriel J., et al. “A humid climate state during the Palaeocene/Eocene thermal maximum.” Nature 432.7016 (2004): 495. An abrupt climate warming of 5 to 10 °C during the Palaeocene/Eocene boundary thermal maximum (PETM) 55 Myr ago is linked to the catastrophic release of 1,050–2,100 Gt of carbon from sea-floor methane hydrate reservoirs1. Although atmospheric methane, and the carbon dioxide derived from its oxidation, probably contributed to PETM warming, neither the magnitude nor the timing of the climate change is consistent with direct greenhouse forcing by the carbon derived from methane hydrate. Here we demonstrate significant differences between marine2,3 and terrestrial4,5,6 carbon isotope records spanning the PETM. We use models of key carbon cycle processes7,8,9 to identify the cause of these differences. Our results provide evidence for a previously unrecognized discrete shift in the state of the climate system during the PETM, characterized by large increases in mid-latitude tropospheric humidity and enhanced cycling of carbon through terrestrial ecosystems. A more humid atmosphere helps to explain PETM temperatures, but the ultimate mechanisms underlying the shift remain unknown.
  10. 2005: Tripati, Aradhna, and Henry Elderfield. “Deep-sea temperature and circulation changes at the Paleocene-Eocene thermal maximum.” Science 308.5730 (2005): 1894-1898. A rapid increase in greenhouse gas levels is thought to have fueled global warming at the Paleocene-Eocene Thermal Maximum (PETM). Foraminiferal magnesium/calcium ratios indicate that bottom waters warmed by 4° to 5°C, similar to tropical and subtropical surface ocean waters, implying no amplification of warming in high-latitude regions of deep-water formation under ice-free conditions. Intermediate waters warmed before the carbon isotope excursion, in association with down-welling in the North Pacific and reduced Southern Ocean convection, supporting changing circulation as the trigger for methane hydrate release. A switch to deep convection in the North Pacific at the PETM onset could have amplified and sustained warming.
  11. 2005: Zachos, James C., et al. “Rapid acidification of the ocean during the Paleocene-Eocene thermal maximum.” Science308.5728 (2005): 1611-1615. The Paleocene-Eocene thermal maximum (PETM) has been attributed to the rapid release of ∼2000 × 109 metric tons of carbon in the form of methane. In theory, oxidation and ocean absorption of this carbon should have lowered deep-sea pH, thereby triggering a rapid (<10,000-year) shoaling of the calcite compensation depth (CCD), followed by gradual recovery. Here we present geochemical data from five new South Atlantic deep-sea sections that constrain the timing and extent of massive sea-floor carbonate dissolution coincident with the PETM. The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years). These findings indicate that a large mass of carbon (»2000 × 109 metric tons of carbon) dissolved in the ocean at the Paleocene-Eocene boundary and that permanent sequestration of this carbon occurred through silicate weathering feedback.
  12. 2006: Higgins, John A., and Daniel P. Schrag. “Beyond methane: towards a theory for the Paleocene–Eocene thermal maximum.” Earth and Planetary Science Letters 245.3-4 (2006): 523-537. Extreme global warmth and an abrupt negative carbon isotope excursion during the Paleocene–Eocene Thermal Maximum (PETM) have been attributed to a massive release of methane hydrate from sediments on the continental slope [1]. However, the magnitude of the warming (5 to 6 °C [2],[3]) and rise in the depth of the CCD (> 2 km; [4]) indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis. Additional carbon sources associated with methane hydrate release (e.g. pore-water venting and turbidite oxidation) are also insufficient. We find that the oxidation of at least 5000 Gt C of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the PETM, for which there are several potential mechanisms. Production of thermogenic CH4 and CO2during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments [5] is capable of supplying large amounts of carbon, but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments, as well as the abrupt onset and termination of carbon release during the PETM. A global conflagration of Paleocene peatlands [6] highlights a large terrestrial carbon source, but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky. In addition, this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat. The isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision, followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of CO2. In addition to the oxidation of the underlying marine sediments, the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior, resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands.
  13. 2006: Zachos, James C., et al. “Extreme warming of mid-latitude coastal ocean during the Paleocene-Eocene Thermal Maximum: Inferences from TEX86 and isotope data.” Geology34.9 (2006): 737-740. Changes in sea surface temperature (SST) during the Paleocene-Eocene Thermal Maximum (PETM) have been estimated primarily from oxygen isotope and Mg/Ca records generated from deep-sea cores. Here we present a record of sea surface temperature change across the Paleocene-Eocene boundary for a nearshore, shallow marine section located on the eastern margin of North America. The SST record, as inferred from TEX86 data, indicates a minimum of 8 °C of warming, with peak temperatures in excess of 33 °C. Similar SSTs are estimated from planktonic foraminifer oxygen isotope records, although the excursion is slightly larger. The slight offset in the oxygen isotope record may reflect on seasonally higher runoff and lower salinity.
  14. 2006: Sluijs, Appy, et al. “Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum.” Nature441.7093 (2006): 610. The Palaeocene/Eocene thermal maximum, ∼55 million years ago, was a brief period of widespread, extreme climatic warming1,2,3, that was associated with massive atmospheric greenhouse gas input4. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition5. We show that sea surface temperatures near the North Pole increased from ∼18 °C to over 23 °C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean’s bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations6, but the absolute polar temperatures that we derive before, during and after the event are more than 10 °C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms—perhaps polar stratospheric clouds7 or hurricane-induced ocean mixing8—to amplify early Palaeogene polar temperatures.
  15. 2006: Gingerich, Philip D. “Environment and evolution through the Paleocene–Eocene thermal maximum.” Trends in ecology & evolution 21.5 (2006): 246-253. The modern orders of mammals, Artiodactyla, Perissodactyla and Primates (APP taxa), first appear in the fossil record at the Paleocene–Eocene boundary, c. 55 million years ago. Their appearance on all three northern continents has been linked to diversification and dispersal in response to rapid environmental change at the beginning of a worldwide 100 000–200 000-year Paleocene–Eocene thermal maximum (PETM) and carbon isotope excursion. As I discuss here, global environmental events such as the PETM have had profound effects on evolution in the geological past and must be considered when modeling the history of life. The PETM is also relevant when considering the causes and consequences of global greenhouse warming.
  16. 2007: Röhl, Ursula, et al. “On the duration of the PaleoceneEocene thermal maximum (PETM).” Geochemistry, Geophysics, Geosystems 8.12 (2007). The Paleocene‐Eocene thermal maximum (PETM) is one of the best known examples of a transient climate perturbation, associated with a brief, but intense, interval of global warming and a massive perturbation of the global carbon cycle from injection of isotopically light carbon into the ocean‐atmosphere system. One key to quantifying the mass of carbon released, identifying the source(s), and understanding the ultimate fate of this carbon is to develop high‐resolution age models. Two independent strategies have been employed, cycle stratigraphy and analysis of extraterrestrial helium (HeET), both of which were first tested on Ocean Drilling Program (ODP) Site 690. These two methods are in agreement for the onset of the PETM and initial recovery, or the clay layer (“main body”), but seem to differ in the final recovery phase of the event above the clay layer, where the carbonate contents rise and carbon isotope values return toward background values. Here we present a state‐of‐the‐art age model for the PETM derived from a new orbital chronology developed with cycle stratigraphic records from sites drilled during ODP Leg 208 (Walvis Ridge, Southeastern Atlantic) integrated with published records from Site 690 (Weddell Sea, Southern Ocean, ODP Leg 113). During Leg 208, five Paleocene‐Eocene (P‐E) boundary sections (Sites 1262 to 1267) were recovered in multiple holes over a depth transect of more than 2200 m at the Walvis Ridge, yielding the first stratigraphically complete P‐E deep‐sea sequence with moderate to relatively high sedimentation rates (1 to 3 cm/ka, where “a” is years). A detailed chronology was developed with nondestructive X‐ray fluorescence (XRF) core scanning records on the scale of precession cycles, with a total duration of the PETM now estimated to be ∼170 ka. The revised cycle stratigraphic record confirms original estimates for the duration of the onset and initial recovery but suggests a new duration for the final recovery that is intermediate to the previous estimates by cycle stratigraphy and HeET. The Paleocene Eocene thermal maximum (PETM) is one of the most abrupt and transient climatic events documented in the geologic record [e.g., Zachos et al., 2001, 2005]. This event was associated with pronounced warming of the oceans and atmosphere, changes in ocean chemistry, and reorganization of the global carbon cycle [Kennett and Stott, 1991; Koch et al., 1992; Thomas et al., 2002; Zachos et al., 2003, 2005; Tripati and Elderfield, 2005; Sluijs et al., 2006]. Warming of deep waters and subsequent oxygen deficiency may have been responsible for extinction of 30–50% of deep‐sea benthic foraminiferal species [Thomas and Shackleton, 1996] and planktonic biota were affected by changes in surface water habitats [e.g., Kelly et al., 1996; Bralower et al., 2002; Kelly, 2002; Raffi et al., 2005; Gibbs et al., 2006a, 2006b]; global warming also may have led to a pulse of speciation or migration among mammalian groups [e.g., Koch et al., 1992, Bowen et al., 2001; Gingerich, 2003]. The PETM corresponds to a significant (∼3.5–4.5‰) negative carbon isotope excursion (CIE) recorded in marine and terrestrial sections [e.g., Kennett and Stott, 1991; Koch et al., 1992; Bralower et al., 1997; Zachos et al., 2004, 2005; Schouten et al., 2007]. The source and triggering mechanism of this event are still the focus of much debate [e.g., Lourens et al., 2005; Sluijs et al., 2007; Storey et al., 2007]. An orbital trigger for the PETM and similar (but less severe) events has been suggested [Lourens et al., 2005], but the specific orbital parameter association is still not completely resolved [Westerhold et al., 2007]. Other mechanisms that might explain the abruptness of the CIE include the input of methane into the ocean and atmosphere from the dissociation of methane hydrates in continental margin sediments or from the cracking of coal during rifting of the northern North Atlantic Ocean [Dickens et al., 1995, 1997; Svensen et al., 2004]. Identifying potential triggering mechanisms for the PETM, as well as understanding the relationship between forcing and consequences requires a very precise and high‐resolution chronology. For example, quantifying the climate sensitivity requires robust estimates of the mass of carbon released, and hence the rate of the CIE. Until recently, however, estimates of the absolute age of the onset and the duration of the event were poorly constrained, varying between 54.88 and 55.50 Ma, and 100 and 250 ka, respectively [e.g., Kennett and Stott, 1991; Koch et al., 1992; Aubry et al., 1996; Röhl and Abrams, 2000; Röhl et al., 2000; Farley and Eltgroth, 2003; Giusberti et al., 2007]. By using an astronomically calibrated but floating timescale, the age of the onset (54.93 to 54.98 Ma) and the duration (150 to 220 ka) of the CIE were initially determined at Ocean Drilling Program (ODP) Site 1051 [Norris and Röhl, 1999] then refined using combined records from Sites 690 and 1051 [Röhl et al., 2000]. However, because the onset of the PETM in pelagic sequences is marked by a pronounced dissolution layer or condensed interval and the recovery by a lithologically uniform carbonate‐rich interval, an alternative constant flux age model was developed [Farley and Eltgroth, 2003]. This model is based on the concentrations of extraterrestrial He (3HeET) and the assumption that the flux of this isotope to the Earth remained constant during the PETM. Both age models are in agreement for the duration of the main body of the PETM (70–80 ka for the “core”, the onset, peak, and initial recovery phase (rapid rise in δ13C, but low carbonate; here termed phase 1)), but diverge for the final recovery phase of the CIE (slow rise in δ13C, high carbonate; here termed phase II), with orbital age models producing 140 ka for this interval and He age models 30 ka. Identification of cycles in the Ca (or Fe) records in the recovery interval of the Site 690 section is complicated due to the high and uniform carbonate content of the sediments. A new era in Cenozoic paleoceanography was launched with the recovery of Paleogene sediments in multisite depth transects during Ocean Drilling Program Legs 198 (Shatsky Rise, Pacific Ocean [Bralower et al., 2002; Westerhold and Röhl, 2006]) and 208 (Walvis Ridge, Southeast Atlantic Ocean [Zachos et al., 2004]). These expeditions yielded the first high‐quality, stratigraphically complete sedimentary sequences of the early Paleogene, recovered in offset, multiple‐hole sites. The lithologic and geochemical records generated from these cores exhibit the highly cyclic nature of early Paleogene climate, while also demonstrating that the early Eocene Greenhouse World was punctuated by multiple transient global warming events, or hyperthermals [Thomas et al., 2000; Zachos et al., 2004]. The occurrence of multiple hyperthermals within the late Paleocene–early Eocene suggests a repeated trigger as their cause. Recently, X‐ray fluorescence (XRF) core scanning records from ODP Leg 208 sites and from ODP Site 1051 spanning a ∼4.3 million year interval of the late Paleocene to early Eocene were used to establish a longer time series and to develop a robust and improved chronology of magnetochrons [Westerhold et al., 2007] which is consistent with records from the Bighorn Basin [Wing et al., 2000; Clyde et al., 2007]. One of the obstacles to developing age models for PETM sections is providing a exact definition of the termination of the CIE on a global scale, e.g., at Site 690, the location of the termination is somewhat subjective because of the asymptotic shape of the CIE. In addition, the low signal‐to‐noise ratio of the XRF Ca concentrations in this high‐carbonate interval has made cycle extraction difficult and somewhat subjective. Here we develop a revised chronology for the PETM using high‐resolution geochemical data from the ODP Leg 208 depth transect in combination with new Barium (Ba) XRF intensity data of the expanded section at ODP Site 690 from the Weddell Sea, Southern Ocean (Figure 1). The Barium (Ba) records, in combination with Fe, Ca, and carbon isotope data from the Leg 208 sites and Site 690, show similar patterns that allow for refinement of correlation and age calibrations. These new data provide much better constraints on the durations of each phase of the CIE, particularly the recovery phases (I and II). These records will also allow for a more accurate recalibration of the He isotope chronology from Site 690 [Farley and Eltgroth, 2003]. Moreover, we propose that the definition of the termination of the CIE be based on a combination of cyclostratigraphic proxies derived from XRF scanner and other methods rather than carbon isotopes which gradually become uniform, thus making it difficult to define a globally recognizable termination point for the recovery2009: Zeebe, Richard E., James C. Zachos, and Gerald R. Dickens. “Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming.” Nature Geoscience 2.8 (2009): 576.
  17. 2008: Panchuk, K., A. Ridgwell, and L. R. Kump. “Sedimentary response to Paleocene-Eocene Thermal Maximum carbon release: A model-data comparison.” Geology 36.4 (2008): 315-318. Possible sources of carbon that may have caused global warming at the Paleocene-Eocene boundary are constrained using an intermediate complexity Earth-system model configured with early Eocene paleogeography. We find that 6800 Pg C (δ13C of –22‰) is the smallest pulse modeled here to reasonably reproduce observations of the extent of seafloor CaCO3 dissolution. This pulse could not have been solely the result of methane hydrate destabilization, suggesting that additional sources of CO2 such as volcanic CO2, the oxidation of sedimentary organic carbon, or thermogenic methane must also have contributed. Observed contrasts in dissolution intensity between Atlantic and Pacific sites are reproduced in the model by reducing bioturbation in the Atlantic during the event, simulating a potential consequence of the spread of low-oxygen bottom waters.
  18. 2009: Zeebe, Richard E., James C. Zachos, and Gerald R. Dickens. “Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming.” Nature Geoscience 2.8 (2009): 576. The Palaeocene–Eocene Thermal Maximum (about 55 Myr ago) represents a possible analogue for the future and thus may provide insight into climate system sensitivity and feedbacks1,2. The key feature of this event is the release of a large mass of 13C-depleted carbon into the carbon reservoirs at the Earth’s surface, although the source remains an open issue3,4. Concurrently, global surface temperatures rose by 5–9 C within a few thousand years5,6,7,8,9. Here we use published palaeorecords of deep-sea carbonate dissolution10,11,12,13,14and stable carbon isotope composition10,15,16,17 along with a carbon cycle model to constrain the initial carbon pulse to a magnitude of 3,000 Pg C or less, with an isotopic composition lighter than −50‰. As a result, atmospheric carbon dioxide concentrations increased during the main event by less than about 70% compared with pre-event levels. At accepted values for the climate sensitivity to a doubling of the atmospheric CO2 concentration1, this rise in CO2 can explain only between 1 and 3.5 C of the warming inferred from proxy records. We conclude that in addition to direct CO2 forcing, other processes and/or feedbacks that are hitherto unknown must have caused a substantial portion of the warming during the Palaeocene–Eocene Thermal Maximum. Once these processes have been identified, their potential effect on future climate change needs to be taken into account.
  19. 2011: Dickens, Gerald R. “Down the rabbit hole: Toward appropriate discussion of methane release from gas hydrate systems during the Paleocene-Eocene thermal maximum and other past hyperthermal events.” Climate of the Past 7.3 (2011): 831-846. Enormous amounts of 13C-depleted carbon rapidly entered the exogenic carbon cycle during the onset of the Paleocene-Eocene thermal maximum (PETM), as attested to by a prominent negative carbon isotope (δ13C) excursion and deep-sea carbonate dissolution. A widely cited explanation for this carbon input has been thermal dissociation of gas hydrate on continental slopes, followed by release of CH4 from the seafloor and its subsequent oxidation to CO2 in the ocean or atmosphere. Increasingly, papers have argued against this mechanism, but without fully considering existing ideas and available data. Moreover, other explanations have been presented as plausible alternatives, even though they conflict with geological observations, they raise major conceptual problems, or both. Methane release from gas hydrates remains a congruous explanation for the δ13C excursion across the PETM, although it requires an unconventional framework for global carbon and sulfur cycling, and it lacks proof. These issues are addressed here in the hope that they will prompt appropriate discussions regarding the extraordinary carbon injection at the start of the PETM and during other events in Earth’s history.
  20. 2011: Cui, Ying, et al. “Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum.” Nature Geoscience4.7 (2011): 481. The transient global warming event known as the Palaeocene–Eocene Thermal Maximum occurred about 55.9 Myr ago. The warming was accompanied by a rapid shift in the isotopic signature of sedimentary carbonates, suggesting that the event was triggered by a massive release of carbon to the ocean–atmosphere system. However, the source, rate of emission and total amount of carbon involved remain poorly constrained. Here we use an expanded marine sedimentary section from Spitsbergen to reconstruct the carbon isotope excursion as recorded in marine organic matter. We find that the total magnitude of the carbon isotope excursion in the ocean–atmosphere system was about 4‰. We then force an Earth system model of intermediate complexity to conform to our isotope record, allowing us to generate a continuous estimate of the rate of carbon emissions to the atmosphere. Our simulations show that the peak rate of carbon addition was probably in the range of 0.3–1.7 Pg C yr−1, much slower than the present rate of carbon emissions.
  21. 2011: McInerney, Francesca A., and Scott L. Wing. “The Paleocene-Eocene Thermal Maximum: A perturbation of carbon cycle, climate, and biosphere with implications for the future.” Annual Review of Earth and Planetary Sciences 39 (2011): 489-516. During the Paleocene-Eocene Thermal Maximum (PETM), ∼56 Mya, thousands of petagrams of carbon were released into the ocean-atmosphere system with attendant changes in the carbon cycle, climate, ocean chemistry, and marine and continental ecosystems. The period of carbon release is thought to have lasted <20 ka, the duration of the whole event was ∼200 ka, and the global temperature increase was 5–8°C. Terrestrial and marine organisms experienced large shifts in geographic ranges, rapid evolution, and changes in trophic ecology, but few groups suffered major extinctions with the exception of benthic foraminifera. The PETM provides valuable insights into the carbon cycle, climate system, and biotic responses to environmental change that are relevant to long-term future global changes.
  22. 2016: Gehler, Alexander, Philip D. Gingerich, and Andreas Pack. “Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite.” Proceedings of the National Academy of Sciences 113.28 (2016): 7739-7744. The Paleocene–Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene–Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO2 and CH4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene–Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO2 but also massive release of seabed methane was the driver for CIE and PETM.

 

 

FIGURE 1: HADCRUT4 GLOBAL TEMPERATURE ANOMALIES 1850-20171CWARMING1CWARMINGGIF

 

FIGURE 2: GISTEMP GLOBAL TEMPERATURE ANOMALIES 1880-2017GISSTABLEGISSGIF

 

FIGURE 3: BERKELEY1 GLOBAL TEMPERATURE ANOMALIES 1850-2017TABLEBERKELEY1GIF

 

FIGURE 4: BERKELEY2 GLOBAL TEMPERATURE ANOMALIES 1850-2017TABLEBERKELEY2GIF

 

 

FIGURE 5: RCP8.5 GLOBAL TEMPERATURES 1861-2017TABLERCP85GIF

 

FIGURE 6: CORRELATION ANALYSIS OF THE TOTAL WARMING CURVESCORRTABLECORRCHART

 

FIGURE 7: THE AVERAGE WARMING AMOUNT ACROSS DATASETSAVGWARMT1AVGWARMT2AVGWARMCHART

 

 

FIGURE 8: COMPARISON OF THE FIVE TEMPERATURE SERIESECPGIF

 

 

 

FIGURE 9: HUMAN CAUSE FINGERPRINT FROM CLIMATE MODELS

gavin

texas-sharpshooter

 

[LIST OF POSTS AT THIS SITE]

 

LIST OF FIGURES

  1. FIGURE 1: HADCRUT4 GLOBAL TEMPERATURE ANOMALIES 1850-2017
  2. FIGURE 2: GISTEMP GLOBAL TEMPERATURE ANOMALIES 1880-2017
  3. FIGURE 3: BERKELEY1 GLOBAL TEMPERATURE ANOMALIES 1850-2017
  4. FIGURE 4: BERKELEY2 GLOBAL TEMPERATURE ANOMALIES 1850-2017
  5. FIGURE 5: RCP8.5 GLOBAL TEMPERATURES 1861-2017
  6. FIGURE 6: CORRELATION ANALYSIS OF THE TOTAL WARMING CURVES
  7. FIGURE 7: THE AVERAGE WARMING AMOUNT ACROSS DATASETS
  8. FIGURE 8: COMPARISON OF THE FIVE TEMPERATURE SERIES
  9. FIGURE 9: HUMAN CAUSE FINGERPRINT FROM CLIMATE MODELS

 

 

  1. This work is a critical evaluation of the claim in the IPCC SR15 that by the year 2017 human activity in the form of fossil fuel emissions had caused a warming of 1ºC since pre-Industrial times. Five different global temperature series including four reconstructions and the RCP8.5 theoretical series are used to frame the context of this claim and to test its validity.
  2. The RCP8.5 is a temperature series predicted by climate models with CMIP5 forcings for the “business as usual” emission scenario (no climate action taken).  The four temperature anomaly reconstructions are the HadCRUT4 anomalies 1850-2017 from the Hadley Centre of the Climate Research Unit of the UK Met Office, the GISTEMP anomalies 1880-2017 from NASA-GISS, and the B.E.S.T reconstruction from Berkeley Earth 1850-2017. There are two versions of the Berkeley Earth reconstruction depending on how sea ice temperatures are estimated. Both are used and labeled as Berkeley1 and Berkeley2.
  3. The temperature datasets are studied one calendar month at a time separately as it has been shown that the warming trend behaviors of the months differ significantly and that their combination into an annual temperature risks losing a great deal of trend behavior information [RELATED POST] . For each of five  temperature datasets and for each of twelve calendar months we compute the total amount of warming from all possible start years separated by ten-year increments. The amount of warming is computed as the linear OLS regression trend in ºC/year for each time span, times the length of the time span in years. The analysis consists of a study of these warming amounts in the context of the claim by the IPCC that human emissions of carbon dioxide in the industrial economy generated a warming “since pre-industrial times” of 1ºC.
  4. The HadCRUT4, GISTEMP, Berkeley1, Berkeley2, and RCP8.5 data are presented in Figure 1, Figure 2, Figure 3, Figure 4, and Figure 5 respectively. Each presentation consists of a tabulation of the computed warming amounts in degrees Celsius and their graphical display. The end of the time span for each starting year from 1850 to 1970 is fixed at 2017. Below the tabulated total warming values for each calendar month, is a chart that shows the plot of these values for each calendar month (in red) compared with the average of all twelve calendar months (in blue).
  5. It is noted that as the number of years in the warming period decreases linearly from 168 years for start year 1850 to 48 years for start year 1970, the amount of warming does not show a corresponding linear decrease but rather a complex non-linear pattern of both rising and falling amounts of warming as the time span decreases linearly. This behavior is driven by extreme short term changes in the rate of warming that include both warming and cooling periods with a greater influence of cooling in the earlier part of the time series as seen in the 30-year trend profile shown in Figure 7. As a result the greatest amount of warming is seen for start years around the year 1900, thereafter falling until 1940 and then rising again until the end of the time series likely driven by higher rates of warming. This is an example of the kind of complexity in temperature trend information that becomes lost when seasonal temperatures are combined into annual means as shown in the chart below. Here, the red curve shows the amount of warming computed for each calendar month separately and then averaged. The blue curve shows the result of the more conventional procedure of averaging monthly temperatures into annual means prior to trend analysis. The trend behavior of the calendar months are very different and this information becomes lost when monthly mean temperatures are combined into annual mean temperatures as shown in a related post.  [LINK]  AVERAGING-ANOMALY
  6. Figure 6 is a correlation analysis of the total warming amounts presented in Figure 1 to Figure 5. It shows fairly good agreement among the observational data series  but little or no correlation between the observational data and the theoretical temperature series created by climate models with CMIP5 forcings.  Underneath the tabulation of these correlations are two charts. The one on the left shows correlation between warming amounts in the observational series with the RCP8.5 climate model generated theoretical series. The black horizontal line marks the zero correlation location. Most of the correlations are negative and the few positive correlations found (with the GISS temperature reconstructions) are not statistically significant. The chart on the right shows correlations among the observational data. Mostly strong correlations are seen except where the GISS data are involved. All low correlations seen in this chart involve GISS and all correlations that do not involve GISS show strong statistically significant correlations. The correlation behavior of GISS is anomalous in ways that imply that its construction may have been influenced by climate models.
  7. A direct comparison of the five temperature time series is shown graphically in Figure 8. The four observational data series are shown in thin lines of various colors while the RCP8.5 climate model series appears as a thick black line. The left frame compares temperatures directly. It appear to show good agreement among all five temperatures with the RCP8.5 theoretical series tracking the middle of the distribution. The right frame of the chart compares the the “trend profiles” of the five temperature series computed as trends in a moving 30-year window as ºC/century equivalent (the period of 30-years is recognized as the appropriate span for study of short term trends. See references below). Here we find that in terms of short term trends, the homogeneity seen among the source temperatures is not found. Significant differences between the RCP8.5 and the observational data and also among the observational data are seen. The charts cycle through the twelve calendar months in a GIF animation demonstrating differences in the comparison among calendar months. This comparison implies that short term trends cannot be generalized across the full span of the data or across calendar months; and that the homogeneity among the source temperature data seen in the left frame is illusory.
  8. The “total warming” data in Figure 1 to Figure 5 contain 61 average values (averaged across all twelve calendar months). Of these warming of 1ºC or greater is found in 16 cases for an overall rate of 26%. The highest rate of warming found is 1.11ºC in the RCP8.5 theoretical series and the highest value in the observational data is 1.08ºC in the Berkeley1 series.
  9. A more extensive analysis of the overall assessment of the amount of warming across datasets is presented in Figure 7 where the warming amounts seen in the five datasets are summarized as averages across datasets. There are two tables in Figure 7, one atop the other. The top table contains averages among the four observational data series while the averages in the bottom table also include the RCP8.5 climate model series. The chart below the two tables show the average of the averages across calendar months for the four observational datasets (in blue) and the corresponding averages that include the theoretical RCP8.5 climate model series (in red). The horizontal purple line delineates the grand average as the average of averages as approximately 0.91ºC of warming across all calendar months, all time spans and locations, and all datasets. The dark horizontal line at the top of the cart marks location of the 1ºC warming mark claimed by the IPCC. We conclude from this analysis that although the claimed 1ºC warming (or greater) can be found in specific instances of the data, it is not representative since most of the data show lower warming rates. Thus the most generous assessment possible is that the IPCC’s claim to 1ºC warming since pre-industrial times is an exaggeration possibly motivated by the needs of advocacy for pushing climate action.
  10. However, a more serious issue is the the reference to pre-industrial times as the baseline from which the anthropogenic effect of fossil fuel emissions should be measured. In the AR5 and other publications, the IPCC states that “Human-induced warming reached approximately 1°C (±0.2°C likely range) above pre-industrial levels in 2017. Warming is expressed relative to the period 1850-1900, used as an approximation of pre-industrial temperatures in AR5″. Yet, in the matter of identifying human cause, the IPCC writes that “The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20thcentury” (citations below). In other words, the whole of the 1°C warming from pre-industrial times cannot be shown to be human caused because only the warming since the “mid-20th-century” is human caused. That raises the question with regard to the amount of warming that can be shown to be human caused in this context.
  11. That only the warming since the mid-20th century contains a “fingerprint” of human cause is found elsewhere in climate science. Figure 9 contains a graphic from that “human drivers of climate” are detectable at some time after 1960 using a fingerprinting method climate models are run with and without the human forcings. A demonstration of this fingerprinting methodology by climate scientist Peter Cox of the University of Exeter is shown in the video that appears in the bottom panel of Figure 9. Here, the Hadcrut temperatures since 1850 are plotted in red and then overlaid with two sets of climate model runs one after the other in the video sequence. The first climate model run contains only natural factors and the output is plotted in green. It shows good agreement with the observational data until at some point after 1960 where the green curve and the red curve begin to diverge. A second climate model run is made but this time with human factors included and the output of this run is plotted in yellow and now with human factors included the model output and the data do not diverge proving that “from about 1970 onwards” the climate model and the data show excellent agreement. This analysis and its conclusions are consistent with the IPCC’s identification of the “mid-20th century” when a human hand is detectable in the climate.
  12. The analysis presented above implies that only the amount of warming since 1970 can be ascribed to human cause. The average of the warming amounts in the observational data found in Figure 7 for start-year=1970 is 0.847°C. This is the best unbiased estimate of the total amount of warming caused by human activity. The standard error is 0.02 which yields a 90% confidence interval of [0.814-0.880).
  13. We conclude that the IPCC claims to human caused warming of 1°C or greater “since pre-industrial times” is not an unbiased assessment and that it is inconsistent with the data.

 

 

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HUMAN CAUSE IN GLOBAL WARMING: BIBLIOGRAPHY

  1. [2018: IPCC SR15 SPECIAL REPORT] Human-induced warming reached approximately 1°C (±0.2°C likely range) above pre-industrial levels in 2017, increasing at 0.2°C (±0.1°C) per decade (high confidence). Global warming is defined in this report as an increase in combined surface air and sea surface temperatures averaged over the globe and a 30-year period. Unless otherwise specified, warming is expressed relative to the period 1850-1900, used as an approximation of pre-industrial temperatures in AR5. For periods shorter than 30 years, warming refers to the estimated average temperature over the 30 years centered on that shorter period, accounting for the impact of any temperature fluctuations or trend within those 30 years. Accordingly, warming up to the decade 2006-2015 is assessed at 0.87°C (±0.12°C likely range). Since 2000, the estimated level of human-induced warming has been equal to the level of observed warming with a likely range of ±20% accounting for uncertainty due to contributions from solar and volcanic activity over the historical period (high confidence). {1.2.1} Warming greater than the global average has already been experienced in many regions and seasons, with average warming over land higher than over the ocean?? (high confidence). Most land regions are experiencing greater warming than the global average, while most ocean regions are warming at a slower rate. Depending on the temperature dataset considered, 20-40% of the global human population live in regions that, by the decade 2006-2015, had already experienced warming of more than 1.5°C above pre-industrial in at least one season ?? (medium confidence). {1.2.1 & 1.2.2}
  2. 2018: NASA, Global climate change, vital signs of the planet,  [SOURCE DOCUMENT]The Earth’s climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives. The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20thcentury and proceeding at a rate that is unprecedented over decades to millennia. Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate. The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century. Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response. Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.
  3. 2015: Trenberth, Kevin E., John T. Fasullo, and Theodore G. Shepherd. “Attribution of climate extreme events.” Nature Climate Change 5.8 (2015): 725. There is a tremendous desire to attribute causes to weather and climate events that is often challenging from a physical standpoint. Headlines attributing an event solely to either human-induced climate change or natural variability can be misleading when both are invariably in play. The conventional attribution framework struggles with dynamically driven extremes because of the small signal-to-noise ratios and often uncertain nature of the forced changes. Here, we suggest that a different framing is desirable, which asks why such extremes unfold the way they do. Specifically, we suggest that it is more useful to regard the extreme circulation regime or weather event as being largely unaffected by climate change, and question whether known changes in the climate system’s thermodynamic state affected the impact of the particular event. Some examples briefly illustrated include ‘snowmaggedon’ in February 2010, superstorm Sandy in October 2012 and supertyphoon Haiyan in November 2013, and, in more detail, the Boulder floods of September 2013, all of which were influenced by high sea surface temperatures that had a discernible human component.
  4. [2014: IPCC AR5] Scientific evidence for warming of the climate system is unequivocal according to the IPCC. The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia. [Source: IPCC Fifth Assessment Report, Summary for Policymakers]
  5. 2011: Hegerl, Gabriele, and Francis Zwiers. “Use of models in detection and attribution of climate change.” Wiley interdisciplinary reviews: climate change 2.4 (2011): 570-591. Most detection and attribution studies use climate models to determine both the expected ‘fingerprint’ of climate change and the uncertainty in the estimated magnitude of this fingerprint in observations, given the climate variability. This review discusses the role of models in detection and attribution, the associated uncertainties, and the robustness of results. Studies that use observations only make substantial assumptions to separate the components of observed changes due to radiative forcing from those due to internal climate variability. Results from observation‐only studies are broadly consistent with those from fingerprint studies. Fingerprint studies evaluate the extent to which patterns of response to external forcing (fingerprints) from climate model simulations explain observed climate change in observations. Fingerprints are based on climate models of various complexities, from energy balance models to full earth system models. Statistical approaches range from simple comparisons of observations with model simulations to multi‐regression methods that estimate the contribution of several forcings to observed change using a noise‐reducing metric. Multi‐model methods can address model uncertainties to some extent and we discuss how remaining uncertainties can be overcome. The increasing focus on detecting and attributing regional climate change and impacts presents both opportunities and challenges. Challenges arise because internal variability is larger on smaller scales, and regionally important forcings, such as from aerosols or land‐use change, are often uncertain. Nevertheless, if regional climate change can be linked to external forcing, the results can be used to provide constraints on regional climate projections
  6. 2010: Stott, Peter A., et al. “Detection and attribution of climate change: a regional perspective.” Wiley Interdisciplinary Reviews: Climate Change 1.2 (2010): 192-211. The Intergovernmental Panel on Climate Change fourth assessment report, published in 2007 came to a more confident assessment of the causes of global temperature change than previous reports and concluded that ‘it is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica.’ Since then, warming over Antarctica has also been attributed to human influence, and further evidence has accumulated attributing a much wider range of climate changes to human activities. Such changes are broadly consistent with theoretical understanding, and climate model simulations, of how the planet is expected to respond. This paper reviews this evidence from a regional perspective to reflect a growing interest in understanding the regional effects of climate change, which can differ markedly across the globe. We set out the methodological basis for detection and attribution and discuss the spatial scales on which it is possible to make robust attribution statements. We review the evidence showing significant human‐induced changes in regional temperatures, and for the effects of external forcings on changes in the hydrological cycle, the cryosphere, circulation changes, oceanic changes, and changes in extremes. We then discuss future challenges for the science of attribution. To better assess the pace of change, and to understand more about the regional changes to which societies need to adapt, we will need to refine our understanding of the effects of external forcing and internal variability
  7. 2010: Gleick, Peter H., et al. “Climate change and the integrity of science.” Science 328.5979 (2010): 689-690. Climate change falls into the category of undeniable science along with the big bang theory, the theory of the earth, and the theory of evolution. There is compelling, comprehensive, and consistent objective evidence that humans are changing the climate in ways that threaten our societies and the ecosystems on which we depend. The planet is warming due to increased concentrations of heat-trapping gases in our atmosphere. A snowy winter in Washington does not alter this fact. Most of the increase in the concentration of these gases over the last century is due to human activities, especially the burning of fossil fuels and deforestation. Natural causes always play a role in changing Earth’s climate, but are now being overwhelmed by human-induced changes.(iv) Warming the planet will cause many other climatic patterns to change at speeds unprecedented in modern times, including increasing rates of sea-level rise and alterations in the hydrological cycle. Rising concentrations of carbon dioxide are making the oceans more acidic. The combination of these complex climate changes threatens coastal communities and cities, our food and water supplies, marine and freshwater ecosystems, forests, high mountain environments, and far more. Much more can be, and has been, said by the world’s scientific societies, national academies, and individuals, but these conclusions should be enough to indicate why scientists are concerned about what future generations will face from business-as-usual practices. We urge our policy-makers and the public to move forward immediately to address the causes of climate change, including the unrestrained burning of fossil fuels.
  8. 2009: Shindell, Drew T., et al. “Improved attribution of climate forcing to emissions.” Science 326.5953 (2009): 716-718. Evaluating multicomponent climate change mitigation strategies requires knowledge of the diverse direct and indirect effects of emissions. Methane, ozone, and aerosols are linked throughatmospheric chemistry so that emissions of a single pollutant can affect several species. We calculated atmospheric composition changes, historical radiative forcing, and forcing per unit of emission due to aerosol and tropospheric ozone precursor emissions in a coupled compositionclimate model. We found that gas-aerosol interactions substantially alter the relative importance of the various emissions. In particular, methane emissions have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol. Thus, assessments of multigas mitigation policies, as well as any separate efforts to mitigate warming from short-lived pollutants, should include gas-aerosol interactions.
  9. 2003: Parmesan, Camille, and Gary Yohe. “A globally coherent fingerprint of climate change impacts across natural systems.” Nature 421.6918 (2003): 37. Causal attribution of recent biological trends to climate change is complicated because non-climatic influences dominate local, short-term biological changes. Any underlying signal from climate change is likely to be revealed by analyses that seek systematic trends across diverse species and geographic regions; however, debates within the Intergovernmental Panel on Climate Change (IPCC) reveal several definitions of a ‘systematic trend’. Here, we explore these differences, apply diverse analyses to more than 1,700 species, and show that recent biological trends match climate change predictions. Global meta-analyses documented significant range shifts averaging 6.1 km per decade towards the poles (or metres per decade upward), and significant mean advancement of spring events by 2.3 days per decade. We define a diagnostic fingerprint of temporal and spatial ‘sign-switching’ responses uniquely predicted by twentieth century climate trends. Among appropriate long-term/large-scale/multi-species data sets, this diagnostic fingerprint was found for 279 species. This suite of analyses generates ‘very high confidence’ (as laid down by the IPCC) that climate change is already affecting living systems.
  10. 1999: Allen, Myles R., and Simon FB Tett. “Checking for model consistency in optimal fingerprinting.” Climate Dynamics 15.6 (1999): 419-434. Current approaches to the detection and attribution of an anthropogenic influence on climate involve quantifying the level of agreement between model-predicted patterns of externally forced change and observed changes in the recent climate record. Analyses of uncertainty rely on simulated variability from a climate model. Any numerical representation of the climate is likely to display too little variance on small spatial scales, leading to a risk of spurious detection results. The risk is particularly severe if the detection strategy involves optimisation of signal-to-noise because unrealistic aspects of model variability may automatically be given high weight through the optimisation. The solution is to confine attention to aspects of the model and of the real climate system in which the model simulation of internal climate variability is adequate, or, more accurately, cannot be shown to be deficient. We propose a simple consistency check based on standard linear regression which can be applied to both the space-time and frequency domain approaches to optimal detection and demonstrate the application of this check to the problem of detection and attribution of anthropogenic signals in the radiosonde-based record of recent trends in atmospheric vertical temperature structure. The influence of anthropogenic greenhouse gases can be detected at a high confidence level in this diagnostic, while the combined influence of anthropogenic sulphates and stratospheric ozone depletion is less clearly evident. Assuming the time-scales of the model response are correct, and neglecting the possibility of non-linear feedbacks, the amplitude of the observed signal suggests a climate sensitivity range of 1.2–3.4 K, although the upper end of this range may be underestimated by up to 25% due to uncertainty in model-predicted response patterns
  11. 1998: North, Gerald R., and Mark J. Stevens. “Detecting climate signals in the surface temperature record.” Journal of climate11.4 (1998): 563-577. Optimal signal detection theory has been applied in a search through 100 yr of surface temperature data for the climate response to four specific radiative forcings. The data used comes from 36 boxes on the earth and was restricted to the frequency band 0.06–0.13 cycles yr−1 (16.67–7.69 yr) in the analysis. Estimates were sought of the strengths of the climate response to solar variability, volcanic aerosols, greenhouse gases, and anthropogenic aerosols. The optimal filter was constructed with a signal waveform computed from a two-dimensional energy balance model (EBM). The optimal weights were computed from a 10000-yr control run of a noise-forced EBM and from 1000-yr control runs from coupled ocean–atmosphere models at Geophysical Fluid Dynamics Laboratory (GFDL) and Max-Planck Institute; the authors also used a 1000-yr run using the GFDL mixed layer model. Results are reasonably consistent across these four separate model formulations. It was found that the component of the volcanic response perpendicular to the other signals was very robust and highly significant. Similarly, the component of the greenhouse gas response perpendicular to the others was very robust and highly significant. When the sum of all four climate forcings was used, the climate response was more than three standard deviations above the noise level. These findings are considered to be powerful evidence of anthropogenically induced climate change.
  12. 1997: Hegerl, Gabriele C., et al. “Multi-fingerprint detection and attribution analysis of greenhouse gas, greenhouse gas-plus-aerosol and solar forced climate change.” Climate Dynamics13.9 (1997): 613-634. A multi-fingerprint analysis is applied to the detection and attribution of anthropogenic climate change. While a single fingerprint is optimal for the detection of climate change, further tests of the statistical consistency of the detected climate change signal with model predictions for different candidate forcing mechanisms require the simultaneous application of several fingerprints. Model-predicted climate change signals are derived from three anthropogenic global warming simulations for the period 1880 to 2049 and two simulations forced by estimated changes in solar radiation from 1700 to 1992. In the first global warming simulation, the forcing is by greenhouse gas only, while in the remaining two simulations the direct influence of sulfate aerosols is also included. From the climate change signals of the greenhouse gas only and the average of the two greenhouse gas-plus-aerosol simulations, two optimized fingerprint patterns are derived by weighting the model-predicted climate change patterns towards low-noise directions. The optimized fingerprint patterns are then applied as a filter to the observed near-surface temperature trend patterns, yielding several detection variables. The space-time structure of natural climate variability needed to determine the optimal fingerprint pattern and the resultant signal-to-noise ratio of the detection variable is estimated from several multi-century control simulations with different CGCMs and from instrumental data over the last 136 y. Applying the combined greenhouse gas-plus-aerosol fingerprint in the same way as the greenhouse gas only fingerprint in a previous work, the recent 30-y trends (1966–1995) of annual mean near surface temperature are again found to represent a significant climate change at the 97.5% confidence level. However, using both the greenhouse gas and the combined forcing fingerprints in a two-pattern analysis, a substantially better agreement between observations and the climate model prediction is found for the combined forcing simulation. Anticipating that the influence of the aerosol forcing is strongest for longer term temperature trends in summer, application of the detection and attribution test to the latest observed 50-y trend pattern of summer temperature yielded statistical consistency with the greenhouse gas-plus-aerosol simulation with respect to both the pattern and amplitude of the signal. In contrast, the observations are inconsistent with the greenhouse-gas only climate change signal at a 95% confidence level for all estimates of climate variability. The observed trend 1943–1992 is furthermore inconsistent with a hypothesized solar radiation change alone at an estimated 90% confidence level. Thus, in contrast to the single pattern analysis, the two pattern analysis is able to discriminate between different forcing hypotheses in the observed climate change signal. The results are subject to uncertainties associated with the forcing history, which is poorly known for the solar and aerosol forcing, the possible omission of other important forcings, and inevitable model errors in the computation of the response to the forcing. Further uncertainties in the estimated significance levels arise from the use of model internal variability simulations and relatively short instrumental observations (after subtraction of an estimated greenhouse gas signal) to estimate the natural climate variability. The resulting confidence limits accordingly vary for different estimates using different variability data. Despite these uncertainties, however, we consider our results sufficiently robust to have some confidence in our finding that the observed climate change is consistent with a combined greenhouse gas and aerosol forcing, but inconsistent with greenhouse gas or solar forcing alone.
  13. 1996: Santer, Benjamin D., et al. “A search for human influences on the thermal structure of the atmosphere.” Nature 382.6586 (1996): 39. The observed spatial patterns of temperature change in the free atmosphere from [1963 to 1987] are similar to those predicted by state-of-the-art climate models incorporating various combinations of changes in carbon dioxide, anthropogenic sulphate aerosol and stratospheric ozone concentrations. The degree of pattern similarity between models and observations increases through this period. It is likely that this trend is partially due to human activities, although many uncertainties remain, particularly relating to estimates of natural variability.
  14. 1996: Hegerl, Gabriele C., et al. “Detecting greenhouse-gas-induced climate change with an optimal fingerprint method.” Journal of Climate 9.10 (1996): 2281-2306. A strategy using statistically optimal fingerprints to detect anthropogenic climate change is outlined and applied to near-surface temperature trends. The components of this strategy include observations, information about natural climate variability, and a “guess pattern” representing the expected time–space pattern of anthropogenic climate change. The expected anthropogenic climate change is identified through projection of the observations onto an appropriate optimal fingerprint, yielding a scalar-detection variable. The statistically optimal fingerprint is obtained by weighting the components of the guess pattern (truncated to some small-dimensional space) toward low-noise directions. The null hypothesis that the observed climate change is part of natural climate variability is then tested. This strategy is applied to detecting a greenhouse-gas-induced climate change in the spatial pattern of near-surface temperature trends defined for time intervals of 15–30 years. The expected pattern of climate change is derived from a transient simulation with a coupled ocean-atmosphere general circulation model. Global gridded near-surface temperature observations are used to represent the observed climate change. Information on the natural variability needed to establish the statistics of the detection variable is extracted from long control simulations of coupled ocean-atmosphere models and, additionally, from the observations themselves (from which an estimated greenhouse warming signal has been removed). While the model control simulations contain only variability caused by the internal dynamics of the atmosphere-ocean system, the observations additionally contain the response to various external forcings (e.g., volcanic eruptions, changes in solar radiation, and residual anthropogenic forcing). The resulting estimate of climate noise has large uncertainties but is qualitatively the best the authors can presently offer. The null hypothesis that the latest observed 20-yr and 30-yr trend of near-surface temperature (ending in 1994) is part of natural variability is rejected with a risk of less than 2.5% to 5% (the 5% level is derived from the variability of one model control simulation dominated by a questionable extreme event). In other words, the probability that the warming is due to our estimated natural variability is less than 2.5% to 5%. The increase in the signal-to-noise ratio by optimization of the fingerprint is of the order of 10%–30% in most cases. The predicted signals are dominated by the global mean component; the pattern correlation excluding the global mean is positive but not very high. Both the evolution of the detection variable and also the pattern correlation results are consistent with the model prediction for greenhouse-gas-induced climate change. However, in order to attribute the observed warming uniquely to anthropogenic greenhouse gas forcing, more information on the climate’s response to other forcing mechanisms (e.g., changes in solar radiation, volcanic, or anthropogenic sulfate aerosols) and their interaction is needed. It is concluded that a statistically significant externally induced warming has been observed, but our caveat that the estimate of the internal climate variability is still uncertain is emphasized.
  15. 1995: Santer, B. D., K. E. Taylor, and J. E. Penner. A search for human influences on the thermal structure of the atmosphere. No. UCRL-ID-121956. Lawrence Livermore National Lab., CA (United States), 1995. Several recent studies have compared observed changes in near-surface temperature with patterns of temperature change predicted by climate models in response to combined forcing by carbon dioxide and anthropogenic sulphate aerosols. These results suggest that a combined carbon dioxide + sulphate aerosol signal is easier to identify in the observations than a pattern of temperature change due to carbon dioxide alone. This work compares modelled and observed patterns of vertical temperature change in the atmosphere. Results show that the observed and model-predicted changes in the mid- to low troposphere are in better accord with greenhouse warming predictions when the likely effects of anthropogenic sulphate aerosols and stratospheric ozone reduction are incorporated in model calculations, and that the level of agreement increases with time. This improved correspondence is primarily due to hemispheric-scale temperature contrasts. If current model-based estimates of natural internal variability are realistic, it is likely that the level of time-increasing similarity between modelled and predicted patterns of vertical temperature change is partially due to human activities.
  16. 1995: North, Gerald R., et al. “Detection of forced climate signals. Part 1: Filter theory.” Journal of Climate 8.3 (1995): 401-408. This paper considers the construction of a linear smoothing filter for estimation of the forced part of a change in a climatological field such as the surface temperature. The filter is optimal in the sense that it suppresses the natural variability or “noise” relative to the forced part or “signal” to the maximum extent possible. The technique is adapted from standard signal processing theory. The present treatment takes into account the spatial as well as the temporal variability of both the signal and the noise. In this paper we take the signal’s waveform in space-time to be a given deterministic field in space and lime. Formulation of the expression for the minimum mean-squared error for the problem together with a no-bias constraint leads to an integral equation whose solution is the filter. The problem can be solved analytically in terms of the space-time empirical orthogonal function basis set and its eigenvalue spectrum for the natural fluctuations and the projection amplitudes of the signal onto these eigenfunctions. The optimal filter does not depend on the strength of the assumed waveform used in its construction. A lesser mean-square error in estimating the signal occurs when the space-time spectral characteristics of the signal and the noise are highly dissimilar; for example, if the signal is concentrated in a very narrow spectral band and the noise in a very broad band. A few pedagogical exercises suggest that these techniques might be useful in practical situations.
  17. 1993: Hasselmann, Klaus. “Optimal fingerprints for the detection of time-dependent climate change.” Journal of Climate 6.10 (1993): 1957-1971. An optimal linear filter (fingerprint) is derived for the detection of a given time-dependent, multivariate climate change signal in the presence of natural climate variability noise. Application of the fingerprint to the observed (or model simulated) climate data yields a climate change detection variable (detector) with maximal signal-to-noise ratio. The optimal fingerprint is given by the product of the assumed signal pattern and the inverse of the climate variability covariance matrix. The data can consist of any, not necessarily dynamically complete, climate dataset for which estimates of the natural variability covariance matrix exist. The single-pattern analysis readily generalizes to the multipattern case of a climate change signal lying in a prescribed (in practice relatively low dimensional) signal pattern space: the single-pattern result is simply applied separately to each individual base pattern spanning the signal pattern space. Multipattern detection methods can be applied either to test the statistical significance of individual components of a predicted multicomponent climate change response, using separate single-pattern detection tests, or to determine the statistical significance of the complete signal, using a multivariate test. Both detection modes make use of the same set of detectors. The difference in direction of the assumed signal pattern and computed optimal fingerprint vector allows alternative interpretations of the estimated signal associated with the set of optimal detectors. The present analysis yields an estimated signal lying in the assumed signal space, whereas an earlier analysis of the time-independent detection problem by Hasselmann yielded an estimated signal in the computed fingerprint space. The different interpretations can be explained by different choices of the metric used to relate the signal space to the fingerprint space (inverse covariance matrix versus standard Euclidean metric, respectively). Two simple natural variability models are considered: a space-time separability model, and an expansion in terms of P0Ps (principal oscillation patterns). For each model the application of the optimal fingerprint method is illustrated by an example.

 

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  1. Conventional wisdom about the abrupt glacial melt in the Alps at the end the Little Ice Age   [LINK] holds that it was caused by black carbon soot deposition on the glaciers. “At the end of the Little Ice Age in the European Alps glaciers began to retreat abruptly in the mid-19th century, but reconstructions of temperature and precipitation indicate that glaciers should have instead advanced into the 20th century. We observe that industrial black carbon in snow began to increase markedly in the mid-19th century and show with simulations that the associated increases in absorbed sunlight by black carbon in snow and snowmelt were of sufficient magnitude to cause this scale of glacier retreat. This hypothesis offers a physically based explanation for the glacier retreat that maintains consistency with the temperature and precipitation reconstructions.” [Painter, Thomas H., et al. “End of the Little Ice Age in the Alps forced by industrial black carbon.” Proceedings of the national academy of sciences (2013): 201302570.[FULL TEXT PDF DOWNLOAD]
  2. A more recent paper has pointed out a temporal anomaly in the reasoning in the (Painter etal 2013) paper. It says that “Starting around 1860, many glaciers in the European Alps began to retreat from their maximum mid-19th century terminus positions marking the end of the Little Ice Age in Europe. Radiative forcing by increasing deposition of industrial black carbon to snow has been suggested as the main driver of the abrupt glacier retreats in the Alps. The basis for this hypothesis was model simulations using elemental carbon concentrations at low temporal resolution from two ice cores in the Alps. Here we present sub-annually resolved concentration records of refractory black carbon (rBC; using soot photometry) as well as distinctive tracers for mineral dust, biomass burning and industrial pollution from the Colle Gnifetti ice core in the Alps from 1741 to 2015. These records allow precise assessment of a potential relation between the timing of observed acceleration of glacier melt in the mid-19th century with an increase of rBC deposition on the glacier caused by the industrialization of Western Europe. Our study reveals that in 1875, the time when rBC ice-core concentrations started to significantly increase, the majority of Alpine glaciers had already experienced more than 80% of their total 19th century length reduction, casting doubt on a leading role for soot in terminating of the Little Ice Age. Attribution of glacial retreat requires expansion of the spatial network and sampling density of high alpine ice cores to balance potential biasing effects arising from transport, deposition, and snow conservation in individual ice-core records.  [ Sigl, M., Abram, N. J., Gabrieli, J., Jenk, T. M., Osmont, D., and Schwikowski, M.: 19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers, The Cryosphere, 12, 3311-3331, https://doi.org/10.5194/tc-12-3311-2018, 2018.[FULL TEXT PDF DOWNLOAD]
  3. In other words, by the time the (Painter etal 2013) causation is observed most of the glacial melt had already occurred. These data therefore do not serve as evidence that the end of the Little Ice Age was initiated by the Industrial Economy by way of black carbon soot emissions and later exacerbated by CO2  emissions from the combustion of fossil fuels. This temporal anomaly weakens the AGW argument that the Little Ice Age was ended by the Industrial Revolution and not by nature and that the current warming trend is therefore human caused by way of fossil fuel emissions from the Industrial Economy. The results suggest that if AGW science had studied the same data in the absence of advocacy against fossil fuels, a greater attention may have been paid to natural climate change.
  4. The usual argument that the current rate of warming is unprecedented and therefore too high to be natural is inconsistent with the data as has been shown in a related post here  [LINK] .
  5. With thanks to the Lubos Motl blog for bringing the 2018 paper to public attention.  [LINK]

 

 

COLLE GNIFETTI BIBLIOGRAPHY

  1. 1988: Wagenbach, D., et al. “The anthropogenic impact on snow chemistry at Colle Gnifetti, Swiss Alps.” Annals of Glaciology10 (1988): 183-187. By chemical analysis of the upper 40 m of a 124 m ice core from a high-altitude Alpine glacier (Colle Gnifetti, Swiss Alps; 4450 m a.s.l.), records of mineral dust, pH, melt-water conductivity, nitrate and sulfate are obtained. The characteristics of the drilling site are discussed, as derived from glacio-meteorological and chemical analysis. As a consequence of high snow-erosion rates (usually during the winter months), annual snow accumulation is dominated by summer precipitation. Clean-air conditions prevail even during summer; however, they are frequently interrupted by polluted air masses or by air masses which are heavily loaded with desert dust.Absolutely dated reference horizons for Saharan dust, together with the position of the broad nuclear-weapon tritium peak, provide the time-scale for the following statements: (1) Since at least the turn of the century the background melt-water conductivity has been rising steadily, as has the mean snow acidity. The trend of increasing background conductivity at Colle Gnifetti (1.9μS/cm around the beginning of this century, and at present 3.4 μS/cm) is found to be comparable with the records of mean melt-water conductivity reported from ice cores from the Canadian High Arctic. (2) Sulfate and nitrate concentrations are higher by a factor of 4–5 than they were at the beginning of the century. This is to be compared with the two- to three-fold rise in the concentrations in south Greenland during about the same time span.
  2. 1989: Wagenbach, Dietmar, and Klaus Geis. “The mineral dust record in a high altitude Alpine glacier (Colle Gnifetti, Swiss Alps).” Paleoclimatology and paleometeorology: modern and past patterns of global atmospheric transport. Springer, Dordrecht, 1989. 543-564. Ice-core and snow-pit samples from a non-temperated glacier in the summit range of Monte Rosa, Swiss Alps (4450 m.a.s.l.) has been analyzed for total mineral dust and the size distribution of insoluble particulate matter in the size range 0.63–20 microns. Based on a 50 years-record Saharan dust accounts for two third of the mean mineral dust flux of 60 μgcm-2yr-1. Both, background and Saharan dust influenced samples show a distinct mode in the volume size distribution of insoluble particles over the optical active size range with a typical volume mean diameter of 2.5 and 4.5 μm, respectively. These two size distribution categories are attributed to the insoluble fraction of the long lived background aerosol and to the relatively short lived aerosol dominated by soil derived dust (i.e. ground-level aerosol in aride areas).
  3. 1999: Lavanchy, V. M. H., et al. “Historical record of carbonaceous particle concentrations from a European high‐alpine glacier (Colle Gnifetti, Switzerland).” Journal of Geophysical Research: Atmospheres 104.D17 (1999): 21227-21236. Historical records of the concentrations of black carbon (BC) and elemental carbon (EC), as well as of water insoluble organic carbon (OC) and total carbon (TC) covering the time period ∼1755–1975 are presented. Concentrations were obtained from an ice core of a European high‐alpine glacier, using an optical and a thermal method. Concentrations were found to vary between 7 and 128 μg L−1 for BC, between 5 and 130 μg L−1 for EC, between 53 and 484 μg L−1 for OC, and between 66 and 614 μg L−1 for TC. From preindustrial (1755–1890) to modern times (1950–1975) BC, EC, OC, and TC concentrations increased by a factor of 3.7, 3.0, 2.5, and 2.6, respectively. The sum of BC emissions of Germany, France, Switzerland, and Italy, calculated from fossil fuel consumption, and the EC concentration record correlate well (R2 = 0.56) for the time period from 1890 to 1975; this indicates that the ice core record reflects the emissions of western Europe. High pre‐1860 concentrations indicate that by that time BC emissions to the atmosphere were already significant.
  4. 1999: Schwikowski, M., et al. “Anthropogenic versus natural sources of atmospheric sulphate from an Alpine ice core.” Tellus B: Chemical and Physical Meteorology 51.5 (1999): 938-951. Opposite to greenhouse gases, sulphate aerosol particles are expected to cause climate cooling, but uncertainties exist about source variability and strength. We analysed an ice core from a European glacier to quantify source strengths of aerosol-borne sulphate over a 200-year period. Sulphate from emissions of SO2increased by more than an order of magnitude during this century. This anthropogenic source is responsible for about 80% of total sulphate in the industrial period, and reflects emissions of west European countries. In the pre-industrial period mineral dust was the dominant contributor, followed by sulphate from SO2 emissions with volcanoes or biomass burning as possible sources.
  5. 1999: Schwikowski, M., et al. “A high‐resolution air chemistry record from an Alpine ice core: Fiescherhorn glacier, Swiss Alps.” Journal of Geophysical Research: Atmospheres 104.D11 (1999): 13709-13719. Glaciochemical studies at midlatitudes promise to contribute significantly to the understanding of the atmospheric cycling of species with short atmospheric lifetimes. Here we present results of chemical analyses of environmentally relevant species performed on an ice core from Fiescherhorn glacier, Swiss Alps (3890 m above sea level). This glacier site is unique since it is located near the high‐alpine research station Jungfraujoch. There long‐term meteorological and air quality measurements exist, which were used to calibrate the paleodata. The 77‐m‐long ice core was dated by annual layer counting using the seasonally varying signals of tritium and δ18O. It covers the time period 1946–1988 and shows a high net accumulation of water of 1.4 m yr−1 allowing for the reconstruction of high‐resolution environmental records. Chemical composition was dominated by secondary aerosol constituents as well as mineral dust components, characterizing the Fiescherhorn site as a relatively unpolluted continental site. Concentrations of species like ammonium, nitrate, and sulfate showed an increasing trend from 1946 until about 1975, reflecting anthropogenic emission trends in western Europe. For mineral dust tracers, no trends were obvious, whereas chloride and sodium showed slightly higher levels from 1965 until 1988, indicating a change in the strength of sea‐salt transport. Good agreement between the sulfate paleorecord with direct atmospheric measurements was found (correlation coefficient r2 = 0.41). Thus a “calibration” of the paleorecord over a significant period of time could be conducted, revealing an average scavenging ratio of 180 for sulfate.
  6. 2009: Thevenon, Florian, et al. “Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over the last millennium.” Journal of Geophysical Research: Atmospheres 114.D17 (2009). Black carbon (BC) and mineral dust aerosols were analyzed in an ice core from the Colle Gnifetti glacier (Monte Rosa, Swiss‐Italian Alps, 45°55′N, 7°52′E, 4455 m above sea level) using chemical and optical methods. The resulting time series obtained from this summer ice record indicate that BC transport was primarily constrained by regional anthropogenic activities, i.e., biomass and fossil fuel combustion. More precisely, the δ13C composition of BC suggests that wood combustion was the main source of preindustrial atmospheric BC emissions (C3:C4 ratio of burnt biomass of 75:25). Despite relatively high BC emissions prior to 1570, biomass burning activity and especially C4 grassland burning abruptly dropped between 1570 and 1750 (C3:C4 ratio of burnt biomass of 90:10), suggesting that agricultural practices strongly decreased in Europe during this cold period of the “Little Ice Age” (LIA). On the other hand, optical analysis revealed that the main source for atmospheric dust transport to the southern parts of the Alps during summer months was driven by large‐scale atmospheric circulation control on the dust export from the northern Saharan desert. This southern aerosol source was probably associated with global‐scale hydrologic changes, at least partially forced by variability in solar irradiance. In fact, periods of enhanced Saharan dust deposition in the ice core (around 1200–1300, 1430–1520, 1570–1690, 1780–1800, and after 1870) likely reflect drier winters in North Africa, stronger North Atlantic southwesterlies, and increased spring/summer precipitation in west‐central Europe. These results, therefore, suggest that the climatic pejorations and the resulting socioeconomic crises, which occurred in Europe during periods of the LIA, could have been indirectly triggered by large‐scale meridional advection of air masses and wetter summer climatic conditions.

 

 

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jpteam1970SCOOLING

 

 

FIGURE 1: NEWS MEDIA FEAR OF A COMING ICE AGE

 

 

FIGURE 2: NORTHERNHEMISPHERE LANDlandnhgif

FIGURE 3: SOUTHERNHEMISPHERE LANDlandshgif

 

FIGURE 4: NORTHERNHEMISPHERE OCEANseanhgif

 

FIGURE 5:  SOUTHERNHEMISPHERE OCEANseashgif

 

[LIST OF POSTS ON THIS SITE]

 

  1. The warming trend that began since the Industrial Revolution (coincidental with the end of the Little Ice Age or LIA) after the year 1850 has been attributed to rising atmospheric carbon dioxide concentration in terms of its theoretical heat trapping effect. In turn, rising atmospheric CO2 is attributed to emissions from fossil fuel combustion in the industrial economy. The carbon from fossil fuels is thought of as a perturbation of the carbon cycle and climate system with external carbon dug up from deep under the ground where it had been sequestered for millions of years. The warming trend is thus attributed to the industrial economy and described as artificial (Callendar 1938), human caused(Hansen 1981), anthropogenic (IPCC 2007).
  2. Yet, it is generally recognized that CO2 driven Anthropogenic Global Warming (AGW) was interrupted with significant cooling for a period of 30 years or more even as carbon dioxide from the industrial economy was being released into the atmosphere at record rates. The cooling occurred at some time after the 1930s and before the 1980s with the cooling anomaly generally described as 1940s to 1970s. The cooling trend in this period is recorded in the instrumental temperature record and in global and regional temperature reconstructions. News media archives from that period show a global fear of a return to the Little Ice Age (Figure 1) even though the recovery from the LIA is also feared as catastrophic human caused global warming.
  3. This cooling period is considered to be anomalous and contentious because it appears to be incompatible with the theory of AGW. Skeptics often use this cooling period to argue against AGW theory. Proponents of AGW have either minimized its importance in terms of climate change theory and consensus among climate scientists (Peterson 2008) or have offered explanations for the cooling within the context of global warming. It is argued that the cooling may be explained in terms that are not inconsistent with AGW. For example, it is possible that climate instability is an effect of AGW and the brief period of cooling is an outcome of such instability (Asakura 1981) (Allen 1982) (Suckling 1984).
  4. It is also proposed that an artificial effect of the industrial economy,in addition to the generation of artificial carbon dioxide, is an increase in atmospheric aerosols. It is known that aerosols can cause cooling. Here we examine the aerosol argument in some detail as it is the generally accepted theory of the anomalous 1940s-1970s cooling period in the era of AGW. References to the literature are listed in the AEROSOL BIBLIOGRAPHY below.
  5. Empirical evidence of cooling in a period of approximately 30 to 40 years at some time between 1940 and 1980 is presented in Figure 2 to Figure 5 using regional temperature reconstructions provided by the Hadley Centre Climate Research Unit of the Met Office of the Government of the UK. Four distinct regions, that together encompass the globe, are studied separately. These are LAND areas of the Northern (Figure 2) and Southern (Figure 3) hemispheres and OCEAN areas of the Northern (Figure 4) and Southern (Figure 5) hemispheres. Each figure is a GIF animation that shows a trend profile for each of the twelve calendar months, one month at a time and cycles through all twelve calendar months. Each graphic is a display of the temperature trend in a moving 15-year window. A horizontal line is drawn at the zero trend position. Warming trends (above the zero line) are colored Red and Cooling trends (below the zero line) are colored Blue. Although the data are provided from 1850, only the portion after 1918 is shown for greater clarity of the study period of 1940 to 1980.
  6. We find in these charts that all four regions and all twelve calendar months show 15yr cooling periods of various degrees of persistence and intensity at somewhat different locations within the study period of 1940-1980 within a global warming context. The period 1918-2017 is dominated by more intense and more persistent episodes of warming. Some cooling periods are found outside the study period particularly so in the 1920s when cooling was more intense and after the year 2000 when cooling is less intense but consistent with the so called “warming hiatus” hypothesis that has been explained in terms of changes in ocean heat content (Related post [Ocean Heat Content] ). The ocean heat content argument is not used for the 1940s-1970s cooling because the cooling is also found in ocean heat content.
  7. The location, duration, and intensity of the 1940s-1970s cooling period vary among calendar months, between land and ocean in each hemisphere, and between the two hemispheres for each surface type. However, some kind of a cooling trend is found somewhere within this period. In some cases both short term cooling and warming periods are found. Although cooling dominates, the cooling is not found to be sustained in all cases. It should be noted that a significant and deep blue patch of cooling is seen in the Northern Hemisphere Oceans. This observations is consistent with the cooling in the North Atlantic and Arctic in the 1960s and 1970s described in (Read 1992) & (Hodson 2014).
  8. A great deal of aerosols are created in the industrial economy as can be seen in the current problem with haze in rapidly industrializing countries such as China and India. Aerosol was also created in testing of atomic bombs. One way that aerosols can affect surface temperature is their backscatter property in which they reflect solar radiation back into space high up in the stratosphere thus shielding to some extent the lower atmosphere from solar radiation. In 1971, Stephen Schneider (with co-author Rasool) published the defining paper for the explanation of the 1940s-1970s cooling in the context of a longer period of global warming driven by rising atmospheric CO2. He argued that the warming effect of carbon dioxide is logarithmic so that the greater the CO2 concentration the less the effect on the rate of warming of increasing CO2 concentration. However, that relationship is exactly in reverse for aerosol backscatter cooling – the greater the aerosol concentration, the greater is the effect of additional aerosol. Based on these rate considerations, he concluded that in the long term, CO2 warming will be saturated and more easily overcome by aerosol backscatter cooling so that in the limit, at high atmospheric CO2 levels, the principal determinant of surface temperature will be aerosols. The aerosol backscatter cooling hypothesis was widely held and a number of papers were published in support of this explanation of the 1940s-1970s cooling. Notable are the McCormick 1967 paper postulating a relationship between atmospheric turbidity and cooling (turbidity to the non-transparency or haziness of the atmosphere usually caused by aerosols).
  9. However, the impact of aerosols on surface temperature is more complex than simple backscatter and its other effects are addressed in many of the papers listed below. Aerosols can warm the atmosphere by absorbing solar radiation and retaining that heat. They can also seed high altitude cloud formation thereby increasing cloud albedo and cause cooling. The general case for cloud albedo as an explanation for the anomalous cooling period is presented by Schneider in his 1972 paper which says in effect that since warming increases cloud formation and therefore cloud albedo, warming can lead to periods of cooling.
  10. A specific instance of the warming effect of aerosols relevant to the period under study is found in the so called “Gottschalk curve” attributed to Bernard Gottschalk, Professor of Physics at Harvard University. He found a brief period of warming in global temperature reconstructions towards the end of World War II. A study of the Gottschalk curve is presented in (Herndon 2018). It is argued (by both Gottsschalk and Herndon) that the Gottschalk curve is result of aerosol warming by the large amount of aerosols generated by war activities including for example the carpet bombing of Dresden and the nuclear bombs in Hiroshima. The Gottschalk curve appears in many of the frames of the HadCRU temperature data displayed in Figure 2 to Figure 5 as a brief triangular warming period just prior to 1959 (the war ended in 1945). The brief red warming peak is seen in some but not all months for land surfaces. (Herndon 218) uses the Gottschalk curve to highlight the warming effect of aerosols and to propose an alternate theory of AGW in terms of aerosol warming.
  11. A special consideration is that of sulfate aerosols as their ultrafine aerosol cooling effect is well known and well documented as seen in (Junge 1961, Wiedensohler 1996) below. In terms of sulfate aerosols, the 1940s-1970s cooling effect can be explained by rapid increase in hydrogen sulfide (H2S) emissions from the combustion of hydrocarbon fuels before H2S emissions were regulated and eventually almost eliminated. The rapid increase in sulfate aerosol emissions is recorded in environmental history as the age of acid rain. By the end of the 1970s, tight regulation of sulfate emissions by acid rain programs worldwide, had significantly reduced sulfate aerosol emissions . The 1940s-1970s cooling can be understood in that context as well as the resurgent global warming since the 1980s. Yet another causal connection between the acid rain program and global warming is proposed by NASA-GISS. This bizarre theory holds that acid rain kills bacteria in wetlands and reduces the biological production of methane which in turn causes global warming  [LINK]
  12. IN SUMMARY: The data provided above show conclusive evidence of an anomalous period of cooling in an overall era of global warming within the context of an industrial economy generating fossil fuel emissions. The cooling anomaly is seen in all four regions of the world defined according to hemisphere and surface (land vs ocean). Significant research references exist that have described the cooling and explained it in terms of aerosol backscatter. The attempt by some climate scientists to minimize the importance of the 1940s-1970s cooling to climate science seems incongruous in the context of the data and research papers presented. The end of the cooling period and the return to warming may be explained by the Schneider hypothesis relating cloud albedo to warming in a negative feedback loop but that necessarily implies that another 1940s-1970s type cooling period is forthcoming particularly in light of increasing atmospheric turbidity from rapid industrialization in China and India.

 

 

 

 

STEPHEN SCHNEIDERschneider

 

AEROSOLS AND CLIMATE: BIBLIOGRAPHY

  1. 1961: Junge, Christian E., and James E. Manson. “Stratospheric aerosol studies.” Journal of Geophysical Research 66.7 (1961): 2163-2182. The stratospheric aerosol layer previously identified by balloon measurements has been studied extensively by means of recovered rod impactor samples obtained during aircraft flights at the 20‐km level from 63°S to 72°N during March–November 1960. From a variety of physical and chemical measurements, which are presented in detail, the conclusion is drawn that this layer is stable, constant in time and space, and composed mainly of sulfate particles. The various questions raised by this result, particularly with respect to collection of micrometeorites, are presented and discussed.</p>
  2. 1967: McCormick, Robert A., and John H. Ludwig. “Climate modification by atmospheric aerosols.” Science 156.3780 (1967): 1358-1359. Theoretical considerations and empirical evidence indicate that atmospheric turbidity, a function of aerosol loading, is an important factor in the heat balance of the earth-atmosphere system. Turbidity increase over the past few decades may be primarily responsible for the decrease in worldwide air temperatures since the 1940’s.
  3. 1971: Rasool, S. Ichtiaque, and Stephen H. Schneider. “Atmospheric carbon dioxide and aerosols: Effects of large increases on global climate.” Science 173.3992 (1971): 138-141. Effects on the global temperature of large increases in carbon dioxide and aerosol densities in the atmosphere of Earth have been computed. It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere. For aerosols, however, the net effect of increase in density is to reduce the surface temperature of Earth. Because of the exponential dependence of the backscattering, the rate of temperature decrease is augmented with increasing aerosol content. An increase by only a factor of 4 in global aerosol background concentration may be sufficient to reduce the surface temperature by as much as 3.5 ° K. If sustained over a period of several years, such a temperature decrease over the whole globe is believed to be sufficient to trigger an ice age.
  4. 1971: Mitchell Jr, J. Murray. “The effect of atmospheric aerosols on climate with special reference to temperature near the earth’s surface.” Journal of Applied Meteorology 10.4 (1971): 703-714. A generalized model of the effect of an optically thin atmospheric aerosol on the terrestrial heat budget is proposed, and applied to the problem of estimating the impact of the aerosol on temperatures near the earth’s surface. The distinction between warming and cooling near the surface attributable to the aerosol is found on the basis of this model to depend on whether the ratio of absorption a to backscatter b of incoming solar radiation by the aerosol is greater or less than the critical ratio            (a/b)O = C(1−A)(1−Ak)/[D(1+A)−C(1−A)], where A is the surface albedo, C the fraction of sensible to total (sensible plus latent) solar heating of the surface, D the fraction of aerosol that is in convective contact with the surface, and k a multiple of b that measures the relative aerosol backscattering efficiency with respect to solar radiation reflected upward from the surface.A distinction is drawn between a stratospheric aerosol (D=0) which generally cools the atmosphere near the surface, and a tropospheric aerosol (D→1) which may either cool or warm the atmosphere near the surface depending on various properties of the aerosol and of the surface itself. Over moist surfaces, such as vegetated areas and oceans, the critical ratio (a/b)o is of order 0.1. Over drier surfaces, such as deserts and urban areas, (a/b)o is of order unity. If the actual ratio a/b of most tropospheric aerosols is of order unity, as inferred by previous authors, then the dominant effect of such aerosols is warming except over deserts and urban arms where the effect is somewhat marginal between warming and cooling.Further aerosol climatic effects are found likely to include a slight decrease of cloudiness and precipitation, and an increase of “planetary” albedo above the oceans, although not necessarily above the continents. Suggestions by several previous authors to the effect that the apparent worldwide cooling of climate in recent decades is attributable to large-scale increases of particulate pollution of the atmosphere by human activities are not supported by this analysis.
  5. 1972: Schneider, Stephen H. “Cloudiness as a global climatic feedback mechanism: The effects on the radiation balance and surface temperature of variations in cloudiness.” Journal of the Atmospheric Sciences 29.8 (1972): 1413-1422. The effect of variation in cloudiness on the climate is considered in terms of 1) a relation between the radiation balance of the earth-atmosphere system and variations in the amount of cloud cover or effective cloud top height, 2) the effect on the surface temperature of variations in cloudiness, and 3) the dynamic coupling or “feedback” effects relating changes in surface temperature to the formation of clouds. The first two points are studied by numerical integration of a simple radiation flux model, and the third point is discussed qualitatively. Global-average radiation balance calculations show that an increase in the amount of low and middle level cloud cover (with cloud top height and cloud albedo fixed) decreases the surface temperature. But, this result for the global-average case does not hold near polar regions, where the albedo of the cloudy areas can he comparable to (or even smaller than) the albedo of the snow-covered cloudless areas, and where, especially in the winter season, the amount of incoming solar radiation at high latitudes is much less than the global-average value of insolation. The exact latitude at which surface cooling changes to surface warming from a given increase in cloud cover amount depends critically upon the local values of the cloud albedo and the albedo of the cloudless areas that are used in the calculation. However, an increase in effective cloud top height (with cloud cover and cloud albedo fixed) increases the surface temperature at all latitudes.
  6. 1974: Chýlek, Petr, and James A. Coakley. “Aerosols and climate.” Science 183.4120 (1974): 75-77. To determine the effects of atmospheric aerosols on the radiative heating of the earth-atmosphere system, the radiative transfer equation is solved analytically in the two-stream approximation. It is found that the sign of the heating is independent of optical thickness of an aerosol layer and the amount of heating approaches a finite limit with increasing thickness of a layer. Limitations of the two-stream approximation are discussed.
  7. 1976: Cess, Robert D. “Climate change: An appraisal of atmospheric feedback mechanisms employing zonal climatology.” Journal of the Atmospheric Sciences 33.10 (1976): 1831-1843. The sensitivity of the earth’s surface temperature to factors which can induce long-term climate change, such as a variation in solar constant, is estimated by employing two readily observable climate changes. One is the latitudinal change in annual mean climate, for which an interpretation of climatological data suggests that cloud amount is not a significant climate feedback mechanism, irrespective of how cloud amount might depend upon surface temperature, since there are compensating changes in both the solar and infrared optical properties of the atmosphere. It is further indicated that all other atmospheric feedback mechanisms, resulting, for example, from temperature-induced changes in water vapor amount, cloud altitude and lapse rate, collectively double the sensitivity of global surface temperature to a change in solar constant. The same conclusion is reached by considering a second type of climate change, that associated with seasonal variations for a given latitude zone. The seasonal interpretation further suggests that cloud amount feedback is unimportant zonally as well as globally. Application of the seasonal data required a correction for what appears to be an important seasonal feedback mechanism. This is attributed to a variability in cloud albedo due to seasonal changes in solar zenith angle. No attempt was made to individually interpret the collective feedback mechanisms which contribute to the doubling in surface temperature sensitivity. It is suggested, however, that the conventional assumption of fixed relative humidity for describing feedback due to water vapor amount might not be as applicable as is generally believed. Climate models which additionally include ice-albedo feedback are discussed within the framework of the present results.
  8. 1983: Coakley Jr, James A., Robert D. Cess, and Franz B. Yurevich. “The effect of tropospheric aerosols on the Earth’s radiation budget: A parameterization for climate models.” Journal of the Atmospheric Sciences 40.1 (1983): 116-138. Guided by the results of doubling-adding solutions to the equation of radiative transfer, we develop a simple technique for incorporating in climate models the effect of the background tropospheric aerosol on solar radiation. Because the atmosphere is practically nonabsorbing for much of the solar spectrum the effects of the tropospheric aerosol on the reflectivity, transmissivity and absorptivity of the atmosphere are adequately accounted for by the properties of a two-layered system with the atmosphere placed above the aerosol layer. The two-stream and delta-Eddington approximations to the radiative transfer equation then provide reasonably accurate estimates of the changes brought about by the aerosol. Furthermore, results of the doubling-adding calculations lead to a simple parameterization for the distribution of absorption by the aerosol within the atmosphere. Using these simple techniques, we calculate the changes caused by models for the naturally occurring tropospheric aerosol in a zonal mean energy balance climate model. The 2–30°C surface cooling caused by the background aerosol is comparable in magnitude but opposite in sign to the temperature changes brought about by the current atmospheric concentrations of N20 and CH4 and by a doubling of CO2. The model results also indicate that even though the background aerosol may decrease the planetary albedo at high latitudes, it causes cooling at all latitudes. We also use the simple techniques to calculate the influence of dust on the planetary albedo of a desert. Here we demonstrate that the interaction of the aerosol scattering with the angular dependence of the surface reflectivity strongly influences the planetary albedo.
  9. 1987: Charlson, Robert J., et al. “Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate.” Nature326.6114 (1987): 655. The major source of cloud-condensation nuclei (CCN) over the oceans appears to be dimethylsulphide, which is produced by planktonic algae in sea water and oxidizes in the atmosphere to form a sulphate aerosol Because the reflectance (albedo) of clouds (and thus the Earth’s radiation budget) is sensitive to CCN density, biological regulation of the climate is possible through the effects of temperature and sunlight on phytoplankton population and dimethylsulphide production. To counteract the warming due to doubling of atmospheric CO2, an approximate doubling of CCN would be needed.
  10. 1989: Blanchet, Jean-Pierre. “Toward estimation of climatic effects due to Arctic aerosols.” Atmospheric Environment (1967)23.11 (1989): 2609-2625. During the last decade, the estimation of the climatic implications of principal anthropogenic aerosols (soot and sulphates) has been investigated by observation and modeling efforts at three scales of dimension:(1) the aerosol scale where the optical properties are determined; (2) the kilometer scale where the radiative fluxes and diabatic heating are felt, and finally, (3) the regional and hemispheric scales where the climate questions pertain. This paper reviews the current results on these three scales, with an emphasis on the comparisons between observations and model results.
  11. 1990: Hansen, James E., and Andrew A. Lacis. “Sun and dust versus greenhouse gases: An assessment of their relative roles in global climate change.” Nature 346.6286 (1990): 713. Many mechanisms, including variations in solar radiation and atmospheric aerosol concentrations, compete with anthropogenic greenhouse gases as causes of global climate change. Comparisons of available data show that solar variability will not counteract greenhouse warming and that future observations will need to be made to quantify the role of tropospheric aerosols, for example.
  12. 1992: Clarke, Antomy D. “Atmospheric nuclei in the remote free-troposphere.” Journal of atmospheric chemistry 14.1-4 (1992): 479-488. During May-June of 1990 an extensive flight series to survey aerosol present in the upper-troposphere was undertaken aboard the NASA DC-8 as part of the CLObal Backscatter Experiment (GLOBE). About 50,000 km were characterized between 8–12 km altitude and between 70°N and 58°S. Aerosol with diameters greater than 3nm were counted and sized with a combination of condensation nuclei counters and optical particle counters. Aerosol number and mass concentrations were separately identified with regard to both refractory and volatile components. Regions of the free-troposphere with the lowest mass concentrations were generally found to have the highest number concentrations and appeared to be effective regions for new particle production. These new particle concentrations appear inversely related to available aerosol surface area and their volatility suggests a sulfuric acid composition. The long lifetime of these new particles aloft can result in their growth to sizes effective as CN and CCN that can be mixed throughout the troposphere.
  13. 1992: Charlson, Robert J., et al. “Climate forcing by anthropogenic aerosols.” Science 255.5043 (1992): 423-430. Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwave solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be –1 to –2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.
  14. 1993: Kiehl, J. T., and B. P. Briegleb. “The relative roles of sulfate aerosols and greenhouse gases in climate forcing.” Science260.5106 (1993): 311-314. Calculations of the effects of both natural and anthropogenic tropospheric sulfate aerosols indicate that the aerosol climate forcing is sufficiently large in a number of regions of the Northern Hemisphere to reduce significantly the positive forcing from increased greenhouse gases. Summer sulfate aerosol forcing in the Northern Hemisphere completely offsets the greenhouse forcing over the eastern United States and central Europe. Anthropogenic sulfate aerosols contribute a globally averaged annual forcing of –0.3 watt per square meter as compared with +2.1 watts per square meter for greenhouse gases. Sources of the difference in magnitude with the previous estimate of Charlson et al. are discussed.
  15. 1994: Schneider, Stephen H. “Detecting climatic change signals: are there any” fingerprints“?.” Science 263.5145 (1994): 341-347. Projected changes in the Earth’s climate can be driven from a combined set of forcing factors consisting of regionally heterogeneous anthropogenic and natural aerosols and land use changes, as well as global-scale influences from solar variability and transient increases in human-produced greenhouse gases. Thus, validation of climate model projections that are driven only by increases in greenhouse gases can be inconsistent when one attempts the validation by looking for a regional or time-evolving “fingerprint” of such projected changes in real climatic data. Until climate models are driven by time-evolving, combined, multiple, and heterogeneous forcing factors, the best global climatic change “fingerprint” will probably remain a many-decades average of hemispheric-scale to global-scale trends in surface air temperatures. Century-long global warming (or cooling) trends of 0.5°C appear to have occurred infrequently over the past several thousand years—perhaps only once or twice a millennium, as proxy records suggest. This implies an 80 to 90 percent heuristic likelihood that the 20th-century 0.5 ± 0.2°C warming trend is not a wholly natural climatic fluctuation.
  16. 1995: Pilinis, Christodoulos, Spyros N. Pandis, and John H. Seinfeld. “Sensitivity of direct climate forcing by atmospheric aerosols to aerosol size and composition.” Journal of Geophysical Research: Atmospheres 100.D9 (1995): 18739-18754. We evaluate, using a box model, the sensitivity of direct climate forcing by atmospheric aerosols for a “global mean” aerosol that consists of fine and coarse modes to aerosol composition, aerosol size distribution, relative humidity (RH), aerosol mixing state (internal versus external mixture), deliquescence/crystallization hysteresis, and solar zenith angle. We also examine the dependence of aerosol upscatter fraction on aerosol size, solar zenith angle, and wavelength and the dependence of single scatter albedo on wavelength and aerosol composition. The single most important parameter in determining direct aerosol forcing is relative humidity, and the most important process is the increase of the aerosol mass as a result of water uptake. An increase of the relative humidity from 40 to 80% is estimated for the global mean aerosol considered to result in an increase of the radiative forcing by a factor of 2.1. Forcing is relatively insensitive to the fine mode diameter increase due to hygroscopic growth, as long as this mode remains inside the efficient scattering size region. The hysteresis/deliquescence region introduces additional uncertainty but, in general, errors less than 20% result by the use of the average of the two curves to predict forcing. For fine aerosol mode mean diameters in the 0.2–0.5 μm range direct aerosol forcing is relatively insensitive (errors less than 20%) to variations of the mean diameter. Estimation of the coarse mode diameter within a factor of 2 is generally sufficient for the estimation of the total aerosol radiative forcing within 20%. Moreover, the coarse mode, which represents the nonanthropogenic fraction of the aerosol, is estimated to contribute less than 10% of the total radiative forcing for all RHs of interest. Aerosol chemical composition is important to direct radiative forcing as it determines (1) water uptake with RH, and (2) optical properties. The effect of absorption by aerosol components on forcing is found to be significant even for single scatter albedo values of ω=0.93–0.97. The absorbing aerosol component reduces the aerosol forcing from that in its absence by roughly 30% at 60% RH and 20% at 90% RH. The mixing state of the aerosol (internal versus external) for the particular aerosol considered here is found to be of secondary importance. While sulfate mass scattering efficiency (m2 (g SO42−)−1) and the normalized sulfate forcing (W (g SO42−)−1) increase strongly with RH, total mass scattering efficiency (m2 g−1) and normalized forcing (W g−1) are relatively insensitive to RH, wherein the mass of all species, including water, are accounted for. Following S. Nemesure et al. (Direct shortwave forcing of climate by anthropogenic sulfate aerosol: sensitivity to particle size, composition, and relative humidity, submitted to Journal of Geophysical Research, 1995), we find that aerosol feeing achieves a maximum at a particular solar zenith angle, reflecting a balance between increasing upscatter fraction with increasing solar zenith angle and decreasing solar flux (from Rayleigh scattering) with increasing solar zenith angle.
  17. 1996: Wiedensohler, Alfred, et al. “Occurrence of an ultrafine particle mode less than 20 nm in diameter in the marine boundary layer during Arctic summer and autumn.” Tellus B 48.2 (1996): 213-222. The International Arctic Ocean Expedition 1991 (IAOE‐91) provided a platform to study the occurrence and size distributions of ultrafine particles in the marine boundary layer (MBL) during Arctic summer and autumn. Measurements of both aerosol physics, and gas/particulate chemistry were taken aboard the Swedish icebreaker Oden. Three separate submicron aerosol modes were found: an ultrafine mode (Dp < 20 nm), the Aitken mode (20 < Dp < 100 nm), and the accumulation mode (Dp > 100 nm). We evaluated correlations between ultrafine particle number concentrations and mean diameter with the entire measured physical, chemical, and meteorological data set. Multivariate statistical methods were then used to make these comparisons. A principal component (PC) analysis indicated that the observed variation in the data could be explained by the influence from several types of air masses. These were characterised by contributions from the open sea or sources from the surrounding continents and islands. A partial least square (PLS) regression of the ultrafine particle concentration was also used. These results implied that the ultrafine particles were produced above or in upper layers of the MBL and mixed downwards. There were also indications that the open sea acted as a source of the precursors for ultrafine particle production. No anti‐correlation was found between the ultrafine and accumulation particle number concentrations, thus indicating that the sources were in separate air masses.
  18. 1995: Andreae, Meinrat O. “Climatic effects of changing atmospheric aerosol levels.” World survey of climatology 16 (1995): 347-398. bandicam 2018-10-18 10-15-51-596
  19. 1997: Raes, Frank, et al. “Observations of aerosols in the free troposphere and marine boundary layer of the subtropical Northeast Atlantic: Discussion of processes determining their size distribution.” Journal of Geophysical Research: Atmospheres 102.D17 (1997): 21315-21328. During July 1994, submicron aerosol size distributions were measured at two sites on Tenerife, Canary Islands. One station was located in the free troposphere (FT), the other in the marine boundary layer (MBL). Transport toward these two sites was strongly decoupled: the FT was first affected by dust and sulfate‐laden air masses advecting from North Africa and later by clean air masses originating over the North Atlantic, whereas the MBL was always subject to the northeasterly trade wind circulation. In the FT the submicron aerosol distribution was predominantly monomodal with a geometric mean diameter of 120 nm and 55 nm during dusty and clean conditions, respectively. The relatively small diameter during the clean conditions indicates that the aerosol originated in the upper troposphere rather than over continental areas or in the lower stratosphere. During dusty conditions the physical and chemical properties of the submicron aerosol suggest that it has an anthropogenic origin over southern Europe and that it remains largely externally mixed with the supermicron mineral dust particles during its transport over North Africa to Tenerife. Apart from synoptic variations, a strong diurnal variation in the aerosol size distribution is observed at the FT site, characterized by a strong daytime mode of ultrafine particles. This is interpreted as being the result of photoinduced nucleation in the upslope winds, which are perturbed by anthropogenic and biogenic emissions on the island. No evidence was found for nucleation occurring in the undisturbed FT. The MBL site was not strongly affected by European pollution during the period of the measurements. The MBL aerosol size distribution was bimodal, but the relative concentration of Aitken and accumulation mode varied strongly. The accumulation mode can be related to cloud processing of the Aitken mode but also to pollution aerosol which was advected within the MBL or entrained from the FT. No bursts of nucleation were observed within the MBL.
  20. 1997: Andreae, Meinrat O., and Paul J. Crutzen. “Atmospheric aerosols: Biogeochemical sources and role in atmospheric chemistry.” Science 276.5315 (1997): 1052-1058. Atmospheric aerosols play important roles in climate and atmospheric chemistry: They scatter sunlight, provide condensation nuclei for cloud droplets, and participate in heterogeneous chemical reactions. Two important aerosol species, sulfate and organic particles, have large natural biogenic sources that depend in a highly complex fashion on environmental and ecological parameters and therefore are prone to influence by global change. Reactions in and on sea-salt aerosol particles may have a strong influence on oxidation processes in the marine boundary layer through the production of halogen radicals, and reactions on mineral aerosols may significantly affect the cycles of nitrogen, sulfur, and atmospheric oxidants.
  21. 1997: Hansen, J., Mki Sato, and R. Ruedy. “Radiative forcing and climate response.” Journal of Geophysical Research: Atmospheres 102.D6 (1997): 6831-6864. We examine the sensitivity of a climate model to a wide range of radiative forcings, including changes of solar irradiance, atmospheric CO2, O3, CFCs, clouds, aerosols, surface albedo, and a “ghost” forcing introduced at arbitrary heights, latitudes, longitudes, seasons, and times of day. We show that, in general, the climate response, specifically the global mean temperature change, is sensitive to the altitude, latitude, and nature of the forcing; that is, the response to a given forcing can vary by 50% or more depending upon characteristics of the forcing other than its magnitude measured in watts per square meter. The consistency of the response among different forcings is higher, within 20% or better, for most of the globally distributed forcings suspected of influencing global mean temperature in the past century, but exceptions occur for certain changes of ozone or absorbing aerosols, for which the climate response is less well behaved. In all cases the physical basis for the variations of the response can be understood. The principal mechanisms involve alterations of lapse rate and decrease (increase) of large‐scale cloud cover in layers that are preferentially heated (cooled). Although the magnitude of these effects must be model‐dependent, the existence and sense of the mechanisms appear to be reasonable. Overall, we reaffirm the value of the radiative forcing concept for predicting climate response and for comparative studies of different forcings; indeed, the present results can help improve the accuracy of such analyses and define error estimates. Our results also emphasize the need for measurements having the specificity and precision needed to define poorly known forcings such as absorbing aerosols and ozone change. Available data on aerosol single scatter albedo imply that anthropogenic aerosols cause less cooling than has commonly been assumed. However, negative forcing due to the net ozone change since 1979 appears to have counterbalanced 30–50% of the positive forcing due to the increase of well‐mixed greenhouse gases in the same period. As the net ozone change includes halogen‐driven ozone depletion with negative radiative forcing and a tropospheric ozone increase with positive radiative forcing, it is possible that the halogen‐driven ozone depletion has counterbalanced more than half of the radiative forcing due to well‐mixed greenhouse gases since 1979.
  22. 2000: Robock, Alan. “Volcanic eruptions and climate.” Reviews of Geophysics 38.2 (2000): 191-219. Volcanic eruptions are an important natural cause of climate change on many timescales. A new capability to predict the climatic response to a large tropical eruption for the succeeding 2 years will prove valuable to society. In addition, to detect and attribute anthropogenic influences on climate, including effects of greenhouse gases, aerosols, and ozone‐depleting chemicals, it is crucial to quantify the natural fluctuations so as to separate them from anthropogenic fluctuations in the climate record. Studying the responses of climate to volcanic eruptions also helps us to better understand important radiative and dynamical processes that respond in the climate system to both natural and anthropogenic forcings. Furthermore, modeling the effects of volcanic eruptions helps us to improve climate models that are needed to study anthropogenic effects. Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e‐folding residence time of about 1 year. Large ash particles fall out much quicker. The radiative and chemical effects of this aerosol cloud produce responses in the climate system. By scattering some solar radiation back to space, the aerosols cool the surface, but by absorbing both solar and terrestrial radiation, the aerosol layer heats the stratosphere. For a tropical eruption this heating is larger in the tropics than in the high latitudes, producing an enhanced pole‐to‐equator temperature gradient, especially in winter. In the Northern Hemisphere winter this enhanced gradient produces a stronger polar vortex, and this stronger jet stream produces a characteristic stationary wave pattern of tropospheric circulation, resulting in winter warming of Northern Hemisphere continents. This indirect advective effect on temperature is stronger than the radiative cooling effect that dominates at lower latitudes and in the summer. The volcanic aerosols also serve as surfaces for heterogeneous chemical reactions that destroy stratospheric ozone, which lowers ultraviolet absorption and reduces the radiative heating in the lower stratosphere, but the net effect is still heating. Because this chemical effect depends on the presence of anthropogenic chlorine, it has only become important in recent decades. For a few days after an eruption the amplitude of the diurnal cycle of surface air temperature is reduced under the cloud. On a much longer timescale, volcanic effects played a large role in interdecadal climate change of the Little Ice Age. There is no perfect index of past volcanism, but more ice cores from Greenland and Antarctica will improve the record. There is no evidence that volcanic eruptions produce El Niño events, but the climatic effects of El Niño and volcanic eruptions must be separated to understand the climatic response to each.
  23. 2001: Jacobson, Mark Z. “Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols.” Nature409.6821 (2001): 695. Aerosols affect the Earth’s temperature and climate by altering the radiative properties of the atmosphere. A large positive component of this radiative forcing from aerosols is due to black carbon—soot—that is released from the burning of fossil fuel and biomass, and, to a lesser extent, natural fires, but the exact forcing is affected by how black carbon is mixed with other aerosol constituents. From studies of aerosol radiative forcing, it is known that black carbon can exist in one of several possible mixing states; distinct from other aerosol particles (externally mixed1,2,3,4,5,6,7) or incorporated within them (internally mixed1,3,7), or a black-carbon core could be surrounded by a well mixed shell7. But so far it has been assumed that aerosols exist predominantly as an external mixture. Here I simulate the evolution of the chemical composition of aerosols, finding that the mixing state and direct forcing of the black-carbon component approach those of an internal mixture, largely due to coagulation and growth of aerosol particles. This finding implies a higher positive forcing from black carbon than previously thought, suggesting that the warming effect from black carbon may nearly balance the net cooling effect of other anthropogenic aerosol constituents. The magnitude of the direct radiative forcing from black carbon itself exceeds that due to CH4, suggesting that black carbon may be the second most important component of global warming after CO2in terms of direct forcing.
  24. 2002: Kaufman, Yoram J., Didier Tanré, and Olivier Boucher. “A satellite view of aerosols in the climate system.” Nature419.6903 (2002): 215. Anthropogenic aerosols are intricately linked to the climate system and to the hydrologic cycle. The net effect of aerosols is to cool the climate system by reflecting sunlight. Depending on their composition, aerosols can also absorb sunlight in the atmosphere, further cooling the surface but warming the atmosphere in the process. These effects of aerosols on the temperature profile, along with the role of aerosols as cloud condensation nuclei, impact the hydrologic cycle, through changes in cloud cover, cloud properties and precipitation. Unravelling these feedbacks is particularly difficult because aerosols take a multitude of shapes and forms, ranging from desert dust to urban pollution, and because aerosol concentrations vary strongly over time and space. To accurately study aerosol distribution and composition therefore requires continuous observations from satellites, networks of ground-based instruments and dedicated field experiments. Increases in aerosol concentration and changes in their composition, driven by industrializationand an expanding population, may adversely affect the Earth’s climate and water supply.
  25. 2002: Menon, Surabi, et al. “Climate effects of black carbon aerosols in China and India.” Science 297.5590 (2002): 2250-2253. In recent decades, there has been a tendency toward increased summer floods in south China, increased drought in north China, and moderate cooling in China and India while most of the world has been warming. We used a global climate model to investigate possible aerosol contributions to these trends. We found precipitation and temperature changes in the model that were comparable to those observed if the aerosols included a large proportion of absorbing black carbon (“soot”), similar to observed amounts. Absorbing aerosols heat the air, alter regional atmospheric stability and vertical motions, and affect the large-scale circulation and hydrologic cycle with significant regional climate effects.
  26. 2005: Andreae, Meinrat O., Chris D. Jones, and Peter M. Cox. “Strong present-day aerosol cooling implies a hot future.” Nature 435.7046 (2005): 1187. Atmospheric aerosols counteract the warming effects of anthropogenic greenhouse gases by an uncertain, but potentially large, amount. This in turn leads to large uncertainties in the sensitivity of climate to human perturbations, and therefore also in carbon cycle feedbacks and projections of climate change. In the future, aerosol cooling is expected to decline relative to greenhouse gas forcing, because of the aerosols’ much shorter lifetime and the pursuit of a cleaner atmosphere. Strong aerosol cooling in the past and present would then imply that future global warming may proceed at or even above the upper extreme of the range projected by the Intergovernmental Panel on Climate Change.
  27. 2005: Pöschl, Ulrich. “Atmospheric aerosols: composition, transformation, climate and health effects.” Angewandte Chemie International Edition 44.46 (2005): 7520-7540. Aerosols are of central importance for atmospheric chemistry and physics, the biosphere, climate, and public health. The airborne solid and liquid particles in the nanometer to micrometer size range influence the energy balance of the Earth, the hydrological cycle, atmospheric circulation, and the abundance of greenhouse and reactive trace gases. Moreover, they play important roles in the reproduction of biological organisms and can cause or enhance diseases. The primary parameters that determine the environmental and health effects of aerosol particles are their concentration, size, structure, and chemical composition. These parameters, however, are spatially and temporally highly variable. The quantification and identification of biological particles and carbonaceous components of fine particulate matter in the air (organic compounds and black or elemental carbon, respectively) represent demanding analytical challenges. This Review outlines the current state of knowledge, major open questions, and research perspectives on the properties and interactions of atmospheric aerosols and their effects on climate and human health.
  28. 2005: Jickells, T. D., et al. “Global iron connections between desert dust, ocean biogeochemistry, and climate.” science 308.5718 (2005): 67-71. The environmental conditions of Earth, including the climate, are determined by physical, chemical, biological, and human interactions that transform and transport materials and energy. This is the “Earth system”: a highly complex entity characterized by multiple nonlinear responses and thresholds, with linkages between disparate components. One important part of this system is the iron cycle, in which iron-containing soil dust is transported from land through the atmosphere to the oceans, affecting ocean biogeochemistry and hence having feedback effects on climate and dust production. Here we review the key components of this cycle, identifying critical uncertainties and priorities for future research.
  29. 2005: Lohmann, Ulrike, and Johann Feichter. “Global indirect aerosol effects: a review.” Atmospheric Chemistry and Physics5.3 (2005): 715-737.  Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei, they may inhibit freezing and they could have an influence on the hydrological cycle. While the cloud albedo enhancement (Twomey effect) of warm clouds received most attention so far and traditionally is the only indirect aerosol forcing considered in transient climate simulations, here we discuss the multitude of effects. Different approaches how the climatic implications of these aerosol effects can be estimated globally as well as improvements that are needed in global climate models in order to better represent indirect aerosol effects are discussed in this paper.
  30. 2009: Ramanathan, Veerabhadran, and Yan Feng. “Air pollution, greenhouse gases and climate change: Global and regional perspectives.” Atmospheric environment 43.1 (2009): 37-50. Greenhouse gases (GHGs) warm the surface and the atmosphere with significant implications for rainfall, retreat of glaciers and sea ice, sea level, among other factors. About 30 years ago, it was recognized that the increase in tropospheric ozone from air pollution (NOx, CO and others) is an important greenhouse forcing term. In addition, the recognition of chlorofluorocarbons (CFCs) on stratospheric ozone and its climate effects linked chemistry and climate strongly. What is less recognized, however, is a comparably major global problem dealing with air pollution. Until about ten years ago, air pollution was thought to be just an urban or a local problem. But new data have revealed that air pollution is transported across continents and ocean basins due to fast long-range transport, resulting in trans-oceanic and trans-continental plumes of atmospheric brown clouds (ABCs) containing sub micron size particles, i.e., aerosols. ABCs intercept sunlight by absorbing as well as reflecting it, both of which lead to a large surface dimming. The dimming effect is enhanced further because aerosols may nucleate more cloud droplets, which makes the clouds reflect more solar radiation. The dimming has a surface cooling effect and decreases evaporation of moisture from the surface, thus slows down the hydrological cycle. On the other hand, absorption of solar radiation by black carbon and some organics increase atmospheric heating and tend to amplify greenhouse warming of the atmosphere. ABCs are concentrated in regional and mega-city hot spots. Long-range transport from these hot spots causes widespread plumes over the adjacent oceans. Such a pattern of regionally concentrated surface dimming and atmospheric solar heating, accompanied by widespread dimming over the oceans, gives rise to large regional effects. Only during the last decade, we have begun to comprehend the surprisingly large regional impacts. In S. Asia and N. Africa, the large north-south gradient in the ABC dimming has altered both the north-south gradients in sea surface temperatures and land–ocean contrast in surface temperatures, which in turn slow down the monsoon circulation and decrease rainfall over the continents. On the other hand, heating by black carbon warms the atmosphere at elevated levels from 2 to 6 km, where most tropical glaciers are located, thus strengthening the effect of GHGs on retreat of snow packs and glaciers in the Hindu Kush-Himalaya-Tibetan glaciers. Globally, the surface cooling effect of ABCs may have masked as much 47% of the global warming by greenhouse gases, with an uncertainty range of 20–80%. This presents a dilemma since efforts to curb air pollution may unmask the ABC cooling effect and enhance the surface warming. Thus efforts to reduce GHGs and air pollution should be done under one common framework. The uncertainties in our understanding of the ABC effects are large, but we are discovering new ways in which human activities are changing the climate and the environment.
  31. 2009: Jimenez, Jose L., et al. “Evolution of organic aerosols in the atmosphere.” science 326.5959 (2009): 1525-1529. Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high–time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.
  32. 2017: Stanley, S. (2017), Satellite data reveal effects of aerosols in Earth’s atmosphere, Eos, 98,https://doi.org/10.1029/2017EO069945. Published on 24 March 2017.  Earth’s atmosphere is dusted with tiny particles known as aerosols, which include windblown ash, sea salt, pollution, and other natural and human-produced materials. Aerosols can absorb or scatter sunlight, affecting how much light reflects back into space or stays trapped in the atmosphere. Despite aerosols’ known impact on Earth’s temperature, major uncertainties plague current estimates of their overall effects, which in turn limit the certainty of climate change models. In an effort to reduce this uncertainty, Lacagnina et al. have combined new satellite data, providing, for the first time, data on aerosols’ ability to absorb or reflect light globally, through model simulations In this new study, the team focused on the direct effects of aerosols on shortwave radiation in 2006. These effects depended on the particles’ vertical location with respect to clouds, the reflective properties of the underlying land or water, and the optical properties of the aerosol particles themselves, including how much light they are prone to scatter or absorb.The researchers used instruments aboard the French Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar (PARASOL) satellite and NASA’s Aura spacecraft to measure aerosol optical properties around the world. Data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument provided measurements of cloud characteristics and land reflectance, and an aerosol climate model known as ECHAM5-HAM2 helped fill in any gaps in the observations. Using these data, calculations of the global average radiative effect for 2006 revealed an overall cooling effect due to aerosols. At regional scales, however, different mixtures of aerosols led to widely varying effects. For example, the cooling effects of aerosols were larger in the Northern Hemisphere because of higher pollution emissions and infiltration by desert dust. Overall, the heat transfer measurements in this study were consistent with past measurements using other methods. The authors call for additional studies that also integrate data from multiple sources and for improved global measurements of aerosol absorption to better understand and predict the future effects of aerosols on climate change.
  33. 2017: Lacagnina, Carlo, Otto P. Hasekamp, and Omar Torres. “Direct radiative effect of aerosols based on PARASOL and OMI satellite observations.” Journal of Geophysical Research: Atmospheres 122.4 (2017): 2366-2388. Accurate portrayal of the aerosol characteristics is crucial to determine aerosol contribution to the Earth’s radiation budget. We employ novel satellite retrievals to make a new measurement‐based estimate of the shortwave direct radiative effect of aerosols (DREA), both over land and ocean. Global satellite measurements of aerosol optical depth, single‐scattering albedo (SSA), and phase function from PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) are used in synergy with OMI (Ozone Monitoring Instrument) SSA. Aerosol information is combined with land‐surface bidirectional reflectance distribution function and cloud characteristics from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite products. Eventual gaps in observations are filled with the state‐of‐the‐art global aerosol model ECHAM5‐HAM2. It is found that our estimate of DREA is largely insensitive to model choice. Radiative transfer calculations show that DREA at top‐of‐atmosphere is −4.6 ± 1.5 W/m2 for cloud‐free and −2.1 ± 0.7 W/m2 for all‐sky conditions, during year 2006. These fluxes are consistent with, albeit generally less negative over ocean than, former assessments. Unlike previous studies, our estimate is constrained by retrievals of global coverage SSA, which may justify different DREA values. Remarkable consistency is found in comparison with DREA based on CERES (Clouds and the Earth’s Radiant Energy System) and MODIS observations.
  34. 2018: Ralph Kahn, NASAAerosol Remote Sensing and Modeling, 2018. [FULL TEXT] The global scope of aerosol environmental influences makes satellite remote sensing a key tool for the study of these particles. Desert dust storms, wildfire smoke and volcanic ash plumes, and urban pollution palls on hot, cloud-free summer days are among the most dramatic manifestations of aerosol particles visible in satellite imagery [LINK] .  Our group includes the core aerosol science team for the NASA Earth Observing System’s MODerate resolution Imaging Spectroradiometer (MODIS)instruments, and the aerosol scientist for the Multi-angle Imaging SpectroRadiometer (MISR).The MODIS Dark Target, Deep Blue, and MAIAC aerosol algorithms are developed and maintained here, along with the MISR Research Aerosol Retrieval algorithm. We also contribute to the Total Ozone Mapping Spectrometer (TOMS) the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Suomi National Polar-orbiting Partnership’s Visible Infrared Imaging Radiometer Suite (SNPP-VIIRS) aerosol retrieval algorithms. We perform validation studies on all these satellite aerosol products using ground-based remote-sensing aerosol measurements, such as those provided by the global Aerosol Robotic Network (AERONET) of Sun- and sky-scanning photometers and the Micro-Pulse Lidar Network (MPLNet). And through the Goddard Interactive Online Visualization ANd aNalysis Infrastructure (GIOVANNI), we have participated in the development of web-based tools to collocate multiple satellite and AERONET products and to analyze them statistically. In addition, we have developed and maintain a state-of-the-art, ground-based mobile facility for measuring the physical and chemical properties of aerosol and clouds, along with the ambient radiation fields (SMART-COMMIT-ACHIEVE), and the Cloud Absorption Radiometer (CAR) deployed in an aircraft nosecone, that can obtain radiance measurements over the entire sphere in 14 spectral bands. The aerosol applications which we lead, and to which we contribute, range from the fundamental radiative transfer used in satellite aerosol retrieval algorithms, to detailed studies of wildfire smoke and volcanic ash plumes, aerosol pollution events and long-term exposure, as well as large-scale aerosol transports, global energy balance assessments, and climate change studies.
  35. 2018: Herndon, J. Marvin. “Air Pollution, Not Greenhouse Gases: The Principal Cause of Global Warming.” 2018: Time series of global surface temperature presentations often exhibit a bump coincident with World War II (WW2) as did one such image on the front page of the January 19, 2017 New York Times. Intrigued by the front-page New York Times graph, Bernie Gottschalk of Harvard University applied sophisticated curve-fitting techniques and demonstrated that the bump, which shows a global burst in Earth temperature during WW2, is a robust feature showing up in eight independent NOAA databases, four land and four oceans. The broader activities of WW2, especially those capable of altering Earth’s delicate energy balance by particulate aerosols can be generalized to post-WW2 global warming. Increases in aerosolized particulates over time is principally responsible for the concomitant global warming increases. Proxies for global particulate pollution – increasing global coal and crude oil production, as well as aviation fuel consumption – rise in strikingly parallel fashion to the rise in global temperature as shown in the accompanying figure. The World War II wartime particulate-pollution had the same global-warming consequence as the subsequent ever-increasing global aerosol particulate-pollution from (1) increases in aircraft and vehicular traffic, and the industrialization of China and India with their smoke stacks spewing out smoke and coal fly ash, as well as from recently documented studies that show (2) coal fly ash [is being] covertly jet-sprayed into the region where clouds form on a near-daily, near-global basis. It is further noted that the integrity of [IPCC] models and assessments is compromised, because of their failure to take into account the aerosolized pollution particulates that have been intentionally and covertly sprayed into the atmosphere for decades in the region where clouds form. Instead of cooling Earth, as many scientists still believed it would, covert military geoengineering activity increases global warming.
    [FULL TEXT]

 

 

 

ATMOSPHERIC TURBIDITY BIBLIOGRAPHY

  1. 1964: Ångström, Anders. “The parameters of atmospheric turbidity.” Tellus 16.1 (1964): 64-75. The methods for evaluating the atmospheric turbidity parameters, introduced by the present author in 1929–30, are subjected to a critical examination. A method first suggested by M. Herovanu (1959) is here simplified and expanded, and used for deriving the named parameters in adherence to a procedure described by the present author in a previous paper in this journal (1961). The procedure is applied to the pyrheliometric observations at Potsdam in 1932–36, published by Hoelper (1939) A comparison between the frequency distribution of the coefficient of wave‐length dependence α at the high level station Davos and the low level station Potsdam gives results which are discussed in detail. In all the figures of the present paper, where the turbidity coefficients occur, they are multiplied by 103.
  2. 1967: McCormick, Robert A., and John H. Ludwig. “Climate modification by atmospheric aerosols.” Science 156.3780 (1967): 1358-1359. Theoretical considerations and empirical evidence indicate that atmospheric turbidity, a function of aerosol loading, is an important factor in the heat balance of the earth-atmosphere system. Turbidity increase over the past few decades may be primarily responsible for the decrease in worldwide air temperatures since the 1940′s.
  3. 1969: Flowers, E. C., R. A. McCormick, and K. R. Kurfis. “Atmospheric turbidity over the United States, 1961–1966.” Journal of Applied Meteorology 8.6 (1969): 955-962. Five years of turbidity measurements from a network of stations in the United States are analyzed. Measurements are made with the Volz sunphotometer; the instrument, its calibration, and its use are described. The relationship of these measurements to those of Linke and Ångström is briefly discussed. Analysis of the data indicates the following: 1) an annual mean pattern of low turbidity (near 0.05) over the western plains and Rocky Mountains and high turbidity (near 0.14) in the east; 2) observed minimum turbidity near 0.02; 3) an annual cycle of low turbidity in winter and high in summer; 4) lowest turbidity in continental polar air masses and highest in maritime tropical; and 5) no noticeable lowering of turbidity following precipitation.
  4. 1972: Lovelock, James E. “Atmospheric turbidity and CCl3F concentrations in rural southern England and southern Ireland.” Atmospheric Environment (1967) 6.12 (1972): 917-925. The seasonal changes in atmospheric turbidity in rural Southern England and Southern Ireland have been observed and are compared with wind direction and with the concentration of CCl3F a material whose origins are unequivocally anthropogenic. The observations suggest that the dense summertime aerosol is probably an end product of the atmospheric photochemistry of air pollutants and that Continental Europe is the principal source.
  5. 1979: Carlson, Toby N. “Atmospheric turbidity in Saharan dust outbreaks as determined by analyses of satellite brightness data.” Monthly Weather Review 107.3 (1979): 322-335. Using VHRR brightness data obtained from the NOAA 3 satellite, isopleths of aerosol Optical depth for Saharan dust have been drawn for seven days during summer 1974 over a portion of the eastern equatorial North Atlantic. The large-scale patterns reveal an elongated dust plume which emerges from a narrow region along the African coast. Thereafter, the plume moves westward and spreads laterally though maintaining rather discrete boundaries associated with sharp gradients of turbidity, especially along the southern border. Exceptionally large values of optical depth (>2.0) are found near the centers of some dust outbreaks but these high values contribute Little to the total dust loading, which, in typical episodes, are estimated to represent a loss of topsoil from Africa of ∼8 million metric tons of material in a period of 4–5 days. There appeared to be no direct intrusion of the dust plume into the ITCZ or north of 25°N in that region. Outbreaks of dust appear often to be in the rear of a well-developed easterly wave disturbance and inverted V-shaped cloud pattern. This paper demonstrates the feasibility of using satellite brightness data to quantitatively map dust outbreaks.
  6. 1981: Peterson, James T., et al. “Atmospheric turbidity over central North Carolina.” Journal of Applied Meteorology 20.3 (1981): 229-241. Some 8500 observations of atmospheric turbidity, taken at Raleigh, North Carolina from July 1969 to July 1975 are analyzed for within-day and day-to-day variations and their dependence on meteorological parameters. The annual average turbidity of 0.147 (0.336 aerosol optical thickness) is near the highest non-urban turbidity in the United States. A distinct diurnal turbidity cycle was evident with a maximum in early afternoon. Annually, highest turbidity and day-to-day variation occurred during summer with lowest values and variation during winter. Daily averages revealed an asymmetric annual cycle, with a minimum on 1 January and a maximum on 1 August. Turbidity showed a slight inverse dependence on surface wind speed. Aside from winter, highest turbidities occurred with southeast surface winds. Turbidity was directly proportional to both humidity and dew point. Correlations between turbidity and local visibility were best for visibilities <7 mi. Air mass trajectories arriving at Raleigh were used to study the dependence of turbidity on synoptic air mass. Air masses with a southern origin had greatest turbidities. Turbidity of an air mass significantly increased as the residence time of that air mass over the continental United States increased, with the most rapid changes during summer. A combination of Raleigh (1969–present) and Greensboro, North Carolina (1965–76) records showed a distinct summer increase through 1976, but no change during winter. A linear regression of annual averages for the complete record gave an 18% per decade turbidity increase.
  7. 1982: Shaw, Glenn E. “Atmospheric turbidity in the polar regions.” Journal of Applied meteorology 21.8 (1982): 1080-1088. Analysis is presented of 800 measurements of atmospheric monochromatic aerosol optical depth made poleward of ∼65° latitude. The atmosphere of the southern polar region appears to be uncontaminated but is charged with a background aerosol having a mean size of 0.1 μm radius, an almost constant mixing ratio throughout the troposphere, a sea level optical depth (λ = 500 nm) of ∼0.025 and an inferred columnar mass loading of 4-15 × 10−7 g cm−2.At around the time of spring equinox the northern polar region (all longitudes) is invaded with Arctic Haze, an aerosol showing a strong anthropogenic chemical fingerprint. The optical depth anomaly introduced by this man-caused haze is τ0 ≈ 0.110 and the associated columnar mass loading is ∼1.5 × 10−6 g cm−2. Turbidity measured seven decades ago at the solar observatory at Uppsala (60°N), suggests that Arctic optical depth has been rising at a rate of dτ/dt ≈ 0.01 ± 0.005 per decade.
  8. 1994: Jacovides, C. P., et al. “Atmospheric turbidity parameters in the highly polluted site of Athens basin.” Renewable Energy4.5 (1994): 465-470. Data on atmospheric turbidity coefficients, i.e. Linke factor TL and Angstrom coefficient β, calculated from measurements of broad-band filter at Athens Observatory (NOA), are reported. A linear model fitted to β vs TL for Athens is similar to the models reported for Avignon (France) and Dhahran (Saudi Arabia). The variation in the monthly average values of β and TL is of similar trend to that of Avignon and Dhahran. However, Athens has shown higher values of atmospheric turbidity coefficients than Avignon and similar turbidity levels to Dhahran. Finally, the long-term variation of the monthly mean values of the mid-day turbidity parameters and the broad-band direct and diffuse irradiances under cloudless skies are evaluated for the same period. The turbidity trends in conjunction with the trends of solar radiation components reflect the rapid urbanization and industrialization of the Athens basin.
  9. 1994: Gueymard, Christian. “Analysis of monthly average atmospheric precipitable water and turbidity in Canada and northern United States.” Solar Energy 53.1 (1994): 57-71. Atmospheric turbidity and precipitable water data are necessary as inputs to solar radiation or daylight availability models, and to daylighting simulation programs. A new model is presented to obtain precipitable water from long-term averages of temperature and humidity. Precipitable water data derived from this model are tabulated for some Canadian and northern U.S. sites. A discussion on the available turbidity data is presented. An analysis of the datasets from the WMO turbidity network is detailed. The effect of volcanic eruptions is discussed, as well as the possible comparisons with indirect determinations of turbidity from radiation data. A tabulation of the monthly average turbidity coefficients for ten Canadian stations and seven northern U.S. stations of the WMO network is presented.

 

 

 

 

OTHER THEORIES OF COOLING DURING AGW: BIBLIOGRAPHY

  1. 1961: Budyko, Mikhail Ivanovich. “The heat balance of the earth’s surface.” Soviet Geography 2.4 (1961): 3-13. The article discusses the present state of knowledge of the basic components of the heat balance of the earth’s surface (radiation balance, loss of heat to evaporation, turbulent heat exchange) and the distribution of these components in time and space. Soviet research is concerned with applying heat-balance data to the study of physical-geographical processes (hydrologic regime, plant and soil cover), to the study of integrated geographic problems (geographic zonality) and practical problems (weather and hydrologic forecasting, the use of solar energy for productive purposes, and the use of heat-balance data for planning reclamation projects and other nature-transforming measures
  2. 1969: Budyko, Mikhail I. “The effect of solar radiation variations on the climate of the earth.” tellus 21.5 (1969): 611-619. It follows from the analysis of observation data that the secular variation of the mean temperature of the Earth can be explained by the variation of short-wave radiation, arriving at the surface of the Earth. In connection with this, the influence of long-term changes of radiation, caused by variations of atmospheric transparency on the thermal regime is being studied. Taking into account the influence of changes of planetary albedo of the Earth under the development of glaciations on the thermal regime, it is found that comparatively small variations of atmospheric transparency could be sufficient for the development of quaternary glaciations.  [FULL TEXT]
  3. 1978: Angell, J. K., and J. Korshover. “Global temperature variation, surface-100 mb: An update into 1977.” Monthly Weather Review 106.6 (1978): 755-770. Based on a network of 63 well-spaced radiosonde stations around the world, the global temperature within the surface to 100 mb layer was lower in 1976 than in any year since commencement of the record in 1958, and the 1976 surface temperature equated the global record for the lowest temperature set in 1964; but even so the trend in global temperature since 1965 has been small compared to the 0.5°C decrease during 1960–65. Between 1958 and 1976 the surface to 100 mb temperature in north extratropics decreased by about 1°C, with the decrease twice as great in winter as in summer, and in 1976 this region was 0.2°C lower than in any previous year of record. During the northern winter of 1976–77, both temperate zones were very cold but the polar and tropical zones were quite warm, so that in the hemispheric or global average the season was not anomalous. In the Eastern Hemisphere of the northern extratropics there has been considerable surface warming during the past decade (although a cooling aloft), and this may explain the Soviet concern with warming related to carbon dioxide emissions. There has been a slight overall increase in temperature in the tropics since 1965, mostly in the Western Hemisphere, on which have been superimposed large and significant temperature variations of about a three-year period. These variations, probably related to the Southern Oscillation (and recently not so pronounced), extend in obvious fashion also into north extratropics, and should be taken into account for diagnoses and prognoses in northern latitudes. The rate of increase of carbon dioxide at Mauna Loa and the South Pole is augmented in the warm phase of the tropical oscillation, presumably because of a relation between atmospheric and oceanic temperature. There is evidence for a consistent quasi-biennial variation in temperature at all latitudes, with the temperature approximately 0.1°C higher than average about six months prior to the quasi-biennial west wind maximum at 50 mb in the tropics. The spatial and temporal variability in temperature have tended to increase over the period of record, in accord with the increase in meridional temperature gradient in both hemispheres and the indicated increase in lapse rate in the Northern Hemisphere.  [FULL TEXT]
  4. 1981: Asakura, T., and S. Ikeda. “Recent climatic change and unusual weather in the northern hemisphere.” GeoJournal 5.2 (1981): 113-116. Occurrence frequency of unusual weather caused by anomalous synoptic patterns has its peaks in the middle latitude regions and the subtropical regions. Height anomaly patterns at the 500 mb level for the last three decades show the expansion of negative area in the northern hemisphere, resulting in increase of variability in space and time.
  5. 1982: Perry, Allen. “Is the climate becoming more variable?.” Progress in Physical Geography 6.1 (1982): 108-114. bandicam 2018-10-21 16-28-58-252
  6. 1984: Suckling, Philip W. “TRENDS IN MONTHLY TEMPERATURE DEPARTURES FOR THE CONTINGUOUS UNITED STATES, 1940-1983.” Physical Geography 5.2 (1984): 150-163. A temperature departure index is calculated for each month of the year for 10 regions within the contiguous United States utilizing a total of 193 sites for the 44-year period 1940 to 1983. Five-year moving averages of the index values are plotted on graphs for each region by month in an attempt to detect trends toward an increase or decrease in the occurrence of well above or well below normal monthly temperatures in recent years. Considerable regional differences are found with respect to the size and temporal trend of monthly temperature departures. For example, the Northwest and Southwest regions are often exceptions to the average national trend supporting the concept of considerable east-west differences in temperature variation patterns. Only April, June and December show increases in temperature departure index values in the most recent years for a majority of regions while the summer months of July and August do not exhibit a clear national trend. For a majority of months (January, February, March, May, September, October, November), there has been a decrease in the occurrence of unusually above or below normal monthly temperatures for most regions during the late 1970s/early 1980s.
  7. 1984: Suckling, Philip W. “Temperature variability in Georgia in recent years.” Southeastern Geographer 24.1 (1984): 30-41. Southeastern Geographer Vol. 24, No. 1, May 1984,  In recent years several examples of temperature extremes have occurred in Georgia and across the southeast. These include extreme cold in the winter of 1976—77, above normal summer temperatures in 1980 and 1981, and the exceptionally warm Christmas season of 1982. Do these occurrences indicate that temperature variability has increased? Some writers have suggested that there has been an increase in climatic variability in recent years. The following are some relevant quotes: “droughts, floods, heat waves and cold spells unprecedented in living memory “; “record low temperatures reported with increasing frequency in many parts of the United States”; and “the range of short-term variations has widened since the middle of the century.” (J) Studies have addressed the issue of whether the climatic trend is towards cooling or warming. (2) Although the issue of climatic trends of cooling versus warming is important, it is the frequency of extremes (i.e., climatic variability) that may be of more significance to man and his activities, especially in agriculture. (3) In the past, it has been suggested that overall climatic cooling should cause increased temperature variability. However, a study by Van Loon and Williams indicated this concept to be wrong. (4) Previous studies on temperature variability have supported the contention that in recent years an increase in the frequency of extremes has occurred. Asakura and Ikeda concluded that an increase in temperature extremes for the northern hemisphere has occurred in the last two decades compared to the mid-twentieth century . (5) Similarly, Jones, Wigley and Kelly found increased year-toyear variability during the 1970s in a study of northern hemisphere temperature variations over the last century. (6) By contrast, Ratcliffe, Weiler and Collison in a study covering parts of Britain found no trend toward increased climatic variability in the last century. (7) In an assessment of interannual temperature variability for the United States * The technical assistance of Jeon Lee is gratefully acknowledged. Dr. Suckling is Associate Professor of Geography at the University of Georgia in Athens, GA 30602. Vol. XXIV, No. 1 31 since 1896, Chico and Sellers found a decrease in variability for the 1930s to the 1970s. (S) Boer and Higuchi found no evidence to support the contention that the climate has generally become more variable in the northern hemisphere for the last 25 years although, in a later article, they did find evidence suggesting increased summertime temperature variability. (9) Hoyt has shown that the popular opinion that more weather “records” have been set in recent years in the United States is mistaken. If anything, less “records” are being established than statistically expected. (JO) Regional differences in climatic change and variability are to be expected. (JJ) Using a limited number of sites, the study by Van Loon and Williams found decreasing temperature variability for U.S. locations in the midwest and northeast but increasing variability in the south and west. (J2) It is the purpose of the present study to assess temperature variability for the southern state of Georgia. Has there been an increase in the occurrence of unusually above or below normal monthly temperatures in recent years? METHODOLOGY. Mean monthly temperatures for the period 19401982 for seven sites in Georgia plus the nearby locations ofChattanooga, TN, Tallahassee, FL, and Jacksonville, FL, were used for study (Fig. 1). The three non-Georgia stations were included to provide surrogate data for the far northern and southern regions ofthe state in the absence ofappropriate in-state sites. Monthly average temperature and standard deviation values for the 43-year period are given in Table 1. It is notable that winter months have much more temperature variability than summer months as indicated by consistently higher standard deviation values at all sites. In order to assess interannual changes in temperature variability, it is therefore appropriate to conduct the analysis on a month by month basis.
  8. 1987: Suckling, Philip W. “A climate departure index for the study of climatic variability.” Physical Geography 8.2 (1987): 179-188. Three versions of a Climate Departure Index (CDI) are presented for studying how “normal” or “unusual” a particular year or event is compared to the long-term average for the region under consideration. Comparisons of a Simple CDI, Absolute Value CDI and Least-Squares CDI are made through the use of hypothetical examples and two case studies involving seasonal snowfall variations in northern New England and last spring-freeze date variations in the southeastern United States. Results clearly show that the Simple CDI is the inferior formulation owing to a compensation problem whereby above and below average sites within a region for a particular year cancel each other when computing the index value. Little difference in identifying extreme years was found between use of the Absolute Value CDI and Least-Squares CDI in the case studies examined. Nevertheless, a hypothetical example suggests that the least-squares approach for closeness of fit is the more appropriate method, thus making the Least-Squares CDI the preferred version.
  9. 1992: Read, J. F., and W. J. Gould. “Cooling and freshening of the subpolar North Atlantic Ocean since the 1960s.” Nature360.6399 (1992): 55. LITTLE is known of the interdecadal variability in the thermohaline circulation of the world’s oceans, yet such knowledge is essential as a background to studies of the effects of natural and anthropogenic climate change. The subpolar North Atlantic is an area of extensive water mass modification by heat loss to the atmosphere. Lying as it does at the northern limit of the global thermohaline “conveyor belt”12, changes in this region may ultimately have global consequences. Here we report that in August 1991 the waters between Greenland and the United Kingdom were on average 0.08 °C and 0.15 °C colder than in 1962 and 1981, respectively, and slightly less saline than in 1962. The cause appears to be renewed formation of intermediate water in the Labrador Sea from cooler and fresher source waters, and the spreading of this water mass from the west. Variations in the source characteristics of Labrador Sea Water can be traced across the North Atlantic, with a circulation time of 18–19 years between the Labrador Sea and Rockall Trough. More recently formed Labrador Sea Water, with even lower temperature and salinity, should cool and freshen the North Atlantic still further as it circulates around the ocean in the coming decade.
  10. 2000: Andronova, Natalia G., and Michael E. Schlesinger. “Causes of global temperature changes during the 19th and 20th centuries.” Geophysical Research Letters 27.14 (2000): 2137-2140. During the past two decades there has been considerable discussion about the relative contribution of different factors to the temperature changes observed now over the past 142 years. Among these factors are the “external’ factors of human (anthropogenic) activity, volcanoes and putative variations in the irradiance of the sun, and the “internal” factor of natural variability. Here, by using a simple climate/ocean model to simulate the observed temperature changes for different state‐of‐the‐art radiative‐forcing models, we present strong evidence that while the anthropogenic effect has steadily increased in size during the entire 20th century such that it presently is the dominant external forcing of the climate system, there is a residual factor at work within the climate system, whether a natural oscillation or something else as yet unknown. This has an important implication for our expectation of future temperature changes.
  11. 2008: Peterson, Thomas C., William M. Connolley, and John Fleck. “The myth of the 1970s global cooling scientific consensus.” Bulletin of the American Meteorological Society 89.9 (2008): 1325-1338. Climate science as we know it today did not exist in the 1960s and 1970s. The integrated enterprise embodied in the Nobel Prize winning work of the IPCC existed then as separate threads of research pursued by isolated groups of scientists. Atmospheric chemists and modelers grappled with the measurement of changes in carbon dioxide and atmospheric gases, and the changes in climate that might result. Meanwhile, geologists and paleoclimate researchers tried to understand when Earth slipped into and out of ice ages, and why. An enduring popular myth suggests that in the 1970s the climate science community was predicting “global cooling” and an “imminent” ice age, an observation frequently used by those who would undermine what climate scientists say today about the prospect of global warming. A review of the literature suggests that, on the contrary, greenhouse warming even then dominated scientists’ thinking as being one of the most important forces shaping Earth’s climate on human time scales. More importantly than showing the falsehood of the myth, this review describes how scientists of the time built the foundation on which the cohesive enterprise of modern climate science now rests. NOAA/National Climatic Data Center, Asheville
  12. 2014: Hodson, Daniel LR, Jon I. Robson, and Rowan T. Sutton. “An anatomy of the cooling of the North Atlantic Ocean in the 1960s and 1970s.” Journal of Climate 27.21 (2014): 8229-8243. In the 1960s and early 1970s, sea surface temperatures in the North Atlantic Ocean cooled rapidly. There is still considerable uncertainty about the causes of this event, although various mechanisms have been proposed. In this observational study, it is demonstrated that the cooling proceeded in several distinct stages. Cool anomalies initially appeared in the mid-1960s in the Nordic Seas and Gulf Stream extension, before spreading to cover most of the subpolar gyre. Subsequently, cool anomalies spread into the tropical North Atlantic before retreating, in the late 1970s, back to the subpolar gyre. There is strong evidence that changes in atmospheric circulation, linked to a southward shift of the Atlantic ITCZ, played an important role in the event, particularly in the period 1972–76. Theories for the cooling event must account for its distinctive space–time evolution. The authors’ analysis suggests that the most likely drivers were 1) the “Great Salinity Anomaly” of the late 1960s; 2) an earlier warming of the subpolar North Atlantic, which may have led to a slowdown in the Atlantic meridional overturning circulation; and 3) an increase in anthropogenic sulfur dioxide emissions. Determining the relative importance of these factors is a key area for future work.

 

[LIST OF POSTS ON THIS SITE]

 

 

 

 

 

FIGURE 1: ATLANTIC OCEANatlantic700ATLANTIC2000

 

FIGURE 2: PACIFIC OCEANPACIFIC700PACIFIC2000

 

FIGURE 3: INDIAN OCEANINDIAN700INDIAN2000

 

FIGURE 4: SUMMARY OF RESULTS: FULL SPAN TRENDSFULLSPAN-TABLE

 

FIGURE 5: SUMMARY OF RESULTS: DECADAL TRENDSDECADALTABLEDECADAL-TRENDS-700DECADAL-TRENDS-2000

 

FIGURE 6: DECADAL TREND STATISTICSDECADAL-STATISTICSDECSTAT01DECSTAT02

 

FIGURE 7: GEOTHERMAL SOURCES IN THE ARCTIC  [JAMES KAMIS]

ArcticGeothermals

 

FIGURE 8: MID OCEAN RIDGES  [PSU.EDU] World_Distribution_of_Mid-Oceanic_Ridges

 

FIGURE 9: PLATE TECTONICS   [USGS]

map_plate_tectonics_world_med

 

FIGURE 10: THE INDIAN OCEAN  [VOLCANO DISCOVERY]

indian_ocean

 

FIGURE 11: DISTRIBUTION OF HYDROTHERMAL VENTS ( [SOURCE]

Distribution_of_hydrothermal_vent_fields

 

  1. The theory of anthropogenic global warming (AGW) is discussed more fully in a related post [THE GREENHOUSE EFFECT OF ATMOSPHERIC CO2] where it is shown that there has been some unexplained divergence between the expected surface temperature due to AGW forcing and the observational data. Climate science has proposed that these anomalies may be explained in terms of ocean heat uptake because some of the warming due to AGW may become absorbed into ocean heat content (References in paragraphs 21 to 31 in the OCEAN HEAT CONTENT BIBLIOGRAPHY section below). This work is a critical evaluation of the interpretation of changes in ocean heat content in terms of the “uptake” of AGW generated heat by the oceans.
  2. The data used in this work consist primarily of ocean heat content estimations by the NOAA from many measurements of ocean temperatures globally down to depths of 3,000 meters [NOAA OCEAN HEAT CONTENT DATABASE] . The data are provided in two distinct data formats for the two different depths for which data are available namely surface to 700 meters (700M) and surface to 2000 meters (2000M). The 700M data are provided as annual means (YEARLY) for the 63-year period from mid 1955 to mid 2017 and the 2000M data are provided as moving 5-year averages (PENTA) for the 59-year period from mid 1957 to mid 2015. Both data sets are provided for northern and southern segments of the Atlantic, Pacific, and Indian oceans.
  3. The data as received are displayed graphically in Figure 1 to Figure 3 for the three different oceans. Each figure represents an ocean and consists of an upper and lower panel each with two frames for a total of four charts per ocean. The 700M data re displayed in the upper panel and the 2,000M data in the lower panel. The left frame of each panel is a display of the heat content data in units of 1E22 Joules (10^22 Joules) against time in years. The right frame of each panel displays the corresponding “trend profile” in terms of decadal trends (units of 1E22 Joules/year) in a moving window. Each chart contains four color-coded lines for different sections of the ocean as South (purple), North (red), both North and South (blue), and a neutral zero line (black).
  4. As expected, the annual data for 700M shows greater volatility and uncertainty than the smoothed Pentadal data for 2000M. An additional difference seen in the case of the Pacific is that the steady and sustained upward trend in OHC at 2000M is not found in the 700M data where no trend is evident until the 1990’s. This distinction is seen more clearly in the trend profiles where we find that in the smoothed data for 2000M, the moving decadal trends are all positive whereas in the data for 700 meters we see violent and unsynchronized swings of cooling and warming periods with North cooling while the South warms and vice versa. This disconnect between North and South is not seen in the smoothed data for 2000M. The smoothed full span data for 2000M indicate steadily rising Ocean Heat Content (OHC) for both the Northern and Southern segments in the Atlantic and Pacific Oceans.
  5. A very different pattern is seen in the Indian Ocean where the whole of the gain in OHC at either depth derives from warming in the South with no trend seen in the OHC of the North. The trend pattern seen for the annual 700M data in the Atlantic and Pacific where the upward trend in OHC begins in the 1990s is seen in the Indian Ocean data at both depths and at both annual and pentadal time scales.
  6. The results of trend analysis of the data depicted in in Figure 1 to Figure 3 are summarized in Figure 4 and Figure 5. Figure 4 contains the results of full span trend analysis and here we find a great variance in total OHC gain among the oceanic regions. The greatest gain in OHC occurred in the North Atlantic (with gains of 5.5E22 Joules at 700M and 7.4E22 Joules at 2000M) followed by the North Pacific (3.5E22 Joules at 700M) and the South Atlantic at (5.4E22 Joules at 200M). The lowest OHC accumulation is seen in the North Indian Ocean at 0.63E22 Joules at 700M and 0.91E22 Joules at 2000M. The last column of Figure 4 marked “Percent” shows the distribution of each ocean’s heat gain between its Northern and Southern portions. The distribution is most even in the Pacific at close to 50-50 and most unbalanced in the Indian Ocean where more than 80% of the warming is found in the South at both 700M and 2000M depths.
  7. Greater trend information is found in the full span trends of the 700M and 2000M OHC time series is found in the plot of decadal trends in a 10-year moving window shown in the trend profile curves of Figure 1 to Figure 3. A summary of decadal trends in a moving window is presented in Figure 5 where decadal OHC gains are tabulated in distinct decades. With some overlap there are seven distinct decades in the annual data for 700M and six for 2000M. The data are displayed in charts below the table. The “acceleration” in OHC gain claimed by many authors (see for example paragraph #28 in the Ocean Heat Content Bibliography below), is evident in the Atlantic (both North and South) at 700M and weaker evidence of acceleration with large variance is found in the Pacific (North and South) at 700M. No evidence of acceleration is seen in the Indian Ocean at either depth or at 2000M in any ocean.
  8. Further analysis and summary of the decadal trends are presented in Figure 6. Each chart below the table displays data for both 700M (in blue on the left) and 2000M (in red on the right). Each ocean name occurs twice in each depth section for the northern and southern segments of the ocean respectively.
  9. At 700M the greatest decadal OHC decline rates are seen in the North Pacific at a decline rate of 0.29E22 JPY (Joules per year) and in the South Pacific and at a rate of 0.25E22 JPY. The greatest OHC accretion rates are seen in the North Pacific at a rate of 0.32E22 JPY and also in the South Indian Ocean at a rate of 0.30E22 JPY. At 2000M the greatest decadal OHC decline rates are seen in the North Pacific at a decline rate of 0.23E22 JPY (Joules per year) and in the South Indian Ocean and at a rate of 0.20E22 JPY. The greatest OHC accretion rates are seen in the South Indian Ocean at a rate of 0.33E22 JPY and also in the North Atlantic at a rate of 0.30E22 JPY.
  10. In terms of average decadal rate of gain in OHC, at700M and 2000M, the lowest trends are found in the North Indian Ocean at rates of 0.013E22JPY and 0.02E22JPY respectively and the highest rates of OHC gain are found in the North Atlantic at rates of 0.07E22JPY and 0.2E22JPY respectively. The OHC trend patterns across the oceans in terms of minimum, maximum, and average decadal trends are thus found to be grossly non-uniform and incongruent. A specific case of non-uniformity in OHC trends globally is the case of the Indian Ocean. As seen in Figure 3, decadal trends in OHC in the Indian Ocean are driven almost exclusively by the South Indian Ocean with little if any contribution by the North except for a slight warming trend since the year 2000. If this minor trend is to be interpreted in terms of the so called warming “hiatus” that began in the year 2000, more reason than its mere existence is needed to support the attribution without the risk of circular reasoning.
  11. The comparisons above describe a state of incongruity in OHC trends according to location and an absence of the kind of homogeneity in the rate of gain in ocean heat content one would expect if they were driven by common and uniform global force. It is therefore proposed that this pattern of trends in ocean heat content is not consistent with a uniform global source of heat from the greenhouse effect of atmospheric carbon dioxide concentration and that other sources of heat known to exist must also be considered. These conclusions are supported by similar works carried out by James Edward Kamis (paragraphs #31-#34 in Geothermal Heat Bibliography) and Robert Stevenson (paragraph#8 in Ocean Heat Content Bibliography). See also the Wyss paper  [ wyss episodic geothermal ] and the recently published Zanna et al 2018 [LINK] .
  12. Figure 7 through Figure 11 are maps that identify sources of submarine geothermal heat. These include submarine volcanism, mantle plumes, plate tectonics, and hydrothermal vents. It is clear in these maps, and also generally accepted, that the North Atlantic contains more submarine geothermal heat sources than the South and the South Indian Ocean contains more geothermal heat sources than the North. These patterns are consistent with the patterns of OHC trends seen in Figure 1, Figure 2, and Figure 3. These data may not provide conclusive evidence that geothermal heat drives OHC but they provide sufficient reason to question the usual assumption that changes in OHC can and should be understood only in terms of a proposed heat trapping effect of atmospheric composition.
  13. It is also noted that the use of OHC to explain anomalies in the theory of the heat trapping effect of atmospheric composition is a form of circular reasoning. Rather than supporting the theory of the heat trapping effect of atmospheric composition, the need for circular reasoning exposes weaknesses in that theory. The connection between OHC and AGW theory should be established with direct empirical evidence of such causation with a heat balance that includes all internal heat sources of the planet – and not on the basis of a need for heat sinks.
  14. That geothermal heat sources in the ocean floor are not trivial and that they are quite possibly a significant force in the earth’s energy balance can be seen in their effect during the Paleocene-Eocene Thermal Maximum (PETM) event described in a related post at this site  [LINK] and in the Mid Miocene warming that is thought to have been a deep ocean phenomenon [LINK] . It should also be considered that the total mass of the oceans and atmosphere taken together is 1.41e21 kg of which the ocean is 99.63% and the atmosphere 0.37% and this mass difference would make it difficult for the atmosphere to control the ocean’s heat content. 
  15. The conclusion stated above is supported by: Roach, W. T. “Can geothermal heat perturb climate?.” Weather 53.1 (1998): 11-19.. where the author notes: “Heat from the earth’s interior – geothermal heat (GH) – leaks through the earth‘s crust into the atmosphere and oceans at a rate which is very small compared to meteorological heat fluxes (Table 1). Therefore, climate modellers make no allowance for geothermal heat flux (GHF) in current climate models (e.g. Peixoto and Oort 1992). While this exclusion of GHF is justified for land surfaces, even in volcanic eruptions, what happens to GH entering the deep ocean? The residence time of deep-ocean water has been estimated to be of order 3000 years (Woods 1984), and raises the question as to whether a slow accumulation of trapped GH might have thermal and dynamical consequences for the ocean – and perhaps, therefore, for climate – on some time-scales? A search of oceanographic or meteorological literature failed to reveal any discussion of this topic, but limited references have been found in some geophysical journals, mainly in connection with geothermal heat emitted from mid-ocean submarine ridges. This note discusses the possibility of a link between geothermal heat and climate and raises the following issues about the role of geothermal heat (GH) in climate. Can GH flowing through the ocean floor generate enough circulation to perturb the principal ocean circulation? This is the dynamical aspect of the issue. What is the balance between GH entering the ocean and GH eventually dispersed
    into the atmosphere from the ocean surface? This is the thermal aspect of the issue. Depending on some consideration of these questions, could GH significantly perturb climate and, if so, on what time-scale?  Citations in this paper
  16. Bemis, Karen G., Richard P. Von Herzen, and Michael J. Mottl. “Geothermal heat flux from hydrothermal plumes on the Juan de Fuca Ridge.” Journal of Geophysical Research: Solid Earth 98.B4 (1993): 6351-6365.  Estimates of the heat output of hydrothermal vents, identified along the Endeavor and Southern segments of the Juan de Fuca Ridge, are used to evaluate the total heat flux associated with hydrothermal circulation for the ridge segment. A 50‐m array carried by DSV Alvin sampled the temperature and vertical velocity structure of hydrothermal plumes from individual vents. These measurements are used to estimate the thermal flux associated with such plumes. The maximum heat flux calculated for a single vent is 50 MW (1 MW = 1×106 W). The median heat flux per vent is 9 MW and 3 MW, respectively, for the Endeavour Segment (18 vents) and Southern Segment (18 vents). The estimates for any given vent may vary over an order of magnitude. This uncertainty is due mainly to the difficulty of locating the centerline of the plume relative to the point of measurement, although the uncertainties in the constants for the appropriate equations based on laboratory experiments also contribute significantly to the net error. For the Endeavor Segment, the minimum total geothermal heat flux due to hydrothermal circulation exceeds 70 MW. The minimum estimate for the Southern Segment is 16 MW. The maximum estimate is probably closer to the total heat flux from high‐temperature venting (239 MW and 66 MW respectively). High‐temperature hydrothermal venting accounts for only a small fraction of the heat available according to steady state predictions of conductive heat flux; other hydrothermal phenomena (e.g., diffuse flow) probably account for a greater proportion of the total hydrothermal heat flux.
  17. Bretherton, Francis P. “Recent developments in dynamical oceanography.” Quarterly Journal of the Royal Meteorological Society 101.430 (1975): 705-721.  The classical view of the ocean circulation posits steady anticyclonic subtropical gyres in the major ocean basins above nearly quiescent deep water. Recent evidence from water mass analysis and from mesoscale velocity measurements contradicts this picture, showing that the water circulates in a more complex manner and that the flow must be regarded as turbulent. Numerical simulations of the mesoscale eddies show good agreement with the observed statistical structure, suggesting that the latter is locally determined in mid‐ocean by nonlinear quasi‐geostrophic dynamics above topographic irregularities of the same scale. The energy source for the eddies and the implications for the general circulation are still undetermined.
  18. Bullard, Edward Crisp. “Heat flow in south africa.” Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 173.955 (1939): 474-502. It has been known for many years that the increase of temperature with depth on the Witwatersrand is exceptionally slow. The normal gradient in Europe and America is about 33° C/km., whilst that in the gold mines near Johannesburg is only about 10° C/km. It has been generally supposed that the conductivities did not differ by any large factor,* and that the low-temperature gradient indicated a heat flow much less than that in other parts of the world. As there is reason to suppose (Jeffreys 1929) that most of the heat is generated by the radioactivity of a layer of granite underlying the continents, and since the principle of isostasy requires this layer to be thicker under the African plateau than elsewhere, a greater heat flow would be expected in Africa than in Europe. The conductivity data are meagre and of doubtful reliability, and it seemed desirable to make a systematic study of the question. The temperatures and conductivities in a number of English bores have been studied by Benfield in this laboratory, and detailed and accurate temperature measurements have been made by Dr Krige (1939) and Mr Weiss (1938) in deep boreholes in South Africa. When the author was invited to visit Johannesburg as a guest of the Bernard Price Institute of Geophysical Research he took the opportunity to measure the conductivities of specimens of rock from some of the boreholes in which temperature measurements had been made. It is the purpose of this paper to describe these measurements and to discuss the results. As the conditions were exceptionally favourable, both for the temperature and for the conductivity measurements, the problem has been investigated in considerable detail. It was thought that, in addition to the direct interest of the results, they may be useful in indicating the disturbances to be feared in cases where no such detailed study is possible.
  19. Charnock, H. “Air-sea exchanges and meridional fluxes.” Ocean Processes in Climate Dynamics: Global and Mediterranean Examples. Springer, Dordrecht, 1994. 1-27. Understanding and simulation of the interaction between the atmosphere and the ocean needs information on the magnitude of the exchanges between them, at the sea surface. The processes at this interfacial zone are complicated and the flux estimates uncertain: this short review provides a selective account of the present position. Understanding and simulation of the climate of the earth, and possible changes, need information on the magnitude of the meridional fluxes that redress the radiation imbalance between low and high latitudes. These are becoming better known, though inconsistencies between the various methods of estimation remain.
  20. LATER WORKS ON THE IMPACT OF GEOTHERMAL HEAT ON OCEANS ARE LISTED IN THE OCEAN HEAT CONTENT BIBLIOGRAPHY BELOW.

 

 

 

 

 

 

 

OCEAN HEAT CONTENT BIBLIOGRAPHY

  1. 1959: Rossby, C. G. “The atmosphere and the sea in motion.” Current problems in meteorology (1959): 9-50.  n  [THE WORKS OF CARL GUSTAV ROSSBY]
  2. 1980: White, Warren, et al. “The thermocline response to transient atmospheric forcing in the interior midlatitude North PAcific 1976–1978.” Journal of Physical Oceanography 10.3 (1980): 372-384. The Ekman pumping mechanism for altering the depth of the main thermocline in response to wind stress curl is tested in the central midlatitude North Pacific. According to this mechanism, the depth of the main thermocline should decrease under cyclonic wind stress curl and increase under anticyclonic wind stress curl. For the two years 1976–78, temperature measurements from an XBT measurement program between North America and Japan have allowed the monthly thermal structure to be measured over an area 30–50°N, 130–170°W, accompanied with synoptic estimates of wind stress curl. Working with anomalous estimates that deviate from the normal seasonal cycle, the month-to-month secular change in the depth of the main thermocline during the nine months of each year from February to October is found to have responded to the anomalous wind stress curl according to what was expected from the Ekman pumping mechanism. The expected and observed secular changes in the thermocline depth for these times of the year were correlated with each other at the 1% significance level in the latitudinal band from 35–45°N (except in the near field of the Subarctic Front) along 160°W. However, during the other part of each year (November, December and January), when synoptic storm forcing was at its peak, the depth of the main thermocline did not respond to the wind stress curl in the manner expected. Rather, the depth of the main thermocline tended to respond in the opposite fashion. This suggests that other mechanisms associated with autumn/winter forcing may have been important.
  3. 1994: Trenberth, Kevin E., and James W. Hurrell. “Decadal atmosphere-ocean variations in the Pacific.” Climate Dynamics 9.6 (1994): 303-319. Considerable evidence has emerged of a substantial decade-long change in the north Pacific atmosphere and ocean lasting from about 1976 to 1988. Observed significant changes in the atmospheric circulation throughout the troposphere revealed a deeper and eastward shifted Aleutian low pressure system in the winter half year which advected warmer and moister air along the west coast of North America and into Alaska and colder air over the north Pacific. Consequently, there were increases in temperatures and sea surface temperatures (SSTs) along the west coast of North America and Alaska but decreases in SSTs over the central north Pacific, as well as changes in coastal rainfall and streamflow, and decreases in sea ice in the Bering Sea. Associated changes occurred in the surface wind stress, and, by inference, in the Sverdrup transport in the north Pacific Ocean. Changes in the monthly mean flow were accompanied by a southward shift in the storm tracks and associated synoptic eddy activity and in the surface ocean sensible and latent heat fluxes. In addition to the changes in the physical environment, the deeper Aleutian low increased the nutrient supply as seen through increases in total chlorophyll in the water column, phytoplankton and zooplankton. These changes, along with the altered ocean currents and temperatures, changed the migration patterns and increased the stock of many fish species. A north Pacific (NP) index is defined to measure the decadal variations, and the temporal variability of the index is explored on daily, annual, interannual and decadal time scales. The dominant atmosphere-ocean relation in the north Pacific is one where atmospheric changes lead SSTs by one to two months. However, strong ties are revealed with events in the tropical Pacific, with changes in tropical Pacific SSTs leading SSTs in the north Pacific by three months. Changes in the storm tracks in the north Pacific help to reinforce and maintain the anomalous circulation in the upper troposphere. A hypothesis is put forward outlining the tropical and extratropical realtionships which stresses the role of tropical forcing but with important feed-backs in the extratropics that serve to emphasize the decadal relative to interannual time scales. The Pacific decadal timescale variations are linked to recent changes in the frequency and intensity of El Niño versus La Nina events but whether climate change associated with “global warming” is a factor is an open question.
  4. 1996: Deser, Clara, Michael A. Alexander, and Michael S. Timlin. “Upper-ocean thermal variations in the North Pacific during 1970–1991.” Journal of Climate 9.8 (1996): 1840-1855. A newly available, extensive compilation of upper-ocean temperature profiles was used to study the vertical structure of thermal anomalies between the surface and 400-m depth in the North Pacific during 1970–1991. A prominent decade-long perturbation in climate occurred during this time period: surface waters cooled by ∼1°C in the central and western North Pacific and warmed by about the same amount along the west coast of North America from late 1976 to 1988. Comparison with data from COADS suggests that the relatively sparse sampling of the subsurface data is adequate for describing the climate anomaly.The vertical structure of seasonal thermal anomalies in the central North Pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400-m depth. Individual cold events descend rapidly (∼100 m yr−1), superimposed upon a slower cooling (∼15 m yr−1). The interdecadal climate change, while evident at the surface, is most prominent below ∼150 m where interannual variations are small. Unlike the central North Pacific, the temperature changes along the west coast of North America appear to be confined to approximately the upper 200–250 m. The structure of the interdecadal thermal variations in the eastern and central North Pacific appears to be consistent with the dynamics of the ventilated thermocline. In the western North Pacific, strong cooling is observed along the axis of the Kuroshio Current Extension below ∼200 m depth during the 1980s. Changes in mixed layer depth accompany the SST variations, but their spatial distribution is not identical to the pattern of SST change. In particular, the decade-long cool period in the central North Pacific was accompanied by a ∼20 m deepening of the mixed layer in winter, but no significant changes in mixed layer depth were found along the west coast of North America. It is suggested that other factors such as stratification beneath the mixed layer and synoptic wind forcing may play a role in determining the distribution of mixed layer depth anomalies.
  5. 1997: Deser, C., M. A. Alexander, and M. S. Timlin. “Upper-Ocean thermal variations in the North Pacific during 1970-1991.” Oceanographic Literature Review 4.44 (1997): 308-309. The vertical structure of seasonal thermal anomalies in the central North Pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400-m depth. Individual cold events descend rapidly, superimposed upon a slower cooling. The interdecadal climate change, while evident at the surface, is most prominent below ≃ 150 m. The temperature changes along the west coast of North America appear to be confined to approximately the upper 200-250 m. In the western North Pacific, strong cooling is observed along the axis of the Kuroshio Current Extension below ∼ 200 m depth during the 1980s. Changes in mixed layer depth accompany the SST variations.
  6. 1997: White, Warren B., et al. “Response of global upper ocean temperature to changing solar irradiance.” Journal of Geophysical Research: Oceans 102.C2 (1997): 3255-3266.  By focusing on time sequences of basin‐average and global‐average upper ocean temperature (i.e., from 40°S to 60°N) we find temperatures responding to changing solar irradiance in three separate frequency bands with periods of >100 years, 18–25 years, and 9–13 years. Moreover, we find them in two different data sets, that is, surface marine weather observations from 1990 to 1991 and bathythermograph (BT) upper ocean temperature profiles from 1955 to 1994. Band‐passing basin‐average temperature records find each frequency component in phase across the Indian, Pacific, and Atlantic Oceans, yielding global‐average records with maximum amplitudes of 0.04°±0.01°K and 0.07°±0.01°K on decadal and interdecadal scales, respectively. These achieve maximum correlation with solar irradiance records (i.e., with maximum amplitude 0.5 W m−2 at the top of the atmosphere) at phase lags ranging from 30° to 50°. From the BT data set, solar signals in global‐average temperature penetrate to 80–160 m, confined to the upper layer above the main pycnocline. Operating a global‐average heat budget for the upper ocean yields sea surface temperature responses of 0.01°–0.03°K and 0.02°–0.05°K on decadal and interdecadal scales, respectively, from the 0.1 W m−2 penetration of solar irradiance to the sea surface. Since this is of the same order as that observed (i.e., 0.04°–0.07°K), we can infer that anomalous heat from changing solar irradiance is stored in the upper layer of the ocean.
  7. 1998: White, Warren B., and Daniel R. Cayan. “Quasi‐periodicity and global symmetries in interdecadal upper ocean temperature variability.” Journal of Geophysical Research: Oceans103.C10 (1998): 21335-21354. Recent studies find interannual (i.e., 3 to 7 year), decadal (i.e., 9 to 13 year), and interdecadal (i.e., 18 to 23 year) periodicities, and a trend dominating global sea surface temperature (SST) and sea level pressure (SLP) variability over the past hundred years, with the interdecadal signal dominating sub‐El Niño‐Southern Oscillation (ENSO) frequencies. We isolate interdecadal frequencies in SST and SLP records by band passing with a window admitting 15 to 30 year periods. From 1900 to 1989, the rms of interdecadal‐filtered SST and SLP anomalies is largest in the extratropics and eastern boundaries. First‐mode empirical orthogonal functions (EOFs) explain about half the interdecadal variance in both variables, with the tropical warm phase peaking near 1900, 1920, 1940, 1960, and 1980. From 1955 to 1994, EOF spatial patterns of interdecadal SST, SLP, and 400m temperature (T400) anomalies reveals global reflection symmetries about the equator and global translation symmetries between ocean basins, with tropical and eastern ocean SSTs warmer (cooler) than normal, covarying with stronger (weaker) extratropical westerly winds, cooler (warmer) SSTs in western‐central subarctic and subantarctic frontal zones (SAFZs), stronger (weaker) subtropic and subarctic gyre circulations in North Pacific and North Atlantic Oceans, and warmer (cooler) basin and global average SSTs of 0.1°C or so. Evolution of interdecadal variability from the tropical warm phase to the tropical cool phase is propagative, also characterized by reflection and translation symmetries. During the tropical warm phase, cool SST anomalies along western‐central SAFZs are advected slowly eastward to the eastern boundaries and subsequently advected poleward and equatorward by the mean gyre circulation, the latter conducting extratropical SST anomalies into the tropics. A delayed action oscillation model is constructed that yields the quasiperiodicity of interdecadal variability in a manner consistent with these global symmetries in both pattern and evolution.
  8. 2000: Stevenson, Robert E. “Yes, the ocean has warmed; no, it’s not global warming’.” 21ST CENTURY SCIENCE AND TECHNOLOGY 13.2 (2000): 60-65. Contrary to recent press reports that the oceans hold the still-undetected global atmospheric warming predicted by climate models, ocean warming occurs in 100-year cycles, independent of both radiative and human influences. [FULL TEXT] 
  9. 2000: Levitus, Sydney, et al. “Warming of the world ocean.” Science287.5461 (2000): 2225-2229. We quantify the interannual-to-decadal variability of the heat content (mean temperature) of the world ocean from the surface through 3000-meter depth for the period 1948 to 1998. The heat content of the world ocean increased by ∼2 × 1023 joules between the mid-1950s and mid-1990s, representing a volume mean warming of 0.06°C. This corresponds to a warming rate of 0.3 watt per meter squared (per unit area of Earth’s surface). Substantial changes in heat content occurred in the 300- to 1000-meter layers of each ocean and in depths greater than 1000 meters of the North Atlantic. The global volume mean temperature increase for the 0- to 300-meter layer was 0.31°C, corresponding to an increase in heat content for this layer of ∼1023 joules between the mid-1950s and mid-1990s. The Atlantic and Pacific Oceans have undergone a net warming since the 1950s and the Indian Ocean has warmed since the mid-1960s, although the warming is not monotonic.
  10. 2001: Levitus, Sydney, et al. “Anthropogenic warming of Earth’s climate system.” Science 292.5515 (2001): 267-270. We compared the temporal variability of the heat content of the world ocean, of the global atmosphere, and of components of Earth’s cryosphere during the latter half of the 20th century. Each component has increased its heat content (the atmosphere and the ocean) or exhibited melting (the cryosphere). The estimated increase of observed global ocean heat content (over the depth range from 0 to 3000 meters) between the 1950s and 1990s is at least one order of magnitude larger than the increase in heat content of any other component. Simulation results using an atmosphere-ocean general circulation model that includes estimates of the radiative effects of observed temporal variations in greenhouse gases, sulfate aerosols, solar irradiance, and volcanic aerosols over the past century agree with our observation-based estimate of the increase in ocean heat content. The results we present suggest that the observed increase in ocean heat content may largely be due to the increase of anthropogenic gases in Earth’s atmosphere.
  11. 2003: McPhaden, Michael J. “Tropical Pacific Ocean heat content variations and ENSO persistence barriers.” Geophysical research letters9 (2003).Data from the tropical Pacific Ocean for the period 1980–2002 are used to examine the persistence of sea surface temperature (SST) and upper ocean heat content variations in relation to El Niño and the Southern Oscillation (ENSO). The present study demonstrates that, unlike for SST, there is no spring persistence barrier when considering upper ocean heat content. Conversely, there is a persistence barrier for heat content in boreal winter related to a seasonal reduction in variance. These results are consistent with ENSO forecast model studies indicating that accurate initialization of upper ocean heat content often reduces the prominence of the spring prediction barrier for SST. They also suggest that initialization of upper ocean heat content variations may lead to seasonally varying enhancements of forecast skill, with the most pronounced enhancements for forecasts starting early and late in the development of ENSO events.2004: 
  12. 2004: Gregory, J. M., et al. “Simulated and observed decadal variability in ocean heat content.” Geophysical Research Letters15 (2004). Previous analyses by Levitus et al.[2000] (“Levitus”) of ocean temperature data have shown that ocean heat content has increased over the last fifty years with substantial temporal variability superimposed. The HadCM3 coupled atmosphere–ocean general circulation model (AOGCM) simulates the Levitus trend if both natural and anthropogenic forcings are included. In the relatively well‐observed northern hemisphere upper ocean, HadCM3 has similar temporal variability to Levitus but, like other AOGCMs, it has generally less variability than Levitus for the world ocean. We analyse the causes of this discrepancy, which could result from deficiencies in either the model or the observational dataset. A substantial contribution to the Levitus variability comes from a strong maximum around 500 m depth, absent in HadCM3. We demonstrate a possibly large sensitivity to the method of filling in the observational dataset outside the well‐observed region, and advocate caution in using it to assess AOGCM heat content changes.
  13. 2004: Willis, Josh K., Dean Roemmich, and Bruce Cornuelle. “Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales.” Journal of Geophysical Research: OceansC12 (2004). Satellite altimetric height was combined with approximately 1,000,000 in situ temperature profiles to produce global estimates of upper ocean heat content, temperature, and thermosteric sea level variability on interannual timescales. Maps of these quantities from mid‐1993 through mid‐2003 were calculated using the technique developed byWillis et al. [2003]. The time series of globally averaged heat content contains a small amount of interannual variability and implies an oceanic warming rate of 0.86 ± 0.12 watts per square meter of ocean (0.29 ± 0.04 pW) from 1993 to 2003 for the upper 750 m of the water column. As a result of the warming, thermosteric sea level rose at a rate of 1.6 ± 0.3 mm/yr over the same time period. Maps of yearly heat content anomaly show patterns of warming commensurate with ENSO variability in the tropics, but also show that a large part of the trend in global, oceanic heat content is caused by regional warming at midlatitudes in the Southern Hemisphere. In addition to quantifying interannual variability on a global scale, this work illustrates the importance of maintaining continuously updated monitoring systems that provide global coverage of the world’s oceans. Ongoing projects, such as the Jason/TOPEX series of satellite altimeters and the Argo float program, provide a critical foundation for characterizing variability on regional, basin, and global scales and quantifying the oceans’ role as part of the climate system.
  14. 2004: Antonov, John I., Sydney Levitus, and Timothy P. Boyer. “Climatological annual cycle of ocean heat content.” Geophysical Research Letters 31.4 (2004). Ocean heat content is a major component of earth’s energy budget. This paper presents estimates of the climatological annual cycle of upper (0–250 m layer) ocean heat content based on World Ocean Atlas 2001. The land‐ocean ratio is responsible for the geographical distribution of the annual cycle of ocean heat content. Globally, the amplitude of annual harmonic of upper ocean heat content is 3.7 × 1022 J for the World Ocean, 10.2 × 1022J for the Southern Hemisphere, and 6.5 × 1022J for the Northern Hemisphere.  [FULL TEXT]
  15. 2005: Levitus, Sydney, J. Antonov, and T. Boyer. “Warming of the world ocean, 1955–2003.” Geophysical Research Letters 32.2 (2005). We present new estimates of the variability of ocean heat content based on: a) additional data that extends the record to more recent years; b) additional historical data for earlier years. During 1955–1998 world ocean heat content (0–3000 m) increased 14.5 × 1022 J corresponding to a mean temperature increase of 0.037°C at a rate of 0.20 Wm−2 (per unit area of Earth’s total surface area). Based on the physical properties and mass of the world ocean as compared to other components of Earth’s climate system, Rossby [1959] suggested that ocean heat content may be the dominant component of the variability of Earth’s heat balance. Recent work [Levitus et al., 2000, 2001] has confirmed Rossby’s suggestion. Warming of the world ocean due to increasing atmospheric greenhouse gases was first identified in a report by Revelle et al. [1965]. The delay of atmospheric warming by increasing greenhouse gases due to initial heating of the world ocean was suggested by the National Research Council [NRC, 1979]. Here we present new yearly estimates for the 1955–2003 period for the upper 300 m and 700 m layers and pentadal (5‐year) estimates for the 1955–1959 through 1994–1998 period for the upper 3000 m of the world ocean.[3] The heat content estimates we present are based on an additional 1.7 million (S. Levitus et al., Building ocean profile‐plankton databases for climate and ecosystem research, submitted to Bulletin of the American Meteorological Society, 2004) temperature profiles that have become available as part of the World Ocean Database 2001 [Conkright et al., 2002]. Also, we have processed approximately 310,000 additional temperature profiles since the release of WOD01 and include these in our analyses. Heat content computations are similar to those described by Levitus and Antonov [1997]. Here we use 1957–1990 as the reference period for our estimates.  [FULL TEXT]
  16. 2005: Church, John A., Neil J. White, and Julie M. Arblaster. “Significant decadal-scale impact of volcanic eruptions on sea level and ocean heat content.” Nature7064 (2005): 74.  Ocean thermal expansion contributes significantly to sea-level variability and rise1. However, observed decadal variability in ocean heat content2,3and sea level4 has not been reproduced well in climate models5. Aerosols injected into the stratosphere during volcanic eruptions scatter incoming solar radiation, and cause a rapid cooling of the atmosphere6,7 and a reduction in rainfall6,8,9, as well as other changes in the climate system7. Here we use observations of ocean heat content2,3 and a set of climate simulations to show that large volcanic eruptions result in rapid reductions in ocean heat content and global mean sea level. For the Mt Pinatubo eruption, we estimate a reduction in ocean heat content of about 3 × 1022 J and a global sea-level fall of about 5 mm. Over the three years following such an eruption, we estimate a decrease in evaporation of up to 0.1 mm d-1, comparable to observed changes in mean land precipitation6,8,9. The recovery of sea level following the Mt Pinatubo eruption in 1991 explains about half of the difference between the long-term rate of sea-level rise4 of 1.8 mm yr-1 (for 1950–2000), and the higher rate estimated for the more recent period where satellite altimeter data are available (1993–2000)4
  17. 2009: Levitus, Sydney, et al. “Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems.” Geophysical Research Letters7 (2009).We provide estimates of the warming of the world ocean for 1955–2008 based on historical data not previously available, additional modern data, correcting for instrumental biases of bathythermograph data, and correcting or excluding some Argo float data. The strong interdecadal variability of global ocean heat content reported previously by us is reduced in magnitude but the linear trend in ocean heat content remain similar to our earlier estimate.
  18. 2009: Ishii, Masayoshi, and Masahide Kimoto. “Reevaluation of historical ocean heat content variations with time-varying XBT and MBT depth bias corrections.” Journal of Oceanography3 (2009): 287-299. As reported in former studies, temperature observations obtained by expendable bathythermographs (XBTs) and mechanical bathythermographs (MBTs) appear to have positive biases as much as they affect major climate signals. These biases have not been fully taken into account in previous ocean temperature analyses, which have been widely used to detect global warming signals in the oceans. This report proposes a methodology for directly eliminating the biases from the XBT and MBT observations. In the case of XBT observation, assuming that the positive temperature biases mainly originate from greater depths given by conventional XBT fall-rate equations than the truth, a depth bias equation is constructed by fitting depth differences between XBT data and more accurate oceanographic observations to a linear equation of elapsed time. Such depth bias equations are introduced separately for each year and for each probe type. Uncertainty in the gradient of the linear equation is evaluated using a non-parametric test. The typical depth bias is +10 m at 700 m depth on average, which is probably caused by various indeterminable sources of error in the XBT observations as well as a lack of representativeness in the fall-rate equations adopted so far. Depth biases in MBT are fitted to quadratic equations of depth in a similar manner to the XBT method. Correcting the historical XBT and MBT depth biases by these equations allows a historical ocean temperature analysis to be conducted. In comparison with the previous temperature analysis, large differences are found in the present analysis as follows: the duration of large ocean heat content in the 1970s shortens dramatically, and recent ocean cooling becomes insignificant. The result is also in better agreement with tide gauge observations.
  19. 2011: Johnson, Gregory C., et al. “Ocean heat content.”  Am. Meteorol. Soc92 (2011): S81-S84. Three different upper ocean estimates (0–700 m) of globally integrated in situ OHCA (Fig. OHCA3) reveal a large increase in global integrals of that quantity since 1993. While levels appear to be increasing more slowly since around 2003 or 2004 than over the previous decade, the mass and thermal expansion terms of the global sea level budget agree with observed sea level rise rates over the latter time period (Section ****). The highest values for each global OHCA estimate are for 2011, although uncertainties only permit statistically significant trends to be estimated over about ten years or longer (Lyman, 2011). Interannual details of the time series differ for a variety of reasons including differences in climatology, treatment of the seasonal cycle, mapping methods, instrument bias corrections, quality control, and other factors (Lyman et al. 2010). Some of these factors are not taken into account in some of the displayed uncertainties, so while the error bars shown do not always overlap among the three estimates, they are not necessarily statistically different from each other. However, all three curves agree on a significant decadal warming of the upper ocean since 1993, accounting for a large portion of the global energy imbalance over this time period (Church et al. 2011).
  20. 2012: Levitus, Sydney, et al. “World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010.” Geophysical Research Letters10 (2012). We provide updated estimates of the change of ocean heat content and the thermosteric component of sea level change of the 0–700 and 0–2000 m layers of the World Ocean for 1955–2010. Our estimates are based on historical data not previously available, additional modern data, and bathythermograph data corrected for instrumental biases. We have also used Argo data corrected by the Argo DAC if available and used uncorrected Argo data if no corrections were available at the time we downloaded the Argo data. The heat content of the World Ocean for the 0–2000 m layer increased by 24.0 ± 1.9 × 1022J (±2S.E.) corresponding to a rate of 0.39 W m−2 (per unit area of the World Ocean) and a volume mean warming of 0.09°C. This warming corresponds to a rate of 0.27 W m−2 per unit area of earth’s surface. The heat content of the World Ocean for the 0–700 m layer increased by 16.7 ± 1.6 × 1022 J corresponding to a rate of 0.27 W m−2(per unit area of the World Ocean) and a volume mean warming of 0.18°C. The World Ocean accounts for approximately 93% of the warming of the earth system that has occurred since 1955. The 700–2000 m ocean layer accounted for approximately one‐third of the warming of the 0–2000 m layer of the World Ocean. The thermosteric component of sea level trend was 0.54 ± .05 mm yr−1 for the 0–2000 m layer and 0.41 ± .04 mm yr−1 for the 0–700 m layer of the World Ocean for 1955–2010.
  21. 2013: Trenberth, Kevin E., and John T. Fasullo. “An apparent hiatus in global warming?.” Earth’s Future 1.1 (2013): 19-32. Global warming first became evident beyond the bounds of natural variability in the 1970s, but increases in global mean surface temperatures have stalled in the 2000s. Increases in atmospheric greenhouse gases, notably carbon dioxide, create an energy imbalance at the top‐of‐atmosphere (TOA) even as the planet warms to adjust to this imbalance, which is estimated to be 0.5–1 W m−2 over the 2000s. Annual global fluctuations in TOA energy of up to 0.2 W m−2 occur from natural variations in clouds, aerosols, and changes in the Sun. At times of major volcanic eruptions the effects can be much larger. Yet global mean surface temperatures fluctuate much more than these can account for. An energy imbalance is manifested not just as surface atmospheric or ground warming but also as melting sea and land ice, and heating of the oceans. More than 90% of the heat goes into the oceans and, with melting land ice, causes sea level to rise. For the past decade, more than 30% of the heat has apparently penetrated below 700 m depth that is traceable to changes in surface winds mainly over the Pacific in association with a switch to a negative phase of the Pacific Decadal Oscillation (PDO) in 1999. Surface warming was much more in evidence during the 1976–1998 positive phase of the PDO, suggesting that natural decadal variability modulates the rate of change of global surface temperatures while sea‐level rise is more relentless. Global warming has not stopped; it is merely manifested in different ways. [FULL TEXT]
  22. 2013: Kosaka, Yu, and Shang-Ping Xie. “Recent global-warming hiatus tied to equatorial Pacific surface cooling.” Nature501.7467 (2013): 403. Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century1,2, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming3,4,5,6, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970–2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.
  23. 2013: Balmaseda, Magdalena A., Kevin E. Trenberth, and Erland Källén. “Distinctive climate signals in reanalysis of global ocean heat content.” Geophysical Research Letters9 (2013): 1754-1759. The elusive nature of the post‐2004 upper ocean warming has exposed uncertainties in the ocean’s role in the Earth’s energy budget and transient climate sensitivity. Here we present the time evolution of the global ocean heat content for 1958 through 2009 from a new observation‐based reanalysis of the ocean. Volcanic eruptions and El Niño events are identified as sharp cooling events punctuating a long‐term ocean warming trend, while heating continues during the recent upper‐ocean‐warming hiatus, but the heat is absorbed in the deeper ocean. In the last decade, about 30% of the warming has occurred below 700 m, contributing significantly to an acceleration of the warming trend. The warming below 700 m remains even when the Argo observing system is withdrawn although the trends are reduced. Sensitivity experiments illustrate that surface wind variability is largely responsible for the changing ocean heat vertical distribution.
  24. 2014: Lin, I‐I., Iam‐Fei Pun, and Chun‐Chi Lien. ““Category‐6” supertyphoon Haiyan in global warming hiatus: Contribution from subsurface ocean warming.” Geophysical Research Letters 41.23 (2014): 8547-8553. With the extra‐ordinary intensity of 170 kts, supertyphoon Haiyan devastated the Philippines in November 2013. This intensity is among the highest ever observed for tropical cyclones (TCs) globally, 35 kts well above the threshold (135kts) of the existing highest category of 5. Though there is speculation to associate global warming with such intensity, existing research indicate that we have been in a warming hiatus period, with the hiatus attributed to the La Niña‐like multi‐decadal phenomenon. It is thus intriguing to understand why Haiyan can occur during hiatus. It is suggested that as the western Pacific manifestation of the La Niña‐like phenomenon is to pile up warm subsurface water to the west, the western North Pacific experienced evident subsurface warming and created a very favorable ocean pre‐condition for Haiyan. Together with its fast traveling speed, the air‐sea flux supply was 158% as compared to normal for intensification.
  25. 2014: Watanabe, Masahiro, et al. “Contribution of natural decadal variability to global warming acceleration and hiatus.” Nature Climate Change 4.10 (2014): 893. Reasons for the apparent pause in the rise of global-mean surface air temperature (SAT) after the turn of the century has been a mystery, undermining confidence in climate projections1,2,3. Recent climate model simulations indicate this warming hiatus originated from eastern equatorial Pacific cooling4 associated with strengthening of trade winds5. Using a climate model that overrides tropical wind stress anomalies with observations for 1958–2012, we show that decadal-mean anomalies of global SAT referenced to the period 1961–1990 are changed by 0.11, 0.13 and −0.11 °C in the 1980s, 1990s and 2000s, respectively, without variation in human-induced radiative forcing. They account for about 47%, 38% and 27% of the respective temperature change. The dominant wind stress variability consistent with this warming/cooling represents the deceleration/acceleration of the Pacific trade winds, which can be robustly reproduced by atmospheric model simulations forced by observed sea surface temperature excluding anthropogenic warming components. Results indicate that inherent decadal climate variability contributes considerably to the observed global-mean SAT time series, but that its influence on decadal-mean SAT has gradually decreased relative to the rising anthropogenic warming signal.
  26. 2014: Chen, Xianyao, and Ka-Kit Tung. “Varying planetary heat sink led to global-warming slowdown and acceleration.” Science345.6199 (2014): 897-903. Global warming seems to have paused over the past 15 years while the deep ocean takes the heat instead. The thermal capacity of the oceans far exceeds that of the atmosphere, so the oceans can store up to 90% of the heat buildup caused by increased concentrations of greenhouse gases such as carbon dioxide. Chen and Tung used observational data to trace the pathways of recent ocean heating. They conclude that the deep Atlantic and Southern Oceans, but not the Pacific, have absorbed the excess heat that would otherwise have fueled continued warming. [FULL TEXT]
  27. 2014: Meehl, Gerald A., Haiyan Teng, and Julie M. Arblaster. “Climate model simulations of the observed early-2000s hiatus of global warming.” Nature Climate Change 4.10 (2014): 898. The slowdown in the rate of global warming in the early 2000s is not evident in the multi-model ensemble average of traditional climate change projection simulations1. However, a number of individual ensemble members from that set of models successfully simulate the early-2000s hiatus when naturally-occurring climate variability involving the Interdecadal Pacific Oscillation (IPO) coincided, by chance, with the observed negative phase of the IPO that contributed to the early-2000s hiatus. If the recent methodology of initialized decadal climate prediction could have been applied in the mid-1990s using the Coupled Model Intercomparison Project Phase 5 multi-models, both the negative phase of the IPO in the early 2000s as well as the hiatus could have been simulated, with the multi-model average performing better than most of the individual models. The loss of predictive skill for six initial years before the mid-1990s points to the need for consistent hindcast skill to establish reliability of an operational decadal climate prediction system.
  28. 2014: Nuccitelli, Dana, et al. “Comment on” Cosmic-ray-driven reaction and greenhouse effect of halogenated molecules: Culprits for atmospheric ozone depletion and global climate change”.” International Journal of Modern Physics B 28.13 (2014): 1482003. Lu (2013) (L13) argued that solar effects and anthropogenic halogenated gases can explain most of the observed warming of global mean surface air temperatures since 1850, with virtually no contribution from atmospheric carbon dioxide (CO2) concentrations. Here we show that this conclusion is based on assumptions about the saturation of the CO2-induced greenhouse effect that have been experimentally falsified. L13 also confuses equilibrium and transient response, and relies on data sources that have been superseeded due to known inaccuracies. Furthermore, the statistical approach of sequential linear regression artificially shifts variance onto the first predictor. L13’s artificial choice of regression order and neglect of other relevant data is the fundamental cause of the incorrect main conclusion. Consideration of more modern data and a more parsimonious multiple regression model leads to contradiction with L13’s statistical results. Finally, the correlation arguments in L13 are falsified by considering either the more appropriate metric of global heat accumulation, or data on longer timescales. [FULL TEXT]
  29. 2015: Stenchikov, Georgiy. “The role of volcanic activity in climate and global change.” Climate Change (Second Edition). 2015. 419-447. Explosive volcanic eruptions are magnificent events that in many ways affect the Earth’s natural processes and climate. They cause sporadic perturbations of the planet’s energy balance, activating complex climate feedbacks and providing unique opportunities to better quantify those processes. We know that explosive eruptions cause cooling in the atmosphere for a few years, but we have just recently realized that volcanic signals can be seen in the subsurface ocean for decades. The volcanic forcing of the previous two centuries offsets the ocean heat uptake and diminishes global warming by about 30%. The explosive volcanism of the twenty-first century is unlikely to either cause any significant climate signal or to delay the pace of global warming. The recent interest in dynamic, microphysical, chemical, and climate impacts of volcanic eruptions is also excited by the fact that these impacts provide a natural analogue for climate geoengineering schemes involving deliberate development of an artificial aerosol layer in the lower stratosphere to counteract global warming. In this chapter we aim to discuss these recently discovered volcanic effects and specifically pay attention to how we can learn about the hidden Earth-system mechanisms activated by explosive volcanic eruptions. To demonstrate these effects we use our own model results when possible along with available observations, as well as review closely related recent publications.
  30. 2015: Karl, Thomas R., et al. “Possible artifacts of data biases in the recent global surface warming hiatus.” Science (2015): aaa5632. Much study has been devoted to the possible causes of an apparent decrease in the upward trend of global surface temperatures since 1998, a phenomenon that has been dubbed the global warming “hiatus.” Here we present an updated global surface temperature analysis that reveals that global trends are higher than reported by the IPCC, especially in recent decades, and that the central estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a “slowdown” in the increase of global surface temperature. [FULL TEXT]
  31. 2015: Goodwin, Philip, Richard G. Williams, and Andy Ridgwell. “Sensitivity of climate to cumulative carbon emissions due to compensation of ocean heat and carbon uptake.” Nature Geoscience 8.1 (2015): 29. Climate model experiments reveal that transient global warming is nearly proportional to cumulative carbon emissions on multi-decadal to centennial timescales1,2,3,4,5. However, it is not quantitatively understood how this near-linear dependence between warming and cumulative carbon emissions arises in transient climate simulations6,7. Here, we present a theoretically derived equation of the dependence of global warming on cumulative carbon emissions over time. For an atmosphere–ocean system, our analysis identifies a surface warming response to cumulative carbon emissions of 1.5 ± 0.7 K for every 1,000 Pg of carbon emitted. This surface warming response is reduced by typically 10–20% by the end of the century and beyond. The climate response remains nearly constant on multi-decadal to centennial timescales as a result of partially opposing effects of oceanic uptake of heat and carbon8. The resulting warming then becomes proportional to cumulative carbon emissions after many centuries, as noted earlier9. When we incorporate estimates of terrestrial carbon uptake10, the surface warming response is reduced to 1.1 ± 0.5 K for every 1,000 Pg of carbon emitted, but this modification is unlikely to significantly affect how the climate response changes over time. We suggest that our theoretical framework may be used to diagnose the global warming response in climate models and mechanistically understand the differences between their projections.
  32. 2017: Medhaug, Iselin, et al. “Reconciling controversies about the ‘global warming hiatus’.” Nature 545.7652 (2017): 41. Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the ‘global warming hiatus’, caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of ‘hiatus’ and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.
  33. 2018: Lewis, Nicholas, and Judith Curry. “The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity.” Journal of Climate 2018 (2018). Energy budget estimates of equilibrium climate sensitivity (ECS) and transient climate response (TCR) are derived based on the best estimates and uncertainty ranges for forcing provided in the IPCC Fifth Assessment Report (AR5). Recent revisions to greenhouse gas forcing and post-1990 ozone and aerosol forcing estimates are incorporated and the forcing data extended from 2011 to 2016. Reflecting recent evidence against strong aerosol forcing, its AR5 uncertainty lower bound is increased slightly. Using an 1869–82 base period and a 2007–16 final period, which are well matched for volcanic activity and influence from internal variability, medians are derived for ECS of 1.50 K (5%–95% range: 1.05–2.45 K) and for TCR of 1.20 K (5%–95% range: 0.9–1.7 K). These estimates both have much lower upper bounds than those from a predecessor study using AR5 data ending in 2011. Using infilled, globally complete temperature data give slightly higher estimates: a median of 1.66 K for ECS (5%–95% range: 1.15–2.7 K) and 1.33 K for TCR (5%–95% range: 1.0–1.9 K). These ECS estimates reflect climate feedbacks over the historical period, assumed to be time invariant. Allowing for possible time-varying climate feedbacks increases the median ECS estimate to 1.76 K (5%–95% range: 1.2–3.1 K), using infilled temperature data. Possible biases from non–unit forcing efficacy, temperature estimation issues, and variability in sea surface temperature change patterns are examined and found to be minor when using globally complete temperature data. These results imply that high ECS and TCR values derived from a majority of CMIP5 climate models are inconsistent with observed warming during the historical period.

 

 

 

 

 

GEOTHERMAL HEAT BIBLIOGRAPHY

  1. 1968: Weyl, Peter K. “The role of the oceans in climatic change: A theory of the ice ages.” Causes of climatic change. American Meteorological Society, Boston, MA, 1968. 37-62. Changes in the surface salinity distribution in the World Ocean, by changing the extent of sea ice in the North Atlantic and Antarctic, can lead to climatic change. By reducing the water vapor flux across Central America, the salinity of the North Atlantic is reduced. If this change persists over a sufficient length of time, a glacial climate could be initiated. An examination of the “Little Ice Age” tends to confirm this hypothesis. A return to an interglacial climate may be the result of overextension of glaciers followed by stagnation of the bottom water. Stagnation is terminated by geothermal heating at the ocean floor, followed by vertical mixing of the warmed, saltier water into the subarctic gyre of the North Atlantic. This, in turn, results in a reduction of sea ice and in climatic warming.
  2. 1978: Bickle, M. J. “Heat loss from the Earth: a constraint on Archaean tectonics from the relation between geothermal gradients and the rate of plate production.” Earth and Planetary Science Letters 40.3 (1978): 301-315. The models suggested for the oceanic lithosphere which best predict oceanic heat flow and depth profiles are the constant thickness model and a model in which the lithosphere thickens away from the ridge with a heat source at its base. The latter is considered to be more physically realistic. Such a model, constrained by the observed oceanic heat flow and depth profiles and a temperature at the ridge crest of between 1100°C and 1300°C, requires a heat source at the base of the lithosphere of between 0.5 and 0.9 h.f.u., thermal conductivities for the mantle between 0.005 and 0.0095 cal cm−1 °C−1 s−1 and a coefficient of thermal expansion at 840°C between 4.1 × 10−5 and 5.1 × 10−5°C−1. Plate creation and subduction are calculated to dissipate about 45% of the total earth heat loss for this model. The efficiency of this mechanism of heat loss is shown to be strongly dependent on the magnitude of the basal heat source. A relation is derived for total earth heat loss as a function of the rate of plate creation and the amount of heat transported to the base of plates. The estimated heat transport to the base of the oceanic lithosphere is similar to estimates of mantle heat flow into the base of the continental lithosphere. If this relation existed in the past and if metamorphic conditions in late Archaean high-grade terrains can be used to provide a maximum constraint on equilibrium Archaean continental thermal gradients, heat flow into the base of the lithosphere in the late Archaean must have been less than about 1.2–1.5 h.f.u. The relation between earth heat loss, the rate of plate creation and the rate of heat transport to the base of the lithosphere suggests that a significant proportion of the heat loss in the Archaean must have taken place by the processes of plate creation and subduction. The Archaean plate processes may have involved much more rapid production of plates only slightly thinner than at present.
  3. 1980: Sclater, JjG, C. Jaupart, and D_ Galson. “The heat flow through oceanic and continental crust and the heat loss of the Earth.” Reviews of Geophysics 18.1 (1980): 269-311. The principal objective of this paper is to present a simple and self‐consistent review of the basic physical processes controlling heat loss from the earth. To accomplish this objective, we give a short summary of the oceanic and continental data and compare and contrast the respective mechanisms of heat loss. In the oceans we concentrate on the effect of hydrothermal circulation, and on the continents we consider in some detail a model relating surface heat flow to varying depth scales for the distribution of potassium, thorium, and uranium. From this comparison we conclude that the range in possible geotherms at depths below 100 to 150 km under continents and oceans overlaps and that the thermal structure beneath an old stable continent is indistinguishable from that beneath an ocean were it at equilibrium. Oceans and continents are part of the same thermal system. Both have an upper rigid mechanical layer where heat loss is by conduction and a lower thermal boundary layer where convection is dominant. The simple conductive definition of the plate thickness is an oversimplification. The observed distribution of area versus age in the ocean allows us to investigate the dominant mechanism of heat loss which is plate creation. This distribution and an understanding of the heat flow through oceans and continents can be used to calculate the heat loss of the earth. This heat loss is 1013 cal/s (4.2 × 1013W) of which more than 60% results from the creation of oceanic plate. The relation between area and age of the oceans is coupled to the ridge and subducting slab forces that contribute to the driving mechanism for plate motions. These forces are self‐regulating and maintain the rate of plate generation required to achieve a balance between heat loss and heat generation.
  4. 1981: Sclater, John G., Barry Parsons, and Claude Jaupart. “Oceans and continents: similarities and differences in the mechanisms of heat loss.” Journal of Geophysical Research: Solid Earth86.B12 (1981): 11535-11552. The principal objective of this paper is to present a simple and self‐consistent review of the basic physical processes controlling heat loss from the earth. To accomplish this objective, we give a short summary of the oceanic and continental data and compare and contrast the respective mechanisms of heat loss. In the oceans we concentrate on the effect of hydrothermal circulation, and on the continents we consider in some detail a model relating surface heat flow to varying depth scales for the distribution of potassium, thorium, and uranium. From this comparison we conclude that the range in possible geotherms at depths below 100 to 150 km under continents and oceans overlaps and that the thermal structure beneath an old stable continent is indistinguishable from that beneath an ocean were it at equilibrium. Oceans and continents are part of the same thermal system. Both have an upper rigid mechanical layer where heat loss is by conduction and a lower thermal boundary layer where convection is dominant. The simple conductive definition of the plate thickness is an oversimplification. The observed distribution of area versus age in the ocean allows us to investigate the dominant mechanism of heat loss which is plate creation. This distribution and an understanding of the heat flow through oceans and continents can be used to calculate the heat loss of the earth. This heat loss is 1013 cal/s (4.2 × 1013W) of which more than 60% results from the creation of oceanic plate. The relation between area and age of the oceans is coupled to the ridge and subducting slab forces that contribute to the driving mechanism for plate motions. These forces are self‐regulating and maintain the rate of plate generation required to achieve a balance between heat loss and heat generation.  [FULL TEXT]
  5. 1984: Abbott, Dallas Helen, and S. E. Hoffman. “Archaean plate tectonics revisited 1. Heat flow, spreading rate, and the age of subducting oceanic lithosphere and their effects on the origin and evolution of continents.” Tectonics 3.4 (1984): 429-448. A simple model which relates the rate of seafloor creation and the age of the oceanic lithosphere at subduction to the rate of continental accretion can successfully explain the apparent differences between Archaean and Phanerozoic terrains in terms of plate tectonics. The model has been derived using the following parameters: (1) the spreading rate at mid‐ocean ridges; (2) the age of the oceanic lithosphere at the time of subduction; (3) the area‐age distribution of the seafloor; (4) the continental surface area as a fraction of the total surface area of the earth; and (5) the erosion rate of continents as a function of continental surface area and the total number of continental masses. Observations in Phanerozoic terranes suggest that there are profound differences in the nature and volume of subduction zone igneous activity depending upon the age of the oceanic lithosphere being subducted and the nature of the overriding plate (that is, either continental or oceanic). The subduction of young oceanic lithosphere (less than 50 m.y. old) which is thermally buoyant appears to result in a reduced volume of igneous activity. Most of the igneous activity caused by subduction of young oceanic lithosphere is either siliceous plutonism or bimodal tholeiitic‐rhyolitic volcanism. When very young lithosphere is being subducted (<30 m.y. old), volcanism appears to cease. The subduction of old oceanic lithosphere (>50 m.y. old) appears to result in greater volumes of igneous activity, including the eruption of andesitic magmas. Thus andesites could only begin to be abundant in the rock record when older oceanic lithosphere began to be subducted. Our model predicts that as the earth aged and as heat flow from the interior of the earth diminished, the proportion of old oceanic lithosphere being subducted increased, fundamentally changing the nature of subduction zone igneous activity and the rate of continental accretion. If the subduction of old oceanic lithosphere results in an 8–10 times greater volume of subduction zone magmatism, our model predicts or explains all of the following observed features of earth history: (1) Archaean terranes appear to record two periods of rapid continental accretion, between 3.8 and 3.5 b.y. ago and between 3.1 and 2.6 b.y. ago; (2) there are very few differences and many marked similarities between rocks from Archaean terranes and equivalent rocks from Phanerozoic terranes; (3) the total continental area appears to have remained essentially constant for the past 2 b.y. (4) Archaean andesites are comparatively rare, and the relative abundances of mafic and siliceous rocks appear to change during the Archaean and the Proterozoic, with siliceous volcanics becoming proportionately more abundant in the geologic record with time; (5) plutonic tonalites and trondhjemites appear to have been relatively much more abundant during the Archaean. Plate tectonics is thus shown to have evolved over time due to a gradually decreasing rate of creation of oceanic lithosphere, meaning that Archaean tectonics and Phanerozoic tectonics are but two points on an evolutionary continuum.  [FULL TEXT]
  6. 1984: Abbott, Dallas Helen, and S. E. Hoffman. “Archaean plate tectonics revisited 1. Heat flow, spreading rate, and the age of subducting oceanic lithosphere and their effects on the origin and evolution of continents.” Tectonics 3.4 (1984): 429-448. A simple model which relates the rate of seafloor creation and the age of the oceanic lithosphere at subduction to the rate of continental accretion can successfully explain the apparent differences between Archaean and Phanerozoic terrains in terms of plate tectonics. The model has been derived using the following parameters: (1) the spreading rate at mid‐ocean ridges; (2) the age of the oceanic lithosphere at the time of subduction; (3) the area‐age distribution of the seafloor; (4) the continental surface area as a fraction of the total surface area of the earth; and (5) the erosion rate of continents as a function of continental surface area and the total number of continental masses. Observations in Phanerozoic terranes suggest that there are profound differences in the nature and volume of subduction zone igneous activity depending upon the age of the oceanic lithosphere being subducted and the nature of the overriding plate (that is, either continental or oceanic). The subduction of young oceanic lithosphere (less than 50 m.y. old) which is thermally buoyant appears to result in a reduced volume of igneous activity. Most of the igneous activity caused by subduction of young oceanic lithosphere is either siliceous plutonism or bimodal tholeiitic‐rhyolitic volcanism. When very young lithosphere is being subducted (<30 m.y. old), volcanism appears to cease. The subduction of old oceanic lithosphere (>50 m.y. old) appears to result in greater volumes of igneous activity, including the eruption of andesitic magmas. Thus andesites could only begin to be abundant in the rock record when older oceanic lithosphere began to be subducted. Our model predicts that as the earth aged and as heat flow from the interior of the earth diminished, the proportion of old oceanic lithosphere being subducted increased, fundamentally changing the nature of subduction zone igneous activity and the rate of continental accretion. If the subduction of old oceanic lithosphere results in an 8–10 times greater volume of subduction zone magmatism, our model predicts or explains all of the following observed features of earth history: (1) Archaean terranes appear to record two periods of rapid continental accretion, between 3.8 and 3.5 b.y. ago and between 3.1 and 2.6 b.y. ago; (2) there are very few differences and many marked similarities between rocks from Archaean terranes and equivalent rocks from Phanerozoic terranes; (3) the total continental area appears to have remained essentially constant for the past 2 b.y. (4) Archaean andesites are comparatively rare, and the relative abundances of mafic and siliceous rocks appear to change during the Archaean and the Proterozoic, with siliceous volcanics becoming proportionately more abundant in the geologic record with time; (5) plutonic tonalites and trondhjemites appear to have been relatively much more abundant during the Archaean. Plate tectonics is thus shown to have evolved over time due to a gradually decreasing rate of creation of oceanic lithosphere, meaning that Archaean tectonics and Phanerozoic tectonics are but two points on an evolutionary continuum.  [FULL TEXT]
  7. 1984: Abbott, Dallas H. “Archaean plate tectonics revisited 2. Paleo‐sea level changes, continental area, oceanic heat loss and the area‐age distribution of the ocean basins.” Tectonics 3.7 (1984): 709-722. In a previous paper, we derived plate tectonic models for continental accretion from the early Archaean (3800 m.y. B.P.) until the present. The models are dependent upon the number of continental masses, the seafloor creation rate and the continental surface area. The models can be tested by examining their predictions for three key geological indicators: sea level changes, stable isotopic evolution (e.g., continental surface area), and oceanic heat loss. Models of paleo‐sea level changes produced by the accretion of the continents reproduce the following features of earth history: (1) greater continental emergence (lower sea level) during the Archaean than the Proterozoic; (2) maximum continental emergence about 3000 m.y. B.P.; and (3) maximum continental submergence (high sea level) from 30 to 125 m.y. B.P. The high sea level stand between 380–525 m.y. B.P. is only weakly reproduced, probably due to the simplified nature of the model. Changes in the number of continental masses can result in tectonic erosion or accretion of the continents, with resulting changes in sea level. The two major transgressions in the Phanerozoic, although still requiring some increase in the total terrestrial heat loss, can be sucessfully explained by a combination of increases in continental surface area and in seafloor creation rate. Changes in the total heat loss of the ocean basins predicted by our plate tectonic models closely parallel the changes in terrestrial heat production predicted by Wasserburg et al. (1964). This result is consistent with thermal history models which assume whole mantle convection. The history of changes in continental surface area predicted by our best continental accretion models lies within the ranges of estimated continental surface area derived from independent geochemical models of isotope evolution.  [FULL TEXT]
  8. 1984: Gargett, A. E. “Vertical eddy diffusivity in the ocean interior.” Journal of Marine Research 42.2 (1984): 359-393. Vertical turbulent transport of density (mass) in a system of stable stratification ∂p/∂z < 0 (z positive upward) is often modelled by an “eddy” diffusivity Kv ≡ −/(∂p/∂z), normally assumed to be constant. Recent evidence from stratified lakes, fjords and oceans suggests that Kv may be more accurately described as a decreasing function of buoyancy frequency N ≡ (–g(o)–1 (∂p/∂z))1/2. A main purpose of this paper is to review available estimates of Kv from a variety of stratified geophysical systems. Particular emphasis is placed upon the degree to which these estimates are dependent upon underlying models used to derive values for Kv from observable quantities. Most techniques reveal a disagreeable degree of model-dependence, frequently providing only upper bounds to the magnitude of Kv. I have coupled the functional dependence which emerges from the least model-dependent of available techniques with ensemble-averaged values of oceanic turbulent kinetic energy dissipation rate per unit mass ε as a function of N, and show that the resulting parameterization for Kv is consistent with a wide range of present oceanic data. Finally, brief re-examination of a simple vertical advection/diffusion model of thermohaline circulation illustrates possible dynamical significance of a stratification-dependent Kv.
  9. 1986: Joyce, Terrence M., Bruce A. Warren, and Lynne D. Talley. “The geothermal heating of the abyssal subarctic Pacific Ocean.” Deep Sea Research Part A. Oceanographic Research Papers 33.8 (1986): 1003-1015. Recent deep CTD-O2 measurements in the abyssal North Pacific along 175°W, 152°W, and 47°N indicate large-scale changes in the O-S characteristics in the deepest kilometer of the water column. Geothermal heat flux from the abyssal sediments can be invoked as the agent for causing large-scale modification of abyssal temperatures (but not salinities) in the subarctic Pacific Ocean. East-west and north-south thermal age differences of about 100 years are inferred using a spatially uniform geothermal heat flux of 5 x 10-2 WrmW m-2.
  10. 1988: Warren, Bruce A., and W. Brechner Owens. “Deep currents in the central subarctic Pacific Ocean.” Journal of Physical Oceanography 18.4 (1988): 529-551.Sections of closely spaced CTD stations along Longs. 165°W, 175°W and 175°E, in combination with 14-month current records from the central longitude, define two deep, nearly zonal currants, with speed increasing upward, in the subarctic Pacific. One flows eastward above the Aleutian Rise and Aleutian Trench, and appears to be a concentration of geostrophic flow forced by the bottom topography. The other flows westward along the Aleutian Island Arc, and is the northern-boundary current predicted by deep-circulation theory. Both currents reach to the sea surface, the boundary current being simply the deep part of the Alaskan Stream. The current records were too few to permit better than rough estimates of volume transports but to the extent that they could be combined with thermal-wind calculations they suggest, at 175°W, (1) a transport of 28 × 106 m3 s−1 for the Alaskan Stream, of whch 5 × 106 m3 s−1was found below 1500 m, and (2) a transport of around 20 × 1O6 m3 s−1 for the eastward jet, of which some 5 × 106–10 × 106 m3 s−1 was estimated below 1500 m. The deep water in the area surveyed was so nearly homogeneous that salinity, oxygen, and nutrients could generally be calculated from potential temperature within measurement error, these additional properties were therefore of only limited use in tracing the deep flow. However, temperature maps at depths of 2 and 4 km demonstrate continuity of the two deep currents across the 60° of longitude between Japan and the Gulf of Alaska. The eastward jet can be tracked back through the Emperor Seamount chain to the Zenkevich Rise off Japan, while the deep Alaskan Stream can be followed downstream to Long. 180°, where it separates from the boundary and flows due westward to the Emperor Seamount chain, which it rounds to the north, prior to its becoming the southward flowing deep western boundary current of the subarctic Pacific. Other details of the water-property fields are described in the text, and comparisons are made with the deep subpolar boundary flow of the North Atlantic.
  11. 1989: Roemmich, Dean, and Tracy McCallister. “Large scale circulation of the North Pacific Ocean.” Progress in Oceanography 22.2 (1989): 171-204. Roemmich, Dean, and Tracy McCallister. “Large scale circulation of the North Pacific Ocean.” Progress in Oceanography 22.2 (1989): 171-204. A least squares inversion procedure is used to estimate the large scale cirulation and transport of the subtropical and subpolar North Pacific Ocean from a modern data set of long hydrographic transects. Initially a deep surface of known motion is specified using information derived from abyssal property distributions, moored current meter observations, and basin scale topographic constraints. A geostrophic solution is obtained which conserves mass while devaiting as little as possible in a least squares sense from the initial field. The sensitivity of the solution is tested with regard to changes in the initial field and to the addition of conservation constraints in layers. It is found that about 10 Sv of abyssal water flows northward across 24°N, principally between the dateline and 160°E, in the deepest part of the Northwest Pacific Basin. The flow turns westward across 152°E and then mostly northward again near the Izu-Ogasawara Ridge and the coast of Japan. It then feeds a strong deep anti-cyclonic recirculation beneath the cyclonic subpolar gyre in the Northwest Pacific Basin. The abyssal waters near the western boundary region are found to have a strong component of flow that is upward and across isopycnal surfaces. Here, the abyssal waters complete an important loop in the global thermohaline circulation, entering as bottom water from the South Pacific and returning southward in a less dense and shallower layer. Deep flow into the Northeast Pacific Basin, and circulation within that basin, appear to be weak, making it remote from the main pathway of deep water renewal.The circulation of the subtropical and subpolar gyres dominates transport in the upper layers. The subtropical gyre appears to penetrate to about 1500–2000 m on both sides of the Izu-Ogasawara Ridge, which blocks deeper flow between the Philippine Basin and the Northwest Pacific Basin. The Kuroshio is estimated to carry about 32 Sv northward in the East China Sea. Farther east, as the thermocline slopes upward toward the eastern boundary, the eastward flow is even shallower. In terms of eddy activity, three regimes are observed at 24°N. Peak-to-rough eddy fluctuations in geostrophically balanced sea level diminish from about 40 cm in the west to about 5 cm in the east. Overall, the western boudary of the ocean is about 25 cm higher than the eastern boundary in the 24°N section. Patterns of heat and freshwater flux determined in the North Pacific are in accord with those from air-sea heat flux estimates and hydrological data although the magnitudes are in some cases different. There is large heat loss in the western ocean amounting to about 9.6 × 1014 W and modest heat gain elsewhere. Heat transport across 24°N is estimated to be 7.5 × 1014 W. The subpolar ocean has a large excess of precipitation and runoff over evaporation, about 5.6 × 105 m3s−3 north of 35°N, while in the subtropics there is excess evaporation, about 2.7 × 105 m3s−1 between 24°N and 35°N.
  12. 1991: Duncan, Robert A., and M. A. Richards. “Hotspots, mantle plumes, flood basalts, and true polar wander.” Reviews of Geophysics 29.1 (1991): 31-50. Persistent, long‐lived, stationary sites of excessive mantle melting are called hotspots. Hotspots leave volcanic trails on lithospheric plates passing across them. The global constellation of fixed hotspots thus forms a convenient frame of reference for plate motions, through the orientations and age distributions of volcanic trails left by these melting anomalies. Hotspots appear to be maintained by whole‐mantle convection, in the form of upward flow through narrow plumes. Evidence suggests that plumes are deflected little by horizontal flow of the upper mantle. Mantle plumes are largely thermal features and arise from a thermal boundary layer, most likely the mantle layer just above the core‐mantle boundary. Experiments and theory show that gravitational instability drives flow, beginning with the formation of diapirs. Such a diapir will grow as it rises, fed by flow through the trailing conduit and entrainment of surrounding mantle. The structure thus develops a large, spherical plume head and a long, narrow tail. On arrival at the base of the lithosphere the plume head flattens and melts by decompression, producing enormous quantities of magma which erupt in a short period. These are flood basalt events that have occurred on continents and in ocean basins and that signal the beginning of major hotspot tracks. The plume‐supported hotspot reference frame is fixed in the steady state convective flow of the mantle and is independent of the core‐generated (axial dipole) paleomagnetic reference frame. Comparison of plate motions measured in the two frames reveals small but systematic differences that indicate whole‐mantle motion relative to the Earth’s spin axis. This is termed true polar wander and has amounted to some 12° since early Tertiary time. The direction and magnitude of true polar wander have varied sporadically through the Mesozoic, probably in response to major changes in plate motions (particularly subduction zone location) that change the planet’s moments of inertia.
  13. 1992: Mahoney, J., et al. “Southwestern limits of Indian Ocean Ridge Mantle and the origin of low 206Pb/204Pb mid‐ocean ridge basalt: Isotope systematics of the central Southwest Indian Ridge (17°–50° E).” Journal of Geophysical Research: Solid Earth 97.B13 (1992): 19771-19790. Basalts from the Southwest Indian Ridge reflect a gradual, irregular isotopic transition in the MORB (mid‐ocean ridge basalt) source mantle between typical Indian Ocean‐type compositions on the east and Atlantic‐like ones on the west. A probable southwestern limit to the huge Indian Ocean isotopic domain is indicated by incompatible‐element‐depleted MORBs from 17° to 26°E, which possess essentially North Atlantic‐ or Pacific‐type signatures. Superimposed on the regional along‐axis gradient are at least three localized types of isotopically distinct, incompatible‐element‐enriched basalts. One characterizes the ridge between 36° and 39°E, directly north of the proposed Marion hotspot, and appears to be caused by mixing between hotspot and high ∈Nd, normal MORB mantle; oceanic island products of the hotspot itself exhibit a very restricted range of isotopic values (e.g., 206Pb/204Pb = 18.5–18.6) which are more MORB‐like than those of other Indian Ocean islands. Between 39° and 41°E, high Ba/Nb lavas with unusually low 206Pb/204Pb (16.87–17.44) and ∈Nd (−4 to +3) are dominant; these compositions are not only unlike those of the Marion (or any other) hotspot but also are unique among MORBs globally. Incompatible‐elementenriched lavas in the vicinity of the Indomed Fracture Zone (∼46°E) differ isotopically from those at 39°–41°E, 36°–39°E, and both the Marion and Crozet hotspots. Thus, no simple model of ridgeward flow of plume mantle can explain the presence or distribution of all the incompatible‐element‐enriched MORBs on the central Southwest Indian Ridge. The upper mantle at 39°–41°E, in particular, may contain stranded continental lithosphere, thermally eroded from Indo‐Madagascar in the middle Cretaceous. Alternatively, the composition of the; Marion hotspot must be grossly heterogeneous in space and/or time, and one of its intrinsic components must have substantially lower 206Pb/204Pb than yet measured for any hotspot. The origin of the broadly similar but much less extreme isotopic signatures of MORBs throughout most of the Indian Ocean could be related to the initiation of the Marion, Kerguelen, and Crozet hotspots, which together may have formed a more than 4400‐km‐long band of juxtaposed plume heads beneath the nearly stationary lithosphere of prebreakup Gondwana.
  14. 1993: Müller, R. Dietmar, Jean-Yves Royer, and Lawrence A. Lawver. “Revised plate motions relative to the hotspots from combined Atlantic and Indian Ocean hotspot tracks.” Geology21.3 (1993): 275-278. We use an updated model for global relative plate motions during the past 130 m.y. together with a compilation of bathymetry and recently published radiometric dates of major hotspot tracks to derive a plate-motion model relative to major hotspots in the Atlantic and Indian oceans. Interactive computer graphics were used to find the best fit of dated hotspot tracks on the Australian, Indian, African, and North and South American plates relative to present-day hotspots assumed fixed in the mantle. One set of rotation parameters can be found that satisfies all data constraints back to chron 34 (84 Ma) and supports little motion between the major hotspots in this hemisphere. For times between 130 and 84 Ma, the plate model is based solely on the trails of the Tristan da Cunha and Great Meteor hotspots. This approach results in a location of the Kerguelen hotspot distinct from and south of the Rajmahal Traps for this time interval. Between 115 and 105 Ma, our model locates the hotspot underneath the southern Kerguelen Plateau, which is compatible with an age estimate of this part of the plateau of 115-95 Ma. Our model suggests that the 85°E ridge between lat 10°N and the Afanasiy Nikitin seamounts may have been formed by a hotspot now located underneath the eastern Conrad rise.
  15. 1993: Pollack, Henry N., Suzanne J. Hurter, and Jeffrey R. Johnson. “Heat flow from the Earth’s interior: analysis of the global data set.” Reviews of Geophysics 31.3 (1993): 267-280. We present a new estimate of the Earth’s heat loss based on a new global compilation of heat flow measurements comprising 24,774 observations at 20,201 sites. On a 5° × 5° grid, the observations cover 62% of the Earth’s surface. Empirical estimators, referenced to geological map units and derived from the observations, enable heat flow to be estimated in areas without measurements. Corrections for the effects of hydrothermal circulation in the oceanic crust compensate for the advected heat undetected in measurements of the conductive heat flux. The mean heat flows of continents and oceans are 65 and 101 mW m−2, respectively, which when areally weighted yield a global mean of 87 mW m−2 and a global heat loss of 44.2 × 1012 W, an increase of some 4–8% over earlier estimates. More than half of the Earth’s heat loss comes from Cenozoic oceanic lithosphere. A spherical harmonic analysis of the global heat flow field reveals strong sectoral components and lesser zonal strength. The spectrum principally reflects the geographic distribution of the ocean ridge system. The rate at which the heat flow spectrum loses strength with increasing harmonic degree is similar to the decline in spectral strength exhibited by the Earth’s topography. The spectra of the gravitational and magnetic fields fall off much more steeply, consistent with field sources in the lower mantle and core, respectively. Families of continental and oceanic conductive geotherms indicate the range of temperatures existing in the lithosphere under various surface heat flow conditions. The heat flow field is very well correlated with the seismic shear wave velocity distribution near the top of the upper mantle. [FULL TEXT]
  16. 1994: Stein, Carol A., and Seth Stein. “Constraints on hydrothermal heat flux through the oceanic lithosphere from global heat flow.” Journal of Geophysical Research: Solid Earth 99.B2 (1994): 3081-3095. A significant discrepancy exists between the heat flow measured at the seafloor and the higher values predicted by thermal models of the cooling lithosphere. This discrepancy is generally interpreted as indicating that the upper oceanic crust is cooled significantly by hydrothermal circulation. The magnitude of this heat flow discrepancy is the primary datum used to estimate the volume of hydrothermal flow, and the variation in the discrepancy with lithospheric age is the primary constraint on how the hydrothermal flux is divided between near‐ridge and off‐ridge environments. The resulting estimates are important for investigation of both the thermal structure of the lithosphere and the chemistry of the oceans. We reevaluate the magnitude and age variation of the discrepancy using a global heat flow data set substantially larger than in earlier studies, and the GDH1 (Global Depth and Heat flow) model that better predicts the heat flow. We estimate that of the predicted global oceanic heat flux of 32×1012 W, 34% (11×1012 W) occurs by hydrothermal flow. Approximately 30% of the hydrothermal heat flux occurs in crust younger than 1 Ma, so the majority of this flux is off‐ridge. These hydrothermal heat flux estimates are upper bounds, because heat flow measurements require sediment at the site and so are made preferentially at topographic lows, where heat flow may be depressed. Because the water temperature for the near‐ridge flow exceeds that for the off‐ridge flow, the near‐ridge water flow will be even a smaller fraction of the total water flow. As a result, in estimating fluxes from geochemical data, use of the high water temperatures appropriate for the ridge axis may significantly overestimate the heat flux for an assumed water flux or underestimate the water flux for an assumed heat flux. Our data also permit improved estimates of the “sealing” age, defined as the age where the observed heat flow approximately equals that predicted, suggesting that hydrothermal heat transfer has largely ceased. Although earlier studies suggested major differences in sealing ages for different ocean basins, we find that the sealing ages for the Atlantic, Pacific, and Indian oceans are similar and consistent with the sealing age for the entire data set, 65±10 Ma. The previous inference of a young (∼20 Ma) sealing age for the Pacific appears to have biased downward several previous estimates of the global hydrothermal flux. The heat flow data also provide indirect evidence for the mechanism by which the hydrothermal heat flux becomes small, which has often been ascribed to isolation of the igneous crust from seawater due to the hydraulic conductivity of the intervening sediment. We find, however, that even the least sedimented sites show the systematic increase of the ratio of observed to predicted heat flow with age, although the more sedimented sites have a younger sealing age. Moreover, the heat flow discrepancy persists at heavily sedimented sites until ∼50 Ma. It thus appears that ∼100–200 m of sediment is neither necessary nor sufficient to stop hydrothermal heat transfer. We therefore conclude that the age of the crust is the primary control on the fraction of heat transported by hydrothermal flow and that sediment thickness has a lesser effect. This inference is consistent with models in which hydrothermal flow decreases with age due to reduced crustal porosity and hence permeability.
  17. 1996: Thompson, Luanne, and Gregory C. Johnson. “Abyssal currents generated by diffusion and geothermal heating over rises.” Deep Sea Research Part I: Oceanographic Research Papers 43.2 (1996): 193-211. A continuously stratified (in both salinity and temperature) diffusive time-dependent one-dimensional f-plane model over a sloping bottom is constructed. The model is used to investigate the role of mixing of density near the bottom on large-scale abyssal flow near mid-ocean rises. For realistic abyssal values, both geothermal heating from the bottom and diffusion can be important to the dynamics of flow over mid-ocean rises. When diffusion dominates, buoyancy is transported toward the bottom and the θS (potential temperature-salinity) relation remains nearly linear. When geothermal heating dominates, the θSrelation hooks near the bottom and a convectively driven mixed layer forms. Both effects reduce the density and stratification near the bottom. In contrast, bottom-intensified diffusion has the same effect near the bottom but results in an increase of density and stratification some distance above the bottom. If the bottom slopes, a horizontal density gradient results, setting up a geostrophic, bottom-intensified, along-slope flow that can effect mass transport. Evidence of the importance of these processes is found in the abyssal Pacific. Just over the western flank of the East Pacific Rise, a 700–900 m thick layer of low N2(buoyancy frequency) is warmer, saltier, and lighter than interior water at the same depth. This layer is described with CTD data from recent hydrographic sections at nominal latitudes 15°S and 10°N. If the interior is motionless, this low N2 layer transports 4 and 8 × 106 m3 s−1 equatorward above the western flank of the rise at 15°S and 10°N, respectively. This equatorward current, a direct result of diffusion and heating over a sloping sea-floor, has a volume transport comparable to those of the deep western boundary current at these latitudes.
  18. 2001: Scott, Jeffery R., Jochem Marotzke, and Alistair Adcroft. “Geothermal heating and its influence on the meridional overturning circulation.” Journal of Geophysical Research: Oceans 106.C12 (2001): 31141-31154. The effect of geothermal heating on the meridional overturning circulation is examined using an idealized, coarse‐resolution ocean general circulation model. This heating is parameterized as a spatially uniform heat flux of 50 m W m−2 through the (flat) ocean floor, in contrast with previous studies that have considered regional circulation changes caused by an isolated hot spot or a series of plumes along the Mid‐Atlantic Ridge. In our model results the equilibrated response is largely advective: a deep perturbation of the meridional overturning cell on the order of several sverdrups is produced, connecting with an upper level circulation at high latitudes, allowing the additional heat to be released to the atmosphere. Rising motion in the perturbation deep cell is concentrated near the equator. The upward penetration of this cell is limited by the thermocline, analogous to the role of the stratosphere in limiting the upward penetration of convective plumes in the atmosphere. The magnitude of the advective response is inversely proportional to the deep stratification; with a weaker background meridional overturning circulation and a less stratified abyss the overturning maximum of the perturbation deep cell is increased. This advective response also cools the low‐latitude thermocline. The qualitative behavior is similar in both a single‐hemisphere and a double‐hemisphere configuration. In summary, the anomalous circulation driven by geothermal fluxes is more substantial than previously thought. We are able to understand the structure and strength of the response in the idealized geometry and further extend these ideas to explain the results of Adcroft et al. [2001], where the impact of geothermal heating was examined using a global configuration. [FULL TEXT]
  19. 2001: Adcroft, Alistair, Jeffery R. Scott, and Jochem Marotzke. “Impact of geothermal heating on the global ocean circulation.” Geophysical Research Letters 28.9 (2001): 1735-1738. The response of a global circulation model to a uniform geothermal heat flux of 50 mW m−2 through the sea floor is examined. If the geothermal heat input were transported upward purely by diffusion, the deep ocean would warm by 1.2°C. However, geothermal heating induces a substantial change in the deep circulation which is larger than previously assumed and subsequently the warming of the deep ocean is only a quarter of that suggested by the diffusive limit. The numerical ocean model responds most strongly in the Indo‐Pacific with an increase in meridional overturning of 1.8 Sv, enhancing the existing overturning by approximately 25%.  [FULL TEXT]
  20. 2003: Bai, Wuming, Wenyue Xu, and Robert P. Lowell. “The dynamics of submarine geothermal heat pipes.” Geophysical Research Letters 30.3 (2003). To better understand natural two‐phase hydrothermal systems, we have constructed one‐dimensional heat‐pipe solutions for NaCl‐H2O fluids and explored the effects of basal heat flux and permeability on their behavior. For seafloor conditions, saline brines form quickly at the base of the heat pipe; and in some cases halite is precipitated. NaCl‐H2O heat pipes may become liquid or vapor dominated but, in contrast to their pure‐water counterparts, often do not achieve steady state. When steady state solutions do exist, they are characterized either by broad, weak counter‐flow or by vigorous counter‐flow across a thin layer. The latter behavior may be analogous to that occurring in the Salton Sea Geothermal System, California.
  21. 2004: Fukasawa, Masao, et al. “Bottom water warming in the North Pacific Ocean.” Nature 427.6977 (2004): 825. Observations of changes in the properties of ocean waters have been restricted to surface1 or intermediate-depth waters2,3, because the detection of change in bottom water is extremely difficult owing to the small magnitude of the expected signals. Nevertheless, temporal changes in the properties of such deep waters across an ocean basin are of particular interest, as they can be used to constrain the transport of water at the bottom of the ocean and to detect changes in the global thermohaline circulation. Here we present a comparison of a trans-Pacific survey completed in 1985 (refs 45) and its repetition in 1999 (ref. 6). We find that the deepest waters of the North Pacific Ocean have warmed significantly across the entire width of the ocean basin. Our observations imply that changes in water properties are now detectable in water masses that have long been insulated from heat exchange with the atmosphere.
  22. 2005: Oskooi, Behrooz, et al. “The deep geothermal structure of the Mid-Atlantic Ridge deduced from MT data in SW Iceland.” Physics of the Earth and Planetary Interiors 150.1-3 (2005): 183-195. Iceland is very active tectonically as it is crossed by the Mid-Atlantic Ridge and its associated rift zones and transform faults. The high-temperature geothermal systems are located within the neo-volcanic zone. A detailed comparison of the main features of the resistivity models and well data in exploited geothermal fields has shown that the resistivity structure of Iceland is mainly controlled by alteration mineralogy. In areas where the geothermal circulation and related alteration take place at depths of more than 1.5 km, the investigation depth of the DC and TEM methods is inadequate and the MT method appears to be the most suitable survey method. MT soundings were carried out to determine the deep structure between two neighboring Quaternary geothermal fields: the Hengill volcanic complex and the Brennisteinsfjoll geothermal system, both known as high-temperature systems. MT data were analyzed and modeled using 1D and 2D inversion schemes. Our model of electrical conductivity can be related to secondary mineralization from geothermal fluids. At shallow depths, the resistivity model obtained from the MT data is consistent with the general geoelectrical models of high-temperature geothermal systems in Iceland, as revealed by shallow DC and TEM surveys. The current MT results reveal the presence of an outcropping resistive layer, identified as the typical unaltered porous basalt of the upper crust. This layer is underlain by a highly conductive cap resolved as the smectite–zeolite zone. Below this cap a less conductive zone is identified as the epidote–chlorite zone. A highly conductive material has been recognized in the middle of the profile, at about 5 km depth, and has been interpreted as cooling partial melt representing the main heat source of the geothermal system. This conductor may be connected to the shallow structure through a vertical fault zone located close to the southern edge of the profile
  23. 2005: Adkins, Jess F., Andrew P. Ingersoll, and Claudia Pasquero. “Rapid climate change and conditional instability of the glacial deep ocean from the thermobaric effect and geothermal heating.” Quaternary Science Reviews 24.5-6 (2005): 581-594. Previous results from deep-sea pore fluid data demonstrate that the glacial deep ocean was filled with salty, cold water from the South. This salinity stratification of the ocean allows for the possible accumulation of geothermal heat in the deep-sea and could result in a water column with cold fresh water on top of warm salty water and with a corresponding increase in potential energy. For an idealized 4000 dbar two-layer water column, we calculate that there are ∼106 J/m2 (∼0.2 J/kg) of potential energy available when a 0.4 psu salinity contrast is balanced by a ∼2 °C temperature difference. This salt-based storage of heat at depth is analogous to Convectively Available Potential Energy (CAPE) in the atmosphere. The “thermobaric effect” in the seawater equation of state can cause this potential energy to be released catastrophically. Because deep ocean stratification was dominated by salinity at the Last Glacial Maximum (LGM), the glacial climate is more sensitive to charging this “thermobaric capacitor” and can plausibly explain many aspects of the record of rapid climate change. Our mechanism could account for the grouping of Dansgaard/Oeschger events into Bond Cycles and for the different patterns of warming observed in ice cores from separate hemispheres.
  24. 2006: Kawano, Takeshi, et al. “Bottom water warming along the pathway of lower circumpolar deep water in the Pacific Ocean.” Geophysical Research Letters 33.23 (2006). The role of the Thermo‐Haline Circulation (THC) in climate is an important aspect of the planetary response to global warming. Model studies suggest that the THC in the Atlantic Ocean is sensitive to anthropogenic climate change [Cubash and Meehl, 2001]. Recently Bryden et al. [2005] reported that the Atlantic meridional circulation had slowed by about 30% between 1957 and 2004, based on five sets of repeated trans‐Atlantic observations along 25°N. The warming trend of the global ocean [Levitus et al., 2000], decreases in the signature of North Atlantic Deep Water (NADW) in the South Pacific [Johnson et al., 1994], and the warming at mid‐depths in the Southern Ocean [Gille, 2002] could all potentially affect the THC in the Pacific Ocean. [3] Lower Circumpolar Deep Water (LCDW) formed in the Southern Ocean flows along the bottom in the Pacific Ocean as the northward component of the THC. It enters the Pacific east of New Zealand and flows northward to the North Pacific through the Samoan Passage. It upwells in the North Pacific and returns southward as modified North Pacific Deep Water (mNPDW) [Schmitz, 1996]. Repeated trans‐Pacific surveys along 47°N show that the deepest waters of the North Pacific Ocean have warmed significantly owing to a decrease in the volume of the colder portion of modified NADW, which is the upper part of LCDW [Fukasawa et al., 2004], but the relationship between this warming and reported decreases in the NADW signature in the South Pacific Ocean [Johnson et al., 1994Johnson and Orsi, 1997] is not clear. Here we analyze data collected between 2003 and 2006 by trans‐Pacific surveys along 32°S, 149°E, 24°N, and 30°N. These surveys were designed to revisit the hydrographic stations previously occupied during the World Ocean Circulation Experiment (WOCE) and thus improve our understanding of temperature changes in the deep and bottom water of the Pacific Ocean.
  25. 2006: Mullarney, Julia C., Ross W. Griffiths, and Graham O. Hughes. “The effects of geothermal heating on the ocean overturning circulation.” Geophysical research letters 33.2 (2006). We examine the response of an overturning circulation, driven by differential thermal forcing along the top horizontal boundary, to a small additional heat flux applied at the bottom horizontal boundary. The system forms a simple thermally‐driven flow that provides insight into the ocean’s meridional overturning circulation. We conclude that the additional destabilising (geothermal) heat flux tends to promote a more vigorous full‐depth overturning having approximately 10% greater volume flux than with no bottom heating. No significant change is observed in the vertical density structure. In contrast, the addition of a stabilising heat flux at the base leads to a shallow, partial‐depth circulation. The key diagnostic for the significance of the geothermal flux appears to be the ratio of the buoyancy flux supplied at the bottom to the residual buoyancy flux driving the downwelling plume through the base of the thermocline.
  26. 2006: Björk, Göran, and Peter Winsor. “The deep waters of the Eurasian Basin, Arctic Ocean: Geothermal heat flow, mixing and renewal.” Deep Sea Research Part I: Oceanographic Research Papers 53.7 (2006): 1253-1271. Hydrographic observations from four separate expeditions to the Eurasian Basin of the Arctic Ocean between 1991 and 2001 show a 300–700 m thick homogenous bottom layer. The layer is characterized by slightly warmer temperature compared to ambient, overlying water masses, with a mean layer thickness of 500±100 m and a temperature surplus of 7.0±2×10−3 °C. The layer is present in the deep central parts of the Nansen and Amundsen Basins away from continental slopes and ocean ridges and is spatially coherent across the interior parts of the deep basins. Here we show that the layer is most likely formed by convection induced by geothermal heat supplied from Earth’s interior. Data from 1991 to 1996 indicate that the layer was in a quasi steady state where the geothermal heat supply was balanced by heat exchange with a colder boundary. After 1996 there is evidence of a reformation of the layer in the Amundsen Basin after a water exchange. Simple numerical calculations show that it is possible to generate a layer similar to the one observed in 2001 in 4–5 years, starting from initial profiles with no warm homogeneous bottom layer. Limited hydrographic observations from 2001 indicate that the entire deep-water column in the Amundsen Basin is warmer compared to earlier years. We argue that this is due to a major deep-water renewal that occurred between 1996 and 2001.
  27. 2006: Kawano, Takeshi, et al. “Bottom water warming along the pathway of lower circumpolar deep water in the Pacific Ocean.” Geophysical Research Letters 33.23 (2006). Repeat trans‐Pacific hydrographic observations along the pathway of Lower Circumpolar Deep Water (LCDW) reveal that bottom water has warmed by about 0.005 to 0.01°C in recent decades. The warming is probably not from direct heating of LCDW, but is manifest as a decrease of the coldest component of LCDW evident at each hydrographic section. This result is consistent with numerical model results of warming associated with decreased bottom water formation rates around Antarctica.  [FULL TEXT]
  28. 2009: Emile-Geay, Julien, and Gurvan Madec. “Geothermal heating, diapycnal mixing and the abyssal circulation.” Ocean Science5.2 (2009): 203-217. The dynamical role of geothermal heating in abyssal circulation is reconsidered using three independent arguments. First, we show that a uniform geothermal heat flux close to the observed average (86.4 mW m−2) supplies as much heat to near-bottom water as a diapycnal mixing rate of ~10−4 m2 s−1 – the canonical value thought to be responsible for the magnitude of the present-day abyssal circulation. This parity raises the possibility that geothermal heating could have a dynamical impact of the same order. Second, we estimate the magnitude of geothermally-induced circulation with the density-binning method (Walin, 1982), applied to the observed thermohaline structure of Levitus (1998). The method also allows to investigate the effect of realistic spatial variations of the flux obtained from heatflow measurements and classical theories of lithospheric cooling. It is found that a uniform heatflow forces a transformation of ~6 Sv at σ4=45.90, which is of the same order as current best estimates of AABW circulation. This transformation can be thought of as the geothermal circulation in the absence of mixing and is very similar for a realistic heatflow, albeit shifted towards slightly lighter density classes. Third, we use a general ocean circulation model in global configuration to perform three sets of experiments: (1) a thermally homogenous abyssal ocean with and without uniform geothermal heating; (2) a more stratified abyssal ocean subject to (i) no geothermal heating, (ii) a constant heat flux of 86.4 mW m−2, (iii) a realistic, spatially varying heat flux of identical global average; (3) experiments (i) and (iii) with enhanced vertical mixing at depth. Geothermal heating and diapycnal mixing are found to interact non-linearly through the density field, with geothermal heating eroding the deep stratification supporting a downward diffusive flux, while diapycnal mixing acts to map near-surface temperature gradients onto the bottom, thereby altering the density structure that supports a geothermal circulation. For strong vertical mixing rates, geothermal heating enhances the AABW cell by about 15% (2.5 Sv) and heats up the last 2000 m by ~0.15°C, reaching a maximum of by 0.3°C in the deep North Pacific. Prescribing a realistic spatial distribution of the heat flux acts to enhance this temperature rise at mid-depth and reduce it at great depth, producing a more modest increase in overturning than in the uniform case. In all cases, however, poleward heat transport increases by ~10% in the Southern Ocean. The three approaches converge to the conclusion that geothermal heating is an important actor of abyssal dynamics, and should no longer be neglected in oceanographic studies.
  29. 2009: Hofmann, M., and Morales Maqueda. “Geothermal heat flux and its influence on the oceanic abyssal circulation and radiocarbon distribution.” Geophysical Research Letters 36.3 (2009). Geothermal heating of abyssal waters is rarely regarded as a significant driver of the large‐scale oceanic circulation. Numerical experiments with the Ocean General Circulation Model POTSMOM‐1.0 suggest, however, that the impact of geothermal heat flux on deep ocean circulation is not negligible. Geothermal heating contributes to an overall warming of bottom waters by about 0.4°C, decreasing the stability of the water column and enhancing the formation rates of North Atlantic Deep Water and Antarctic Bottom Water by 1.5 Sv (10%) and 3 Sv (33%), respectively. Increased influx of Antarctic Bottom Water leads to a radiocarbon enrichment of Pacific Ocean waters, increasing Δ14C values in the deep North Pacific from −269‰ when geothermal heating is ignored in the model, to −242‰ when geothermal heating is included. A stronger and deeper Atlantic meridional overturning cell causes warming of the North Atlantic deep western boundary current by up to 1.5°C.
  30. 2010: Masuda, Shuhei, et al. “Simulated rapid warming of abyssal North Pacific waters.” Science (2010): 1188703. Recent observational surveys have shown significant oceanic bottom-water warming. However, the mechanisms causing such warming remain poorly understood and their time scales are uncertain. Here, we report computer simulations that reveal a fast teleconnection between changes in the surface air-sea heat flux off the Adélie Coast of Antarctica and the bottom-water warming in the North Pacific. In contrast to conventional estimates of a multicentennial timescale, this link is established over only four decades through the action of internal waves. Changes in the heat content of the deep ocean are thus far more sensitive to the air-sea thermal interchanges than previously considered. Our findings require a reassessment of the role of the Southern Ocean in determining the impact of atmospheric warming on deep oceanic waters
  31. 2015: James Edward Kamis, Deep Ocean Rock Layer Mega-Fluid Flow Systems  [LINK]  Fluid flow of chemically charged seawater through and within very deep ocean rock layers is virtually unknown until recently. It is here proposed that the flow rate, flow amount, and flow duration of these systems is many orders of magnitude greater than previously thought. As a result the affect these systems have on our climate has been dramatically underestimated. It is proposed that Deep Ocean Rock Layer fluid Flow Systems are quite possibly an extremely important factor in influencing earth’s atmospheric climate, earth’s ocean climate, and earth’s ocean biologic communities. The mechanism for these relationships are strong El Nino’s / La Nina’s, altering major ocean currents, locally altering polar ice cap melting, infusing the ocean with needed minerals, affecting ocean fish migration patterns, acting to maintain huge chemosynthetic communities, acting to spread new species, and acting to eliminate weak species. It is possible that these systems will be proved to be unique/ different from land based hydrodynamic systems in many ways, and if proven correct this would be an extremely important new concept. Scientists have assumed that land based fluid flow / hydrologic systems would be a good analogy. It is here contended that this is an incorrect assumption. These deep ocean systems do not act like land based systems. The major difference of deep ocean fluid flow systems is that they likely flow significantly greater amounts of heat and chemically charged fluid than previously realized. Deep ocean hydrothermal vents and cold seeps are here hypothesized be a just a small part of these here-to-for unrecognized and much larger deep ocean fluid flow systems. This is a very different way of perceiving fluid flow through deep ocean basin rock and sediment layers. To date most scientists have thought of deep ocean rock and sediment layers as basically bottom seals that largely did not and do not interact with the overlying ocean. It is here contended that these systems will be some day be proven to be immense, many of them covering huge regions and extending to great depths of many thousands of feet into ocean rock and sediment layers. In essence they will be found to be part of a continuum between the ocean crust, which they are part of, and upper mantle. Some of the perceived important differences between deep ocean fluid flow systems and land hydrologic systems are as follows
  32. 2016: James Edward Kamis, How Geological Forces Rock the Earth’s Climate [LINK]  Geological forces influence the planet’s climate in many specific and measurable ways. They melt the base of polar glaciers, abruptly change the course of deep ocean currents, influence the distribution of plankton blooms, infuse our atmosphere with volcanic sulfur rich ash, modify huge sub-ocean biologic communities, and generate all El Niño / La Niñas’ cycles. Given all of this very convincing information, many of today’s supposedly expert scientists still vehemently insist that our climate is completely / exclusively driven by atmospheric forces. This work challenges that orthodoxy. Three new game-changing pieces of geological information have been revealed: the discovery of an extensive field of active seafloor volcanoes and faults in the far western Pacific, iron enrichment of a huge ocean region off the coast of Antarctica, and the timing of western Pacific Ocean earthquakes vs. El Niños. A significant portion of the Earth’s climate is driven by massive fluid flow of super-heated and chemically charged seawater up and out from major fault zones and associated volcanic features. New geological information is changing the way we view long term climate variability. The data covers significant areas of the ocean measured in hundreds of miles laterally and thousands of feet vertically, and lastly the data is clearly related to geological forces and rather than the exclusive domain of the atmosphere.
  33. 2017: James Edward Kamis, Global Warming and Plate Climatology Theory [LINK] The Plate Climatology Theory was originally posted on Climate Change Dispatch October 7, 2014. Since that time other information in the form of several relatively new publications has been incorporated into the theory, and as a result key aspects of the theory have been strengthened. Not proven, but strengthened. This new information does prove one thing, that this theory should be given strong consideration by all scientists studying Global Climate. I am in no way attempting to prove the other guys wrong. Rather Plate Climatology is intended to be additive to the excellent work done to date. It may open the way to resolving the “Natural Variation” question currently being debated by Climate Scientists. What could be more natural than geological events influencing Climate? It is expected that this work will act as a catalyst for future research and provide a platform to join what are now several independently researched branches of science; Geology, Climatology, Meteorology, and Biology. The science of Climate is extremely complex and necessitates a multi-disciplinary approach.
  34. 2018: James Edward Kamis, The influence of oceanic and continental fault boundaries on climate [LINK] Another giant piece of the climate science puzzle just fell into place, specifically that geological heat flow is now proven to be the primary force responsible for anomalous bottom melting and break-up of many West Antarctica glaciers, and not atmospheric warming. This new insight is the result of a just released National Aeronautics and Space Administration (NASA) Antarctica geological research study (see here). Results of this study have forever changed how consensus climate scientists and those advocating the theory of Climate Change / Global Warming, view Antarctica’s anomalous climate and climate related events. In a broader theoretical sense, results of the NASA study challenge the veracity of the most important building block principle of the Climate Change Theory, specifically that emissions of CO2 and carbon by humans is responsible for the vast majority of earth’s anomalous climate phenomena. This article will provide evidence that geological forces associated with major oceanic and continental fault boundaries influence and in some cases completely control a significant portion of earth’s anomalous climate and many of its anomalous climate related events.

 

 

OTHER STUDIES OF GEOTHERMAL HEAT IN OCEAN HEAT CONTENT 2000-2018

  1. [PAUL HOMEWOOD, OCTOBER 10 2018]
  2. [WILLIS ESCHENBACH AUGUST 15 2011]
  3. [WILLIS ESCHENBACH FEBRUARY 25 2013]
  4. [BOB TISDALE MARCH 13 2013]
  5. [KEN RICE APRIL 15 2013]
  6. [KEN RICE APRIL 18 2013]
  7. [KEN RICE APRIL 23 2013]
  8. [KEN RICE JULY 23 2013]
  9. [KEN RICE SEPTEMBER 27 2013]
  10. [KEN RICE SEPTEMBER 30 2013]
  11. [WILLIS ESCHENBACH JANUARY 1 2014]
  12. [WILLIS ESCHENBACH JANUARY 5 2014]
  13. [KEN RICE JANUARY 22 2014]
  14. [KEN RICE JANUARY 23 2014]
  15. [KEN RICE FEBRUARY 12 2014]
  16. [KEN RICE MAY 1 2014]
  17. [KEN RICE MAY 7 2014]
  18. [KEN RICE OCTOBER 6 2014]*
  19. [KEN RICE DECEMBER 1 2014]
  20. [WILLIS ESCHENBACH DECEMBER 4 2014]
  21. [BOB TISDALE DECEMBER 9 2014]
  22. [WILLIS ESCHENBACH JANUARY 22 2015]
  23. [KEN RICE JUNE 22 2015]
  24. [BOB TISDALE AUGUST 26 2015]
  25. [KEN RICE JANUARY 19 2016]
  26. [KEN RICE JULY 28 2016]
  27. [ANTHONY WATTS DECEMBER 1 2017]
  28. [DAVID MIDDLETON JANUARY 4 2018]
  29. [ANTHONY WATTS JANUARY 4 2018]

 

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