[LIST OF POSTS ON THIS SITE]

RELATED POST:  AN EXCLUSIVE RELIANCE ON FOSSIL FUEL EMISSIONS OVERLOOKS NATURAL CARBON FLOWS. [LINK]  

THESE QUOTES ARE FROM CLIMATE SCIENTISTS.

THEY PROVIDE CLEAR EVIDENCE OF CONFIRMATION BIAS IN CLIMATE SCIENCE. 

1. Reporting on climate change means forever being on the hunt for inflection points. Have global emissions peaked? When will the building of coal-fired power plants slow in, say, China? Has Arctic sea ice extent reached a record low?
2. Every time the International Energy Agency (IEA) publishes a fresh report, journalists and analysts dive in to search for such nuggets buried in the data. This week, it released its latest annual “World Energy Investment” report and Carbon Brief’s Josh Gabbatiss rolled up his sleeves and pulled out the key charts for his summary article.
3. Predictably, the Covid-19 crisis has had a dramatic impact on energy investment around the world. This year will see the largest ever fall in both investment and consumer spending on energy, said the IEA. However, the report also reveals various other insights. For example, it shows that, as demand and prices collapse, consumer spending on oil is expected to drop by more than $1tn, prompting a “historic switch” as spending on electricity exceeds oil for the first time.

MORE ABOUT CONFIRMATION BIAS:  [LINK]

A STATEMENT FROM NASA GISS AND JAMES HANSEN ON THE PROBLEM WITH THE SCIENTIFIC METHOD

Scientific reticence hinders communication with the public about the dangers of global warming. It is important that policy-makers recognize the potential influence of this phenomenon. Scientific reticence may be a consequence of the scientific method. Success in science depends on objective skepticism. Scientific reticence has its merits. However, in a case such as ice sheet instability and sea level rise, there is a danger of excessive reticence. [LINK TO SOURCE DOCUMENT]

TRANSLATION: ADHERENCE TO UNBIASED OBJECTIVE SCIENTIFIC INQUIRY INTERFERES WITH CLIMATE ACTIVISM. 

SOME DETAILS ON THE CORRUPTION OF CLIMATE SCIENCE BY ADVOCACY AS EXPLAINED BY JAMES HANSEN ABOVE.

1. DATA SELECTION BIAS:  There have been many Quaternary Interglacials in the past that humans had experienced in their caves but the Holocene is the first interglacial experienced by civilized humans because human civilization is a creation of the Holocene. A related post  describes a 10,000-year climate history of the Holocene from a literature review of proxy paleoclimate data [LINK]  where we find that the Holocene interglacial from the end of the Younger Dryas to the present has not been sustained period of warming, ice melt, and sea level rise  but chaotic cycles of about ten alternating periods of glacial retreat warming with sea level rise and glacial advance cooling with sea level decline at millennial and centennial time scales.
2. The current period of warming and glacial retreat can only be understood in this context and not in isolation. The most significant and outrageous violation of the scientific method in the climate science of the fear of warming described as a creation of the industrial economy is that climate science has selected one of the ten Holocene climate cycles to explain in terms of the cause and effect phenomenon.
3. If climate science can explain these Holocene temperature cycles as deterministic cause and effect phenomena, they must explain all of them and not just pick one of them to explain in that way because that kind of empirical research is subject to data selection bias, confirmation bias, and circular reasoning.
4. The climate science of Anthropogenic Global Warming and Climate Change that has selected only the post LIA warming cycle to explain as a cause and effect phenomenon is rejected solely on that basis. Such objections to climate science based on an insistence on the scientific method cannot be described as science denial as eloquently clarified by James Hansen in the quote above. 
5. Unbiased and objective scientific inquiry is not possible if the scientist has an advocacy agenda related to the research question in terms of activism needs. In climate science the hidden hand of activism favors findings that support activism against fossil fuels.
6. In climate science, the researcher’s activism needs can be served with an excessive reliance on climate models. This is because climate models are pre-programmed with a well connected causation sequence from CO2 emissions to rising atmospheric CO2 concentration to warming driven by way of climate sensitivity.
7. In climate models thus constructed by climate scientists, empirical tests of theory will always support the theory because climate models are an expression of theory. Objective scientific inquiry requires that empirical tests of theory must be independent of theory. In climate science, the use of climate models corrupts this fundamental principle of empirical tests.
8. Once objective scientific inquiry is corrupted in this way, the role of observational data is to verify the models and not to challenge the models. This attitude in climate research leads to research methodologies in which assumptions about the data that verify the climate models also verify the correctness of the data. By the same token, data that are inconsistent with the climate models are suspected of having been compromised in some way, perhaps by data collection methods or perhaps cherry-picked by climate deniers, or rendered irrelevant in other ways. Such methodologies often lead to the use of circular reasoning that is then defended with the shifting the burden of proof fallacy.
9. For example, in the case of the conclusion by climate scientists that the observed increase in atmospheric CO2 concentration is caused by fossil fuel emissions, natural flows in the carbon cycle that are an order of magnitude larger than fossil fuel emissions and that cannot be directly measured are inferred with the implicit assumption that the increase in atmospheric CO2 comes from fossil fuel emissions. The flow balance can then be carried out and it does of course show that the increase in atmospheric CO2 derives from fossil fuel emissions  [LINK] . The same is true in the ocean acidification issue. The arguments thus constructed by climate scientists are so convincing to themselves that when challenged they respond with the shifting the burden of proof fallacy which implies that if the critic does not have an alternative explanation for the phenomenon, the one proposed must be correct. These two examples  – that of emissions to atmospheric CO2 [LINK] and emissions to ocean acidification  [LINK] are presented in some detail in related posts on this site.
10. Another variety of circular reasoning is the so called Texas Sharpshooter Fallacy in which the data to be used to test the theory are changed until a dataset is found or a time span within a time series is found in which the theory is supported by the data. The theory is then tested with those chosen constraints and declared to be empirically verified. A famous example is the claim by a well known MIT climatologist that fossil fuel emissions are causing Atlantic Hurricanes to become “more destructive” [LINK]  . Yet another example is the claim by climate scientists  that the proof of GHG forcing of surface temperature is found if the time span to be tested is limited to a period in which they have been able to find the pattern they were looking for  [LINK]  [LINK] .
11. Circular reasoning derived form data selection bias takes another form in climate science where the data used to construct a hypothesis are then used to test that hypothesis. For example, we find in this related post [LINK]  that the hypothesis that climate change is changing the spatial pattern of tropical  cyclones is derived from the historical data and then tested with the same data – yet another form of the Texas Sharpshooter fallacy.
12. Activism needs of researchers also corrupt how the statistical property of variance is viewed and interpreted. In statistics and also in information theory, high variance implies low information content. In other words, the higher the variance the less we know. In this context high variance is undesirable because it degrades the information we can derive from the data. However, high variance also yields large confidence intervals and where either end of this confidence interval is extreme enough to support the activism needs of climate researchers, high variance is interpreted not as absence of information but as information about a danger of how extreme it could be. This interpretation in conjunction with the precautionary principle leads to a perverse interpretation of uncertainty such that uncertainty becomes transformed into certainty of extreme values.
13. In a related post on uncertainty  [WHAT DOES UNCERTAINTY MEAN]  we show that a perverse and biased interpretation of uncertainty in climate science leads to the understantind of variance only in terms of a confidence interval and only in terms of the end of the confidence interval that contains the greater fear of climate change. To quote, “BRIEFLY, UNCERTAINTY DOES NOT MEAN OH! LOOK HOW HIGH IT COULD BE. IT MEANS WE DON’T REALLY KNOW. THE LESS WE KNOW THE HIGHER IT COULD BE AND IN PERFECT IGNORANCE IT COULD BE AS HIGH AS INFINITY BECAUSE THE ANSWER IS NOT CONSTRAINED BY INFORMATION“.
14. This kind of interpretation of uncertainty leads to the climate science position that the less they know the greater the risk of harm by climate change [LINK]  . This principle is pervasive in climate science such that it follows that the the truth of AGW climate change theory and it’s catastrophic impacts and consequences is the null hypothesis and it can be rejected only if convincing evidence can be provided by climate deniers against it.
15. This methodology is claimed to be science. However, it works exactly the other way around in science where the null hypothesis is the absence of the effects predicted by theory and it is necessary for empirical tests to provide convincing evidence against it so that the null can be rejected. It is only then that we can accept the alternate hypothesis that the proposed catastrophic AGW climate change theory is correct.
16. An uncertainty problem that has been difficult and contentious for climate science is that of climate sensitivity (ECS), a proposed relationship between the logarithm of atmospheric CO2 concentration and surface temperature that sits at the foundation of AGW theory. A large range of values for the ECS parameter is reported in the observational data as shown in a related post [LINK] . Such a large range of observed values means that both high warming at low CO2 & low warming at high CO2 are seen in the data. The high variance implies that the ECS is not a useful concept but in climate science the high end of the range is presented as an alarming condition that should be taken into account in terms of the precautionary principle. The ECS uncertainty issue is a high profile example of a parameter which contains little useful information because of uncertainty but is treated as certainty of high values.
17. Perhaps the clearest evidence of fear based activism in climate science is the oft repeated pattern in which first a “tipping point” is declared. The declaration is quickly followed by its retraction with the statement that “there is still time” if we act quickly and decisively to limit or eliminate our use of fossil fuels. Some examples of these tipping point declarations are cited in a related post [LINK] . The pattern likely derives from a failure of climate science, at a given level of fear, to convince consumers that they should not be using fossil fuels. That requires a gradual escalation of the level of fear such that at some point the fear level is escalated to the tipping point . Soon after the declaration of the tipping point fear, however, climate science realizes that it has been overdone since it is now impossible for them to use the fear for activism against fossil fuels. “Tipping point” implies that no corrective action can be taken. Thus, soon thereafter, the “but there is still time”  statement is issued. This statement is nonsensical because it is inconsistent with the very concept of tipping point. Yet this “tipping point – there is still time” cycle has been played out a number of times  [LINK] . A specific example of the tipping point cycle is the case of sea ice extent in the Arctic that has been used as a high profile fear factor since at least the 1990s as shown in a related post [LINK] with climate scientists closely tracking year to year changes in the September minimum Arctic sea ice extent and raising an alarm of impending doom when a low sea ice extent is observed. The most intense of these tipping point alarms was raised in 2007 when it was declared that “The Arctic is Screaming” [LINK] . These alarms were raised with the assumption that the observed changes in Arctic sea ice extent were caused by fossil fuel emissions by way of global warming and could be moderated by reducing or eliminating the use of fossil fuels. However, no empirical evidence has ever been presented to establish that relationship possibly because none exists (as shown in a related post [LINK] ).
18. Much of the distance between rational and objective scientific inquiry and research guided by activism needs derives from the noble cause fallacy in which no matter how perverse the methods, they can be justified as long as they serve a noble purpose and as long as the researcher’s goals are noble. That the cause of climate activism is noble is firmly established by their stated goal of saving the planet. It implies that to be critical of climate science is to be opposed to saving the planet and therefore in some way endangering the planet, the biota, and all things natural and organic. In this way, the noble cause fallacy is also useful in vilifying and discrediting critics and skeptics with holocaust language as “climate change deniers” with the implication that they stand in the way of the good scientists who are trying to save the planet.
19. These are the foundations needed to support fear based activism in which we have been taught to fear warming of surface temperatures, melting ice sheets and glaciers, rising sea level, warming of oceans, the possibility that warming will bring new weather patterns that may be more extreme, that there may be heat waves, droughts, and floods, that these changes will affect the biota and that not all species will fare well. Yet all of these changes are normal in interglacials. The net information content of these changes is that we are in fact in an interglacial period although not a particularly severe one when compared with prior interglacial events [LINK] [LINK] . In other words a well constructed propaganda machine was employed to get humanity to fear the brief warm and balmy interglacials the earth gets in between 100,000-year glaciations in the Quaternary ice age; and to imagine that the planet needs to be saved from the effects of the interglacial and that we humans can and must save the planet from the ill effects of this interglacial period.
20. The following quote from Professor Stephen Schneider, Stanford University climatologist and IPCC lead author is relevant to the activism issue. He is quoted as saying that “We need to get some broad based support to capture the public’s imagination. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubt. Each of us has to decide what the right balance is between being effective and being honest” [SOURCE] .
21. It should be mentioned that the theory of global warming “since pre-industrial times” driven by fossil fuel emissions from the industrial economy was first forwarded by Guy Callendar in 1938 (discussed in a related post [LINK] ) at a time when temperatures were rising but that paper along with the fear of warming driven by “the industrial economy” was shelved when soon thereafter the world went into the 1940s-1970s cooling period (discussed in a related post [LINK] ).
22. The defining paper on climate change during this cooling period was authored by Professor Stephen Schneider where he argued that since fossil fuel emissions contain not just CO2 but aerosols, the warming effect of CO2 must be computed net of the cooling effect of stratospheric aerosols. He wrote that since the warming effect of additional CO2 decreases as atmospheric CO2 concentration increases, and since the cooling effect of additional aerosols increases as aerosol concentration increases, at some point the net effect of the industrial economy will be cooling and not warming (citation below). 
23. By 1980, however, the 30-year cooling trend had switched back to warming such that the Schneider 1971 aerosol paper was now shelved and the Callendar 1938 warming paper was dusted off and a new paper extolling the dangers of human caused global warming and climate change in the form of ice sheet melt, sea level rise, extreme weather, heat waves, droughts, and floods by NASA GISS scientist James Hansen gave us the current version of the theory of anthropogenic global warming and climate change. Once the Hansen scenario took hold, Schneider himself set aside his aerosol theory and joined the Hansen movement for climate action against the dangers of global warming.
24. This pattern in which the theory of anthropogenic climate change changes with the weather was played out again after the warming slowed since 1998 into what became known as a “warming hiatus” even as atmospheric CO2 continued its accelerated climb. Climate science struggled to explain it in many different ways with the most significant papers (Trenberth, Karl, etc) explaining the apparent anomaly with an energy balance that transferred the heat that could not be explained into the ocean in terms of ocean heat content. The ocean heat content issue is described in a related post [LINK] as an example of circular reasoning in climate science. These examples show a flexible and malleable theory that survives by simply being flexible so that no matter what the data, the data always supports a theory that climate science needs to support its activism against fossil fuels in an unusual scientific method in which the activism needs drives the science.
25. An entirely different kind of activism in climate science is the use of obvious falsehoods, that one imagines that climatologists know to be falsehoods, to heighten the level of fear and thereby of the urgency of “climate action” in the form of action against the use of fossil fuels. Consider for example, that climate science on the one hand lectures that only long term trends in temperature and not temperature events (events being described as “weather” and not climate) serve as evidence of AGW, particularly so when the temperature events are not high temperature events. On the other hand, when a sufficiently high temperature event occurs, it is widely disseminated in the media as “hottest year on record” or “hottest month on record” and used to ratchet up the fear of climate change. A particularly dishonest example of this practice was the the use of high temperatures in the two strong El Nino years of 1998 and 2016 to promote them as “hottest year on record” as a way of raising the fear of AGW and thereby to push through the “climate action” agenda of eliminating the use of fossil fuels. The NASA website on climate change still carries this alarming message about 1998 and 2016 [LINK] .
26. SEA LEVEL RISE ACCELERATING: The use of sea level rise in climate change activism against fossil fuels takes the form of claiming that sea level rise is accelerating in concert with the assumption that acceleration proves human cause. Since the AGW argument is based on rising temperatures, acceleration in sea level rise is a given. Acceleration in sea level rise is the norm in deglaciation and into interglacials as is evident in the paleo data for the Eemian interglacial described in a related post [LINK] and also in the onset of the Holocene as seen in this related post [LINK]. The use of these dishonest methods to create fear in the public and in government officials as advocacy for the prescribed climate action of eliminating fossil fuels provides the evidence that climate science is a tool for activism against fossil fuels; and that serves to discredit the science of climate science. The sea level rise issue is discussed in two related posts [LINK] [LINK] .
27. The active engagement of top level climate scientists in activism can be seen in the flagrant cooperation with and dependence on climate activism groups such as Carbon Brief and also in their direct involvement in promoting and encouraging anti fossil fuel activism as can be seen in these tweets and retweets by eminent climate scientist Stefan Rahmstorf: (1) We have now thousands of pages of documented evidence and it all points one way, and that’s that Big Oil is the new Big Tobacco. #ExxonKnew. They Have Lied for Decades’: European Parliament to Scrutinise Exxon’s Climate Science Denial. (2) Stefan Rahmstorf @rahmstorf Mar 19 School climate strikes: 1.4 million people took part, say campaigners. Children walked out of schools on Friday in 2,233 cities and towns in 128 countries, with demonstrations held from Australia to India, the UK and the US.. (3) Anders Levermann @ALevermann Mar 19 Will future weather extremes change the economic structure on the planet? If that sounds as exciting to you as it is & you want to do a #PhD @PIK_Climate let us know http://www.pik-potsdam.de/~anders (4) Stefan Rahmstorf @rahmstorf Mar 18 Cyclone Idai death toll in Mozambique ‘could rise above 1,000. (5) Stefan Rahmstorf @rahmstorf Mar 18 Over 25,000 scientists from Austria, Germany and Switzerland have now signed a statement supporting #FridaysForFuture!! @BrigitteKnopf and myself present it here @F4F_Potsdam in Potsdam on Friday. Full statement here: https://www.scientists4future.org/ #ScientistsForFuture @sciforfuture (6) Greta Thunberg @GretaThunberg Mar 17 Over 1,5 million students on school strike 15/3. We proved that it does matter what you do and that no one is too small to make a difference. (7) Stefan Rahmstorf @rahmstorf Mar 16 “Aktivismus” ist einfach nur ein Etikett, das Leute benutzen, denen es am liebsten wäre, Wissenschafter würden den Mund halten. Die Wiener Zeitung hat verschiedene Forscher gefragt, warum sie die Schülerproteste unterstützen. Translated from German by Microsoft”Activism” is simply a Label that People who would most like to, Scientists would keep their Mouths shut. The Wiener Zeitung has asked various Researchers why they support the Student Protests. (8) Stefan Rahmstorf @rahmstorf Mar 16 Ein Radio-Interview zu #ScientistsForFuture – Wissenschaftler stellen sich hinter die Schüler, die für Klimaschutz demonstrieren. Translated from German by Microsoft A radio interview too #ScientistsForFuture-Scientists rally behind The students demonstrating for Climate action. (9) Stefan Rahmstorf @rahmstorf Mar 15 Today is not just #fridaysforfuture but also the 20th anniversary day of the famous “hockey stick curve” by Mike Mann and colleagues. Here’s how this reconstruction of past temperatures stacks up to the latest paleo research, the PAGES2k project. (10) Stefan Rahmstorf @rahmstorf Mar 15 Höchste Zeit für die Regierungen der Welt endlich die Klimakrise entschlossen anzupacken statt nur Ziele zu verkünden! Klima-Demos – von Berlin bis Sydney Translated from German by Microsoft High Time for the governments of the World Finally to tackle the Climate Crisis decisively instead of just announcing Goals! Climate demos-from Berlin to Sydney (11) Stefan Rahmstorf @rahmstorf Mar 15 “The 20 warmest years on record have all come in the past 22 years, essentially the lifetime of today’s children and young adults.” Great collection of images of #schoolstrike4climate #ClimateStrike from around the world! #FridaysForFuture
28. The active engagement of Climate Brief in fear based activism against fossil fuels is seen in these tweets:              https://twitter.com/CarbonBrief/status/1109547370021339136https://twitter.com/CarbonBrief/status/1109493769156603906https://twitter.com/CarbonBrief/status/1109438150659788800https://twitter.com/CarbonBrief/status/1109364446202351616https://twitter.com/CarbonBrief/status/1109335466250305537https://twitter.com/CarbonBrief/status/1109245130597416960https://twitter.com/CarbonBrief/status/1109201864120303617https://twitter.com/CarbonBrief/status/1109184981069430784
29. A new tactic being used (as of 2019) to push climate activism is the use of children as activists claiming that climate action is necessary to ensure that as adults they will inherit a livable world. That these children are being used as stooges by the real activists behind the scene is evident in this text attributed to 16-year-old high school student Greta Thunberg:  “Perhaps the most dangerous misconception about the climate crisis is that we have to LOWER our emissions. Lowering emissions is far from enough. Our emissions have to STOP if we are to stay below 1.5C of warming since pre-industrial times. That rules out most of today’s politics. “Lowering” of emissions is necessary but it is only the beginning that must lead to a complete cessation of emissions within two decades. And then we need to get to negative emissions by removing CO2 from the atmosphere. The fact that we are talking of lowering instead of stopping emissions is the greatest force behind the business as usual scenario. “

[LIST OF POSTS ON THIS SITE]

REFERENCES

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 (D_p < 20 nm), the Aitken mode (20 < D_p < 100 nm), and the accumulation mode (D_p > 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. 
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 mixed^{1,2,3,4,5,6,7}) or incorporated within them (internally mixed^1,3,7), 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 (NO_x, 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, NASA, Aerosol 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.
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36. 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.
37. 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.
38. 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.
39. 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.
40. 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.
41. 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.
42. 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.
43. 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 T_L and Angstrom coefficient β, calculated from measurements of broad-band filter at Athens Observatory (NOA), are reported. A linear model fitted to β vs T_L 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 T_L 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.
44. 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.
45. 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
46. 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]
47. 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]
48. 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.
49. 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.
50. 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.
51. 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.
52. 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.
53. 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.
54. 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
55. 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.
56. 1963: Möller, Fritz. “On the influence of changes in the CO2 concentration in air on the radiation balance of the earth’s surface and on the climate.” Journal of Geophysical Research68.13 (1963): 3877-3886. The numerical value of a temperature change under the influence of a CO₂ change as calculated by Plass is valid only for a dry atmosphere. Overlapping of the absorption bands of CO₂ and H₂O in the range around 15 μ essentially diminishes the temperature changes. New calculations give ΔT = + 1.5° when the CO₂ content increases from 300 to 600 ppm. Cloudiness diminishes the radiation effects but not the temperature changes because under cloudy skies larger temperature changes are needed in order to compensate for an equal change in the downward long‐wave radiation. The increase in the water vapor content of the atmosphere with rising temperature causes a self‐amplification effect which results in almost arbitrary temperature changes, e.g. for constant relative humidity ΔT = +10° in the above mentioned case. It is shown, however, that the changed radiation conditions are not necessarily compensated for by a temperature change. The effect of an increase in CO₂ from 300 to 330 ppm can be compensated for completely by a change in the water vapor content of 3 per cent or by a change in the cloudiness of 1 per cent of its value without the occurrence of temperature changes at all. Thus the theory that climatic variations are effected by variations in the CO₂ content becomes very questionable.
57. 1964: Manabe, Syukuro, and Robert F. Strickler. “Thermal equilibrium of the atmosphere with a convective adjustment.” Journal of the Atmospheric Sciences 21.4 (1964): 361-385. The states of thermal equilibrium (incorporating an adjustment of super-adiabatic stratification) as well as that of pure radiative equilibrium of the atmosphere are computed as the asymptotic steady state approached in an initial value problem. Recent measurements of absorptivities obtained for a wide range of pressure are used, and the scheme of computation is sufficiently general to include the effect of several layers of clouds. The atmosphere in thermal equilibrium has an isothermal lower stratosphere and an inversion in the upper stratosphere which are features observed in middle latitudes. The role of various gaseous absorbers (i.e., water vapor, carbon dioxide, and ozone), as well as the role of the clouds, is investigated by computing thermal equilibrium with and without one or two of these elements. The existence of ozone has very little effect on the equilibrium temperature of the earth’s surface but a very important effect on the temperature throughout the stratosphere; the absorption of solar radiation by ozone in the upper and middle stratosphere, in addition to maintaining the warm temperature in that region, appears also to be necessary for the maintenance of the isothermal layer or slight inversion just above the tropopause. The thermal equilibrium state in the absence of solar insulation is computed by setting the temperature of the earth’s surface at the observed polar value. In this case, the stratospheric temperature decreases monotonically with increasing altitude, whereas the corresponding state of pure radiative equilibrium has an inversion just above the level of the tropopause. A series of thermal equilibriums is computed for the distributions of absorbers typical of different latitudes. According to these results, the latitudinal variation of the distributions of ozone and water vapor may be partly responsible for the latitudinal variation of the thickness of the isothermal part of the stratosphere. Finally, the state of local radiative equilibrium of the stratosphere overlying a troposphere with the observed distribution of temperature is computed for each season and latitude. In the upper stratosphere of the winter hemisphere, a large latitudinal temperature gradient appears at the latitude of the polar-night jet stream, while in the upper statosphere of the summer hemisphere, the equilibrium temperature varies little with latitude. These features are consistent with the observed atmosphere. However, the computations predict an extremely cold polar night temperature in the upper stratosphere and a latitudinal decrease (toward the cold pole) of equilibrium temperature in the middle or lower stratosphere for winter and fall. This disagrees with observation, and suggests that explicit introduction of the dynamics of large scale motion is necessary.
58. 1967: Manabe, Syukuro, and Richard T. Wetherald. “Thermal equilibrium of the atmosphere with a given distribution of relative humidity.” Journal of the Atmospheric Sciences 24.3 (1967): 241-259. [ECS=2]
59. 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.
60. 1969: Sellers, William D. “A global climatic model based on the energy balance of the earth-atmosphere system.” Journal of Applied Meteorology 8.3 (1969): 392-400. A relatively simple numerical model of the energy balance of the earth-atmosphere is set up and applied. The dependent variable is the average annual sea level temperature in 10° latitude belts. This is expressed basically as a function of the solar constant, the planetary albedo, the transparency of the atmosphere to infrared radiation, and the turbulent exchange coefficients for the atmosphere and the oceans. The major conclusions of the analysis are that removing the arctic ice cap would increase annual average polar temperatures by no more than 7C, that a decrease of the solar constant by 2–5% might be sufficient to initiate another ice age, and that man’s increasing industrial activities may eventually lead to a global climate much warmer than today.
61. 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.
62. 1975: Manabe, Syukuro, and Richard T. Wetherald. “The effects of doubling the CO2 concentration on the climate of a general circulation model.” Journal of the Atmospheric Sciences 32.1 (1975): 3-15. An attempt is made to estimate the temperature changes resulting from doubling the present CO2 concentration by the use of a simplified three-dimensional general circulation model. This model contains the following simplifications: a limited computational domain, an idealized topography, no beat transport by ocean currents, and fixed cloudiness. Despite these limitations, the results from this computation yield some indication of how the increase of CO2 concentration may affect the distribution of temperature in the atmosphere. It is shown that the CO2 increase raises the temperature of the model troposphere, whereas it lowers that of the model stratosphere. The tropospheric warming is somewhat larger than that expected from a radiative-convective equilibrium model. In particular, the increase of surface temperature in higher latitudes is magnified due to the recession of the snow boundary and the thermal stability of the lower troposphere which limits convective beating to the lowest layer. It is also shown that the doubling of carbon dioxide significantly increases the intensity of the hydrologic cycle of the model. 
63. 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.
64. 1978: Ramanathan, V., and J. A. Coakley. “Climate modeling through radiative‐convective models.” Reviews of geophysics16.4 (1978): 465-489. We present a review of the radiative‐convective models that have been used in studies pertaining to the earth’s climate. After familiarizing the reader with the theoretical background, modeling methodology, and techniques for solving the radiative transfer equation the review focuses on the published model studies concerning global climate and global climate change. Radiative‐convective models compute the globally and seasonally averaged surface and atmospheric temperatures. The computed temperatures are in good agreement with the observed temperatures. The models include the important climatic feedback mechanism between surface temperature and H₂O amount in the atmosphere. The principal weakness of the current models is their inability to simulate the feedback mechanism between surface temperature and cloud cover. It is shown that the value of the critical lapse rate adopted in radiative‐convective models for convective adjustment is significantly larger than the observed globally averaged tropospheric lapse rate. The review also summarizes radiative‐convective model results for the sensitivity of surface temperature to perturbations in (1) the concentrations of the major and minor optically active trace constituents, (2) aerosols, and (3) cloud amount. A simple analytical model is presented to demonstrate how the surface temperature in a radiative‐convective model responds to perturbations.
65. 1985: Wigley, Thomas ML, and Michael E. Schlesinger. “Analytical solution for the effect of increasing CO2 on global mean temperature.” Nature 315.6021 (1985): 649. Increasing atmospheric carbon dioxide concentration is expected to cause substantial changes in climate. Recent model studies suggest that the equilibrium warming for a CO2 doubling (Δ T2×) is about 3–4°C. Observational data show that the globe has warmed by about 0.5°C over the past 100 years. Are these two results compatible? To answer this question due account must be taken of oceanic thermal inertia effects, which can significantly slow the response of the climate system to external forcing. The main controlling parameters are the effective diffusivity of the ocean below the upper mixed layer (κ) and the climate sensitivity (defined by Δ T2×). Previous analyses of this problem have considered only limited ranges of these parameters. Here we present a more general analysis of two cases, forcing by a step function change in CO2 concentration and by a steady CO2 increase. The former case may be characterized by a response time which we show is strongly dependent on both κ and Δ T2×. In the latter case the damped response means that, at any given time, the climate system may be quite far removed from its equilibrium with the prevailing CO2 level. In earlier work this equilibrium has been expressed as a lag time, but we show this to be misleading because of the sensitivity of the lag to the history of past CO2 variations. Since both the lag and the degree of disequilibrium are strongly dependent on κ and Δ T2×, and because of uncertainties in the pre-industrial CO2 level, the observed global warming over the past 100 years can be shown to be compatible with a wide range of CO2-doubling temperature changes.
66. 1991: Lawlor, D. W., and R. A. C. Mitchell. “The effects of increasing CO2 on crop photosynthesis and productivity: a review of field studies.” Plant, Cell & Environment 14.8 (1991): 807-818. Only a small proportion of elevated CO₂ studies on crops have taken place in the field. They generally confirm results obtained in controlled environments: CO₂increases photosynthesis, dry matter production and yield, substantially in C₃ species, but less in C₄, it decreases stomatal conductance and transpiration in C₃ and C₄ species and greatly improves water‐use efficiency in all plants. The increased productivity of crops with CO₂ enrichment is also related to the greater leaf area produced. Stimulation of yield is due more to an increase in the number of yield‐forming structures than in their size. There is little evidence of a consistent effect of CO₂ on partitioning of dry matter between organs or on their chemical composition, except for tubers. Work has concentrated on a few crops (largely soybean) and more is needed on crops for which there are few data (e.g. rice). Field studies on the effects of elevated CO₂ in combination with temperature, water and nutrition are essential; they should be related to the development and improvement of mechanistic crop models, and designed to test their predictions.
67. 2009: Danabasoglu, Gokhan, and Peter R. Gent. “Equilibrium climate sensitivity: Is it accurate to use a slab ocean model?.” Journal of Climate 22.9 (2009): 2494-2499. The equilibrium climate sensitivity of a climate model is usually defined as the globally averaged equilibrium surface temperature response to a doubling of carbon dioxide. This is virtually always estimated in a version with a slab model for the upper ocean. The question is whether this estimate is accurate for the full climate model version, which includes a full-depth ocean component. This question has been answered for the low-resolution version of the Community Climate System Model, version 3 (CCSM3). The answer is that the equilibrium climate sensitivity using the full-depth ocean model is 0.14°C higher than that using the slab ocean model, which is a small increase. In addition, these sensitivity estimates have a standard deviation of nearly 0.1°C because of interannual variability. These results indicate that the standard practice of using a slab ocean model does give a good estimate of the equilibrium climate sensitivity of the full CCSM3. Another question addressed is whether the effective climate sensitivity is an accurate estimate of the equilibrium climate sensitivity. Again the answer is yes, provided that at least 150 yr of data from the doubled carbon dioxide run are used.
68. 2010: Connell, Sean D., and Bayden D. Russell. “The direct effects of increasing CO2 and temperature on non-calcifying organisms: increasing the potential for phase shifts in kelp forests.” Proceedings of the Royal Society of London B: Biological Sciences (2010): rspb20092069. Predictions about the ecological consequences of oceanic uptake of CO₂ have been preoccupied with the effects of ocean acidification on calcifying organisms, particularly those critical to the formation of habitats (e.g. coral reefs) or their maintenance (e.g. grazing echinoderms). This focus overlooks the direct effects of CO₂ on non-calcareous taxa, particularly those that play critical roles in ecosystem shifts. We used two experiments to investigate whether increased CO₂ could exacerbate kelp loss by facilitating non-calcareous algae that, we hypothesized, (i) inhibit the recovery of kelp forests on an urbanized coast, and (ii) form more extensive covers and greater biomass under moderate future CO₂ and associated temperature increases. Our experimental removal of turfs from a phase-shifted system (i.e. kelp- to turf-dominated) revealed that the number of kelp recruits increased, thereby indicating that turfs can inhibit kelp recruitment. Future CO₂ and temperature interacted synergistically to have a positive effect on the abundance of algal turfs, whereby they had twice the biomass and occupied over four times more available space than under current conditions. We suggest that the current preoccupation with the negative effects of ocean acidification on marine calcifiers overlooks potentially profound effects of increasing CO₂and temperature on non-calcifying organisms.
69. 2011: Schmittner, Andreas, et al. “Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum.” Science 334.6061 (2011): 1385-1388. Assessing the impact of future anthropogenic carbon emissions is currently impeded by uncertainties in our knowledge of equilibrium climate sensitivity to atmospheric carbon dioxide doubling. Previous studies suggest 3 kelvin (K) as the best estimate, 2 to 4.5 K as the 66% probability range, and nonzero probabilities for much higher values, the latter implying a small chance of high-impact climate changes that would be difficult to avoid. Here, combining extensive sea and land surface temperature reconstructions from the Last Glacial Maximum with climate model simulations, we estimate a lower median (2.3 K) and reduced uncertainty (1.7 to 2.6 K as the 66% probability range, which can be widened using alternate assumptions or data subsets). Assuming that paleoclimatic constraints apply to the future, as predicted by our model, these results imply a lower probability of imminent extreme climatic change than previously thought.
70. 2012: Fasullo, John T., and Kevin E. Trenberth. “A less cloudy future: The role of subtropical subsidence in climate sensitivity.” science 338.6108 (2012): 792-794. An observable constraint on climate sensitivity, based on variations in mid-tropospheric relative humidity (RH) and their impact on clouds, is proposed. We show that the tropics and subtropics are linked by teleconnections that induce seasonal RH variations that relate strongly to albedo (via clouds), and that this covariability is mimicked in a warming climate. A present-day analog for future trends is thus identified whereby the intensity of subtropical dry zones in models associated with the boreal monsoon is strongly linked to projected cloud trends, reflected solar radiation, and model sensitivity. Many models, particularly those with low climate sensitivity, fail to adequately resolve these teleconnections and hence are identifiably biased. Improving model fidelity in matching observed variations provides a viable path forward for better predicting future climate.
71. 2012: Andrews, Timothy, et al. “Forcing, feedbacks and climate sensitivity in CMIP5 coupled atmosphere‐ocean climate models.” Geophysical Research Letters 39.9 (2012). We quantify forcing and feedbacks across available CMIP5 coupled atmosphere‐ocean general circulation models (AOGCMs) by analysing simulations forced by an abrupt quadrupling of atmospheric carbon dioxide concentration. This is the first application of the linear forcing‐feedback regression analysis of Gregory et al. (2004) to an ensemble of AOGCMs. The range of equilibrium climate sensitivity is 2.1–4.7 K. Differences in cloud feedbacks continue to be important contributors to this range. Some models show small deviations from a linear dependence of top‐of‐atmosphere radiative fluxes on global surface temperature change. We show that this phenomenon largely arises from shortwave cloud radiative effects over the ocean and is consistent with independent estimates of forcing using fixed sea‐surface temperature methods. We suggest that future research should focus more on understanding transient climate change, including any time‐scale dependence of the forcing and/or feedback, rather than on the equilibrium response to large instantaneous forcing.
72. 2012: Bitz, Cecilia M., et al. “Climate sensitivity of the community climate system model, version 4.” Journal of Climate 25.9 (2012): 3053-3070.Equilibrium climate sensitivity of the Community Climate System Model, version 4 (CCSM4) is 3.20°C for 1° horizontal resolution in each component. This is about a half degree Celsius higher than in the previous version (CCSM3). The transient climate sensitivity of CCSM4 at 1° resolution is 1.72°C, which is about 0.2°C higher than in CCSM3. These higher climate sensitivities in CCSM4 cannot be explained by the change to a preindustrial baseline climate. This study uses the radiative kernel technique to show that, from CCSM3 to CCSM4, the global mean lapse-rate feedback declines in magnitude and the shortwave cloud feedback increases. These two warming effects are partially canceled by cooling because of slight decreases in the global mean water vapor feedback and longwave cloud feedback from CCSM3 to CCSM4. A new formulation of the mixed layer, slab-ocean model in CCSM4 attempts to reproduce the SST and sea ice climatology from an integration with a full-depth ocean, and it is integrated with a dynamic sea ice model. These new features allow an isolation of the influence of ocean dynamical changes on the climate response when comparing integrations with the slab ocean and full-depth ocean. The transient climate response of the full-depth ocean version is 0.54 of the equilibrium climate sensitivity when estimated with the new slab-ocean model version for both CCSM3 and CCSM4. The authors argue the ratio is the same in both versions because they have about the same zonal mean pattern of change in ocean surface heat flux, which broadly resembles the zonal mean pattern of net feedback strength.
73. 2012: Rogelj, Joeri, Malte Meinshausen, and Reto Knutti. “Global warming under old and new scenarios using IPCC climate sensitivity range estimates.” Nature climate change 2.4 (2012): 248. Climate projections for the fourth assessment report¹ (AR4) of the Intergovernmental Panel on Climate Change (IPCC) were based on scenarios from the Special Report on Emissions Scenarios² (SRES) and simulations of the third phase of the Coupled Model Intercomparison Project³ (CMIP3). Since then, a new set of four scenarios (the representative concentration pathways or RCPs) was designed⁴. Climate projections in the IPCC fifth assessment report (AR5) will be based on the fifth phase of the Coupled Model Intercomparison Project⁵ (CMIP5), which incorporates the latest versions of climate models and focuses on RCPs. This implies that by AR5 both models and scenarios will have changed, making a comparison with earlier literature challenging. To facilitate this comparison, we provide probabilistic climate projections of both SRES scenarios and RCPs in a single consistent framework. These estimates are based on a model set-up that probabilistically takes into account the overall consensus understanding of climate sensitivity uncertainty, synthesizes the understanding of climate system and carbon-cycle behaviour, and is at the same time constrained by the observed historical warming.
74. 2014: Sherwood, Steven C., Sandrine Bony, and Jean-Louis Dufresne. “Spread in model climate sensitivity traced to atmospheric convective mixing.” Nature 505.7481 (2014): 37. Equilibrium climate sensitivity refers to the ultimate change in global mean temperature in response to a change in external forcing. Despite decades of research attempting to narrow uncertainties, equilibrium climate sensitivity estimates from climate models still span roughly 1.5 to 5 degrees Celsius for a doubling of atmospheric carbon dioxide concentration, precluding accurate projections of future climate. The spread arises largely from differences in the feedback from low clouds, for reasons not yet understood. Here we show that differences in the simulated strength of convective mixing between the lower and middle tropical troposphere explain about half of the variance in climate sensitivity estimated by 43 climate models. The apparent mechanism is that such mixing dehydrates the low-cloud layer at a rate that increases as the climate warms, and this rate of increase depends on the initial mixing strength, linking the mixing to cloud feedback. The mixing inferred from observations appears to be sufficiently strong to imply a climate sensitivity of more than 3 degrees for a doubling of carbon dioxide. This is significantly higher than the currently accepted lower bound of 1.5 degrees, thereby constraining model projections towards relatively severe future warming.
75. 2015: Mauritsen, Thorsten, and Bjorn Stevens. “Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models.” Nature Geoscience 8.5 (2015): 346. Equilibrium climate sensitivity to a doubling of CO₂ falls between 2.0 and 4.6 K in current climate models, and they suggest a weak increase in global mean precipitation. Inferences from the observational record, however, place climate sensitivity near the lower end of this range and indicate that models underestimate some of the changes in the hydrological cycle. These discrepancies raise the possibility that important feedbacks are missing from the models. A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models. We find that inclusion of such an effect in a climate model moves the simulated responses of both temperature and the hydrological cycle to rising atmospheric greenhouse gas concentrations closer to observations. Alternative suggestions for shortcomings of models — such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake — may explain a slow observed transient warming relative to models, but not the observed enhancement of the hydrological cycle. We propose that, if precipitating convective clouds are more likely to cluster into larger clouds as temperatures rise, this process could constitute a plausible physical mechanism for an iris effect.
76. 2015: Schimel, David, Britton B. Stephens, and Joshua B. Fisher. “Effect of increasing CO2 on the terrestrial carbon cycle.” Proceedings of the National Academy of Sciences 112.2 (2015): 436-441. Feedbacks from terrestrial ecosystems to atmospheric CO₂ concentrations contribute the second-largest uncertainty to projections of future climate. These feedbacks, acting over huge regions and long periods of time, are extraordinarily difficult to observe and quantify directly. We evaluated in situ, atmospheric, and simulation estimates of the effect of CO₂ on carbon storage, subject to mass balance constraints. Multiple lines of evidence suggest significant tropical uptake for CO₂, approximately balancing net deforestation and confirming a substantial negative global feedback to atmospheric CO₂ and climate. This reconciles two approaches that have previously produced contradictory results. We provide a consistent explanation of the impacts of CO₂ on terrestrial carbon across the 12 orders of magnitude between plant stomata and the global carbon cycle.
77. 2016: Tan, Ivy, Trude Storelvmo, and Mark D. Zelinka. “Observational constraints on mixed-phase clouds imply higher climate sensitivity.” Science 352.6282 (2016): 224-227. How much global average temperature eventually will rise depends on the Equilibrium Climate Sensitivity (ECS), which relates atmospheric CO₂ concentration to atmospheric temperature. For decades, ECS has been estimated to be between 2.0° and 4.6°C, with much of that uncertainty owing to the difficulty of establishing the effects of clouds on Earth’s energy budget. Tan et al. used satellite observations to constrain the radiative impact of mixed phase clouds. They conclude that ECS could be between 5.0° and 5.3°C—higher than suggested by most global climate models.
78. 2018: Watanabe, Masahiro, et al. “Low clouds link equilibrium climate sensitivity to hydrological sensitivity.” Nature Climate Change (2018): 1. Equilibrium climate sensitivity (ECS) and hydrological sensitivity describe the global mean surface temperature and precipitation responses to a doubling of atmospheric CO₂. Despite their connection via the Earth’s energy budget, the physical linkage between these two metrics remains controversial. Here, using a global climate model with a perturbed mean hydrological cycle, we show that ECS and hydrological sensitivity per unit warming are anti-correlated owing to the low-cloud response to surface warming. When the amount of low clouds decreases, ECS is enhanced through reductions in the reflection of shortwave radiation. In contrast, hydrological sensitivity is suppressed through weakening of atmospheric longwave cooling, necessitating weakened condensational heating by precipitation. These compensating cloud effects are also robustly found in a multi-model ensemble, and further constrained using satellite observations. Our estimates, combined with an existing constraint to clear-sky shortwave absorption, suggest that hydrological sensitivity could be lower by 30% than raw estimates from global climate models.
79. 2010: Moss, Richard H., et al. “The next generation of scenarios for climate change research and assessment.” Nature 463.7282 (2010): 747. Advances in the science and observation of climate change are providing a clearer understanding of the inherent variability of Earth’s climate system and its likely response to human and natural influences. The implications of climate change for the environment and society will depend not only on the response of the Earth system to changes in radiative forcings, but also on how humankind responds through changes in technology, economies, lifestyle and policy. Extensive uncertainties exist in future forcings of and responses to climate change, necessitating the use of scenarios of the future to explore the potential consequences of different response options. To date, such scenarios have not adequately examined crucial possibilities, such as climate change mitigation and adaptation, and have relied on research processes that slowed the exchange of information among physical, biological and social scientists. Here we describe a new process for creating plausible scenarios to investigate some of the most challenging and important questions about climate change confronting the global community.
80. 2011: Meinshausen, Malte, et al. “The RCP greenhouse gas concentrations and their extensions from 1765 to 2300.” Climatic change 109.1-2 (2011): 213. We present the greenhouse gas concentrations for the Representative Concentration Pathways (RCPs) and their extensions beyond 2100, the Extended Concentration Pathways (ECPs). These projections include all major anthropogenic greenhouse gases and are a result of a multi-year effort to produce new scenarios for climate change research. We combine a suite of atmospheric concentration observations and emissions estimates for greenhouse gases (GHGs) through the historical period (1750–2005) with harmonized emissions projected by four different Integrated Assessment Models for 2005–2100. As concentrations are somewhat dependent on the future climate itself (due to climate feedbacks in the carbon and other gas cycles), we emulate median response characteristics of models assessed in the IPCC Fourth Assessment Report using the reduced-complexity carbon cycle climate model MAGICC6. Projected ‘best-estimate’ global-mean surface temperature increases (using inter alia a climate sensitivity of 3°C) range from 1.5°C by 2100 for the lowest of the four RCPs, called both RCP3-PD and RCP2.6, to 4.5°C for the highest one, RCP8.5, relative to pre-industrial levels. Beyond 2100, we present the ECPs that are simple extensions of the RCPs, based on the assumption of either smoothly stabilizing concentrations or constant emissions: For example, the lower RCP2.6 pathway represents a strong mitigation scenario and is extended by assuming constant emissions after 2100 (including net negative CO₂ emissions), leading to CO₂ concentrations returning to 360 ppm by 2300. We also present the GHG concentrations for one supplementary extension, which illustrates the stringent emissions implications of attempting to go back to ECP4.5 concentration levels by 2250 after emissions during the 21^st century followed the higher RCP6 scenario. Corresponding radiative forcing values are presented for the RCP and ECPs
81. 2012: Taylor, Karl E., Ronald J. Stouffer, and Gerald A. Meehl. “An overview of CMIP5 and the experiment design.” Bulletin of the American Meteorological Society 93.4 (2012): 485-498. The fifth phase of the Coupled Model Intercomparison Project (CMIP5) will produce a state-of-the- art multimodel dataset designed to advance our knowledge of climate variability and climate change. Researchers worldwide are analyzing the model output and will produce results likely to underlie the forthcoming Fifth Assessment Report by the Intergovernmental Panel on Climate Change. Unprecedented in scale and attracting interest from all major climate modeling groups, CMIP5 includes “long term” simulations of twentieth-century climate and projections for the twenty-first century and beyond. Conventional atmosphere–ocean global climate models and Earth system models of intermediate complexity are for the first time being joined by more recently developed Earth system models under an experiment design that allows both types of models to be compared to observations on an equal footing. Besides the longterm experiments, CMIP5 calls for an entirely new suite of “near term” simulations focusing on recent decades and the future to year 2035. These “decadal predictions” are initialized based on observations and will be used to explore the predictability of climate and to assess the forecast system’s predictive skill. The CMIP5 experiment design also allows for participation of stand-alone atmospheric models and includes a variety of idealized experiments that will improve understanding of the range of model responses found in the more complex and realistic simulations. An exceptionally comprehensive set of model output is being collected and made freely available to researchers through an integrated but distributed data archive. For researchers unfamiliar with climate models, the limitations of the models and experiment design are described.
82. 2012: Meehl, Gerald A., et al. “Climate system response to external forcings and climate change projections in CCSM4.” Journal of Climate 25.11 (2012): 3661-3683. Results are presented from experiments performed with the Community Climate System Model, version 4 (CCSM4) for the Coupled Model Intercomparison Project phase 5 (CMIP5). These include multiple ensemble members of twentieth-century climate with anthropogenic and natural forcings as well as single-forcing runs, sensitivity experiments with sulfate aerosol forcing, twenty-first-century representative concentration pathway (RCP) mitigation scenarios, and extensions for those scenarios beyond 2100–2300. Equilibrium climate sensitivity of CCSM4 is 3.20°C, and the transient climate response is 1.73°C. Global surface temperatures averaged for the last 20 years of the twenty-first century compared to the 1986–2005 reference period for six-member ensembles from CCSM4 are +0.85°, +1.64°, +2.09°, and +3.53°C for RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. The ocean meridional overturning circulation (MOC) in the Atlantic, which weakens during the twentieth century in the model, nearly recovers to early twentieth-century values in RCP2.6, partially recovers in RCP4.5 and RCP6, and does not recover by 2100 in RCP8.5. Heat wave intensity is projected to increase almost everywhere in CCSM4 in a future warmer climate, with the magnitude of the increase proportional to the forcing. Precipitation intensity is also projected to increase, with dry days increasing in most subtropical areas. For future climate, there is almost no summer sea ice left in the Arctic in the high RCP8.5 scenario by 2100, but in the low RCP2.6 scenario there is substantial sea ice remaining in summer at the end of the century.
83. 2012: Taylor, Karl E., Ronald J. Stouffer, and Gerald A. Meehl. “An overview of CMIP5 and the experiment design.” Bulletin of the American Meteorological Society 93.4 (2012): 485-498. The fifth phase of the Coupled Model Intercomparison Project (CMIP5) will produce a state-of-the- art multimodel dataset designed to advance our knowledge of climate variability and climate change. Researchers worldwide are analyzing the model output and will produce results likely to underlie the forthcoming Fifth Assessment Report by the Intergovernmental Panel on Climate Change. Unprecedented in scale and attracting interest from all major climate modeling groups, CMIP5 includes “long term” simulations of twentieth-century climate and projections for the twenty-first century and beyond. Conventional atmosphere–ocean global climate models and Earth system models of intermediate complexity are for the first time being joined by more recently developed Earth system models under an experiment design that allows both types of models to be compared to observations on an equal footing. Besides the longterm experiments, CMIP5 calls for an entirely new suite of “near term” simulations focusing on recent decades and the future to year 2035. These “decadal predictions” are initialized based on observations and will be used to explore the predictability of climate and to assess the forecast system’s predictive skill. The CMIP5 experiment design also allows for participation of stand-alone atmospheric models and includes a variety of idealized experiments that will improve understanding of the range of model responses found in the more complex and realistic simulations. An exceptionally comprehensive set of model output is being collected and made freely available to researchers through an integrated but distributed data archive. For researchers unfamiliar with climate models, the limitations of the models and experiment design are described.
84. 2013: Zou, Liwei, and Tianjun Zhou. “Near future (2016-40) summer precipitation changes over China as projected by a regional climate model (RCM) under the RCP8. 5 emissions scenario: Comparison between RCM downscaling and the driving GCM.” Advances in Atmospheric Sciences 30.3 (2013): 806-818. Multi-decadal high resolution simulations over the CORDEX East Asia domain were performed with the regional climate model RegCM3 nested within the Flexible Global Ocean-Atmosphere-Land System model, Grid-point Version 2 (FGOALS-g2). Two sets of simulations were conducted at the resolution of 50 km, one for present day (1980–2005) and another for near-future climate (2015–40) under the Representative Concentration Pathways 8.5 (RCP8.5) scenario. Results show that RegCM3 adds value with respect to FGOALS-g2 in simulating the spatial patterns of summer total and extreme precipitation over China for present day climate. The major deficiency is that RegCM3 underestimates both total and extreme precipitation over the Yangtze River valley. The potential changes in total and extreme precipitation over China in summer under the RCP8.5 scenario were analyzed. Both RegCM3 and FGOALS-g2 results show that total and extreme precipitation tend to increase over northeastern China and the Tibetan Plateau, but tend to decrease over southeastern China. In both RegCM3 and FGOALS-g2, the change in extreme precipitation is weaker than that for total precipitation.RegCM3 projects much stronger amplitude of total and extreme precipitation changes and provides more regional-scale features than FGOALS-g2. A large uncertainty is found over the Yangtze River valley, where RegCM3 and FGOALS-g2 project opposite signs in terms of precipitation changes. The projected change of vertically integrated water vapor flux convergence generally follows the changes in total and extreme precipitation in both RegCM3 and FGOALS-g2, while the amplitude of change is stronger in RegCM3. Results suggest that the spatial pattern of projected precipitation changes may be more affected by the changes in water vapor flux convergence, rather than moisture content itself.
85. 2013: Forster, Piers M., et al. “Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models.” Journal of Geophysical Research: Atmospheres 118.3 (2013): 1139-1150. We utilize energy budget diagnostics from the Coupled Model Intercomparison Project phase 5 (CMIP5) to evaluate the models’ climate forcing since preindustrial times employing an established regression technique. The climate forcing evaluated this way, termed the adjusted forcing (AF), includes a rapid adjustment term associated with cloud changes and other tropospheric and land‐surface changes. We estimate a 2010 total anthropogenic and natural AF from CMIP5 models of 1.9 ± 0.9 W m⁻² (5–95% range). The projected AF of the Representative Concentration Pathway simulations are lower than their expected radiative forcing (RF) in 2095 but agree well with efficacy weighted forcings from integrated assessment models. The smaller AF, compared to RF, is likely due to cloud adjustment. Multimodel time series of temperature change and AF from 1850 to 2100 have large intermodel spreads throughout the period. The intermodel spread of temperature change is principally driven by forcing differences in the present day and climate feedback differences in 2095, although forcing differences are still important for model spread at 2095. We find no significant relationship between the equilibrium climate sensitivity (ECS) of a model and its 2003 AF, in contrast to that found in older models where higher ECS models generally had less forcing. Given the large present‐day model spread, there is no indication of any tendency by modelling groups to adjust their aerosol forcing in order to produce observed trends. Instead, some CMIP5 models have a relatively large positive forcing and overestimate the observed temperature change.
86. 2014: Friedlingstein, Pierre, et al. “Uncertainties in CMIP5 climate projections due to carbon cycle feedbacks.” Journal of Climate27.2 (2014): 511-526. In the context of phase 5 of the Coupled Model Intercomparison Project, most climate simulations use prescribed atmospheric CO₂ concentration and therefore do not interactively include the effect of carbon cycle feedbacks. However, the representative concentration pathway 8.5 (RCP8.5) scenario has additionally been run by earth system models with prescribed CO₂ emissions. This paper analyzes the climate projections of 11 earth system models (ESMs) that performed both emission-driven and concentration-driven RCP8.5 simulations. When forced by RCP8.5 CO₂ emissions, models simulate a large spread in atmospheric CO₂; the simulated 2100 concentrations range between 795 and 1145 ppm. Seven out of the 11 ESMs simulate a larger CO₂ (on average by 44 ppm, 985 ± 97 ppm by 2100) and hence higher radiative forcing (by 0.25 W m⁻²) when driven by CO₂ emissions than for the concentration-driven scenarios (941 ppm). However, most of these models already overestimate the present-day CO₂, with the present-day biases reasonably well correlated with future atmospheric concentrations’ departure from the prescribed concentration. The uncertainty in CO₂ projections is mainly attributable to uncertainties in the response of the land carbon cycle. As a result of simulated higher CO₂ concentrations than in the concentration-driven simulations, temperature projections are generally higher when ESMs are driven with CO₂ emissions. Global surface temperature change by 2100 (relative to present day) increased by 3.9° ± 0.9°C for the emission-driven simulations compared to 3.7° ± 0.7°C in the concentration-driven simulations. Although the lower ends are comparable in both sets of simulations, the highest climate projections are significantly warmer in the emission-driven simulations because of stronger carbon cycle feedbacks.
87. 2015: Kay, J. E., et al. “The Community Earth System Model (CESM) large ensemble project: A community resource for studying climate change in the presence of internal climate variability.” Bulletin of the American Meteorological Society 96.8 (2015): 1333-1349. While internal climate variability is known to affect climate projections, its influence is often underappreciated and confused with model error. Why? In general, modeling centers contribute a small number of realizations to international climate model assessments [e.g., phase 5 of the Coupled Model Intercomparison Project (CMIP5)]. As a result, model error and internal climate variability are difficult, and at times impossible, to disentangle. In response, the Community Earth System Model (CESM) community designed the CESM Large Ensemble (CESM-LE) with the explicit goal of enabling assessment of climate change in the presence of internal climate variability. All CESM-LE simulations use a single CMIP5 model (CESM with the Community Atmosphere Model, version 5). The core simulations replay the twenty to twenty-first century (1920–2100) 30 times under historical and representative concentration pathway 8.5 external forcing with small initial condition differences. Two companion 1000+-yr-long preindustrial control simulations (fully coupled, prognostic atmosphere and land only) allow assessment of internal climate variability in the absence of climate change. Comprehensive outputs, including many daily fields, are available as single-variable time series on the Earth System Grid for anyone to use. Early results demonstrate the substantial influence of internal climate variability on twentieth- to twenty-first-century climate trajectories. Global warming hiatus decades occur, similar to those recently observed. Internal climate variability alone can produce projection spread comparable to that in CMIP5. Scientists and stakeholders can use CESM-LE outputs to help interpret the observational record, to understand projection spread and to plan for a range of possible futures influenced by both internal climate variability and forced climate change.
88. 2015: Feldman, Daniel R., et al. “Observational determination of surface radiative forcing by CO 2 from 2000 to 2010.” Nature519.7543 (2015): 339. The climatic impact of CO₂ and other greenhouse gases is usually quantified in terms of radiative forcing¹, calculated as the difference between estimates of the Earth’s radiation field from pre-industrial and present-day concentrations of these gases. Radiative transfer models calculate that the increase in CO₂ since 1750 corresponds to a global annual-mean radiative forcing at the tropopause of 1.82 ± 0.19 W m⁻²(ref. 2). However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the radiative impact of increasing atmospheric CO₂. Here we present observationally based evidence of clear-sky CO₂ surface radiative forcing that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO₂. The time series of this forcing at the two locations—the Southern Great Plains and the North Slope of Alaska—are derived from Atmospheric Emitted Radiance Interferometer spectra³together with ancillary measurements and thoroughly corroborated radiative transfer calculations⁴. The time series both show statistically significant trends of 0.2 W m⁻² per decade (with respective uncertainties of ±0.06 W m⁻² per decade and ±0.07 W m⁻² per decade) and have seasonal ranges of 0.1–0.2 W m⁻². This is approximately ten per cent of the trend in downwelling longwave radiation^5,6,7. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO₂ levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.
89. 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]
90. 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.
91. 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.
92. 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.
93. 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.
94. 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.
95. 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.
96. 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] 
97. 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.
98. 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.
99. 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: 
100. 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.
101. 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.
102. 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]
103. 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]
104. 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 content^2,3and 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 atmosphere^6,7 and a reduction in rainfall^6,8,9, as well as other changes in the climate system⁷. Here we use observations of ocean heat content^2,3 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 precipitation^6,8,9. 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
105. 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.
106. 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.
107. 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).
108. 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.
109. 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]
110. 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 century^1,2, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming^3,4,5,6, 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.
111. 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.
112. 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.
113. 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 projections^1,2,3. 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.
114. 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]
115. 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.
116. 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]
117. 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.
118. 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]
119. 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 timescales^1,2,3,4,5. However, it is not quantitatively understood how this near-linear dependence between warming and cumulative carbon emissions arises in transient climate simulations^6,7. 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.
120. 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.
121. 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.
122. 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.
123. 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.
124. 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.
125. 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]
126. 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]
127. 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]
128. 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]
129. 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 K_v ≡ −/(∂p/∂z), normally assumed to be constant. Recent evidence from stratified lakes, fjords and oceans suggests that K_v 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 K_v 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 K_v from observable quantities. Most techniques reveal a disagreeable degree of model-dependence, frequently providing only upper bounds to the magnitude of K_v. 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 K_v 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 K_v.
130. 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.
131. 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.
132. 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.
133. 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.
134. 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.
135. 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.
136. 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]
137. 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.
138. 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 θ–S (potential temperature-salinity) relation remains nearly linear. When geothermal heating dominates, the θ–Srelation 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.
139. 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]
140. 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]
141. 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.
142. 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 waters^2,3, 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 4, 5) 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.
143. 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
144. 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.
145. 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., 1994; Johnson 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.
146. 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.
147. 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.
148. 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]
149. 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.
150. 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.
151. 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
152. 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
153. 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.
154. 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.
155. 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.

Don’t you understand, what I’m trying to say?
Can’t you feel the fears I’m feeling today?
If the carbon budget is crossed, there’s no running away,
There’ll be no one to save when the planet’s in the grave,
Take a look around you, boy, the climate’s bound to scare you, boy,
And you tell me over and over and over again my friend,
Ah, you don’t believe we’re on the eve of destruction.
Yeah, my blood’s so mad, feels like coagulatin’,
I’m sittin’ here, just contemplatin’,
I can twist the truth, until it is a scarin’,
The bad bad deniers want to stop climate action
And consensus alone must stop the denyin’,
When the climate system is disintegratin’,
And the sea level rise is just too frustratin’,
And you tell me over and over and over again my friend,
Ah, you don’t believe we’re on the eve of destruction.
Think of all the coal there is in Red China!
Then take a look around at Trump’s West Virginia!
Ah, you may leave here, for four days in space,
But when your return, it’s the climate change place,
Our carbon emission is a goddam disgrace,
If you drive your SUV don’t show your face,
Your carbon lifestyle is killing this place,
And you tell me over and over and over and over again my friend,
You don’t believe we’re on the eve of destruction.
No, no, you don’t believe we’re on the eve of destruction.

With apologies to Barry McGuire and P.F. Sloan

Press Conference at the Launch of the IPCC Synthesis Report (Tivoli Conference Center, Lumbye Room) (REMARKS, Q&A) (with Mrs. Ban) (Nesirky)