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MIOCENE HOMINIDS

 

 

MIOCENE ANIMALS

 

 

 

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MIOCENE TEMPERATURES

1. The Miocene Age extends over a period of ≈18 million years from ≈23Ma to ≈5Ma. As seen in the deep sea and air temperature charts above, over this period the earth continued the cooling and glaciation trend that had started in the Oligocene (warmer than the Miocene) and that continued into the Pliocene (cooler than the Miocene) in a series of ice ages.  Of interest in this post is the period of warming in middle of the Miocene labeled in the chart above as the “Mid Miocene Climate Optimum”  that began ≈16 Ma and that returned to the glaciation cooling trend ≈14 Ma (Ma=millions of years ago) with a rapid expansion of the East Antarctic Ice Sheet.
2. This two million years of warming is thought to have parallels with and important lessons for the current 160-year warming trend attributed to CO2 emissions from the use of fossil fuels by the industrial economy, particularly so in terms of the greenhouse effect of atmospheric CO2 and in terms of the possible catastrophic consequences, such as ice sheet collapse and sea level rise, of a CO2 driven warming trend. 
3. What makes the comparison of the Mid Miocene Climate Optimum with the current warming event attractive is that temperatures and atmospheric CO2 concentrations of that time were comparable with what we see today in the AGW warming event. Estimates from paleo data show that global mean temperature during the Mid Miocene global warming event peaked at 18.4C, about 3C warmer than the present and equal to the projected temperature in the year 2100 under the RCP8.5 business as usual scenario. This convenient equivalence is the basis for the usual assumption that the horror of our future without climate action can be seen in the past in terms of Mid Miocene warming event.
4. When the world cooled from the warmer late Oligocene to the Miocene in a cooling trend, atmospheric CO2 dropped from 350 ppm to a much lower level in the range 190-260 ppm. This gradual decrease in atmospheric CO2 during a time of cooling is considered to be consistent with the greenhouse effect of atmospheric CO2. This interpretation of the data without further statistical tests is likely to be one of convenience and confirmation bias since the observed association can be interpreted in terms of causation in either direction or of causation of both by a third unobserved variable, or even as a spurious relationship with no causation information.
5. In fact, this interpretation is confounded by what happened in the Mid-Miocene warming event. As temperatures rose from ≈12C to ≈18C, atmospheric CO2 levels dropped to the low end of the (190-260 ppm) range. If these changes are to be interpreted in terms of the CO2 greenhouse effect, the the CO2 level should have been higher at 18C than at 12C. Climate models show that under prevailing conditions in the Mid Miocene, AGW theory predicts atmospheric CO2 concentrations rising from 300 ppm to 600 ppm as described in the You paper below. References in the literature to the atmosphere being “supercharged with carbon dioxide” (Levy and Meyers, 2019) at this time may be a reference to these high values of atmospheric CO2 derived from climate models. These CO2 values are “inferred” and not observed. Their interpretation as observed data involves circular reasoning.
6. A further difficulty in interpreting these changes in terms of the greenhouse effect of CO2 is the spectacular growth of the East Antarctic Ice Sheet during the MMGW event without an associated sharp decrease in atmospheric CO2. In fact, toward the end of the massive growth in the East Antarctic ice sheet, atmospheric CO2 levels were higher at around 280 ppm equivalent to “pre-industrial” levels in the current warming event. As seen in the bibliography below, the general consensus is that the MMGW event is not an analog to the AGW event and not a demonstration of the greenhouse effect of atmospheric CO2. The analogy involves serious anomalies and paradoxical events.
7. The general consensus in the bibliography below seems to be that the Mid Miocene warming event is best explained in terms of deep ocean circulation or the so called “oceanographic control of Miocene climate”. Many of these authors who are still in paleo climate research now tend to soft pedal these anomalies and discrepancies in public discourse to present the Mid Miocene warming in terms of the CO2 greenhouse effect although their new improved assessment appears to contradict what they had written twenty or more years ago. In many of the works below, particularly the later papers, it appears that the authors are struggling to relate grossly anomalous situations to the greenhouse effect of atmospheric CO2.

 

 

 

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KATHERINE FREEMAN AND MARK PAGANI

 

 

 

MIOCENE CO2 BIBLIOGRAPHY

1. 1985: Barron, Eric J., and Warren M. Washington. “Warm Cretaceous climates: High atmospheric CO2 as a plausible mechanism.” The Carbon Cycle and Atmospheric CO2: Natural Variations Archean to Present 32 (1985): 546-553.  Sensitivity experiments with a general circulation model of the atmosphere coupled to a simple ocean model are the basis for an investigation of whether changing geography is a sufficient mechanism to explain warm Cretaceous (≈100 Ma) climates or whether other mechanisms, such as a higher atmospheric CO₂ concentration, are required. Although Cretaceous geography results in a substantial warming in comparison with the present day, the warming is insufficient to explain the geologic data. Several lines of evidence suggest that an estimated two to tenfold increase in CO₂ with respect to present values is a plausible explanation of this problem. Higher values of CO₂ result in additional climate problems. These model experiments have implications for geochemical models with climate‐dependent weathering rates.
2. 1985: Vincent, Edith, and Wolfgang H. Berger. “Carbon dioxide and polar cooling in the Miocene: The Monterey hypothesis.” The carbon cycle and atmospheric CO2: Natural variations Archean to present 32 (1985): 455-468.A pronounced shift in the δ¹³C of foraminifera in the latest early Miocene has been proposed by various authors. Our data in the tropical Indian Ocean show an excursion of δ¹³C signals toward heavier values, lasting for about 4 million years. The excursion is documented for benthic foraminifera as well as for deep‐living and for shallow‐dwelling planktonic species. The initial δ¹³c shift occurs within Magnetic Chron 16, at about 17.5 Ma. It represents a change toward heavier δ¹³C values by about 10/00 in surface and bottom waters. The excursion terminates at approximately 13.5 Ma. The Chron 16 Carbon shift coincides with the cessation of an early Miocene warming trend, seen in the δ¹⁸O signals. The mid‐Miocene cooling step (presumably associated with Antarctic ice buildup, near 15 Ma) is centered on the carbon isotope excursion. We propose that the initial carbon shift was caused by rapid extraction of organic carbon from the ocean‐atmosphere system. Subsequently, the excursion toward heavy values was maintained by continued extraction of organic carbon, into ocean‐margin deposits. Beginning at the end of the early Miocene, fine‐grained diatomaceous sediments rich in organic matter were deposited all around the margins of the northern Pacific. In California, these sediments are known as the Monterey Formation. This formation is the result of coastal upwelling, which arose because of the development of strong zonal winds and a strong permanent thermocline. Zonal winds and thermocline evolution, in turn, depended on increasing temperature contrast between high and low latitudes. We hypothesize that a feedback loop was established, such that an initial increase in the planetary temperature gradient started thermocline development which led to organic carbon extraction at the ocean margins which resulted in a drop in atmospheric carbon dioxide concentration. Concomitant cooling (reverse greenhouse effect) strengthened thermocline development, leading to further cooling. The loop was broken when available nutrients were used up. The total amount of excess carbon buildup, according to the hypothesis, is between 40 and 80 atmospheric carbon masses for the duration of the Monterey carbon isotope excursion. This amount corresponds to that present in the ocean, that is, one ocean carbon mass.
3. 1992: Wright, James D., Kenneth G. Miller, and Richard G. Fairbanks. “Early and middle Miocene stable isotopes: implications for deepwater circulation and climate.” Paleoceanography 7.3 (1992): 357-389.  The middle Miocene δ¹⁸O increase represents a fundamental change in the ocean‐atmosphere system which, like late Pleistocene climates, may be related to deepwater circulation patterns. There has been some debate concerning the early to early middle Miocene deepwater circulation patterns. Specifically, recent discussions have focused on the relative roles of Northern Component Water (NCW) production and warm, saline deep water originating in the eastern Tethys. Our time series and time slice reconstructions indicate that NCW and Tethyan outflow water, two relatively warm deepwater masses, were produced from ∼20 to 16 Ma. NCW was produced again from 12.5 to 10.5 Ma. Another feature of the early and middle Miocene oceans was the presence of a high δ¹³C intermediate water mass in the southern hemisphere, which apparently originated in the Southern Ocean. Miocene climates appear to be related directly to deepwater circulation changes. Deep‐waters warmed in the early Miocene by ∼3°C (∼20 to 16 Ma) and cooled by a similar amount during the middle Miocene δ¹⁸O increase (14.8 to 12.6 Ma), corresponding to the increase (∼20 Ma) and subsequent decrease (∼16 Ma) in the production of NCW and Tethyan outflow water. Large (>0.6 ‰), relatively rapid (∼0.5 m.y.) δ¹⁸O increases in both benthic and planktonic foraminifera (i.e., the Mi zones of Miller et al. (1991a) and Wright and Miller (1992a)) were superimposed in the long‐term deepwater temperature changes; they are interpreted as reflecting continental ice growth events. Seven of these m.y. glacial/interglacial cycles have been recognized in the early to middle Miocene. Two of these glacial/interglacial cycles (Mi3 and Mi4) combined with a 2° to 3°C decrease in deepwater temperatures to produce the middle Miocene δ¹⁸O shift.
4. 1994: Flower, Benjamin P., and James P. Kennett. “The middle Miocene climatic transition: East Antarctic ice sheet development, deep ocean circulation and global carbon cycling.” Palaeogeography, palaeoclimatology, palaeoecology108.3-4 (1994): 537-555. The middle Miocene represents a major change in state in Cenozoic climatic evolution, following the climax of Neogene warmth in the late early Miocene at ∼16 Ma. The early stage of this climatic transition from ∼16 to 14.8 Ma was marked by major short term variations in global climates, East Antarctic Ice Sheet (EAIS) volume, sea level, and deep ocean circulation. In the later stage from ∼14.8 to 12.9 Ma, climatic developments included major growth of the EAIS and associated Antarctic cooling, a distinct increase in the meridional temperature gradient, large fluctuations in sea level followed by a global sea level fall, and important changes in deep water circulation, including increased production of Southern Component Water. East Antarctic ice sheet growth and polar cooling also had large effects on global carbon cycling and on the terrestrial biosphere, including aridification of mid-latitude continental regions. Increased stability of the EAIS after 14.8 Ma represents a crucial step in the establishment of late Neogene global climate systems. What controlled these changes in polar climates and the East Antarctic ice sheet? Deep ocean circulation changes probably played a major role in the evolution and variation in polar climates, as they have throughout the Cenozoic. Oxygen and carbon isotopic evidence for warm, saline deep water production in the eastern Tethyan/northern Indian Ocean indicates that meridional heat transport to the Antarctic inhibited Cenozoic polar cooling and EAIS growth during the early middle Miocene from ∼16 to ∼14.8 Ma. Inferred competition between warm low-latitude sources (derived from the eastern Tethyan-northern Indian Ocean) and a cold high-latitude source (Southern Component Water) from ∼16 to 14.8 Ma may have been associated with instability in the Antarctic climate and cryosphere. Reduction of warm, saline deep water flow to the Southern Ocean at ∼14.8 Ma may have decreased meridional heat transport to the Antarctic, cooling the region and leading to increased production of Southern Component Water.These middle Miocene climatic and cryospheric changes in the Antarctic had profound effects on marine and terrestrial climates. As the meridional surface temperature gradient increased, boundaries between climatic zones strengthened, leading to increased aridification of mid-latitude continental regions in Australia, Africa and North and South America, enhancing the development of grasslands and stimulating the evolution of grazing mammals.
5. 1994: Schoell, M., et al. “A molecular organic carbon isotope record of Miocene climate changes.” Science 263.5150 (1994): 1122-1125.  The difference in carbon-13 (¹³C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in ¹⁸O (δ¹⁸O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (δ¹³C = 25.4 ± 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C₃₅ hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing ¹³C concentrations in Middle and Late Miocene samples (δ¹³C = –29.5 to –31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide—rich cold water mass at the base of the photic zone.
6. 1999: Pagani, Mark, Michael A. Arthur, and Katherine H. Freeman. “Miocene evolution of atmospheric carbon dioxide.” Paleoceanography 14.3 (1999): 273-292.  Changes in pCO₂ or ocean circulation are generally invoked to explain warm early Miocene climates and a rapid East Antarctic ice sheet (EAIS) expansion in the middle Miocene. This study reconstructs late Oligocene to late Miocene pCO₂ from ε_p values based on carbon isotopic analyses of diunsaturated alkenones and planktonic foraminifera from Deep Sea Drilling Project sites 588 and 608 and Ocean Drilling Program site 730. Our results indicate that highest pCO₂ occurred during the latest Oligocene (∼350 ppmv) but decreased rapidly at ∼25 Ma. The early and middle Miocene was characterized by low pCO₂ (260–190 ppmv). Lower intervals of pCO₂ correspond to inferred organic carbon burial events and glacial episodes with the lowest concentrations occurring during the middle Miocene. There is no evidence for either high pCO₂ during the late early Miocene climatic optimum or a sharp pCO₂ decrease associated with EAIS growth. Paradoxically, pCO₂ increased following EAIS growth and obtained preindustrial levels by ∼10 Ma. Although we emphasize an oceanographic control on Miocene climate, low pCO₂ could have primed the climate system to respond sensitively to changes in heat and vapor transport.
7. 1999: Pagani, Mark, Katherine H. Freeman, and Michael A. Arthur. “Late Miocene atmospheric CO2 concentrations and the expansion of C4 grasses.” Science 285.5429 (1999): 876-879.  The global expansion of C₄ grasslands in the late Miocene has been attributed to a large-scale decrease in atmospheric carbon dioxide (CO₂) concentrations. This triggering mechanism is controversial, in part because of a lack of direct evidence for change in the partial pressure of CO₂(pCO₂) and because other factors are also important determinants in controlling plant-type distributions. Alkenone-based pCO₂ estimates for the late Miocene indicate that pCO₂ increased from 14 to 9 million years ago and stabilized at preindustrial values by 9 million years ago. The estimates presented here provide no evidence for major changes in pCO₂ during the late Miocene. Thus, C₄ plant expansion was likely driven by additional factors, possibly a tectonically related episode of enhanced low-latitude aridity or changes in seasonal precipitation patterns on a global scale (or both).
8. 2001: Turco, E., et al. “Punctuated evolution of global climate cooling during the Late Middle to Early Late Miocene: High‐resolution planktonic foraminiferal and oxygen isotope records from the Mediterranean.” Paleoceanography 16.4 (2001): 405-423.  High‐resolution planktonic foraminiferal and oxygen isotope records are presented from a Mediterranean deep marine succession, dated astronomically between 12.12 and 9.78 Ma. Planktonic and benthic oxygen isotope records are punctuated by two episodes of δ¹⁸O increase, which have astronomical ages of 11.4 and 10.4 Ma and correspond to the Mi5 and Mi6 events of Miller et al. [1991a]. These ice growth events coincide with low‐amplitude variations in the 1.2 Myr obliquity cycle and are accompanied by significant faunal changes in the Mediterranean, such as the arrival of neogloboquadrinids, the increase in abundance of the G. apertura‐G. obliquus group, and the areal differentiation between N. atlantica and N. acostaensis. Short‐term variations in the planktonic foraminiferal and oxygen isotope records correspond to dominantly precession‐controlled sedimentary cycles. Features of the sapropel/grey marl layers indicate that the short‐term astronomically controlled circum‐Mediterranean climate changes remained basically the same over the last 12 Myr.
9. 2004: Shevenell, Amelia E., James P. Kennett, and David W. Lea. “Middle Miocene southern ocean cooling and Antarctic cryosphere expansion.” Science 305.5691 (2004): 1766-1770.  Magnesium/calcium data from Southern Ocean planktonic foraminifera demonstrate that high-latitude (∼55°S) southwest Pacific sea surface temperatures (SSTs) cooled 6° to 7°C during the middle Miocene climate transition (14.2 to 13.8 million years ago). Stepwise surface cooling is paced by eccentricity forcing and precedes Antarctic cryosphere expansion by ∼60 thousand years, suggesting the involvement of additional feedbacks during this interval of inferred low-atmospheric partial pressure of CO₂ (pCO₂). Comparing SSTs and global carbon cycling proxies challenges the notion that episodic pCO₂ drawdown drove this major Cenozoic climate transition. SST, salinity, and ice-volume trends suggest instead that orbitally paced ocean circulation changes altered meridional heat/vapor transport, triggering ice growth and global cooling.
10. 2005: Westerhold, T., Torsten Bickert, and Ursula Röhl. “Middle to late Miocene oxygen isotope stratigraphy of ODP site 1085 (SE Atlantic): new constrains on Miocene climate variability and sea-level fluctuations.” Palaeogeography, Palaeoclimatology, Palaeoecology 217.3 (2005): 205-222. The middle Miocene δ¹⁸O increase represents a fundamental change in earth’s climate system due to a major expansion and permanent establishment of the East Antarctic Ice Sheet accompanied by some effect of deepwater cooling. The long-term cooling trend in the middle to late Miocene was superimposed by several punctuated periods of glaciations (Mi-Events) characterized by oxygen isotopic shifts that have been related to the waxing and waning of the Antarctic ice-sheet and bottom water cooling. Here, we present a high-resolution benthic stable oxygen isotope record from ODP Site 1085 located at the southwestern African continental margin that provides a detailed chronology for the middle to late Miocene (13.9–7.3 Ma) climate transition in the eastern South Atlantic. A composite Fe intensity record obtained by XRF core scanning ODP Sites 1085 and 1087 was used to construct an astronomically calibrated chronology based on orbital tuning. The oxygen isotope data exhibit four distinct δ¹⁸O excursions, which have astronomical ages of 13.8, 13.2, 11.7, and 10.4 Ma and correspond to the Mi3, Mi4, Mi5, and Mi6 events. A global climate record was extracted from the oxygen isotopic composition. Both long- and short-term variabilities in the climate record are discussed in terms of sea-level and deep-water temperature changes. The oxygen isotope data support a causal link between sequence boundaries traced from the shelf and glacioeustatic changes due to ice-sheet growth. Spectral analysis of the benthic δ¹⁸O record shows strong power in the 400-kyr and 100-kyr bands documenting a paleoceanographic response to eccentricity-modulated variations in precession. A spectral peak around 180-kyr might be related to the asymmetry of the obliquity cycle indicating that the response of the dominantly unipolar Antarctic ice-sheet to obliquity-induced variations probably controlled the middle to late Miocene climate system. Maxima in the δ¹⁸O record, interpreted as glacial periods, correspond to minima in 100-kyr eccentricity cycle and minima in the 174-kyr obliquity modulation. Strong middle to late Miocene glacial events are associated with 400-kyr eccentricity minima and obliquity modulation minima. Thus, fluctuations in the amplitude of obliquity and eccentricity seem to be the driving force for the middle to late Miocene climate variability.
11. 2006: Jiménez-Moreno, Gonzalo. “Progressive substitution of a subtropical forest for a temperate one during the middle Miocene climate cooling in Central Europe according to palynological data from cores Tengelic-2 and Hidas-53 (Pannonian Basin, Hungary).” Review of Palaeobotany and Palynology 142.1-2 (2006): 1-14. The palynological analysis in the Karpatian–Sarmatian (late Early-Middle Miocene) interval of the cores Tengelic-2 and Hidas-53 (Hungary) reveals the existence of a forest organized in altitudinal belts, developed in a subtropical–warm temperate humid climate, reflecting the so-called Miocene climatic optimum. Pollen changes from the late early Miocene to the late middle Miocene have been observed and are related to climatic changes. The vegetation during the Burdigalian and the Langhian was dominated by thermophilous elements such as evergreen trees and Engelhardia, typical of a present day rain and evergreen forest at low altitudes (i.e. SE China). During the Serravallian several thermophilous elements strongly decreased, and some of them disappeared from the central European area. Thus, the rain and evergreen–deciduous mixed forest suffered a great transformation due to the loss and decrease in the abundance of several evergreen plants. This kind of vegetation was progressively substituted by deciduous and mesothermic plants such as deciduous Quercus, and Fagus, Alnus, Acer, Carpinus, Ulmus, Zelkova, etc. At the same time, the presence of altitude coniferous trees increased. This climatic cooling is correlated with global and regional climatic changes.
12. 2007: Holbourn, Ann, et al. “Orbitally-paced climate evolution during the middle Miocene “Monterey” carbon-isotope excursion.” Earth and Planetary Science Letters 261.3 (2007): 534-550.  One of the most enigmatic features of Cenozoic long-term climate evolution is the long-lasting positive carbon-isotope excursion or “Monterey Excursion”, which started during a period of global warmth after 16.9 Ma and ended at ∼ 13.5 Ma, approximately 400 kyr after major expansion of the Antarctic ice-sheet. We present high-resolution (1–9 kyr) astronomically-tuned climate proxy records in two complete sedimentary successions from the northwestern and southeastern Pacific (ODP Sites 1146 and 1237), which shed new light on the middle Miocene carbon-isotope excursion and associated climatic transition over the interval 17.1–12.7 Ma. We recognize three distinct climate phases with different imprints of orbital variations into the climatic signals (1146 and 1237 δ¹⁸O, δ¹³C; 1237 XRF Fe, fraction > 63 μm): (1) climate optimum prior to 14.7 Ma characterized by minimum ice volume and prominent 100 and 400 kyr variability, (2) long-term cooling from 14.7 to 13.9 Ma, principally driven by obliquity and culminating with rapid cryosphere expansion and global cooling at the onset of the last and most pronounced δ¹³C increase, (3) “Icehouse” mode after 13.9 Ma with distinct 100 kyr variability and improved ventilation of the deep Pacific. The “Monterey” carbon-isotope excursion (16.9–13.5 Ma) consists overall of nine 400 kyr cycles, which show high coherence with the long eccentricity period. Superposed on these low-frequency oscillations are high-frequency variations (100 kyr), which closely track the amplitude modulation of the short eccentricity period. In contrast to δ¹³C, the δ¹⁸O signal additionally shows significant power in the 41 kyr band, and the 1.2 Myr amplitude modulation of the obliquity cycle is clearly imprinted in the 1146 δ¹⁸O signal. Our results suggest that eccentricity was a prime pacemaker of middle Miocene climate evolution through the modulation of long-term carbon budgets and that obliquity-paced changes in high-latitude seasonality favored the transition into the “Icehouse” climate.
13. 2009: You, Y., et al. “Simulation of the middle Miocene climate optimum.” Geophysical Research Letters 36.4 (2009).  Proxy data constraining land and ocean surface paleo‐temperatures indicate that the Middle Miocene Climate Optimum (MMCO), a global warming event at ∼15 Ma, had a global annual mean surface temperature of 18.4°C, about 3°C higher than present and equivalent to the warming predicted for the next century. We apply the latest National Center for Atmospheric Research (NCAR) Community Atmosphere Model CAM3.1 and Land Model CLM3.0 coupled to a slab ocean to examine sensitivity of MMCO climate to varying ocean heat fluxes derived from paleo sea surface temperatures (SSTs) and atmospheric carbon dioxide concentrations, using detailed reconstructions of Middle Miocene boundary conditions including paleogeography, elevation, vegetation and surface temperatures. Our model suggests that to maintain MMCO warmth consistent with proxy data, the required atmospheric CO₂ concentration is about 460–580 ppmv, narrowed from the most recent estimate of 300–600 ppmv.  [FULL TEXT]
14. 2013: Badger, Marcus PS, et al. “CO2 drawdown following the middle Miocene expansion of the Antarctic Ice Sheet.” Paleoceanography 28.1 (2013): 42-53.  The development of a permanent, stable ice sheet in East Antarctica happened during the middle Miocene, about 14 million years (Myr) ago. The middle Miocene therefore represents one of the distinct phases of rapid change in the transition from the “greenhouse” of the early Eocene to the “icehouse” of the present day. Carbonate carbon isotope records of the period immediately following the main stage of ice sheet development reveal a major perturbation in the carbon system, represented by the positive δ¹³C excursion known as carbon maximum 6 (“CM6”), which has traditionally been interpreted as reflecting increased burial of organic matter and atmospheric pCO₂drawdown. More recently, it has been suggested that the δ¹³C excursion records a negative feedback resulting from the reduction of silicate weathering and an increase in atmospheric pCO₂. Here we present high‐resolution multi‐proxy (alkenone carbon and foraminiferal boron isotope) records of atmospheric carbon dioxide and sea surface temperature across CM6. Similar to previously published records spanning this interval, our records document a world of generally low (~300 ppm) atmospheric pCO₂ at a time generally accepted to be much warmer than today. Crucially, they also reveal a pCO₂decrease with associated cooling, which demonstrates that the carbon burial hypothesis for CM6 is feasible and could have acted as a positive feedback on global cooling. [FULL TEXT]
15. 2014: Greenop, Rosanna, et al. “Middle Miocene climate instability associated with high‐amplitude CO2 variability.” Paleoceanography and Paleoclimatology 29.9 (2014): 845-853.  The amplitude of climatic change, as recorded in the benthic oxygen isotope record, has varied throughout geological time. During the late Pleistocene, changes in the atmospheric concentration of carbon dioxide (CO₂) are an important control on this amplitude of variability. The contribution of CO₂ to climate variability during the pre‐Quaternary however is unknown. Here we present a new boron isotope‐based CO₂record for the transition into the middle Miocene Climatic Optimum (MCO) between 15.5 and 17 Myr that shows pronounced variability between 300 ppm and 500 ppm on a roughly 100 kyr time scale during the MCO. The CO₂ changes reconstructed for the Miocene are ~2 times larger in absolute terms (300 to 500 ppm compared to 180 to 280 ppm) than those associated with the late Pleistocene and ~15% larger in terms of climate forcing. In contrast, however, variability in the contemporaneous benthic oxygen isotope record (at ~1‰) is approximately two thirds the amplitude of that seen during the late Pleistocene. These observations indicate a lower overall sensitivity to CO₂ forcing for Miocene (Antarctic only) ice sheets than their late Pleistocene (Antarctic plus lower latitude northern hemisphere) counterparts. When our Miocene CO₂ record is compared to the estimated changes in contemporaneous δ¹⁸O_sw (ice volume), they point to the existence of two reservoirs of ice on Antarctica. One of these reservoirs appears stable, while a second reservoir shows a level of dynamism that contradicts the results of coupled climate‐ice sheet model experiments given the CO₂ concentrations that we reconstruct. [FULL TEXT]

 

 

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1. Climate mitigation pathways are based on carbon budgets  [LINK] .
2. Carbon budgets are derived from the TCRE transient climate response to cumulative emission [LINK] .
3. The TCRE is based on the observed near perfect correlation between mean global temperature and cumulative emissions  [LINK]
4. This correlation contains a fatal statistical flaw. It has neither time scale nor degrees of freedom.  [LINK]
5. When finite time scales are inserted the correlation is lost.  [LINK]
6. Therefore the correlation is spurious and the TCRE is a specious metric. Although a correlation can be computed and found to be statistically significant, the value computed has no interpretation in terms of phenomena under study.  [LINK]
7. The spuriousness of the TCRE can be demonstrated in a parody   [LINK]
8. CONCLUSION: Carbon budgets and emission pathways are just numbers. Though they can be computed, they have no interpretation in terms of phenomena  they apparently represent.
9. The speciousness of such carbon budgets and mitigation pathways is best understood in terms of the utility of counting the number of angels that can dance at the head of a pin.

 

 

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Melting Himalayan Glaciers Will Cause the Ganges to Run Dry

 

1. Reference: Himalayan glacier melts to hit billions of poor, Bangkok Post, December 7, 2009: In 2007, the IPCC issued a report citing data on the retreating Gangotri Glacier in the Himalayan mountains that showed that the rate of retreat had accelerated from 19 m/yr in 1971 to 34 m/yr in 2001. They extrapolated the observed acceleration forward and wrote that global warming devastation due to carbon dioxide was only a decade away for people who depend on the Ganges and other rivers with headwaters in the Himalayas. This scenario continues to be widely disseminated in the media (Himalayan glacier melts to hit billions of poor, Bangkok Post, December 7, 2009) in spite of more recent data that show that the predicted acceleration has not occurred; with the IPCC going so far as to vilify Indian scientists who who published the data as climate change deniers. In any case, the idea that glacial retreat in the Himalayas will cause the Ganges river to dry up is inconsistent with the observation that the river derives less than 5% of its water from glacial melt. Also of note is that a gradual decline in overall glacial mass worldwide began in 1850, well before fossil fuel consumption and atmospheric carbon dioxide rose to levels that the IPCC has identified with man-made global warming. Therefore it is not a carbon dioxide issue.
2. Destruction on a global level, Bangkok Post, December 17, 2009: The soil salinity problem in southern Bangladesh has been misrepresented as an effect of carbon dioxide and “rising seas” (Destruction on a global level, Bangkok Post, December 17, 2009). Shrimp farming did not take root because of soil salinity as claimed in the article. Rather, soil salinity took root because of shrimp farming as explained below. The export oriented shrimp farming boom in Bangladesh started twenty years ago and it caused large coastal agricultural areas to be leased, flooded with sea water, and converted into commercial shrimp farms. The boom went bust in 2008 after the financial crisis dried up the market for large and expensive shrimp in the West and the shrimp farms are being abandoned as a result. Abandoned shrimp farms leave behind agricultural wastelands because the salinity of the soil caused by shrimp farming makes it impossible to grow traditional crops. Farmers who leased their land out to shrimp producers now face a tragic situation because the leases have been terminated and they have taken possession of their farms but they can’t grow anything on them. It is a sad tale of human suffering and it deserves the attention of the appropriate relief agencies but it has absolutely nothing to do with carbon dioxide.
3. Melting ice to spur new climate deal, Bangkok Post, April 30, 2009: An article on global warming (Melting ice to spur new climate deal, Bangkok Post, April 30, 2009) says that carbon dioxide emissions from fossil fuels have caused the following alarming changes to our planet: (1) ice covering the Arctic Ocean shrank in 2007 to its smallest since satellite records began, (2) In Antarctica, a section of the Wilkins Ice Shelf has broken up in recent days, (3) glaciers in the Himalayan mountains are shrinking and threatening to disrupt water supplies to hundreds of millions of people, (4) melting permafrost in Siberia will release large quantities of methane into the atmosphere and hasten global warming, and (5) if all of the land based ice in Antarctica melted it would raise the sea level by 80 meters. The article fails to take note of the following data freely available in the public domain: (1) Arctic sea ice suffers a summer melt in every northern summer and that melt was greater than normal in 2007 and it encouraged global warming scientists to speculate that the sea ice would not fully recover in the following winter and thereby the Arctic would begin a non-linear process of forming less and less ice each winter until it became fully ice free. This speculation has been proven wrong. (2) the observed melting in the Wilkins ice shelf is a natural and insignificant event in the vast ice continent of Antarctica where the total mass of ice is increasing and not decreasing. (3) the Himalayan glacial melt is a reference to the data that the Gangotri glacier there had retreated by several hundred meters from 1780 to 2005 and global warming scientists predicted that the rate of retreat would accelerate and cause water supply devastation downstream. The predicted acceleration did not occur. Instead the rate of retreat actually slowed in 2007 and in 2008 it stopped altogether, (4) they have been telling us for more than five years now that the Siberian permafrost is about to melt and release methane devastation but there has been no sigh of this activity and Russian scientists have disputed these claims, and (5) if all the ice in Antarctica melted it would likely raise the sea level by 80 meters as claimed but this computation is purely a hypotherical and trivial conjecture for the subsumed melt has not started and if and when it does start, it will take many thousands of years to complete and the next ice age will surely intervene for the geological history of the earth shows that it is mostly an icy planet with brief interglacial balmy periods like the one in which we now find ourselves.
4. China’s growth could exceed planet’s resources, Bangkok Post, September 30, 2009: In the good old days the European races consumed all the resources of the planet and lived well and the rest of the world cooperated by staying poor and supplying resources and energy to fuel European wealth. This arrangement is now changing. About 3 billion Asians in China, South Asia, and Southeast Asia are undergoing rapid economic growth with steeply rising income and consumption – particularly the consumption of minerals and fossil fuels – to the point that it now seems that they aspire to live like Europeans. That is a scary prospect for the rich nations (China’s growth could exceed planet’s resources, Bangkok Post, September 30, 2009) because it implies competition for scarce resources with a population many times their own, living at the same standard of living and therefore consuming immense amounts of energy and resources. From their perspective, this scenario is intolerable and cannot be allowed to happen. Initial pleas to the Asians that they must not all drive cars, buy refrigerators, and live in heated and air-conditioned homes, that they must go back to their quaint ways and ride bicycles, have not had any success in stemming the Asian economic onslaught. That is why I believe the Europeans need something like a global warming Armageddon. Armed with that scenario, they can now tell the teeming Asian multitudes that they can’t all live like the Europeans do because that would overload the planet somehow and that overload would destroy them. That, I believe, is the genesis of the fossil fuels to Armageddon connection by way of carbon dioxide and global warming.
5. Himalayan ice is rapidly vanishing: Bangkok Post, December 13, 2009: An article in the Bangkok Post claims that “Himalayan ice is rapidly vanishing and will be gone by 2035 so the great rivers of Asia that are born there will shrivel and cease” to provide water to a quarter of humanity (The giant climate fraud in Copenhagen, Bangkok Post, December 13, 2009). The preposterous and scientifically impossible idea that the Himalayan ice will be gone by 2035 comes from the IPCC which initially cited a research paper that claimed that Himalayan glaciers will be gone by 2350. As this statement may not have contained the fear factor that the warmists wanted, the date has been whittled back to 2035 without explanation and Himalayan glaciers have been gradually expanded to include all Himalayan ice. As for rivers running dry, the IPCC specifically targets the Ganges river claiming it will go bone dry by 2035 because of vanishing ice. Kindly note that the Ganges derives less than 5% of its water from glacial melt.
6. Non-water flushing, Bangkok Post My Home Magazine, April 22, 2010: It has been a long and bitterly cold winter in the Himalayas with record snowfall; and so I was surprised to read in the Bangkok Post that the Mekong River is drying up because “the amount of ice and snow in the Himalayas this winter is less than usual, and much of it melted in January and February” due to global warming (Non-water flushing, Bangkok Post My Home Magazine, April 22, 2010). Has the global warming juggernaut reached such momentum that even actual weather data don’t matter?
7. The failure of climate scientists to make their case at the Copenhagen summit came on the heels of leaked emails from climate scientists that exposed a conspiracy to defraud. Even as the IPCC was in damage control mode to defend itself from these charges, there were further even more damaging revelations of scientific fraud and incompetence. It is now known that scores of their claims about devastation from carbon dioxide emissions including their claim that hurricane Katrina was caused by carbon dioxide emissions, that the Amazon forest will be turned into a savanna, that Africa’s agriculture and coral reefs worldwide would be devastated, that the Himalayan glaciers are melting and will be gone in 25 years, that the sea level is rising and inundating atolls in the Pacific, and that the Arctic will be ice free in 15 years, that that glaciers in the Alps and the Andes are in accelerated and alarming decline; are lies. The IPCC is now busy retracting one scary claim after another apparently in secret as the media that once hyped them have gone silent on the retractions. Even so, the credibility of climate science has been irreparably damaged. The global warming house of cards is falling apart.

 

 

 

FIGURE 1: GLACIATION EXTENT SINCE THE EEMIAN INTERGLACIAL

 

 

FIGURE 2: TEXAS SHARPSHOOTER FALLACY

 

 

 

[LIST OF POSTS ON THIS SITE]

 

 

 

THE NASA STATEMENT THAT PROVES HUMAN CAUSED GLOBAL WARMING AND CLIMATE CHANGE SINCE PRE-INDUSTRIAL TIMES AS A DIRECT RESULT OF FOSSIL FUEL EMISSIONS.[LINK TO SOURCE DOCUMENT]

The Earth’s climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives. Scientific evidence for warming of the climate system is unequivocal according to the Intergovernmental Panel on Climate Change. The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia. Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate. The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.2 Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response. Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming. The evidence for rapid climate change is compelling. Global temperature rise. The planet’s average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century. The planet’s average surface temperature has risen about 1.62 degrees Fahrenheit (0.9 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. Most of the warming occurred in the past 35 years, with the five warmest years on record taking place since 2010. Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year from January through September, with the exception of June were the warmest on record for those respective months. Warming oceans. The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit since 1969. The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit since 1969. Shrinking ice sheets:  The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 281 billion tons of ice per year between 1993 and 2016, while Antarctica lost about 119 billion tons during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade. Glacial retreat: Glaciers are retreating almost everywhere around the world including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa. Decreased snow cover:  Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier. Sea level rise: Global sea level rose about 8 inches in the last century. The rate in the last two decades, however, is nearly double that of the last century and is accelerating slightly every year. Maldives vulnerable to sea level rise. Declining Arctic sea ice: Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades. Extreme events: The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. Ocean acidification: Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.

 

COMMENTS

1. “The abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era and of human civilization”: The last ice age ended more than 2.5 billion years ago. Since then we have been in the Quaternary Ice Age marked by an intact Antarctic ice sheet for its duration. The ice age is punctuated by cycles of long periods of glaciation and brief periods of interglacial warmth. The Last Glacial Period ended about 11,700 years ago and initiated the Holocene warm period in which we live. As for human civilization, it got started with the Neolithic Revolution some 10,000 years ago. Not sure what the 7,000 year figure refers to in this context.
2. With reference to glaciation/interglacial cycles, NASA says “Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives“. It depends on which changes this refers to. Obliquity changes explain 41,000 year periods observed in glaciation cycles older than one million years while eccentricity changes explain 100,000 year glaciation cycles found in the last million years. It is also necessary to explain the violent and rapid changes seen in Heinrich events and D-O cycles in for example the Younger Dryas. It is possible that glaciation cycles are not purely deterministic but contain nonlinear dynamics and chaos as suggested by the glaciation behavior since the Eemian shown in the Figure 1 video clip. The behavior of glaciation cycles is not as straightforward or as unequivocal as the NASA text implies. Rather, it is complex and not well understood. The attempt to present these events as simple, deterministic, and known “scientific” facts is a form of misinformation.
3. Scientific evidence for warming of the climate system is unequivocal according to the Intergovernmental Panel on Climate Change. The IPCC is a UN committee charged with recommending climate change mitigation options to the United Nations. It is not a climate science organization and it does not carry out climate research. Therefore it is not a source of climate science information and can’t be cited to establish scientific evidence. Also, the use of words like “unequivocal” (leaving no doubt) is an unscientific attempt to discourage discussion on the substance of the issue.
4. The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia. The theory of anthropogenic global warming (AGW) is that the rise in atmospheric CO2 concentration and the corresponding rise in temperature since pre-industrial times is due to fossil fuel emissions of the industrial economy. It is generally agreed that the demarcation between industrial times and pre-industrial times lies somewhere between 1850 and 1900. The theory should be tested in that time frame. To hunt and find a period of convenience where the data are more agreeable to theory is a form of circular reasoning and can be described as the Texas Sharpshooter Fallacy shown in Figure 2. It should also be noted that “since the mid-20th century” places the beginning of human caused climate change in the middle of the 1940s to 1970s cooling period and enhances the chances of finding the kind of warming that aligns with data for emissions and atmospheric CO2. These kinds of arguments do not provide good support for AGW theory but rather raises concerns that there must be something wrong with a theory that requires such questionable and devious methods.
5. Extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia.  The argument has been made repeatedly by NASA that the rate of warming is unprecedented and that therefore it must have a human cause. This claim is flawed for two reasons. First, even if it were true, this rate alone does not establish a relationship between emissions and warming or between emissions and atmospheric composition or between atmospheric composition and warming. Second, the claim is false because higher rates of warming are easily found in the paleo data as demonstrated in this related post [LINK] .
6. Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate.  AGW serves as the rationale for an overhaul of the world’s energy infrastructure away from fossil fuels to renewable energy to reduce and eliminate fossil fuel emissions as a way of attenuating the rate of warming. That NASA satellites have seen signals of a changing climate does not address this central issue. The issue is not whether it is warming or whether the climate is changing or whether there are signals of a changing climate but whether there is a causal relationship between the rate of fossil fuel emissions and the rate of warming such that the rate of warming can be attenuated by cutting or eliminating emissions. Not mentioned in the NASA statement is that climate science has in fact presented such evidence in the form of the Transient Climate Response to Cumulative Emissions (TCRE) which shows a near perfect proportionality between cumulative warming and cumulative emissions. The TCRE serves not only as the needed evidence of human cause but also as a tool that may be used to compute the so called “carbon budget” for any target rate of warming. An evaluation of the TCRE is presented in two related posts  [LINK] [LINK] where it is shown that the metric suffers from a fatal statistical flaw and therefore serves neither as evidence of human cause nor as a metric for carbon budgets.
7. The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.  This statement is false. The works of Arrhenius, Hogbom, Tyndal, Langley, and others were a failed attempt to explain glaciation cycles over long periods of time but that relationship was never demonstrated either by them or by modern climate science or by NASA. It has been formalized into the so called Climate Sensitivity by Manabe, Charney, and others and is found in climate models where the CO2 heat trapping effect is programmed in, but attempts to find it in observational data has been thwarted by an unacceptable level of uncertainty as shown in this related post [LINK] . So great is this uncertainty problem that it motivated top climate scientists to declare that it was time to leave the climate sensitivity issue behind and move on to the TCRE which is a more stable metric. See 2017: Knutti, Reto, Maria AA Rugenstein, and Gabriele C. Hegerl. “Beyond equilibrium climate sensitivity.” Nature Geoscience10.10. A related post shows that a statistically significant climate sensitivity is found in the RCP8.5 theoretical series that was derived from this assumption but is not found in the observational data [LINK][LINK]
8. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response.  There may be no question among climate scientists and NASA scientists and there is no question that it is found in climate models where it is programmed in, but empirical evidence for this relationship has yet to be presented. The twin assumptions that changes in atmospheric CO2 concentration and surface temperature are responsive to emissions are not supported by the observational data. These tests are presented in two related posts on this site.[LINK][LINK].
9. Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks.  The paleo data may show a correspondence between high temperature and high CO2 but neither the direction of the causation nor the time scale. These data have more than one interpretation and therefore their use to propose any one of them requires the use of circular reasoning and the Texas Sharpshooter fallacy.
10. Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year from January through September, with the exception of June were the warmest on record for those respective months.  Only long term trends in temperature and not temperature events, however dramatic they may seem, may be used as evidence to support a warming climate. More to the point, the issue is not whether it is warming but whether the proposed overhaul of the world’s energy infrastructure away from fossil fuels and to renewable sources will produce the desired changes. It should also be mentioned that the year 2016 (like the year 1998 before it) is noted for a monster ENSO event and the high temperatures reported here should have been presented in that context. The omission of this piece of critical information in the presentation of 2016 temperatures is a form of scientific fraud.
11. The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit since 1969. The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit since 1969. What is the theoretical significance of the year 1969? If none, then its use is a form of circular reasoning and the Texas Sharpshooter fallacy. Also the observation that oceans have warmed in itself does not serve as evidence that the warming was caused by fossil fuel emissions and that it can be attenuated by cutting emissions; as explained in a related post [LINK] .
12. The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 281 billion tons of ice per year between 1993 and 2016, while Antarctica lost about 119 billion tons per year during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade. The Greenland ice sheet is losing  0.0084% of its ice per year and at that rate will be gone in the next 11,000 to 12,000 years. Antarctica is losing 0.00045% of its ice per year and at that rate will be gone in 20,000 years or so. These behaviors of ice sheets in interglacials does not require human cause. That the melt rate is accelerating is also a normal interglacial phenomenon because these changes are not constant in nature. They accelerate at the beginning of the interglacial and rapidly decelerate into growth when the next glaciation approaches. Since this interglacial is already about 12,000 years old we are no more than a few thousand years away from the next glaciation.
13. Glaciers are retreating almost everywhere around the world including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa. Decreased snow cover: Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier. Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier.  The only information in these changes is that we are in an interglacial period. They do not require an explanation in terms of human cause.
14. Global sea level rose about 8 inches in the last century. The rate in the last two decades, however, is nearly double that of the last century and is accelerating slightly every year. Maldives vulnerable to sea level rise. Sea level rise is normal in interglacials with acceleration from the onset of deglaciation and deceleration at the approach of the next glaciation. These changes do not require human cause. That human activity in terms of fossil fuel emissions plays a role in these changes can only be established by showing a relationship between emissions and sea level rise such that the relationship has a causation interpretation. This was done in Peter Clark’s 2018 paper (Clark, Peter U., et al. “Sea-level commitment as a gauge for climate policy.” Nature Climate Change 8.8 (2018): 653) but the correlation used in the paper is spurious as shown in a related post [LINK] . When this statistical flaw in the paper is corrected no correlation between emissions and sea level rise remains as shown in another related post [LINK] . There is no evidence that these changes in this interglacial are abnormal and that climate action in the form of reducing or even eliminating fossil fuel emissions will moderate these changes.
15. Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades. Sea ice decline is also normal in interglacials. Human cause is not necessary to explain such phenomena in interglacials. A notable issue with sea ice in this interglacial is the difference between the Arctic where summer sea ice is declining and the Antarctic where it is not. This difference may imply a role for other causes of sea ice decline in the Arctic not considered or studied because of the obsession with human caused climate change. This issue is discussed more fully in a related post [LINK] .
16. The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. Extreme weather events happen anyway naturally without the use of fossil fuel emissions as seen in thousands of years of weather records kept by the Chinese government in the Fang-Zhi, in ancient Egyptian records, in the Late Bronze Age Collapse, and in the meticulous weather records of the British colonial government in India where devastating extreme weather events on record include the Bengal droughts of 1770, 1783, 1866, 1873, 1892, 1897, and 1943, the Calcutta cyclone of 1737, and lastly the Bhola cyclone that occurred during a time of global cooling in 1970. Therefore, the occurrence of droughts, floods, extreme storms, and heatwaves in this period of warming does not establish a causal connection to fossil fuel emissions. It  must be shown that there are long term trends related to fossil fuel emissions or that a distinction can be made in the aggregate events in the post industrial era compared with a corresponding pre-industrial era. No such evidence exists. In fact all studies of long term trends have failed to find a trend imposed by the use of fossil fuels in the post industrial era. See for example, the trend in tropical cyclones presented in a related post [LINK] . The only evidence presented is in terms of what is called “Event Attribution Science” where selected weather events are examined after the fact in climate models to compare the probability of the event in a world with fossil fuel emissions with that in a world without fossil fuel emissions and then to use the ratio of these probabilities to make a determination that that particular event was or was not caused by fossil fuel emissions. This procedure is derived from the so called “Warsaw International Mechanism” (WIM) devised by the United Nations for the allocation of climate change impact compensation funding to poor countries deemed “vulnerable” to climate change impacts. The elevation of this procedure to empirical evidence by giving it a different name that includes the word “science” does not make it science because climate models are an expression of theory and empirical evidence must be independent of theory to be free of circular reasoning and confirmation bias. Related Posts: [LINK] [LINK]
17. Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.  The statement that the increase in acidity “is the result of humans emitting more carbon dioxide into the atmosphere” requires empirical evidence. None is provided possibly because no such evidence exists. Kindly note that a simple correlation between rising acidity and rising emissions suffers from a statistical issue with respect to time scale as explained in a related post at this site:  [LINK]
18. Most of the warming occurred in the past 35 years. What is the significance of that in terms of proving the theory that the use of fossil fuels in the industrial economy has caused the world to be warmer than pre-industrial times? The human caused global warming hypothesis is tied to this pre-industrial time reference and to the consequences of the industrial economy. To shift over to arbitrary time spans depending on the data is circular reasoning and an appeal to the Texas Sharpshooter fallacy. Besides, if this 35-year period is the key to human caused climate change, one should consider the absence of empirical evidence for human cause in the last 40 years from 1979 to 2018 as shown in two related posts [LINK]  [LINK]  .

 

 

 

[LIST OF POSTS ON THIS SITE]

 

FIGURE 1: THE LAST GLACIATION

 

 

 

1. Warming of the current interglacial (the Holocene) at the end of the Last Glaciation Period proceeded by way of a series of abrupt returns to glacial climate.  The most intense and most studied of these unstable brief glaciation events is the Younger Dryas which drove temperatures at the summit of Greenland to ≈15 °C colder than today. This brief and unstable glaciation event that started abruptly also ended abruptly, over a period of about 50 years.
2. Figure 1 is video clip from Youtube [LINK] of the Last Glacial Period, also known as the Weichselian, showing glacial growth from ≈115,000 years ago to ≈12,000 years ago, but with a brief and violent return to glaciation and an abrupt end ≈11,000 years ago. The Younger Dryas, serves as a well known example of the violent and unstable nature of the glaciation and interglacial cycles that is apparent in the animation in Figure 1. The paleo data show that almost as soon as the Last Glacial Period had apparently ended, a series of brief but violent return to glaciation conditions intervened.
3. Some features of the Younger Dryas event play important roles in the way climate science has presented the current warming period and the possible dangerous ways that it may evolve in the future. The specific issue discussed here is the repeated fear of “abrupt climate change” due to changes in the North Atlantic Overturning Circulation caused by AGW. It is feared that freshwater discharge from glacial melt in the current warming period will cause a slowdown of the North Atlantic Overturning Circulation portion of the Thermohaline circulation and cause abrupt and dangerous climate change analogous to the Younger Dryas as described in the papers tagged with ACC in the Bibliography below. Outside of the Younger Dryas, these abrupt climate change scenarios are found only in climate models and with large uncertainty in terms of differences from model to model and for different simulations with the same model. A high level of uncertainty is acknowledged by most authors. It implies a low level of information content in the climate model simulation results. In this post we present the case that the high level of interest in the slowdown caused by meltwater in the current warming period is an attempt to insert Younger Dryas realities into AGW without the assumed correspondence between these two climate events.
4. Changes to the Thermohaline Circulation due to fresh water discharge from de-glaciation and Abrupt Climate Change: The Younger Dryas events are derived from Greenland ice core data and they were primarily a feature of the North Atlantic region. One interpretation of the extreme rapidity of these changes is that they may have been responses to some kind of trigger in the North Atlantic climate system. These rapid changes in the Younger Dryas may have been the creation of changes in North Atlantic Ocean circulation triggered by very large volumes  of glacial meltwater. During periods of intense deglaciation meltwater discharge rates exceeded 13,000 cubic kilometers per year. These observations serve as the rationale for the hypothesis that meltwater discharge weakens the Atlantic thermohaline circulation (THC) and associated northward heat flux. Concerns about abrupt climate change in the current AGW warming period due to perturbations of the THC are likely derived from its apparent role in the Younger Dryas. The meridional overturning circulation was slowed to a crawl in the North Atlantic region by way of catastrophic iceberg and meltwater discharge. Following these meltwater events, there was a rapid accelerations of the meridional overturning circulation particularly so in the two strongest regional warming events during deglaciation. These results are thought to confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate change“. These fears of abrupt climate change in the current warming period, derived from similar events in the Younger Dryas, is described in seven papers listed in the Bibliography. They are (Rahmstorf 1995), (Manabe 1995), (Clark 2002), (Vellinga 2002), (McManus 2004), (Zhang 2005), (Stouffer 2006). The essence of all seven papers is that coupled ocean-atmosphere climate models appear to indicate an effect of meltwater in the North Atlantic Thermohaline circulation and that therefore AGW warming may turn out to be much more catastrophic than previously thought. An alternative view is presented by Carl Wunsch in a series of papers on the Thermohaline circulation [LINK]  and on the abrupt climate change issue [LINK] .
5. In the abrupt climate change paper, Professor Wunsch argues that “Suggestions that Dansgaard–Oeschger (D–O) events in Greenland are generated by shifts in the North Atlantic Ocean circulation seem highly implausible, given the weak contribution of the high latitude ocean to the meridional flux of heat. A more likely scenario is that changes in the ocean circulation are a consequence of wind shifts. The disappearance of D–O events in the Holocene coincides with the disappearance also of the Laurentide and Fennoscandian ice sheets. It is thus suggested that D–O events are a consequence of interactions of the windfield with the continental ice sheets and that better understanding of the wind field in the glacial periods is the highest priority. Wind fields are capable of great volatility and very rapid global-scale teleconnections, and they are efficient generators of oceanic circulation changes and (more speculatively) of multiple states relative to great ice sheets. Connection of D–O events to the possibility of modern abrupt climate change rests on a very weak chain of assumptions”.
6. In the Thermohaline Circulation paper he writes, “The ocean is best viewed as a mechanically driven fluid engine, capable of importing, exporting, and transporting vast quantities of heat and freshwater. Although of very great climate influence, this transport is a nearly passive consequence of the mechanical machinery. In its original form, the term “thermohaline circulation” explicitly provided a source of mechanical energy in the form of mixing devices. These devices disappeared in subsequent discussions and extensions of this influential model. For past or future climates, the quantity of first-order importance is the nature of the wind field. It not only shifts the near-surface wind-driven components of the mass flux, but also changes the turbulence at depth; this turbulence appears to control the deep stratification. The wind field will also, in large part, determine the regions of convective sinking and of the resulting 3D water properties. Fluxes and net exports of properties such as heat and carbon are determined by both the mass flux and spatial distribution of the property, and not by either alone. Tidal motions were different in the past than they are today, owing to lower sea level during glacial epochs, and moving continental geometry in the more remote past. The consequent shifts in tidal flow can result in qualitative changes in the oceanic mixing rates, and hence in the mass and consequent property fluxes. The term “thermohaline circulation” should be reserved for the separate circulations of heat and salt, and not conflated into one vague circulation with unknown or impossible energetics. No shortcut exists for determining property fluxes from the mass circulation without knowledge of the corresponding property distribution. His views on paleo climate in general may be found in a related post at this site [LINK] .

 

 

 

 

 

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YOUNGER DRYAS & ABRUPT CLIMATE CHANGE

BIBLIOGRAPHY

Featured Authors

Willi Dansgaard, Richard Fairbanks, Richard Alley, Wally Broecker

 

 

 

1. 1988: Broecker, Wallace S., et al. “The chronology of the last deglaciation: Implications to the cause of the Younger Dryas event.” Paleoceanography and Paleoclimatology 3.1 (1988): 1-19.  It has long been recognized that the transition from the last glacial to the present interglacial was punctuated by a brief and intense return to cold conditions. This extraordinary event, referred to by European palynologists as the Younger Dryas, was centered in the northern Atlantic basin. Evidence is accumulating that it may have been initiated and terminated by changes in the mode of operation of the northern Atlantic Ocean. Further, it appears that these mode changes may have been triggered by diversions of glacial meltwater between the Mississippi River and the St. Lawrence River drainage systems. We report here Accelerator Mass Spectrometry (AMS) radiocarbon results on two strategically located deep‐sea cores. One provides a chronology for surface water temperatures in the northern Atlantic and the other for the meltwater discharge from the Mississippi River. Our objective in obtaining these results was to strengthen our ability to correlate the air temperature history for the northern Atlantic basin with the meltwater history for the Laurentian ice sheet.
2. 1989: Dansgaard, W. H. I. T. E., J. W. C. White, and S. J. Johnsen. “The abrupt termination of the Younger Dryas climate event.” Nature 339.6225 (1989): 532.  PREVIOUS studies on two deep Greenland ice cores have shown that a long series of climate oscillations characterized the late Weichselian glaciation in the North Atlantic region¹, and that the last glacial cold period, the Younger Dryas, ended abruptly 10,700 years ago². Here we further focus on this epoch-defining event, and present detailed heavy-isotope and dust-concentration profiles which suggest that, in less than 20 years, the climate in the North Atlantic region turned into a milder and less stormy regime, as a consequence of a rapid retreat of the sea-ice cover. A warming of 7 °C in South Greenland was completed in about 50 years. 
3. 1989: Fairbanks, Richard G. “A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation.” Nature 342.6250 (1989): 637.  Coral reefs drilled offshore of Barbados provide the first continuous and detailed record of sea level change during the last deglaciation. The sea level was 121 ± 5 metres below present level during the last glacial maximum. The deglacial sea level rise was not monotonic; rather, it was marked by two intervals of rapid rise. Varying rates of melt-water discharge to the North Atlantic surface ocean dramatically affected North Atlantic deep-water production and oceanic oxygen isotope chemistry. A global oxygen isotope record for ocean water has been calculated from the Barbados sea level curve, allowing separation of the ice volume component common to all oxygen isotope records measured in deep-sea cores.
4. 1990: Fairbanks, Richard G. “The age and origin of the “Younger Dryas climate event” in Greenland ice cores.” Paleoceanography and Paleoclimatology 5.6 (1990): 937-948.  ²³⁰Th/²³⁴U and ¹⁴C dating of Barbados corals has extended the calibration of ¹⁴C years B.P. to calendar years B.P. beyond the 9200 year tree ring series (Bard et al., 1990). This now permits the conversion of ¹⁴C chronozones, which delimit major climate shifts in western Europe, to calendar years. The Younger Dryas chronozone, defined as 11,000 to 10,000 ¹⁴C years B.P., corresponds to 13,000 to 11,700 calendar years B.P. This calibration affects the interpretation of an intensely studied example of the “Younger Dryas climate event,” the δ¹⁸O anomaly between 1785 and 1793 m in Dye 3 ice core. The end of the δ¹⁸O anomaly in Dye 3 ice core has been dated by measurements of ¹⁴C in air bubbles (Andree et al., 1984, 1986) and by annual layer counting (Hammer et al., 1986). The older ¹⁴C dates fall out of the range of the tree ring calibration series but can now be calibrated to calendar years using the Barbados ²³⁰Th/²³⁴U calibration. The ¹⁴C_correctedage for the end of the δ¹⁸O event is 10,300 ± 400 calendar years B.P. compared to the annual layer counting age of 10,720 ± 150 years B.P. Thus, the “Younger Dryas” event in the Dye 3 ice core ends in the Preboreal chronozone (11,700 to 10,000 calendar years B.P.) and is not correlative with the end of the Younger Dryas event identified in pollen records marking European vegetation changes. The end of the Dye 3 δ¹⁸O event is, however, correlative with the end of meltwater pulse IB (Fairbanks, 1989), marking a period of intense deglaciation with meltwater discharge rates exceeding 13,000 km³/yr.
5. 1993: Alley, Richard B., et al. “Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event.” Nature362.6420 (1993): 527. THE warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate, the best-known of which is the Younger Dryas event¹. Despite much study of the causes of this event and the mechanisms by which it ended, many questions remain unresolved¹. Oxygen isotope data from Greenland ice cores^2–4 suggest that the Younger Dryas ended abruptly, over a period of about 50 years; dust concentrations^2,4 in these cores show an even more rapid transition (≲20 years). This extremely short timescale places severe constraints on the mechanisms underlying the transition. But dust concentrations can reflect subtle changes in atmospheric circulation, which need not be associated with a large change in climate. Here we present results from a new Greenland ice core (GISP2) showing that snow accumulation doubled rapidly from the Younger Dryas event to the subsequent Preboreal interval, possibly in one to three years. We also find that the accumulation-rate change from the Oldest Dryas to the Bø11ing/Allerød warm period was large and abrupt. The extreme rapidity of these changes in a variable that directly represents regional climate implies that thalleye events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the North Atlantic climate system.
6. 1994: Bard, Edouard, et al. “The North Atlantic atmosphere-sea surface 14C gradient during the Younger Dryas climatic event.” Earth and Planetary Science Letters 126.4 (1994): 275-287. We attempt to quantify the ¹⁴C difference between the atmosphere and the North Atlantic surface during a prominent climatic period of the last deglaciation, the Younger Dryas event (YD). Our working hypothesis is that the North Atlantic may have experienced a measurable change in ¹⁴C reservoir age due to large changes of the polar front position and variations in the mode and rate of North Atlantic Deep Water (NADW) production. We dated contemporaneous samples of terrestrial plant remains and sea surface carbonates in order to evaluate the past atmosphere-sea surface ¹⁴C gradient. We selected terrestrial vegetal macrofossils and planktonic foraminifera (Neogloboquadrina pachyderma left coiling) mixed with the same volcanic tephra (the Vedde Ash Bed) which occurred during the YD and which can be recognized in North European lake sediments and North Atlantic deep-sea sediments. Based on AMS ages from two Norwegian sites, we obtained about 10,300 yr BP for the ‘atmospheric’ ¹⁴C age of the volcanic eruption. Foraminifera from four North Atlantic deep-sea cores selected for their high sedimentation rates ( > 10 cm kyr⁻¹) were dated by AMS (21 samples). For each core the raw ¹⁴C ages assigned to the ash layer peak is significantly older than the ¹⁴C age obtained on land. Part of this discrepancy is due to bioturbation, which is shown by numerical modelling. Nevertheless, after correction of a bioturbation bias, the mean ¹⁴C age obtained on the planktonic foraminifera is still about 11,000–11,100 yr BP. The atmosphere-sea surface ¹⁴C difference was roughly 700–800 yr during the YD, whereas today it is 400–500 yr. A reduced advection of surface waters to the North Atlantic and the presence of sea ice are identified as potential causes of the high ¹⁴C reservoir age during the YD.
7. ACC 1995: Rahmstorf, Stefan. “Bifurcations of the Atlantic thermohaline circulation in response to changes in the hydrological cycle.” Nature 378.6553 (1995): 145.  The sensitivity of the North Atlantic thermohaline circulation to the input of fresh water is studied using a global ocean circulation model coupled to a simplified model atmosphere. Owing to the nonlinearity of the system, moderate changes in freshwater input can induce transitions between different equilibrium states, leading to substantial changes in regional climate. As even local changes in freshwater flux are capable of triggering convective instability, quite small perturbations to the present hydrological cycle may lead to temperature changes of several degrees on timescales of only a few years.
8. ACC 1995: Manabe, Syukuro, and Ronald J. Stouffer. “Simulation of abrupt climate change induced by freshwater input to the North Atlantic Ocean.” Nature 378.6553 (1995): 165.  Temperature records from Greenland ice cores^1,2 suggest that large and abrupt changes of North Atlantic climate occurred frequently during both glacial and post glacial periods; one example is the Younger Dryas cold event. Broecker³ speculated that these changes result from rapid changes in the thermohaline circulation of the Atlantic Ocean, which were caused by the release of large amounts of melt water from continental ice sheets. Here we describe an attempt to explore this intriguing phenomenon using a coupled ocean–atmosphere model. In response to a massive surface flux of fresh water to the northern North Atlantic of the model, the thermohaline circulation weakens abruptly, intensifies and weakens again, followed by a gradual recovery, generating episodes that resemble the abrupt changes of the ocean–atmosphere system recorded in ice and deep-sea cores⁴. The associated change of surface air temperature is particularly large in the northern North Atlantic Ocean and its neighbourhood, but is relatively small in the rest of the world.
9. 1997: Bond, Gerard, et al. “A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates.” science278.5341 (1997): 1257-1266.  Evidence from North Atlantic deep sea cores reveals that abrupt shifts punctuated what is conventionally thought to have been a relatively stable Holocene climate. During each of these episodes, cool, ice-bearing waters from north of Iceland were advected as far south as the latitude of Britain. At about the same times, the atmospheric circulation above Greenland changed abruptly. Pacings of the Holocene events and of abrupt climate shifts during the last glaciation are statistically the same; together, they make up a series of climate shifts with a cyclicity close to 1470 ± 500 years. The Holocene events, therefore, appear to be the most recent manifestation of a pervasive millennial-scale climate cycle operating independently of the glacial-interglacial climate state. Amplification of the cycle during the last glaciation may have been linked to the North Atlantic’s thermohaline circulation.
10. 1997: Alley, Richard B., et al. “Holocene climatic instability: A prominent, widespread event 8200 yr ago.” Geology 25.6 (1997): 483-486.  The most prominent Holocene climatic event in Greenland ice-core proxies, with approximately half the amplitude of the Younger Dryas, occurred ∼8000 to 8400 yr ago. This Holocene event affected regions well beyond the North Atlantic basin, as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane. Widespread proxy records from the tropics to the north polar regions show a short-lived cool, dry, or windy event of similar age. The spatial pattern of terrestrial and marine changes is similar to that of the Younger Dryas event, suggesting a role for North Atlantic thermohaline circulation. Possible forcings identified thus far for this Holocene event are small, consistent with recent model results indicating high sensitivity and strong linkages in the climatic system.
11. 1998: Severinghaus, Jeffrey P., et al. “Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice.” Nature 391.6663 (1998): 141.  Rapid temperature change fractionates gas isotopes in unconsolidated snow, producing a signal that is preserved in trapped air bubbles as the snow forms ice. The fractionation of nitrogen and argon isotopes at the end of the Younger Dryas cold interval, recorded in Greenland ice, demonstrates that warming at this time was abrupt. This warming coincides with the onset of a prominent rise in atmospheric methane concentration, indicating that the climate change was synchronous (within a few decades) over a region of at least hemispheric extent, and providing constraints on previously proposed mechanisms of climate change at this time. The depth of the nitrogen-isotope signal relative to the depth of the climate change recorded in the ice matrix indicates that, during the Younger Dryas, the summit of Greenland was 15 ± 3 °C colder than today.
12. 1997: Broecker, Wallace S. “Thermohaline circulation, the Achilles heel of our climate system: Will man-made CO2 upset the current balance?.” Science 278.5343 (1997): 1582-1588.  During the last glacial period, Earth’s climate underwent frequent large and abrupt global changes. This behavior appears to reflect the ability of the ocean’s thermohaline circulation to assume more than one mode of operation. The record in ancient sedimentary rocks suggests that similar abrupt changes plagued the Earth at other times. The trigger mechanism for these reorganizations may have been the antiphasing of polar insolation associated with orbital cycles. Were the ongoing increase in atmospheric CO₂ levels to trigger another such reorganization, it would be bad news for a world striving to feed 11 to 16 billion people.
13. 1999: Marchal, O., et al. “Modelling the concentration of atmospheric CO2 during the Younger Dryas climate event.” Climate Dynamics 15.5 (1999): 341-354.  The Younger Dryas (YD, dated between 12.7–11.6 ky BP in the GRIP ice core, Central Greenland) is a distinct cold period in the North Atlantic region during the last deglaciation. A popular, but controversial hypothesis to explain the cooling is a reduction of the Atlantic thermohaline circulation (THC) and associated northward heat flux as triggered by glacial meltwater. Recently, a CH₄-based synchronization of GRIP δ¹⁸O and Byrd CO₂ records (West Antarctica) indicated that the concentration of atmospheric CO₂ (CO^atm₂) rose steadily during the YD, suggesting a minor influence of the THC on CO^atm₂ at that time. Here we show that the CO2^atm change in a zonally averaged, circulation-biogeochemistry ocean model when THC is collapsed by freshwater flux anomaly is consistent with the Byrd record. Cooling in the North Atlantic has a small effect on CO2^atm in this model, because it is spatially limited and compensated by far-field changes such as a warming in the Southern Ocean. The modelled Southern Ocean warming is in agreement with the anti-phase evolution of isotopic temperature records from GRIP (Northern Hemisphere) and from Byrd and Vostok (East Antarctica) during the YD. δ¹³C depletion and PO₄ enrichment are predicted at depth in the North Atlantic, but not in the Southern Ocean. This could explain a part of the controversy about the intensity of the THC during the YD. Potential weaknesses in our interpretation of the Byrd CO₂ record in terms of THC changes are discussed.
14. ACC 2002: Clark, Peter U., et al. “The role of the thermohaline circulation in abrupt climate change.” Nature 415.6874 (2002): 863.  The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled ocean–atmosphere system. But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse warming. Analyses of past abrupt climate changes help to solve these problems. Data and models both suggest that abrupt climate change during the last glaciation originated through changes in the Atlantic thermohaline circulation in response to small changes in the hydrological cycle. Atmospheric and oceanic responses to these changes were then transmitted globally through a number of feedbacks. The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state.
15. ACC 2002: Vellinga, Michael, and Richard A. Wood. “Global climatic impacts of a collapse of the Atlantic thermohaline circulation.” Climatic change 54.3 (2002): 251-267.  Part of the uncertainty in predictions by climate models results from limited knowledge of the stability of the thermohaline circulation of the ocean. Here we provide estimates of the response of pre-industrial surface climate variables should the thermohalinecirculation in the Atlantic Ocean collapse. For this we have used HadCM3, an ocean-atmosphere general circulation model that is run without flux adjustments. In this model a temporary collapse was forced by applying a strong initial freshening to the top layers of the NorthAtlantic. In the first five decades after the collapse surface air temperature response is dominated by cooling of much of the Northern Hemisphere (locally up to 8 °C, 1–2 °C on average) and weak warming of the Southern Hemisphere (locally up to 1 °C, 0.2 °C onaverage). Response is strongest around the North Atlantic but significant changes occur over the entire globe and highlight rapid connections. Precipitation is reduced over large parts of the Northern Hemisphere. A southward shift of the Intertropical Convergence Zone over the Atlantic and eastern Pacific creates changes in precipitation that are particularly large in South America and Africa. Colder and drier conditions in much of the Northern Hemisphere reduces oil moisture and net primary productivity of the terrestrial vegetation. This is only partly compensated by more productivity in the Southern Hemisphere.The total global net primary productivity by the vegetation decreases by 5%. It should be noted, however, that in this version of the model the vegetation distribution cannot change, and atmospheric carbon levels are also fixed. After about 100 years the model’s thermohaline circulation has largely recovered, and most climatic anomalies disappear.
16. 2003: Alley, Richard B., et al. “Abrupt climate change.” science299.5615 (2003): 2005-2010.  Large, abrupt, and widespread climate changes with major impacts have occurred repeatedly in the past, when the Earth system was forced across thresholds. Although abrupt climate changes can occur for many reasons, it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events. Were such an event to recur, the economic and ecological impacts could be large and potentially serious. Unpredictability exhibited near climate thresholds in simple models shows that some uncertainty will always be associated with projections. In light of these uncertainties, policy-makers should consider expanding research into abrupt climate change, improving monitoring systems, and taking actions designed to enhance the adaptability and resilience of ecosystems and economies.
17. ACC 2004: McManus, Jerry F., et al. “Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes.” Nature 428.6985 (2004): 834. The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies¹, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning². Here we report measurements of ²³¹Pa/²³⁰Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the ²³¹Pa/²³⁰Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.
18. ACC 2005: Zhang, Rong, and Thomas L. Delworth. “Simulated tropical response to a substantial weakening of the Atlantic thermohaline circulation.” Journal of Climate 18.12 (2005): 1853-1860.  In this study, a mechanism is demonstrated whereby a large reduction in the Atlantic thermohaline circulation (THC) can induce global-scale changes in the Tropics that are consistent with paleoevidence of the global synchronization of millennial-scale abrupt climate change. Using GFDL’s newly developed global coupled ocean–atmosphere model (CM2.0), the global response to a sustained addition of freshwater to the model’s North Atlantic is simulated. This freshwater forcing substantially weakens the Atlantic THC, resulting in a southward shift of the intertropical convergence zone over the Atlantic and Pacific, an El Niño–like pattern in the southeastern tropical Pacific, and weakened Indian and Asian summer monsoons through air–sea interactions.
19. ACC 2006:  Stouffer, Ronald J., et al. “Investigating the causes of the response of the thermohaline circulation to past and future climate changes.” Journal of climate 19.8 (2006): 1365-1387.  The Atlantic thermohaline circulation (THC) is an important part of the earth’s climate system. Previous research has shown large uncertainties in simulating future changes in this critical system. The simulated THC response to idealized freshwater perturbations and the associated climate changes have been intercompared as an activity of World Climate Research Program (WCRP) Coupled Model Intercomparison Project/Paleo-Modeling Intercomparison Project (CMIP/PMIP) committees. This intercomparison among models ranging from the earth system models of intermediate complexity (EMICs) to the fully coupled atmosphere–ocean general circulation models (AOGCMs) seeks to document and improve understanding of the causes of the wide variations in the modeled THC response. The robustness of particular simulation features has been evaluated across the model results. In response to 0.1-Sv (1 Sv ≡ 10⁶ m³ s⁻¹) freshwater input in the northern North Atlantic, the multimodel ensemble mean THC weakens by 30% after 100 yr. All models simulate some weakening of the THC, but no model simulates a complete shutdown of the THC. The multimodel ensemble indicates that the surface air temperature could present a complex anomaly pattern with cooling south of Greenland and warming over the Barents and Nordic Seas. The Atlantic ITCZ tends to shift southward. In response to 1.0-Sv freshwater input, the THC switches off rapidly in all model simulations. A large cooling occurs over the North Atlantic. The annual mean Atlantic ITCZ moves into the Southern Hemisphere. Models disagree in terms of the reversibility of the THC after its shutdown. In general, the EMICs and AOGCMs obtain similar THC responses and climate changes with more pronounced and sharper patterns in the AOGCMs.

 

 

 

 

 

 

 

 

 

 

FIGURE 1: JAMES HANSEN ON EEMIAN SEA LEVEL RISE

 

 

FIGURE 1: LANDSCAPE, ANIMALS, AND HUMANS OF THE EEMIAN

 

FIGURE 2: SINCE THE EEMIAN: THE LAST GLACIAL AND THE HOLOCENE

 

 

FIGURE 3: THE GLACIATION AND INTER-GLACIALS IN THE LAST 400,000 YEARS

 

 

 

 

 

 

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1. A principal feature of the effort by climate science and the UN to motivate an overhaul of the world’s energy infrastructure away from hydrocarbon fuels has been a repeated invocation of the collapse of the Greenland and Antarctic ice sheets and of the devastation by sea level rise that the melting ice sheets would cause. Some examples of the obsession of climate science with the collapse of the Greenland and Antarctic ice sheets, even when the details in the data are at odds with this assessment, are listed in paragraph#7 to paragraph#28 below. James Hansen, a high profile climate scientist and activist, has been the primary spokesman for the ice sheet collapse and sea level rise scenarios and of the necessity of attenuating these changes by cutting emissions. Figure 1 is a clip from a Youtube video [LINK]  in which Hansen describes his sea level rise fears. His reference to the Eemian Interglacial period to describe the horror of ice sheet collapse and sea level rise is noteworthy. The fear of “extreme weather” and of “abrupt climate change” also plays a significant role in the case for “climate action” to curtain the current warming trend; and we show here that they too may have their roots in the Eemian. In this post we present the case that much of the most dramatic and catastrophic fears of human caused global warming and climate change “since pre-industrial times” ostensibly by way of fossil fuel emissions from the industrial economy, derives from prior natural events. In a related post, a case was presented that the fear of ocean acidification by carbon dioxide from fossil fuels and its species extinction possibilities derive from an ocean acidification and extinction devastation in the Paleocene-Eocene Thermal Maximum (PETM)  [LINK] . Other oft repeated alarms about the current warming, that of rising ocean heat content and a runaway positive feedback of methane hydrate decomposition may also have been inspired by the PETM. 
2. We live in an ice age in which the world is mostly an ice planet during glacial periods (about 90% of the time) but with brief balmy interglacial periods between them (about 10% of the time). We are currently in one of these brief balmy interglacials but strangely fearful of the warmth as an unwanted and dangerous impact of a misalignment between human activity and nature. Our interglacial is  called the Holocene. It evolved about 11,700 years ago (YA) when the Last Glacial Period (115,000YA – 12000YA) receded. The interglacial prior to the Last Glacial Period is called the Eemian. These transitions are depicted in a video clip in Figure 2 taken from a Youtube video [LINK] . It shows transitions in the degree of glaciation from the Eemian interglacial through the glaciation of the Last Glacial Period to its end in the balmy warmth of the Holocene interglacial where we are now. Figure 3 is a video clip of three glaciation-interglacial cycles over a period of 400,000 years. This post is a description of the Eemian interglacial and its relevance to the widespread fear of anthropogenic global warming since the 1980s apparently sparked by rising temperatures since the brief glaciation of the Little Ice Age (LIA) described in a related post [LINK] .
3. The Eemian interglacial started 130,000 years ago and ended about 115,000 years ago when the Last Glacial Period got started. Paleo climate research on the Eemian interglacial is presented below as a bibliography. The data are mostly from Greenland ice cores and pollen and the geographical areas most studied are Europe and the Arctic. An interesting feature of this line of research, missing in the study of AGW is that winter and summer temperatures are studied separately as their trend behavior can be very different. Despite the usual claim that the intensity of “post industrial anthropogenic global warming” is unprecedented  [LINK] , it is generally agreed that the Eemian, at times, was warmer than the the present by as much as 5ºC (an opposing view in (Hansen 2015) is that it was never more than 1ºC warmer). In general, the Eemian is described as hotter than today with January (boreal winter) temperatures 3ºC to 5ºC higher and July (boreal summer) temperatures 2ºC to 4ºC higher but with large fluctuations in temperature between conditions hotter than today and colder than today. However, three stages of the Eemian are described by most authors as warmer than today, colder than today, and about the same as today over decades and centuries. Rapid fluctuations between warm and cold periods in multi-decadal time scales are found. Fluctuations in winter temperatures correlate with rise and fall of sea level. These changes can be described as abrupt climate change over decades with great regional variability but with an ability of nature for rapid recovery from abrupt changes. It is generally agreed that Eemian climate was more unstable than the Holocene with multiple cold periods lasting from decades to centuries. A remarkable shift occurred about 5,000 years into the Eemian when it cooled by 6ºC to 10ºC before rising again to warm conditions. There is some disagreement in this regard with some authors presenting evidence of a more stable Eemian (Kukla 2000).
4. A significant feature of the Eemian is sea level rise and fluctuations in sea level caused by fluctuations in temperature. Sea level rise of 3 to 6 meters are reported by some authors and 5 to 9 meters by others and is generally attributed to a complete disintegration of the West Antarctic Ice Sheet. (It is noted that global mean sea level would rise by 6 to 7 meters today if either of the two ice sheets melted completely but it is generally agreed that the Greenland ice sheet was smaller at that time and its complete melt could not have contributed more than 5 meters of sea level rise. The West Antarctic Ice Sheet was likely the main source of the dramatic sea level rise found in the data. Some authors cite sudden warming of 5ºC to 10ºC and “massive surges of icebergs into the North Atlantic” as a perturbation of ocean circulation that was responsible for abrupt climate change in the Eemian. Details of these findings may be found in the Eemian Bibliography presented below.
5. CONCLUSION: We propose in this post that the fear of ice sheet collapse and devastating sea level rise in the current warming episode described by James Hansen and by other climate scientists  (see “AGW COLLAPSE OF ICE SHEETS” bibliography below) can be related to events in the Eemian but not to the post LIA period of the Holocene. However, the concern we raise in this post is that there is not a sufficient correspondence between these two events, i.e., the Eemian and the post Little Ice Age warming usually attributed to the use of hydrocarbon fuels by humans, to draw conclusions about one from the details of the other.
6. EXAMPLES OF EEMIAN NIGHTMARES IN THE HOLOCENE
7. 1999: An article in the Journal Science says that the melting of the West Antarctic Ice Sheet is a natural event not related to global warming contrary to claims by climate scientists. The WAIS is indeed melting quite rapidly receding at the rate of 400 feet per year but it has been doing so for thousands of years long before human activity and greenhouse gas emissions, having receded 800 miles since the last ice age. If the process continues unchecked it will melt completely in another 7000 years.Therefore it seems unlikely that the event is linked to human activity or that the time frame of a collapse of the ice shelf could fall within 100 years.
8. 2001 ABRUPT CLIMATE CHANGE: A report by the National Research Council (USA) says that global warming may trigger climate changes so abrupt that ecosystems will not be able to adapt. Look for local or short term cooling, floods, droughts, and other unexpected changes. A growing CO2 concentration in the atmosphere due to the use of fossil fuels is to blame. Some regional climates have changed by as much as 10C in 10 years. Antarctica’s largest glaciers are rapidly thinning, and in the last 10 years have lost up to 150 feet of thickness in some places, enough to raise global sea levels by 0.4 mm. Global warming is a real problem and it is getting worse.
9. 2002, ICE SHELF COLLAPSE: A piece of ice the size of Rhode island broke off the Larsen ice shelf in Antarctica and within a month it dissipated sending a huge flotsam of ice into the sea. At about the same time an iceberg the size of Delaware broke off the Thwaites Glacier. A few months ago parts of the Ross ice shelf had broken off in a similar way. These events serve as a dramatic reminders that global warming is real and its effects are potentially catastrophic and underscores the urgent need for a binding international agreement to cut greenhouse gas emissions.
10. 2004: An unprecedented 4-year study of the Arctic shows that polar bears, walruses, and some seals are becoming extinct. Arctic summer sea ice may disappear entirely. Combined with a rapidly melting Greenland ice sheet, it will raise the sea level 3 feet by 2100 inundating lowlands from Florida to Bangladesh. Average winter temperatures in Alaska and the rest of the Arctic are projected to rise an additional 7 to 13 degrees over the next 100 years because of increasing emissions of greenhouse gases from human activities. The area is warming twice as fast as anywhere else because of global air circulation patterns and natural feedback loops, such as less ice reflecting sunlight, leading to increased warming at ground level and more ice melt. Native peoples’ ways of life are threatened. Animal migration patterns have changed, and the thin sea ice and thawing tundra make it too dangerous for humans to hunt and travel.
11. 2004: A meltdown of the massive Greenland ice sheet, which is more than 3km-thick would raise sea levels by an average seven meters, threatening countries such as Bangladesh, certain islands in the Pacific and some parts of Florida. Greenland’s huge ice sheet could melt within the next thousand years if emissions of carbon dioxide (CO2) and global warming are not reduced.
12. 2004: The Arctic Climate Impact Assessment (ACIA) report says: increasing greenhouse gases from human activities is causing the Arctic to warm twice as fast as the rest of the planet; in Alaska, western Canada, and eastern Russia winter temperatures have risen by 2C to 4C in the last 50 years; the Arctic will warm by 4C to 7C by 2100. A portion of Greenland’s ice sheet will melt; global sea levels will rise; global warming will intensify. Greenland contains enough melting ice to raise sea levels by 7 meters; Bangkok, Manila, Dhaka, Florida, Louisiana, and New Jersey are at risk of inundation; thawing permafrost and rising seas threaten Arctic coastal regions; climate change will accelerate and bring about profound ecological and social changes; the Arctic is experiencing the most rapid and severe climate change on earth and it’s going to get a lot worse; Arctic summer sea ice will decline by 50% to 100%; polar bears will be driven towards extinction; this report is an urgent SOS for the Arctic; forest fires and insect infestations will increase in frequency and intensity; changing vegetation and rising sea levels will shrink the tundra to its lowest level in 21000 years; vanishing breeding areas for birds and grazing areas for animals will cause extinctions of many species; “if we limit emission of heat trapping carbon dioxide we can still help protect the Arctic and slow global warming”.
13. 2007: A comparison of Landsat photos taken on 8/11/1985 and 9/5/2002 shows that global warming caused by our use of fossil fuels is melting the massive Greenland ice sheet and exposing the rocky peninsula beneath the ice previously covered by ice.
14. 2007: Climate scientists say that the current rate of increase in the use of fossil fuels will melt the Greenland ice sheet and cause sea levels to rise by 7 meters in 100 years and devastate low-lying countries like Bangladesh. When these estimates were challenged and their internal inconsistencies exposed, the forecast was quietly revised downward 100-fold from 7 meters to 7 centimeters on their website but the news media alarm about 7 meters continued unabated with “thousands of years” inserted in place of “100 years. 
15. 2008: IMMINENT COLLAPSE OF PETERMANN GLACIER IN GREENLAND
    Climate scientists looking through satellite pictures found a crack in the Petermann glacier in Greenland and concluded that it could speed up sea level rise because huge chunks of ice the size of Manhattan were hemorrhaging off. Yet, scientists who has been travelling to Greenland for years to study glaciers say that the crack in the glacier is normal and not different from other cracks seen in the 1990s.
16. 2008: When there was a greater focus on Antarctica climate scientists said that global warming was melting the West Antarctic Ice Shelf; but the melting was found to be localized and with an active volcano underneath the melting and the attention of “melt forecast” climate science shifted to Arctic sea ice after the an extensive summer melt was observed in September 2007.
17. 2008: Climate scientists have determined that Adelie penguins in Antarctica are threatened because climate change is melting Antarctic glaciers although it is not clear whether the melting is caused greenhouse gas emissions or by volcanic activity underneath the ice.
18. 2008: Mt. Erebus along with most of the mountains in Antarctica are volcanic mountains and it is now known with certainty that volcanic activity under the ice there is causing great amounts of ice to melt and to cause glaciers to flow faster. The attempt by climate scientists to represent these events as climate change phenomena is inconsistent with this reality.
19. 2008: THE FIRE BELOW: A volcano under the West Antarctic Ice Sheet, that last erupted 2000 years ago, is now active and responsible for melting ice and for retreating glaciers in that part of the continent (The fire below, Bangkok Post, April 28, 2008). Yet, climate scientists claim that these changes are man-made and that they are caused by carbon dioxide emissions from fossil fuels as predicted by their computer model of the earth’s climate.
20. 2009: Carbon dioxide emissions from fossil fuels have caused the Wilkins Ice Shelf to break up. If all of the land based ice in Antarctica melted it would raise the sea level by 80 meters. 
21. 2009: Human caused global warming is causing havoc in Antarctica with potentially incalculable results. Over one hundred icebergs broke off and a huge flotilla of them are floating up to New Zealand. 
22. 2009: Our carbon dioxide emissions are causing the East Antarctic ice shelf to lose 57 billion tonnes of ice per year and that if CO2 emissions are not reduced this process could raise sea levels by 5 meters.
23. 2009: Temperature data 1957-2008 show that the whole of Antarctica including Western Antarctica, the Antarctic Peninsula, and Eastern Antarctica, is warming due to CO2 emissions from fossil fuels.
24. 2009: Man-made global warming is causing Greenland’s glaciers to melt at an alarming rate. By the year 2100 all the ice there will have melted causing a calamitous rise in the sea level that will inundate Bangladesh, the Maldives, Bangkok, New Orleans, and atolls in the Pacific. 
25. 2009: Climate scientists say that the melting of Antarctica is more severe than “previously thought” because the melt is not limited to the Antarctic Peninsula but extends to West Antarctica as well. The melt could cause devastating sea level rise. (although new data show that the West Antarctic ice shelf collapses every 40,000 years or so and that this cyclical process has been regular feature of this ice shelf for millions of years (Antarctica ice collapses were regular, Bangkok Post, March 19, 2009). These melting episodes can raise the sea level by as much as 5 meters but the process takes a thousand years or more.
26. 2009: Climate scientists say that the Wilkins Ice Shelf collapse is caused by warming of the Antarctic Peninsula due to man-made “global climate change”.
27. 2009: In 2005 two glaciers in Greenland were found to be moving faster than they were in 2001. Scientists concluded from these data that the difference observed was a a long term trend of glacial melt in Greenland and that carbon dioxide was the cause of this trend. The assumed trend was then extrapolated forward and we were told that carbon dioxide would cause the land based ice mass of Greenland to be discharged to the sea and raise the sea level by six meters. They said that the only way out of the devastation was to drastically reduce carbon dioxide emissions from fossil fuels. However, in 2009, just before a meeting in Copenhagen where these deep cuts in emissions were to be negotiated, it was found that the glaciers had returned to their normal rate of discharge.
28. 2009: Some glaciers on north and northeast Greenland terminate in fiords with long glacier tongues that extend into the sea. It is found that the warming of the oceans caused by our use of fossil fuels is melting these tongues and raising the specter of devastation by sea level rise.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EEMIAN BIBLIOGRAPHY

Featured Authors

Katrine Andersen, Michael Field, Eugene Karabonov, Willem Vandeberg, Andrew Weaver, Waldo Zagwijn

1. 1993: Dansgaard, Willi, et al. “Evidence for general instability of past climate from a 250-kyr ice-core record.” Nature 364.6434 (1993): 218.  RECENT results^1,2 from two ice cores drilled in central Greenland have revealed large, abrupt climate changes of at least regional extent during the late stages of the last glaciation, suggesting that climate in the North Atlantic region is able to reorganize itself rapidly, perhaps even within a few decades. Here we present a detailed stable-isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale. We find that climate instability was not confined to the last glaciation, but appears also to have been marked during the last interglacial (as explored more fully in a companion paper³) and during the previous Saale–Holstein glacial cycle. This is in contrast with the extreme stability of the Holocene, suggesting that recent climate stability may be the exception rather than the rule. The last interglacial seems to have lasted longer than is implied by the deep-sea SPECMAP record⁴, in agreement with other land-based observations^5,6. We suggest that climate instability in the early part of the last interglacial may have delayed the melting of the Saalean ice sheets in America and Eurasia, perhaps accounting for this discrepancy.
2. 1994: Field, Michael H., Brian Huntley, and Helmut Müller. “Eemian climate fluctuations observed in a European pollen record.” Nature 371.6500 (1994): 779. Recent ice-core data from Greenland^1,2 suggest that the climate during the last interglacial period the Eemian was more unstable than that of the Holocene (about 10,000 years ago to the present), being characterized in particular by a series of cold episodes each lasting about 70 to 750 years. Subsequent analysis of a second Greenland ice core^3,4, however, failed to corroborate the details of these Eemian climate fluctuations, a result that may be attributable to the effects of ice flow⁴. To resolve this discrepancy, it is imperative to seek alternative sources of information about the Eemian climate. Here we present climate reconstructions from pollen data from the annually laminated Eemian lake-sediment record at Bispingen⁵ and from the Eemian and Holocene peat records at La Grande Pile⁶. The former record indicates that an initially warm period of 2,900 yr was followed by cooling and a series of colder episodes, one of which had winter temperatures comparable to those at the end of the preceding cold stage. The latter records show greater climate instability during the Eemian than the Holocene. These results are in broad agreement with those from the GRIP ice core, but contrast both with the GISP2 core^3,4 and with recent high-resolution marine records from the North Atlantic^7,8.
3. 1994: Weaver, Andrew J., and Tertia MC Hughes. “Rapid interglacial climate fluctuations driven by North Atlantic ocean circulation.” Nature 367.6462 (1994): 447. RECENT data from the GRIP ice core^1–3 in Greenland suggest that the climate of the last Eemian interglacial period was much less stable than that of the present interglacial. Rapid transitions between warm and cold periods were found to occur on timescales of just a few decades. The North Atlantic climate during the Eemian period was also shown to be characterized by three states, respectively warmer than, similar to and colder than today^1,2. Recent data from the nearby GISP2 ice core have revealed some discrepancies with these findings, which remain to be resolved^4,5. Here we present simulations using an idealized global ocean model, which suggest that the North Atlantic ocean has three distinct circulation modes, each of which corresponds to a distinct climate state. We find that adding a simple random component to the mean freshwater flux (which forces circulation) can induce rapid transitions between these three modes. We suggest that increased variability in the hydrological cycle associated with the warmer Eemian climate could have caused transition between these distinct modes in the North Atlantic circulation, which may in turn account for the apparent rapid variability of the Eemian climate.
4. 1994: Keigwin, Lloyd D., et al. “The role of the deep ocean in North Atlantic climate change between 70 and 130 kyr ago.” Nature371.6495 (1994): 323.  THE suggestion¹ that changes in North Atlantic Deep Water (NADW) production are linked through surface heat flux to the atmospheric temperature over Greenland is supported by earlier indications^2,3 that NADW production decreased during glacial times, and by the subsequent finding^4–6 that it declined during the Younger Dryas cool period at the end of the last glaciation. Changes in North Atlantic surface temperatures have been found⁷ to mirror high-frequency temperature changes recorded in Greenland ice cores over the past 80 kyr, but the connection to abyssal circulation has yet to be established, except for one or two isolated oscillations^8,9. Here we present carbon and oxygen isotope analyses of benthic foraminifera in a high-resolution North Atlantic deep-sea sediment core for the period ^70–130kyr ago. These data allow us to reconstruct the history of NADW production, which shows a close correlation with Greenland climate variability for much of this time interval, suggesting that the climate influence of NADW variability was widespread. We see no evidence, however, for changes in NADW production during substage 5e (the Eemian interglacial period), in contrast with recent ice-core data¹⁰which suggest severe climate instability in Greenland during this time period. Our results may support suggestions, based on data from a second ice core, that this apparent instability is an artefact caused by ice flow¹¹. Alternatively, the Eemian climate instability may have had a different origin from the subsequent climate events.
5. 1995: Blanchon, Paul, and John Shaw. “Reef drowning during the last deglaciation: evidence for catastrophic sea-level rise and ice-sheet collapse.” Geology 23.1 (1995): 4-8.  Elevations and ages of drowned Acropora palmata reefs from the Caribbean-Atlantic region document three catastrophic, metre-scale sea-level–rise events during the last deglaciation. These catastrophic rises were synchronous with (1) collapse of the Laurentide and Antarctic ice sheets, (2) dramatic reorganization of ocean-atmosphere circulation, and (3) releases of huge volumes of subglacial and proglacial meltwater. This correlation suggests that release of stored meltwater periodically destabilized ice sheets, causing them to collapse and send huge fleets of icebergs into the Atlantic. Massive inputs of ice not only produced catastrophic sea-level rise, drowning reefs and destabilizing other ice sheets, but also rapidly reduced the elevation of the Laurentide ice sheet, flipping atmospheric circulation patterns and forcing warm equatorial waters into the frigid North Atlantic. Such dramatic evidence of catastrophic climate and sea-level change during deglaciation has potentially disastrous implications for the future, especially as the stability of remaining ice sheets—such as in West Antarctica—is in question
6. 1996: Zagwijn, W. H. “An analysis of Eemian climate in western and central Europe.” Quaternary Science Reviews 15.5-6 (1996): 451-469. On the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the Last Interglacial Eemian climatic history in Western and Central Europe. The main tool for this analysis is the climatic indicator species method. Only selected woody species are used for the quantification of data. Partial climatic range diagrams are presented for: Abies alba, Acer monspessulanum, Acer tataricum, Buxus sempervirens, Tilia tomentosa. The problem of time correlation and pollen zonation of the Eemian is discussed. The climatic analysis itself is based on an improved version of the indicator species method. In this version not every site is analysed for its climatic values. Instead maps and tables on the migrational history of Hedera, Ilex, Buxus, Abies and species of Acer, Tilia and Abies are the basis for climatic maps showing respectively January and July isotherms for the periods of the Corylus zone (E4a) and the Carpinus zone (E5). It is concluded that mean January temperatures were as much as 3°C higher at Amsterdam (The Netherlands), than at present, and mean temperatures in July were 2°C higher. However, the thermal maximum in winter was later (zone E5) than the summer thermal maximum (zone E4a). Winter temperatures changed parallel to rise and fall of global sea-level. Precipitation changes are more difficult to estimate. In the first part of the Eemian precipitation must have been relatively low, but from zone E4b onward it increased to higher values, reaching 800 mm and probably substantially more in zones E5 and E6. Hence the Eemian climate was in its beginning relatively more contintental, and later (from E4b onward) more oceanic. However, as compared with the Holocene, the Eemian climate was, generally speaking, more oceanic.
7. 1996: Litt, Thomas, Frank W. Junge, and Tanja Böttger. “Climate during the Eemian in north-central Europe—a critical review of the palaeobotanical and stable isotope data from central Germany.” Vegetation History and Archaeobotany 5.3 (1996): 247-256.  This paper reviews the evidence from terrestrial palaeoenvironmental records in north-central Europe and, in particular, central Germany, which relates to the controversial proposition that there were strong climate oscillations during the last interglacial (oxygen isotope substage 5e). In contrast to the evidence from the GRIP ice core at Summit, Greenland, and a recent palaeoclimate reconstruction based on the pollen profile from Bispingen, Germany, the evaluation of the palaeobotanical and the stable isotope data presented here strongly suggests relatively stable temperature for most of the Eemian and with instability confined to the beginning and end of the interglacial. High amplitude temperature variations can be seen in both the Early Weichselian pollen and isotope records. It is argued that this pattern of climate development is applicable to most of continental north-central Europe.
8. 1997: Johnsen, Sigfús J., et al. “The δ18O record along the Greenland Ice Core Project deep ice core and the problem of possible Eemian climatic instability.” Journal of Geophysical Research: Oceans 102.C12 (1997): 26397-26410.  Over 70,000 samples from the 3029‐m‐long Greenland Ice Core Project (GRIP) ice core drilled on the top of the Greenland Ice Sheet (Summit) have been analyzed for δ⁸O. A highly detailed and continuous δ⁸O profile has thus been obtained and is discussed in terms of past temperatures in Greenland. We also discuss a three‐core stacked annual δ⁸O profile for the past 917 years. The short‐term (<50 years) variability of the annual δ⁸O signal is found to be 1‰ in the Holocene, and estimates for the coldest parts of the last glacial are 3‰ or higher. These data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the Eemian. Spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the δ⁸O signal, which for the Holocene ice is found to be considerably stronger than expected. We suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix. Deconvolution techniques were employed for restoring with great confidence the highly attenuated annual δ⁸O signal in the Holocene. We confirm earlier findings of dramatic temperature changes in Greenland during the last glacial cycle. Abrupt and strong climatic shifts are also found within the Eem/Sangamon Interglaciation, which is normally recorded as a period of warm and stable climate in lower latitudes. The stratigraphic continuity of the Eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile
9. 1998: Cheddadi, R., et al. “Was the climate of the Eemian stable? A quantitative climate reconstruction from seven European pollen records.” Palaeogeography, Palaeoclimatology, Palaeoecology 143.1-3 (1998): 73-85. The aim of the present study is to estimate the range of the climatic variability during the Eemian interglacial, which lasted about 10,000 years (marine isotopic stage 5e). The modern pollen analogue technique is applied to seven high resolution pollen records from France and Poland to infer the annual precipitation and the mean temperature of the coldest month. The succession of pollen taxa and the reconstructed climate can be interpreted coherently. The warmest winter temperatures are centred in the first three millennia of the Eemian interglacial, during the mixed oak forest phase with Quercus and Corylus as dominant trees. A rapid shift to cooler winter temperatures of about 6° to 10°C occurred between 4000 and 5000 years after the beginning of the Eemian, related to the spread of the Carpinus forest. This shift is more obvious for the reconstructed temperatures than for precipitation and is unique and irreversible for the whole Eemian period. Following this climatic shift of the Eemian, variations of temperature and precipitation during the last 5000 years were only slight with an amplitude of about 2° to 4°C and 200 to 400 mm/yr. The estimated temperature changes were certainly not as strong as those reconstructed for the stage 6/5e termination or the transition 5e/5d. This is consistent with the constantly high ratio of tree pollen throughout the Eemian, indicative of a succession of temperate forest types. This gradual transition between different forest landscapes can be related to intrinsic competition between the species rather than to a drastic climatic change.
10. 1998: Aalbersberg, Gerard, and Thomas Litt. “Multiproxy climate reconstructions for the Eemian and Early Weichselian.” Journal of Quaternary Science: Published for the Quaternary Research Association 13.5 (1998): 367-390. Palaeobotanical, coleopteran and periglacial data from 106 sites across northwestern Europe have been analysed in order to reconstruct palaeoclimatic conditions during the Eemian and Early Weichselian. Three time slices in the Eemian and four in the Early Weichselian have been considered. In the Pinus–Quercetum mixtum–Corylus phase of the Eemian, summer temperatures were probably at their highest and the botanic evidence suggests a southeast to northwest gradient for both the warmest and coldest month. Coleoptera indicate that the summers in southern England were several degrees warmer than those of present day. The climate during theCarpinus–Picea phase was uniform and oceanic without obvious gradients. In the final time slice of the Eemian, the Pinus–Picea–Abies phase, temperatures of the warmest month seem to drop slightly with some indication of a shift towards a more boreal and suboceanic climate. The reconstruction of the palaeoclimate in the Herning Stadial and Rederstall Stadial is hampered by the limited number of sites, but botanical evidence suggests a gradient in temperature of the coldest month from east to west. Coleoptera from the Herning Stadial in central England and eastern Germany suggest similarly cold and continental climates. During the Brørup Interstadial and the Odderade Interstadial the botanical evidence suggests that the minimum mean July temperatures rose to 15–16°C but during the coldest month these temperatures show a gradient between −13°C in the east and −5°C in the west. © 1998 John Wiley & Sons, Ltd.
11. 2000: Cuffey, Kurt M., and Shawn J. Marshall. “Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet.” Nature 404.6778 (2000): 591.  During the last interglacial period (the Eemian), global sea level was at least three metres, and probably more than five metres, higher than at present^1,2. Complete melting of either the West Antarctic ice sheet or the Greenland ice sheet would today raise sea levels by 6–7 metres. But the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the West Antarctic ice sheet³, with model studies attributing only 1–2 m of sea-level rise to meltwater from Greenland^4,5. This result was considered consistent with ice core evidence⁴, although earlier work had suggested a much reduced Greenland ice sheet during the last interglacial period⁶. Here we reconsider the Eemian evolution of the Greenland ice sheet by combining numerical modelling with insights obtained from recent central Greenland ice-core analyses. Our results suggest that the Greenland ice sheet was considerably smaller and steeper during the Eemian, and plausibly contributed 4–5.5 m to the sea-level highstand during that period. We conclude that the high sea level during the last interglacial period most probably included a large contribution from Greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the West Antarctic ice sheet. [FULL TEXT PDF]  
12. 2000: Karabanov, Eugene B., et al. “Evidence for mid-Eemian cooling in continental climatic record from Lake Baikal.” Journal of Paleolimnology 23.4 (2000): 365-371. The discussion on climatic instability observed in Greenland ice cores during the Eemian period (substage 5e) resulted in discovery of a pronounced mid-Eemian cooling event. We report that the mid-Eemian cooling is found for the first time in the biogenic silica climatic record and microfossil abundance record of Lake Baikal. Timing of this event in Lake Baikal correlates well with timing of the European pollen records and marine sedimentary records. The presence of the mid-Eemian cooling signal in the Lake Baikal record suggests a much closer link between Asian climate influenced by strong pressure fields over the vast land masses and the climate-controlling processes in the North Atlantic during interglacial periods, than what was generally believed. Furthermore, the Lake Baikal record suggests that after the mid-Eemian cooling, the climatic conditions returned close to the warmth of the 5e optimum and thus argues that the warm conditions of the last interglacial persisted in Siberia throughout 5e, and did not end with the mid-Eemian cooling as suggested by several published marine records.
13. 2000: Kukla, George J. “The last interglacial.” Science 287.5455 (2000): 987-988.  Climate during the last 10,000 years, the Holocene, has been relatively mild and stable. In contrast, the climate during the last interglacial is often portrayed as more variable. But, as Kukla discusses in this Perspective, evidence for a more stable last interglacial is emerging. Furthermore, the transition to the next glacial proceeded in stages and was not uniform across Europe.
14. 2002: Rahmstorf, Stefan. “Ocean circulation and climate during the past 120,000 years.” Nature 419.6903 (2002): 207. Oceans cover more than two-thirds of our blue planet. The waters move in a global circulation system, driven by subtle density differences and transporting huge amounts of heat. Ocean circulation is thus an active and highly nonlinear player in the global climate game. Increasingly clear evidence implicates ocean circulation in abrupt and dramatic climate shifts, such as sudden temperature changes in Greenland on the order of 5–10 °C and massive surges of icebergs into the North Atlantic Ocean — events that have occurred repeatedly during the last glacial cycle.
15. 2002: Cane, Tim, et al. “High-resolution stratigraphic framework for Mediterranean sapropel S5: defining temporal relationships between records of Eemian climate variability.” Palaeogeography, Palaeoclimatology, Palaeoecology 183.1 (2002): 87-101. A high-resolution stratigraphic framework is presented for sapropel S5, which represents the low-mid latitude climate optimum of the previous interglacialperiod (Eemian). The framework is based on three sites along a transect from west to east through the eastern Mediterranean, and is further validated using a fourth site. This method allows expression of S5-based proxy records of Eemianclimate variability along a standardised depth scale that offers unprecedented possibilities for assessment of spatial gradients and signal leads and lags in an interval where high-resolution (radiocarbon-style) dating cannot be performed. Our lateral comparison of S5 sapropels suggests that the onset of S5 in ODPsite 967C (Eratosthenes seamount) was 1–6 centuries delayed relative to the onsets in more westerly sites.  [FULL TEXT PDF]
16. 2003: Klotz, Stefan, Joel Guiot, and Volker Mosbrugger. “Continental European Eemian and early Würmian climate evolution: comparing signals using different quantitative reconstruction approaches based on pollen.” Global and Planetary Change36.4 (2003): 277-294. Analyses of Eemian climate dynamics based on different reconstruction methods were conducted for several pollen sequences in the northern alpine foreland. The modern analogue and mutual climate sphere techniques used, which are briefly presented, complement one another with respect to comparable results. The reconstructions reveal the occurrence of at least two similar thermal periods, representing temperate oceanic conditions warmer and with a higher humidity than today. Intense changes of climate processes become obvious with a shift of winter temperatures of about 15 °C from the late Rissian to the first thermal optimum of the Eemian. The transition shows a pattern of summer temperatures and precipitation increasing more rapidly than winter temperatures. With the first optimum during the Pinus–Quercetum mixtum–Corylus phase (PQC) at an early stage of the Eemian and a second optimum period at a later stage, which is characterised by widespread Carpinus, climate gradients across the study area were less intense than today. Average winter temperatures vary between −1.9 and 0.4 °C (present-day −3.6 to 1.4 °C), summer temperatures between 17.8 and 19.6 °C (present-day 14 to 18.9 °C). The timberline expanded about 350 m when compared to the present-day limit represented by Pinus mugo. Whereas the maximum of temperature parameters is related to the first optimum, precipitation above 1100 mm is higher during the second warm period concomitant to somewhat reduced temperatures. Intermediate, smaller climate oscillations and a cooling becomes obvious, which admittedly represent moderate deterioration but not extreme chills. During the boreal semicontinental Eemian Pinus–Picea–Abies phase, another less distinct fluctuation occurs, initiating the oscillating shift from temperate to cold conditions.
17. 2004: Andersen, Katrine K., et al. “High-resolution record of Northern Hemisphere climate extending into the last interglacial period.” Nature 431.7005 (2004): 147. Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 °C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.  [FULL TEXT PDF] 
18. 2006: Peltier, W. R., and Richard G. Fairbanks. “Global glacial ice volume and Last Glacial Maximum duration from an extended Barbados sea level record.” Quaternary Science Reviews25.23-24 (2006): 3322-3337.  Fundamental characteristics of the climate system during the most recent precessional cycle of the Earth’s orbit around the Sun consist of the final expansion of land ice to its maximum extent, the subsequent episode of deglaciation, and the variations of global sea level that accompanied these events. In order to address the important issue of the variation of continental ice volume and related changes in global sea level through the late glacial period, we employ an extended set of observations of the pre-glacial and postglacial history of sea-level rise at the island of Barbados, together with a refined model of continental deglaciation and an accurate methodology for the prediction of postglacial sea-level change. Although our results provide unambiguous evidence that the post LGM rise of eustatic sea-level was very close to the widely supported estimate of 120 m, the data also provide evidence that LGM must have occurred 26,000 years ago, approximately 5000 yr earlier than the usually assumed age.
19. 2007: Tarasov, Pavel, et al. “Vegetation and climate dynamics during the Holocene and Eemian interglacials derived from Lake Baikal pollen records.” Palaeogeography, Palaeoclimatology, Palaeoecology 252.3-4 (2007): 440-457. The last interglacial (LI) and Holocene changes in annual precipitation (P_ann), the mean temperature of the warmest (T_w) and coldest (T_c) month and the moisture index (α) were reconstructed from continuous pollen records from Lake Baikal. The Holocene core (52°31′N, 106°09′E) presented in this study was recovered from a depth of 355 m in the 25-km wide underwater Buguldeika saddle separating the southern sub-basin of Lake Baikal from its central sub-basin. The biome reconstruction shows that tundra and steppe biomes have highest scores during ca. 15,000–13,300 cal. years B.P. and that taiga becomes a dominant vegetation type after ca. 13,300 cal. years B.P. Our quantitative reconstruction indicates an onset of relatively warm and wet conditions soon after ca. 10,000 cal. years B.P. The warmest and wettest climate with T_w ∼ 16 °C, P_ann ∼ 480 mm and α ∼ 0.9–1 has been reconstructed for ca. 9000–7000 cal. years B.P. In the Lake Baikal region this interval is characterized by the appearance and spread of hunter communities (Kitoi culture). Consistently a hiatus in the regional archaeological record (4900–4200 years B.C. or 6850–6150 cal. years B.P.) coincides with the interval of a major climate deterioration which followed the ‘climatic optimum’. An attempt to find a relationship between the archaeological record and a spread of steppe and meadow communities in the Lake Baikal region demonstrates that despite a long habitation of the area the human impact on vegetation was local rather than regional and likely did not affect the pollen record from Lake Baikal. The reconstructed peaks in the steppe biome scores during the last 9000 years are consistent with short (one to five hundred year) episodes of weak Pacific (summer) monsoon supporting our interpretation that the Holocene vegetation changes around Lake Baikal are associated with large-scale circulation processes controlling regional water balance rather than with human activities. Thus, our study proves the suitability of Lake Baikal pollen data for the reconstruction of natural vegetation and climate dynamics through the whole period from the onset of the LI to the present. Comparison of the recent and the last interglacial suggests that the Holocene ‘climatic optimum’ was less pronounced (e.g. lower summer and winter temperatures and annual precipitation sums) than that of the LI. On the other hand, pollen records demonstrate that the Holocene ‘forest phase’ already lasts some thousand years longer than that of the LI. The interglacial vegetation dynamics derived from the Lake Baikal pollen records can be satisfactorily explained by reconstructed changes in summer and winter temperatures and in available moisture. The interglacial vegetation around Lake Baikal is dominated by the boreal forests, which are associated with a generally warm and wet climate. The high sea level associated with decreased ice volume appears to have had a greater impact on the Siberian environments during the last and the recent interglacial than the direct effect of lower-than-present winter insolation. Reconstructed changes in the winter temperature correlate well with changes in the sea level and global ice volume, while the summer temperatures derived from the Lake Baikal pollen records track changes in the summer insolation.  [FULL TEXT PDF]
20. 2007: Schurgers, Guy, et al. “The effect of land surface changes on Eemian climate.” Climate dynamics 29.4 (2007): 357-373. Transient experiments for the Eemian (128–113 ky BP) were performed with a complex, coupled earth system model, including atmosphere, ocean, terrestrial biosphere and marine biogeochemistry. In order to investigate the effect of land surface parameters (background albedo, vegetation and tree fraction and roughness length) on the simulated changes during the Eemian, simulations with interactive coupling between climate and vegetation were compared with additional experiments in which these feedbacks were suppressed. The experiments show that the influence of land surface on climate is mainly caused by changes in the albedo. For the northern hemisphere high latitudes, land surface albedo is changed partially due to the direct albedo effect of the conversion of grasses into forest, but the indirect effect of forests on snow albedo appears to be the major factor influencing the total absorption of solar radiation. The Western Sahara region experiences large changes in land surface albedo due to the appearance of vegetation between 128 and 120 ky BP. These local land surface albedo changes can be as much as 20%, thereby affecting the local as well as the global energy balance. On a global scale, latent heat loss over land increases more than 10% for 126 ky BP compared to present-day.  [FULL TEXT PDF]
21. 2008: Brewer, S., et al. “The climate in Europe during the Eemian: a multi-method approach using pollen data.” Quaternary Science Reviews 27.25-26 (2008): 2303-2315. The Last Interglacial period, the Eemian, offers a testbed for comparing climate evolution throughout an interglacial with the current warm period. We present here results from climatic reconstructions from 17 sites distributed across the European continent, allowing an assessment of trends and regional averages of climate changes during this period. We use a multi-method approach to allow for an improved assessment of the uncertainties involved in the reconstruction. In addition, the method takes into account the errors associated with the age model. The resulting uncertainties are large, but allow a more robust assessment of the reconstructed climatic variations than in previous studies. The results show a traditional three-part Eemian, with an early optimum, followed by slight cooling and eventually a sharp drop in both temperatures and precipitation. This sequence is however, restricted to the north, as this latter change is not observed in the south where temperatures remain stable for longer. These variations led to marked variation in the latitudinal temperature gradient during the Eemian. The difference between the two regions is also noticeable in the magnitude of changes, with greater variations in the north than the south. Some evidence is found for changes in lapse rates, however, a greater number of sites is needed to confirm this.  [FULL TEXT PDF]
22. 2009: Kopp, Robert E., et al. “Probabilistic assessment of sea level during the last interglacial stage.” Nature 462.7275 (2009): 863.  With polar temperatures ∼3–5 °C warmer than today, the last interglacial stage (∼125 kyr ago) serves as a partial analogue for 1–2 °C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (≥-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr^-1 but is unlikely to have exceeded 9.2 m kyr^-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.
23. 2010: Fischer, N., and J. H. Jungclaus. “Effects of orbital forcing on atmosphere and ocean heat transports in Holocene and Eemian climate simulations with a comprehensive Earth system model.” Climate of the Past 6 (2010): 155-168. Orbital forcing not only exerts direct insolation effects, but also alters climate indirectly through feedback mechanisms that modify atmosphere and ocean dynamics and meridional heat and moisture transfers. We investigate the regional effects of these changes by detailed analysis of atmosphere and ocean circulation and heat transports in a coupled atmosphere-ocean-sea ice-biosphere general circulation model (ECHAM5/JSBACH/MPI-OM). We perform long term quasi equilibrium simulations under pre-industrial, mid-Holocene (6000 years before present – yBP), and Eemian (125 000 yBP) orbital boundary conditions. Compared to pre-industrial climate, Eemian and Holocene temperatures show generally warmer conditions at higher and cooler conditions at lower latitudes. Changes in sea-ice cover, ocean heat transports, and atmospheric circulation patterns lead to pronounced regional heterogeneity. Over Europe, the warming is most pronounced over the north-eastern part in accordance with recent reconstructions for the Holocene. We attribute this warming to enhanced ocean circulation in the Nordic Seas and enhanced ocean-atmosphere heat flux over the Barents Shelf in conduction with retreat of sea ice and intensified winter storm tracks over northern Europe. [FULL TEXT PDF]
24. 2011: Nicholls, Robert J., et al. “Sea-level rise and its possible impacts given a ‘beyond 4 C world’in the twenty-first century.” Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 369.1934 (2011): 161-181.  The range of future climate-induced sea-level rise remains highly uncertain with continued concern that large increases in the twenty-first century cannot be ruled out. The biggest source of uncertainty is the response of the large ice sheets of Greenland and west Antarctica. Based on our analysis, a pragmatic estimate of sea-level rise by 2100, for a temperature rise of 4°C or more over the same time frame, is between 0.5 m and 2 m—the probability of rises at the high end is judged to be very low, but of unquantifiable probability. However, if realized, an indicative analysis shows that the impact potential is severe, with the real risk of the forced displacement of up to 187 million people over the century (up to 2.4% of global population). This is potentially avoidable by widespread upgrade of protection, albeit rather costly with up to 0.02 per cent of global domestic product needed, and much higher in certain nations. The likelihood of protection being successfully implemented varies between regions, and is lowest in small islands, Africa and parts of Asia, and hence these regions are the most likely to see coastal abandonment. To respond to these challenges, a multi-track approach is required, which would also be appropriate if a temperature rise of less than 4°C was expected. Firstly, we should monitor sea level to detect any significant accelerations in the rate of rise in a timely manner. Secondly, we need to improve our understanding of the climate-induced processes that could contribute to rapid sea-level rise, especially the role of the two major ice sheets, to produce better models that quantify the likely future rise more precisely. Finally, responses need to be carefully considered via a combination of climate mitigation to reduce the rise and adaptation for the residual rise in sea level. In particular, long-term strategic adaptation plans for the full range of possible sea-level rise (and other change) need to be widely developed.  [FULL TEXT PDF]
25. 2011: Krzysztof, Bińka, and Nitychoruk Jerzy. “Cyclicity in the Eemian climate? A case study of the Eemian site at Czaple, Eastern Poland.” Review of palaeobotany and palynology164.1-2 (2011): 39-44. The newly discovered lacustrine deposits from Czaple, Eastern Poland, examined by means of pollen analysis, revealed an undisturbed, continuous sequence of vegetational development of the Eemian/Early Vistulian age. We tried to trace the secondary climatic trends, cyclic in part on the basis of plant taxa — representing the second league in the spectra, as to frequency, but forming an important group of the index plants. Their appearance becomes more pronounced and reliable when extraordinarily high numbers of pollen are analyzed. The oscillations of curves of these taxa are more clearly expressed than by traditional counts, revealing the hidden picture in the palynological background. It is interesting that some taxa – e.g. Hedera – form a distinctive intermittent pattern reflecting cyclicity of climatic condition or additional factors which are responsible for it. Pollen curves of other index plants do not show such regular variation. This cyclicity can be traced in many European Eemian diagrams. Especially interesting is the sudden decline of ivy as well as of other indicator plants in the subzone E4b such as the Corylus which marks some increase in a continentality of climate. We can also trace this trend in other sequences. In addition, extra counts allow us to estimate the exact timing of the migration of rarely noted exotic taxa and their range of distribution in the sequence. Buxus, Osmunda cinnamomea and Lycopodium lucidulum types are the best examples illustrating this.
26. 2011: Van de Berg, Willem Jan, et al. “Significant contribution of insolation to Eemian melting of the Greenland ice sheet.” Nature Geoscience 4.10 (2011): 679.  During the Eemian interglacial period, 130,000 to 114,000 years ago, the volume of the Greenland ice sheet was about 30–60% smaller than the present-day volume^1,2. Summer temperatures in the Arctic region were about 2–4 K higher than today^3,4,5, leading to the suggestion that Eemian conditions could be considered an analogue for future warming⁶, particularly for the future stability of the Greenland ice sheet. However, Northern Hemisphere insolation was much higher during the Eemian than today, which could affect the reliability of this analogy. Here we use a high-resolution regional climate model with a realistic ice-sheet surface representation to assess the surface mass balance of the Greenland ice sheet during the Eemian. Our simulations show that Eemian climate led to an 83% lower surface mass balance, compared with the preindustrial simulation. Our sensitivity experiments show that only about 55% of this change in surface mass balance can be attributed to higher ambient temperatures, with the remaining 45% caused by higher insolation and associated nonlinear feedbacks. We show that temperature–melt relations are dependent on changes in insolation. Hence, we suggest that projections of future Greenland ice loss on the basis of Eemian temperature–melt relations may overestimate the future vulnerability of the ice sheet.  [FULL TEXT PDF]
27. 2013: Nikolova, Irina, et al. “The last interglacial (Eemian) climate simulated by LOVECLIM and CCSM3.” Climate of the Past 9.4 (2013): 1789-1806. This paper presents a detailed analysis of the climate of the last interglacial simulated by two climate models of different complexities, CCSM3 (Community Climate System Model 3) and LOVECLIM (LOch-Vecode-Ecbilt-CLio-agIsm Model). The simulated surface temperature, hydrological cycle, vegetation and ENSO variability during the last interglacial are analyzed through the comparison with the simulated pre-industrial (PI) climate. In both models, the last interglacial period is characterized by a significant warming (cooling) over almost all the continents during boreal summer (winter) leading to a largely increased (reduced) seasonal contrast in the Northern (Southern) Hemisphere. This is mainly due to the much higher (lower) insolation received by the whole Earth in boreal summer (winter) during this interglacial. The Arctic is warmer than PI through the whole year, resulting from its much higher summer insolation, its remnant effect in the following fall-winter through the interactions between atmosphere, ocean and sea ice and feedbacks from sea ice and snow cover. Discrepancies exist in the sea-ice formation zones between the two models. Cooling is simulated by CCSM3 in the Greenland and Norwegian seas and near the shelves of Antarctica during DJF but not in LOVECLIM as a result of excessive sea-ice formation. Intensified African monsoon is responsible for the cooling during summer in northern Africa and on the Arabian Peninsula. Over India, the precipitation maximum is found further west, while in Africa the precipitation maximum migrates further north. Trees and grassland expand north in Sahel/Sahara, more clearly seen in LOVECLIM than in CCSM3 results. A mix of forest and grassland occupies continents and expands deep into the high northern latitudes. Desert areas reduce significantly in the Northern Hemisphere, but increase in northern Australia. The interannual SST variability of the tropical Pacific (El-Niño Southern Oscillation) of the last interglacial simulated by CCSM3 shows slightly larger variability and magnitude compared to the PI. However, the SST variability in our LOVECLIM simulations is particularly small due to the overestimated thermocline’s depth.  [FULL TEXT PDF]
28. 2015: Dutton, A., et al. “Sea-level rise due to polar ice-sheet mass loss during past warm periods.” science 349.6244 (2015): aaa4019.  We know that the sea level will rise as climate warms. Nevertheless, accurate projections of how much sea-level rise will occur are difficult to make based solely on modern observations. Determining how ice sheets and sea level have varied in past warm periods can help us better understand how sensitive ice sheets are to higher temperatures. Dutton et al. review recent interdisciplinary progress in understanding this issue, based on data from four different warm intervals over the past 3 million years. Their synthesis provides a clear picture of the progress we have made and the hurdles that still exist.  [FULL TEXT PDF]
29. 2015: Hansen, James, et al. “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2° C global warming is highly dangerous.” Atmospheric Chemistry & Physics Discussions 15.14 (2015).  There is evidence of ice melt, sea level rise to +5–9 m, and extreme storms in the prior interglacial period that was less than 1C warmer than today. Human-made climate forcing is stronger and more rapid than paleo forcings, but much can be learned by 5 combining insights from paleoclimate, climate modeling, and on-going observations. We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years. Paleoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge. Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability. Ocean surface cooling, in the North Atlantic 15 as well as the Southern Ocean, increases tropospheric horizontal temperature gradients, eddy kinetic energy and baroclinicity, which drive more powerful storms. We focus attention on the Southern Ocean’s role in affecting atmospheric CO2 amount, which in turn is a tight control knob on global climate. The millennial (500–2000 year) time scale of deep ocean ventilation affects the time scale for natural CO2 change, thus the time 20 scale for paleo global climate, ice sheet and sea level changes. This millennial carbon cycle time scale should not be misinterpreted as the ice sheet time scale for response to a rapid human-made climate forcing. Recent ice sheet melt rates have a doubling time near the lower end of the 10–40 year range. We conclude that 2C global warming above the preindustrial level, which would spur more ice shelf melt, is highly dangerous. Earth’s energy imbalance, which must be eliminated to stabilize climate, provides a crucial metric.  [FULL TEXT PDF]
30. 2016: DeConto, Robert M., and David Pollard. “Contribution of Antarctica to past and future sea-level rise.” Nature 531.7596 (2016): 591.  Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6–9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics—including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs—that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.  [FULL TEXT PDF]

 

 

 

 

 

AGW COLLAPSE OF ICE SHEETS:  BIBLIOGRAPHY

1. 1983: Zwally, H. Jay, et al. “Surface elevation contours of Greenland and Antarctic ice sheets.” Journal of Geophysical Research: Oceans 88.C3 (1983): 1589-1596. Surface elevations of the ice sheets are contoured at 50‐m intervals for the region of Greenland covered by SEASAT radar altimetry south of 72°N and at 100‐m intervals for a region of East Antarctica north of 72°S. The surface elevations were obtained from computer retracking of the radar altimeter waveforms, which were recorded at 0.1‐s intervals corresponding to 662‐m spacings on the surface. The precision of the elevation measurements before adjustment for radial orbit errors is 1.9 m as shown by analysis of elevation differences at orbital crossover points. This precision is partly determined by radial errors of approximately 1.0 m in orbit determination and partly by noise due to ice surface irregularities. Adjustment of the radial components of the orbits to minimize the differences in elevations at crossovers over a small, relatively flat region reduces the rms difference to 0.25 m, which is indicative of the optimum precision obtainable over the ice sheets. However, the precision degrades as the slope of the surface or amplitude of the undulations increases, yielding an overall precision of ±1.6 m. The preliminary contour maps are not corrected for slope‐induced displacements. A 2‐m contour map in a region of highest data density illustrates the three‐dimensional characteristics of some surface undulations.
   
2. 1999: Huybrechts, Philippe, and Jan de Wolde. “The dynamic response of the Greenland and Antarctic ice sheets to multiple-century climatic warming.” Journal of Climate 12.8 (1999): 2169-2188.  New calculations were performed to investigate the combined response of the Greenland and Antarctic ice sheets to a range of climatic warming scenarios over the next millennium. Use was made of fully dynamic 3D thermomechanic ice sheet models, which were coupled to a two-dimensional climate model. The experiments were initialized with simulations over the last two glacial cycles to estimate the present evolution and were subsequently forced with temperature scenarios resulting from greenhouse emission scenarios which assume equivalent CO₂ increases of two, four, and eight times the present (1990 a.d.) value by the year 2130 a.d. and a stabilization after that. The calculations brought to light that during the next century (short-term effect), the background evolution trend would dominate the response of the Antarctic ice sheet but would be negligible for the Greenland ice sheet. On that timescale, the Greenland and Antarctic ice sheets would roughly balance one another for the middle scenario (similar to the IPCC96 IS92a scenario), with respective contributions to the worldwide sea level stand on the order of about ±10 cm. On the longer term, however, both ice sheets would contribute positively to the worldwide sea level stand and the most important effect would come from melting on the Greenland ice sheet. Sensitivity experiments highlighted the role of ice dynamics and the height–mass-balance feedback on the results. It was found that ice dynamics cannot be neglected for the Greenland ice sheet, not even on a century timescale, but becomes only important for Antarctica on the longer term. The latter is related to an increased outflow of ice into the ice shelves and to the grounding-line retreat of the west Antarctic ice sheet, which are both found to be sensitive to basal melting below ice shelves and the effective viscosity of the ice shelves. Stretching parameters to their limits yielded a combined maximum rate of sea level rise of 85 cm century⁻¹, of which 60 cm would originate from the Greenland ice sheet alone.
3. 2005: Zwally, H. Jay, et al. “Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992–2002.” Journal of Glaciology 51.175 (2005): 509-527.  Changes in ice mass are estimated from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2. For the first time, the dH/dt values are adjusted for changes in surface elevation resulting from temperature-driven variations in the rate of firn compaction. The Greenland ice sheet is thinning at the margins (–42 ± 2Gta¯1 below the equilibrium-line altitude (ELA)) and growing inland (+53 ± 2Gta-1 above the ELA) with a small overall mass gain (+11 ± 3Gta–1; –0.03 mma–1 SLE (sea-level equivalent)). The ice sheet in West Antarctica (WA) is losing mass (–47 ± 4Gta–1) and the ice sheet in East Antarctica (EA) shows a small mass gain (+16 ± 11 Gta–1) for a combined net change of –31 ± 12 Gta–1(+0.08mma–1 SLE). The contribution of the three ice sheets to sea level is +0.05±0.03mma–1. The Antarctic ice shelves show corresponding mass changes of –95 ± 11 Gta–1 in WA and +142 ± 10Gta–1 in EA. Thinning at the margins of the Greenland ice sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate. The marked thinnings in the Pine Island and Thwaites Glacier basins of WA and the Totten Glacier basin in EA are probably ice- dynamic responses to long-term climate change and perhaps past removal of their adjacent ice shelves. The ice growth in the southern Antarctic Peninsula and parts of EA may be due to increasing precipitation during the last century.
4. 2009: Pollard, David, and Robert M. DeConto. “Modelling West Antarctic ice sheet growth and collapse through the past five million years.” Nature 458.7236 (2009): 329.  The West Antarctic ice sheet (WAIS), with ice volume equivalent to ∼5 m of sea level¹, has long been considered capable of past and future catastrophic collapse^2,3,4. Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat^3,5. Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms^6,7. Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around ∼15 kyr ago before retreating to near-modern locations by ∼3 kyr ago⁸. Prior collapses during the warmth of the early Pliocene epoch⁹and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments¹⁰. Until now¹¹, however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model¹² capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing⁵ to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea¹¹, indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at marine isotope stage 31 (∼1.07 Myr ago) and other super-interglacials.
5. 2009: Pritchard, Hamish D., et al. “Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets.” Nature 461.7266 (2009): 971.  Many glaciers along the margins of the Greenland and Antarctic ice sheets are accelerating and, for this reason, contribute increasingly to global sea-level rise^{1,2,3,4,5,6,7}. Globally, ice losses contribute ∼1.8 mm yr^-1(ref. 8), but this could increase if the retreat of ice shelves and tidewater glaciers further enhances the loss of grounded ice⁹ or initiates the large-scale collapse of vulnerable parts of the ice sheets¹⁰. Ice loss as a result of accelerated flow, known as dynamic thinning, is so poorly understood that its potential contribution to sea level over the twenty-first century remains unpredictable¹¹. Thinning on the ice-sheet scale has been monitored by using repeat satellite altimetry observations to track small changes in surface elevation, but previous sensors could not resolve most fast-flowing coastal glaciers¹². Here we report the use of high-resolution ICESat (Ice, Cloud and land Elevation Satellite) laser altimetry to map change along the entire grounded margins of the Greenland and Antarctic ice sheets. To isolate the dynamic signal, we compare rates of elevation change from both fast-flowing and slow-flowing ice with those expected from surface mass-balance fluctuations. We find that dynamic thinning of glaciers now reaches all latitudes in Greenland, has intensified on key Antarctic grounding lines, has endured for decades after ice-shelf collapse, penetrates far into the interior of each ice sheet and is spreading as ice shelves thin by ocean-driven melt. In Greenland, glaciers flowing faster than 100 m yr^-1thinned at an average rate of 0.84 m yr^-1, and in the Amundsen Sea embayment of Antarctica, thinning exceeded 9.0 m yr^-1 for some glaciers. Our results show that the most profound changes in the ice sheets currently result from glacier dynamics at ocean margins.
6. 2009: Velicogna, Isabella. “Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE.” Geophysical Research Letters 36.19 (2009).  We use monthly measurements of time‐variable gravity from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to determine the ice mass‐loss for the Greenland and Antarctic Ice Sheets during the period between April 2002 and February 2009. We find that during this time period the mass loss of the ice sheets is not a constant, but accelerating with time, i.e., that the GRACE observations are better represented by a quadratic trend than by a linear one, implying that the ice sheets contribution to sea level becomes larger with time. In Greenland, the mass loss increased from 137 Gt/yr in 2002–2003 to 286 Gt/yr in 2007–2009, i.e., an acceleration of −30 ± 11 Gt/yr² in 2002–2009. In Antarctica the mass loss increased from 104 Gt/yr in 2002–2006 to 246 Gt/yr in 2006–2009, i.e., an acceleration of −26 ± 14 Gt/yr² in 2002–2009. The observed acceleration in ice sheet mass loss helps reconcile GRACE ice mass estimates obtained for different time periods.
7. 2011: Rignot, Eric, et al. “Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise.” Geophysical Research Letters 38.5 (2011). Ice sheet mass balance estimates have improved substantially in recent years using a variety of techniques, over different time periods, and at various levels of spatial detail. Considerable disparity remains between these estimates due to the inherent uncertainties of each method, the lack of detailed comparison between independent estimates, and the effect of temporal modulations in ice sheet surface mass balance. Here, we present a consistent record of mass balance for the Greenland and Antarctic ice sheets over the past two decades, validated by the comparison of two independent techniques over the last 8 years: one differencing perimeter loss from net accumulation, and one using a dense time series of time‐variable gravity. We find excellent agreement between the two techniques for absolute mass loss and acceleration of mass loss. In 2006, the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise. Notably, the acceleration in ice sheet loss over the last 18 years was 21.9 ± 1 Gt/yr² for Greenland and 14.5 ± 2 Gt/yr² for Antarctica, for a combined total of 36.3 ± 2 Gt/yr². This acceleration is 3 times larger than for mountain glaciers and ice caps (12 ± 6 Gt/yr²). If this trend continues, ice sheets will be the dominant contributor to sea level rise in the 21st century.
   
8. 2012: Pritchard, HDx, et al. “Antarctic ice-sheet loss driven by basal melting of ice shelves.” Nature 484.7395 (2012): 502.  Accurate prediction of global sea-level rise requires that we understand the cause of recent, widespread and intensifying^1,2 glacier acceleration along Antarctic ice-sheet coastal margins³. Atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves, potentially limiting their ability to buttress the flow of grounded tributary glaciers⁴. Indeed, recent ice-shelf collapse led to retreat and acceleration of several glaciers on the Antarctic Peninsula⁵. But the extent and magnitude of ice-shelf thickness change, the underlying causes of such change, and its link to glacier flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted³. Here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum-Antarctic pattern of ice-shelf thinning through increased basal melt. We deduce that this increased melt is the primary control of Antarctic ice-sheet loss, through a reduction in buttressing of the adjacent ice sheet leading to accelerated glacier flow². The highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf. Wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of Antarctic ice shelves, through ocean upwelling in the Amundsen⁶ and Bellingshausen⁷ seas, and atmospheric warming on the Antarctic Peninsula⁸. This implies that climate forcing through changing winds influences Antarctic ice-sheet mass balance, and hence global sea level, on annual to decadal timescales.
9. 2014: Joughin, Ian, Benjamin E. Smith, and Brooke Medley. “Marine ice sheet collapse potentially under way for the Thwaites Glacier Basin, West Antarctica.” Science 344.6185 (2014): 735-738.  Resting atop a deep marine basin, the West Antarctic Ice Sheet has long been considered prone to instability. Using a numerical model, we investigated the sensitivity of Thwaites Glacier to ocean melt and whether its unstable retreat is already under way. Our model reproduces observed losses when forced with ocean melt comparable to estimates. Simulated losses are moderate (<0.25 mm per year at sea level) over the 21st century but generally increase thereafter. Except possibly for the lowest-melt scenario, the simulations indicate that early-stage collapse has begun. Less certain is the time scale, with the onset of rapid (>1 mm per year of sea-level rise) collapse in the different simulations within the range of 200 to 900 years.

 

 

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FIGURE 1: FOSSIL FUEL EMISSIONS AND ATMOSPHERIC COMPOSITION

 

FIGURE 2: EMISSIONS AND CHANGE IN ATMOS-CO2 AT FIVE TIME SCALES

 

FIGURE 3: CORRELATION BETWEEN  ΔCO2 AND EMISSIONS

 

FIGURE 4: SUMMARY OF AIRBORNE FRACTION

 

FIGURE 5: SUMMARY OF CORRELATION ANALYSIS

 

 

 

 

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1. Figure 1 shows that atmospheric CO2 concentration as measured at Mauna Loa has been rising steadily since 1958 while at the same time post industrial humans have been injecting increasing amounts of carbon dioxide from fossil fuels into the atmosphere. It is in this context that the usual assumption is made that observed changes in atmospheric CO2 concentration (ΔCO2) are driven by fossil fuel emissions. This assumed relationship appears to be visually validated in the left panels of the five charts in Figure 3 where changes in atmospheric carbon dioxide (ΔCO2) appear to be strongly correlated with the rate of emissions.
2. The correlation was tested in a related work [LINK] where it was shown with detrended correlation analysis that there is insufficient evidence to claim that atmospheric CO2 concentration is responsive to fossil fuel emissions at an annual time scale and that therefore the attribution of rising atmospheric CO2 to emissions is without empirical support. Detrended correlation analysis extracts the portion of the observed source data correlation that derives from responsiveness at the chosen time scale by removing the portion that derives from shared trends. The motivation for this procedure is described in a related post [LINK] . Briefly, the trend is removed from the data so that only the regression residuals remain and a correlation between these residuals is used to measure the responsiveness of ΔCO2 to emissions.
3. This work is a further investigation into the relationship between changes in atmospheric CO2 concentration and fossil fuel emissions. The failure of the prior study to find a responsiveness of atmospheric CO2 to fossil fuel emissions at an annual time scale leaves open the possibility that a responsiveness may exist at longer time scales. Five time scales from one year to five years in increments of one year are studied. The data for the five time scales are displayed in Figure 2 which contains five charts one for each time scale. Each chart consists of three frames. The left frame shows emissions at the time scale of the chart in gigatons of carbon equivalent (GTC). The middle frame displays the corresponding increase in atmospheric CO2 converted from parts per million in volume (ppmv) to GTC equivalent. The last frame contains the ratio of ΔCO2 to emissions. This ratio, called the “Airborne Fraction (A/F)” is considered to be a constant with a value of approximately 50%. It describes the portion of emissions that end up in the atmosphere. The spread of the Airborne Fraction appears to include the value of A/F = 0.5 and the spread appears to narrow as the time scale is increased. Curiously, a slight downward trend is seen in the A/F at all time scales. The Airborne Fraction concept appears to assume a causal relationship between emissions and change in atmospheric CO2 concentration. The results are summarized in Figure 4. The volatility of the Airborne Fraction decreases sharply from Range=0.8 to Range =0.29 as the time scale is increased from T/S=1 to T/S=5 and at the longer time scales the median A/F converges nicely to the original IPCC figure of A/F=0.5. Later claims to reduced figures of A/F=0.42 seems arbitrary and perhaps a case of circular reasoning as explained in a related post [LINK]
4. The correlation analysis is presented in Figure 3. There are five charts one for each time scale. Each chart consists of two frames, a left frame that displays correlation in the source data and a right frame that shows the correlation between the detrended series. Both of these correlations rise as the time scale is increased from one to five years. At all five time scales we find a significant loss in correlation when the data are detrended. The correlation that survives into the detrended series serves as evidence of responsiveness at each of the five time scales. The survival fraction also rises as the time scale is increased from annual to five years. The results are summarized in Figure 5. Here we see that the source correlation rises from CORR=0.742 to CORR=0.921 as we increase the time scale from T/S=1 to T/S=5. The corresponding detrended correlation also rises from DETCOR=0.145 to DETCOR=0.314 with the corresponding survival fraction rising sharply from 19.5% to 34.1%.
5. The higher and higher detrended correlations and survival fractions at longer time scales raise the intriguing possibility that the failure to find a responsiveness of atmospheric composition to the rate of fossil fuel emissions was an inappropriate choice of an annual time scale. Perhaps a longer time scale will resolve the issue. To test that hypothesis we present one tailed hypothesis tests for each of the five detrended correlations at the five selected time scales. Here the alternate hypothesis is that the detrended correlation is positive or HA: DETCOR>0. The corresponding null hypothesis is that is not positive or H0: DETCOR<=0. The maximum false positive error rate is set to α=0.001, much lower than the usual values of α=0.01 to α=05, in accordance with Revised Standards for Statistical Significance (Johnson, 2013) published by the NAS to address an unacceptable rate of irreproducible results in published research (Siegfried, 2010). Since five comparisons are made for the five different time scales, the probability of finding at least one significant correlation in random data is increased by a factor of five to 0.005 (Holm, 1979). The results of the hypothesis tests are presented in Figure 5. Here EFFN=effective value of the sample size corrected for time scale which decreases from EFFN=60 to EFFN=12 as the time scale is increased from T/S=1 to T/S=5 to account for residual unique information in the time series. The procedure and rationale for this computation are described in a related work [LINK] . Along with the effective sample size, the degrees of freedom also falls since in this case degrees of freedom is computed as DF=EFFN-2. Thus, although the T-statistic rises from TSTAT=1.132 to TSTAT=2.478 as the time scale is increased from T/S=1 to T/S=5, the PVALUE for the hypothesis test does not fall as quickly as one would expect and in fact it actually rises from T/S=4 to T/S=5. More relevant to the research question here, none of the five PVALUEs is even close to the critical value of the PVALUE=0.001. We therefore fail to reject H0: DETCOR<=0  and conclude that the data do not provide evidence that atmospheric CO2 concentration is responsive to fossil fuel emissions at any of the time scales studied. We note also that since the p-value rose from T/S=4 (p-value=0.0135) to T/S=5 (p-value=0.0163), in time scales greater than T/S=4, the effect of longer time scale on degrees of freedom overcomes its effect on detrended correlation at the available time span of the data. Thus even though a stable Airborne Fraction can be computed as A/F=0.5, its interpretation in terms of the contribution of fossil fuel emissions to ΔCO2 requires the use of circular reasoning with an assumed responsiveness that is not found in the data. Related post [LINK] .
6. A rationale for the inability to relate changes in atmospheric CO2 to fossil fuel emissions is described by Geologist James Edward Kamis in terms of natural geological emissions due to plate tectonics [LINK] . The essential argument is that, in the context of significant geological flows of carbon dioxide and other carbon based compounds, it is a form of circular reasoning to describe changes in atmospheric CO2 only in terms of human activity. It is shown in a related post, that in the context of large uncertainties in natural flows, it is not possible to detect the presence of fossil fuel emissions without the help of circular reasoning  [LINK] . 
7. The results of detrended correlation analysis at five time scales shows that the failure to find a responsiveness of atmospheric composition to fossil fuel emissions in a related work  [LINK] cannot be ascribed to the annual time scale used in the study as the result is validated at longer time scales to the point of diminishing returns. We conclude that atmospheric composition specifically in relation to the CO2 concentration is not responsive to the rate of fossil fuel emissions. This finding is a serious weakness in the theory of anthropogenic global warming by way of rising atmospheric CO2 attributed to the use of fossil fuels in the industrial economy; and of the “Climate Action proposition of the UN that reducing fossil fuel emissions will moderate the rate of warming by slowing the rise of atmospheric CO2. 

 

 

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GEOLOGICAL CARBON BIBLIOGRAPHY

1. 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
2. 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.
3. 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.
4. 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.
5. 1983: Garrels, ROBERT M. “The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years.” Am J Sci 283 (1983): 641-683. [FULL TEXT PDF DOWNLOAD]
6. 1992: Raymo, Maureen E., and William F. Ruddiman. “Tectonic forcing of late Cenozoic climate.” nature 359.6391 (1992): 117. Global cooling in the Cenozoic, which led to the growth of large continental ice sheets in both hemispheres, may have been caused by the uplift of the Tibetan plateau and the positive feedbacks initiated by this event. In particular, tectonically driven increases in chemical weathering may have resulted in a decrease of atmospheric C0₂concentration over the past 40 Myr.
7. 1995: Keeling, Charles D., et al. “Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980.” Nature375.6533 (1995): 666. OBSERVATIONS of atmospheric CO₂ concentrations at Mauna Loa, Hawaii, and at the South Pole over the past four decades show an approximate proportionality between the rising atmospheric concentrations and industrial CO₂ emissions¹. This proportionality, which is most apparent during the first 20 years of the records, was disturbed in the 1980s by a disproportionately high rate of rise of atmospheric CO₂, followed after 1988 by a pronounced slowing down of the growth rate. To probe the causes of these changes, we examine here the changes expected from the variations in the rates of industrial CO₂emissions over this time², and also from influences of climate such as El Niño events. We use the¹³C/¹²C ratio of atmospheric CO₂ to distinguish the effects of interannual variations in biospheric and oceanic sources and sinks of carbon. We propose that the recent disproportionate rise and fall in CO₂ growth rate were caused mainly by interannual variations in global air temperature (which altered both the terrestrial biospheric and the oceanic carbon sinks), and possibly also by precipitation. We suggest that the anomalous climate-induced rise in CO₂ was partially masked by a slowing down in the growth rate of fossil-fuel combustion, and that the latter then exaggerated the subsequent climate-induced fall.
8. 1995: Kerrick, Derrill M., et al. “Convective hydrothermal C02 emission from high heat flow regions.” Chemical Geology121.1-4 (1995): 285-293.In addition to volatiles released from volcanoes, the flux of CO2 to the atmosphere from other sources (e.g., metamorphism and subsurface magmatism) represents an important aspect of the global carbon cycle. We have obtained a direct estimate of the present-day atmospheric CO2 flux from convective hydrothermal systems within subaerial, seismically-active, high heat flow regions. Geothermal systems of the Salton Trough (California, U.S.A.) and the Taupo Volcanic Zone (New Zealand) provide benchmarks for quantifying convective hydrothermal CO2 fluxes from such regions. CO2 fluxes from the Salton Trough ( ∼ 109 mol yr−1) and the Taupo Volcanic Zone (∼ 8·109 mol yr−1) were computed using data on convective heat flow and the temperatures and CO2 concentrations of reservoir fluids. The similarity in specific CO2 flux ( ∼ 106 mol km−2 yr−1) from these two disparate geologic/tectonic settings implies that this flux may be used as a baseline to compute convective hydrothermal CO2 emission from other areas of high heat flow. If this specific flux is integrated over high heat flow areas of the circum-Pacific and Tethyan belts, the total global CO2 flux could equal or exceed 1012 mol yr−1 Adding this flux to a present-day volcanic CO2 flux of ∼ 4·1012 mol yr−1 the total present-day Earth degassing flux could balance the amount of CO2 consumed by chemical weathering ( ∼ 7·1012 mol yr−1).
9. 1996: Sano, Yuji, and Stanley N. Williams. “Fluxes of mantle and subducted carbon along convergent plate boundaries.” Geophysical Research Letters 23.20 (1996): 2749-2752. The potential impact of increases in atmospheric CO₂ is a topic of considerable controversy. Even though volcanic emission of CO₂ may be very small as compared to anthropogenic emissions, evaluation of natural degassing of CO₂ is important for any model of the geochemical C cycle and evolution of the Earth’s atmosphere. We report here the mantle C flux in subduction zones based on He and C isotopes and CO₂/³ He ratios of high‐temperature volcanic gases and medium‐ and low‐temperature fumaroles in circum‐Pacific volcanic regions. The calculated volcanic C flux of 3.1 × 10¹² mol/a from subduction zones is larger than the flux of 1.5 × 10¹² mol/a from mid‐ocean ridges, while contributions from the mantle in subduction zone is only 0.30 × 10¹² mol/a, equivalent to about 20% of the C flux in mid‐ocean ridges. Since the estimated mantle C flux in hot spot regions is insignificant, 0.029 × 10¹² mol/a, we propose that the global mantle C flux is 1.8 × 10¹² mol/a in total. The flux, if accumulated over 4.5 billion year of geological time, amounts to 8.3 × 10²¹ mol which agrees well with 9 × 10²¹ mol of the present inventory of C at the Earth’s surface. This may support a continuous degassing model of C or the idea that subducted C is recycled into the lower mantle.
10. 1998: Marty, Bernard, and Igor N. Tolstikhin. “CO 2 fluxes from mid-ocean ridges, arcs and plumes.” Chemical Geology 145.3 (1998): 233-248. Estimates of CO₂ emissions at spreading centres, convergent margins, and plumes have been reviewed and upgraded using observed CO₂/³He ratios in magmatic volatiles, ³He content estimates in the magmatic sources, and magma emplacement rates in the different tectonic settings. The effect of volatile fractionation during magma degassing, investigated using new rare gas and CO₂ abundances determined simultaneously for a suite of Mid-Ocean Ridge (MOR) basalt glasses, is not the major factor controlling the spread of data, which mainly result from volatile heterogeneity in the mantle source. The computed C flux at ridges (2.2±0.9)×10¹² mol/a, is essentially similar to previous estimates based on a more restricted data base. Variation of the C flux in the past can be simply scaled to that of spreading rate since the computed C depends mainly on the volatile content of the mantle source, which can be considered constant during the last 10⁸ a. The flux of CO₂ from arcs may be approximated using the CO₂/³He ratios of volcanic gases at arcs and the magma emplacement rate, assuming that the ³He content of the mantle end-member is that of the MORB source. The resulting flux is ∼2.5×10¹² mol/a, with approx. 80% of carbon being derived from the subducting plate. The flux of CO₂from plumes, based on time-averaged magma production rates and on estimated contributions of geochemical sources to plume magmatism, is ≤3×10¹² mol/a. Significant enhancements of the CO₂ flux from plumes might have occurred in the past during giant magma emplacements, depending on the duration of these events, although the time-integrated effect does not appear important. The global magmatic flux of CO₂ into the atmosphere and the hydrosphere is found to be 6×10¹² mol/a, with a range of (4–10)×10¹² mol/a. Improvement on the precision of this estimate is linked to a better understanding of the volatile inventory at arcs on one hand, and on the dynamics of plumes and their mantle source contribution on the other hand.
11. 2001: Kerrick, Derrill M. “Present and past nonanthropogenic CO2 degassing from the solid Earth.” Reviews of Geophysics 39.4 (2001): 565-585. Global carbon cycle models suggest that CO₂ degassing from the solid Earth has been a primary control of paleoatmospheric CO₂ contents and through the greenhouse effect, of global paleotemperatures. Because such models utilize simplified and indirect assumptions about CO₂ degassing, improved quantification is warranted. Present‐day CO₂ degassing provides a baseline for modeling the global carbon cycle and provides insight into the geologic regimes of paleodegassing. Mid‐ocean ridges (MORs) discharge 1–3 × 10¹² mol/yr of CO₂ and consume ∼3.5 × 10¹² mol/yr of CO₂ by carbonate formation in MOR hydrothermal systems. Excluding MORs as a net source of CO₂ to the atmosphere, the total CO₂ discharge from subaerial volcanism is estimated at ∼2.0–2.5 × 10¹² mol/yr. Because this flux is lower than estimates of the global consumption of atmospheric CO₂ by subaerial silicate weathering, other CO₂ sources are required to balance the global carbon cycle. Nonvolcanic CO₂ degassing (i.e., emission not from the craters or flanks of volcanos), which is prevalent in high heat flow regimes that are primarily located at plate boundaries, could contribute the additional CO₂ that is apparently necessary to balance the global carbon cycle. Oxidation of methane emitted from serpentinization of ultramafics and from thermocatalysis of organic matter provides an additional, albeit unquantified, source of CO₂ to the atmosphere. Magmatic CO₂degassing was probably a major contributor to global warming during the Cretaceous. Metamorphic CO₂ degassing from regimes of shallow, pluton‐related low‐pressure regional metamorphism may have significantly contributed to global warming during the Cretaceous and Paleocene/Eocene. CO₂ degassing associated with continental rifting of Pangaea may have contributed to the global warming that was initiated in the Jurassic. During the Cretaceous, global warming initiated by CO₂ degassing of flood basalts, and consequent rapid release of large quantities of CH₄ by decomposition of gas hydrates (clathrates), could have caused widespread extinctions of organisms.
12. 2008: Zachos, James C., Gerald R. Dickens, and Richard E. Zeebe. “An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics.” Nature 451.7176 (2008): 279. By the year 2400, it is predicted that humans will have released about 5,000 gigatonnes of carbon (Gt C) to the atmosphere since the start of the industrial revolution if fossil-fuel emissions continue unabated and carbon-sequestration efforts remain at current levels¹. This anthropogenic carbon input, predominantly carbon dioxide (CO₂), would eventually return to the geosphere through the deposition of calcium carbonate and organic matter². Over the coming millennium, however, most would accumulate in the atmosphere and ocean. Even if only 60% accumulated in the atmosphere, the partial pressure of CO₂ (pCO2pCO2) would rise to 1,800 parts per million by volume (p.p.m.v.) (Fig. 1). A greater portion entering the ocean would decrease the atmospheric burden but with a consequence: significantly lower pH and carbonate ion concentrations of ocean surface layers¹
13. 2010: Dasgupta, Rajdeep, and Marc M. Hirschmann. “The deep carbon cycle and melting in Earth’s interior.” Earth and Planetary Science Letters 298.1-2 (2010): 1-13. Carbon geochemistry of mantle-derived samples suggests that the fluxes and reservoir sizes associated with deep cycle are in the order of 10^12–13 g C/yr and 10^22–23 g C, respectively. This deep cycle is responsible for the billion year-scale evolution of the terrestrial carbon reservoirs. The petrology of deep storage modulates the long-term evolution and distribution of terrestrial carbon. Unlike water, which in most of the Earth’s mantle is held in nominally anhydrous silicates, carbon is stored in accessory phases. The accessory phase of interest, with increasing depth, typically changes from fluids/melts → calcite/dolomite → magnesite → diamond/Fe-rich alloy/Fe-metal carbide, assuming that the mass balance and oxidation state are buffered solely by silicates. If, however, carbon is sufficiently abundant, it may reside as carbonate even in the deep mantle. If Earth’s deep mantle is Fe-metal saturated, carbon storage in metal alloy and as metal carbide cannot be avoided for depleted and enriched domains, respectively. Carbon ingassing to the interior is aided by modern subduction of the carbonated oceanic lithosphere, whereas outgassing from the mantle is controlled by decompression melting of carbonated mantle. Carbonated melting at > 300 km depth or redox melting of diamond-bearing or metal-bearing mantle at somewhat shallower depth generates carbonatitic and carbonated silicate melts and are the chief agents for liberating carbon from the solid Earth to the exosphere. Petrology allows net ingassing of carbon into the mantle in the modern Earth, but in the hotter subduction zones that prevailed during the Hadean, Archean, and Paleoproterozoic, carbonate likely was released at shallow depths and may have returned to the exosphere. Inefficient ingassing, along with efficient outgassing, may have kept the ancient mantle carbon-poor. The influence of carbon on deep Earth dynamics is through inducing melting and mobilization of structurally bound mineral water. Extraction of carbonated melt on one hand can dehydrate the mantle and enhance viscosity; the presence of trace carbonated melt on other may generate seismic low-velocity zones and amplify attenuation.