Corrected some typos 4:15pm, 3/25/2020 Thai time. 

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THIS POST IS A CRITICAL REVIEW OF AN ARTICLE IN “STATE OF THE PLANET” PUBLISHED BY THE EARTH INSTITUTE AT COLUMBIA UNIVERSITY. THE AUTHOR OF THE ARTICLE IS KEVIN KRAJICK, A WELL KNOWN JOURNALIST AND WRITER WHO SERVES AS THE SENIOR EDITOR AT THE EARTH INSTITUTE.

THE TITLE OF THE ARTICLE IS “THE CLIMATE EPOCHS THAT WEREN’T” [LINK] . THE ARTICLE USES A NOVEL APPROACH TO REVIVE THE MANN-BALL DEBATE ABOUT WHETHER THE MEDIEVAL WARM PERIOD (MWP) WAS WARMER THAN THE CURRENT POST LIA WARM PERIOD WHERE THE WARMING IS ATTRIBUTED TO A HUMAN CAUSE IN THE FORM OF THE FOSSIL FUEL EMISSIONS OF THE INDUSTRIAL ECONOMY (AGW). 

THE POST IS PRESENTED IN THREE PARTS. PART-1 IS A SUMMARY OF THE CASE PRESENTED BY KEVIN KRAJICK IN SUPPORT OF THE MANN HYPOTHESIS THAT THE THE MWP WAS NOT WARMER THAN AGW. PART-2 IS A CRITICAL ANALYSIS OF THE ARGUMENTS PRESENTED BY KEVIN. PART-3 IS A RELEVANT BIBLIOGRAPHY. 

PART-1: THE CASE AGAINST PAST TEMPERATURE SWINGS AS GLOBAL

During the MWP warm period, roughly 800 to 1200 AD, temperatures rose a few degrees above average and is thought to have improved crop yields in parts of Europe, and facilitated the Viking occupation of Greenland. The LIA cold period followed from 1300 to 1850 AD when the Vikings disappeared from Greenland, glaciers from California to the European Alps advanced, and New York harbor froze, enabling people to walk from Manhattan to New Jersey.

Critics of AGW use these temperature swings of the past to argue against human cause of the post LIA warming in the current AGW era. This argument is based on the assumption that the MWP and the LIA were global events. However, paleo climate studies in the past decade covering wide geographical regions of the globe provide convincing evidence that neither the MWP nor the LIA were global and that therefore the comparison of the global AGW climate change event of the current warm period with the MWP and the LIA is meaningless and therefore it can yield no useful information. Some regions appear to have been warming when they were supposed to be cooling, and cooling when they were supposed to be warming. A similar argument against human cause in the AGW climate change of the current warm period put forward by critics cites the Roman Warm Period (100-300 AD) and the Dark Ages Cold Period (400-800 AD). This argument suffers from the same flaw in that there is no evidence that these temperature swings were global.

The assumed global nature of these prior warm and cold periods of the Holocene is challenged in a 2019 paper by lead author Raphael Neukom {Neukom, Raphael, et al. “No evidence for globally coherent warm and cold periods over the preindustrial Common Era.” Nature 571.7766 (2019): 550-554},  ABSTRACT: Earth’s climate history is often understood by breaking it down into constituent climatic epochs. Over the Common Era (the past 2,000 years) these epochs, such as the Little Ice Age have been characterized as having occurred at the same time across extensive spatial scales. Although the rapid global warming seen in observations over the past 150 years does show nearly global coherence, the spatio-temporal coherence of climate epochs earlier in the Common Era has yet to be robustly tested. Here we use global palaeoclimate reconstructions for the past 2,000 years, and find no evidence for preindustrial globally coherent cold and warm epochs. In particular, we find that the coldest epoch of the last millennium, the putative Little Ice Age, is most likely to have experienced the coldest temperatures during the fifteenth century in the central and eastern Pacific Ocean, during the seventeenth century in northwestern Europe and southeastern North America, and during the mid-nineteenth century over most of the remaining regions. Furthermore, the spatial coherence that does exist over the pre-industrial Common Era is consistent with the spatial coherence of stochastic climatic variability. This lack of spatiotemporal coherence indicates that preindustrial forcing was not sufficient to produce globally synchronous extreme temperatures at multidecadal and centennial timescales. By contrast, we find that the warmest period of the past two millennia occurred during the twentieth century for more than 98 per cent of the globe. This provides strong evidence that anthropogenic global warming is not only unparalleled in terms of absolute temperatures, but also unprecedented in spatial consistency within the context of the past 2,000 years.

The (Neukom 2019) study of climate swings during the past 2,000 years uses data from many different sources across the globe, including tree rings, glacier ice, lake sediments and corals. Based on this, the authors say that the supposed warm and cold epochs may represent, more than anything, regional variations that can be explained by random variability. The study analyzes paleoclimate data from across the world, using multiple statistical methods and many sources: tree rings, glacial ice cores, corals, lake sediments. It does not suggest that the periods of high or low temperatures observed during the named epochs did not exist but rather that they did exist but they were not global and that therefore they were probably not caused by some kind of planetary driver as the fossil fuel emissions of the industrial economy. In contrast, the study finds one very coherent period of global warming, an unprecedented warming extending over 98 percent of the globe, starting in the 20th century. This is almost certainly caused by us.

Co-author Nathan Steiger of Columbia University’s Lamont-Doherty Earth Observatory says about the paper that it shows that previously named climate epochs of the Common Era were not coherent phenomena across the globe. This goes against the widespread notion that periods like the Little Ice Age or Medieval Warm Period were global periods of cold or warmth. We’re not the first to point out that there are problems with this idea, but our study is the first to rigorously test the hypothesis on a global scale. In contrast to this, we see that current global warming is remarkably coherent. To tell what temperatures were doing in various parts of the world during these past times we rely on proxies. Trees, for example, can be very sensitive to annual changes in temperature and moisture, and the width and density of their annual rings reflect those year-to-year changes. We can then sample hundreds of trees all over the world along with other natural archives to infer what climate was like in the past. We used several different statistical methods that combine all of these proxies to produce global maps of temperature change going back 2,000 years. During the so-called Little Ice Age, European glaciers advanced. Have scientists been too narrow-minded in their geographical focus? The word “Medieval” calls up part of European history–a period that didn’t exist in Asia, the Americas or Africa. (therefore it is not global).

Paleoclimate is like many fields of study. There are historical biases in where data is collected, and how the stories about the data are developed. The first paleoclimate data were largely collected from Europe by Europeans, and so it’s not terribly surprising that the stories that try to make sense of such data are Euro-focused. Another problem is that until recently, people have been reluctant to share data and to create narratives that include more than a single, or perhaps a few, time series. If you’re a scientist who has spent a lot of time and money in producing a particular proxy time series, then there’s a tendency to emphasize the importance of that particular time series and to develop a story explaining it. The simplest story to develop is one that corresponds to a traditional understanding of what the climate “should” be doing going back in time. It’s only been in the past few years that scientists from across the paleoclimate community have begun to publicly collate a wide range of data types from all over the globe. For example, when one labels any Common Era proxy time series with terms like the “Medieval Climate Anomaly,” they are usually implicitly assuming that such epochs were global, and over well-defined time intervals. Our results show that both of these assumptions are incorrect.

Not that there isn’t already plenty of evidence, but does this study add to the argument that humans are causing global warming? Yes. Conditions during medieval times or during the Little Ice Age are expected to occur naturally. But the large spatial consistency of the present warm phase cannot be explained by natural variability. This result corroborates existing studies that have shown that humans are causing global temperatures to rise since the beginning of the industrial period.

Paleoclimate proxies can be used to infer past temperatures, but they are not thermometers and so they include non-temperature “noise.” We have therefore tried to use as many proxies as feasible for our study, but we are limited by where the data exists and the quality of the data. Uncertainties are usually largest in places without good quality proxy data. But for the particular hypothesis we’re testing, we don’t think these uncertainties significantly impact the results. We find the same results regardless of which proxy networks or which statistical methodologies we use.

PART-2: CRITICAL COMMENTARY

COMMENT#1: THE MWP ISSUE:  This issue goes back to the so called “hockey stick” controversy [LINK] when eminent climate scientist and paleo-climatologist Professor Michael Mann had presented a paleo climate history of the last millennium to argue that the current post LIA warming was unprecedented as proof of its human cause by way of the industrial economy. Mann’s methodology was bitterly contested by Phil Jones, Keith Briffa, and Tim Ball such that Ray Bradley, Mann’s co-author, withdrew his support for the findings of the paper. This controversy has raged since then and has even been taken to court but the issue remains unresolved and the MWP controversy appears to be a permanent feature of the human cause debate for the post LIA warming.

COMMENT#2: PALEO DATA UNCERTAINTY: In a related post [LINK] , we show that the real issue in this debate may be the high level of uncertainty that is characteristic of paleo climate data such that the interpretation of paleo data information is limited by paleo data noise and that therefore “the selection of the type of proxy data (tree ring, sediment, borehole, or climate model) and the geographical location where data were gathered strongly influence findings. It is uncertain whether the MWP was global or localized in Europe and if so whether it was all of Europe or just Northern Europe. It is also uncertain as to exactly when the MWP occurred and for how long it lasted. Most of all it is uncertain as to exactly how warm it got specifically with respect to the current 20th century warming of “the industrial economy since pre-industrial times”.

COMMENT#3: THE INFORMATION CONTENT OF UNCERTAIN DATA:  It is further argued in the related post [LINK] that uncertainty in the data creates a role for the bias of the researcher in the findings. In the related post we write: “Uncertainty creates controversy and given the large uncertainties involved in paleo data and the large stake for the climate science argument for human cause that the current warming is “unprecedented in the last two millennia”, the MWP issue has generated a great deal of acrimonious debate. Such debates are always partisan and they are sustained by the “Texas Sharpshooter” fallacy because uncertainty allows different researchers to pay more attention to the portion of the uncertainty band that supports their hypothesis.

COMMENT#4: THE THE CARL WUNSCH ASSESSMENT OF PALEO DATA:  “From one point of view, scientific communities without adequate data have a distinct advantage because they can construct interesting and exciting stories and rationalizations with little or no risk of observational refutation. Colorful, sometimes charismatic, characters come to dominate the field, constructing their interpretations of a few intriguing, but indefinite observations that appeal to their followers, and which eventually emerge as “textbook truths.” [LINK] .

COMMENT#5: HOLOCENE HISTORY IS LONGER THAN 2000 YEARS:  The climate science argument that the current warming is unprecedented and therefore human caused is supported with comparisons against prior warming periods of the Holocene in the past. However, the definition of “the past” is arbitrary and left to the researcher to decide and the usual definition is either the previous 1,000 years or the previous 2,000 years. In the Neukom 2019 paper both of these time spans are used for different purposes. In this context it is noted that the Holocene Interglacial is about 12,000 years old and the Eemian Interglacial that came prior to the Holocene is more than 120,000 years old. Therefore, research findings with arbitrary definitions of the past to prove that the current warming is unprecedented are not credible because of its inherent circular reasoning feature. Specifically, the data used to construct the “unprecedented” hypothesis may not be used to test the unprecedented hypothesis because such hypothesis tests suffer from circular reasoning, often described as the “Texas Sharpshooter Fallacy” [LINK] . 

COMMENT#6: CHAOTIC WARMING AND COOLING CYCLES OF THE HOLOCENE :  In a related post [LINK] it is shown with a comprehensive bibliography that the Holocene interglacial has not been a period of stable climate interrupted by an anomalous century of human caused warming by the industrial economy. Instead, what it shows is that “Climate appears to exhibit properties of non-linear dynamics and deterministic chaos over a large range of time scales. Glaciation is not a linear and well behaved period of cooling and ice accumulation and deglaciation is not a linear and well behaved period of warming and ice dissipation. Rather, both glaciation and deglaciation are chaotic events consisting of both processes differentiated only by a slight advantage to ice accumulation in glaciation and a slight advantage to ice dissipation in deglaciation and interglacials. The Holocene must be studied and understood as a chaotic system with multiple episodes of warming and ice dissipation and multiple episodes of cooling and ice accumulation. Viewed in this way, the current warming trend can be understood as a continuation this climate pattern of the Holocene. The Industrial Revolution is thought to precede the warming in a way that implies causation. However, it is just as credible if not more so to describe it as coincidental rather than causal when seen in the context of the warming and cooling dynamics of the Holocene and the many vexing issues in AGW  [LINK] , [LINK] , [LINK] , [LINK] , [LINK]    that have not been resolved and that may never be resolved.

COMMENT#7: THE EEMIAN INTERGLACIAL : The interglacial prior to the Holocene was the Eemian. On a millennial time scale, although it had cooled in the later millennials, the first millennium of the Eemian is known for its strong warming event with temperatures 5C warmer than the present. This period is also known for its violent sea level rise mayhem thought to have been caused by a complete disintegration of the West Antarctic Ice Sheet (WAIS). It may be argued that these events more than 120,000 years ago are irrelevant in the AGW context but it should be noted that climate science cites the Eemian as an example of the kind of ice sheet collapse and sea level rise that AGW climate change may cause. It is therefore proposed that the “unprecedented” hypothesis used to prove human cause of the current warming should not be arbitrarily limited to “The Common Era” or to any other time spans of convenience but should be evaluated on the same basis as the time span used for the assessment of other AGW events such as ice sheet melt and sea level rise. 

COMMENT#8: UNPRECEDENTED DOES NOT PROVE HUMAN CAUSE :  The climate science position that “unprecedented” proves human cause has no basis. That a warming event is unprecedented proves only that it is unprecedented and not that therefore it must have a human cause. For example, the PETM (Paleocene Eocene Thermal Maximum) ocean acidification event 55 million years ago is unprecedented in the paleo record but it was not human caused although it serves as the model for the ocean acidification fears in the current warming. The ETE (End Triassic Extinction) is unprecedented in the paleo record but it was not human caused although it serves as a model for a human caused mass extinction of the current warm period. As for deglaciation transitions to interglacials, the extreme climate change events of the Eemian is unprecedented in the paleo record but it was not human caused although it serves as a model for a predicted catastrophic sea level rise event in the current warming period. Briefly, the lengths to which climate science has gone to prove human cause by arguing the case that the current warming is unprecedented is an oddity. That a climate event that is unprecedented is therefore human caused is not credible because it is illogical, unscientific, and without a rational basis. The credibility of this argument is further weakened by the selection of arbitrary  reference time periods such as 1,000 years or 2,000 years for various claims to prove that the current warming is unprecedented.

CONCLUSION: Human cause must be proven in terms of the case against humans made in climate science and not in terms of whether the current warming is unprecedented unless it can be shown that being unprecedented requires a human cause. The case against humans in climate science is that since the Industrial Revolution, humans have been releasing carbon dioxide into the atmosphere by burning fossil fuels and that this carbon dioxide is not in the current account of the carbon cycle but from carbon cycles millions of years ago.  It is claimed therefore, that the carbon in fossil fuels is not part of the current account of the carbon cycle but external carbon. It is thus argued that fossil fuel emissions of the industrial economy have caused atmospheric CO2 concentration to steadily increase and that steady increase has caused warming by way of the climate sensitivity of surface temperature to atmospheric CO2 concentration. An uncertainty issue in climate sensitivity has driven climate science to an alternate measure of the relationship between emissions and warming in terms of the TCRE. That climate science has now resorted to proving human cause by way of whether the current warming is unprecedented may imply a weakness in the science described above. Some sources of this weakness are explored in the related posts linked below. 

[LINK] [LINK] [LINK] [LINK] [LINK] [LINK] [LINK] [LINK] [LINK]

HOLOCENE BIBLIOGRAPHY

1. Denton, George H., and Wibjörn Karlén. “Holocene climatic variations—their pattern and possible cause.” Quaternary Research 3.2 (1973): 155-205. In the northeastern St. Elias Mountains in southern Yukon Territory and Alaska, C14-dated fluctuations of 14 glacier termini show two major intervals of Holocene glacier expansion, the older dating from 3300-2400 calendar yr BP and the younger corresponding to the Little Ice Age of the last several centuries. Both were about equivalent in magnitude. In addition, a less-extensive and short-lived advance occurred about 1250-1050 calendar yr BP (A.D. 700–900). Conversely, glacier recession, commonly accompanied by rise in altitude of spruce tree line, occurred 5975–6175, 4030-3300, 2400-1250, and 1050-460 calendar yr BP, and from A.D. 1920 to the present. Examination of worldwide Holocene glacier fluctuations reinforces this scheme and points to a third major interval of glacier advances about 5800-4900 calendar yrs BP; this interval generally was less intense than the two younger major intervals. Finally, detailed mapping and dating of Holocene moraines fronting 40 glaciers in the Kebnekaise and Sarek Mountains in Swedish Lapland reveals again that the Holocene was punctuated by repeated intervals of glacier expansion that correspond to those found in the St. Elias Mountains and elsewhere. The two youngest intervals, which occurred during the Little Ice Age and again about 2300–3000 calendar yrs BP, were approximately equal in intensity. Advances of the two older intervals, which occurred approximately 5000 and 8000 calendar yr BP, were generally less extensive. Minor glacier fluctuations were superimposed on all four broad expansion intervals; glacial expansions of the Little Ice Age culminated about A.D. 1500–1640, 1710, 1780, 1850, 1890, and 1916. In the mountains of Swedish Lapland, Holocene mean summer temperature rarely, if ever, was lower than 1°C below the 1931–1960 summer mean. Summer temperatures varied by less than 3.5°C over the last two broad intervals of Holocene glacial expansion and contraction. Viewed as a whole, therefore, the Holocene experienced alternating intervals of glacier expansion and contraction that probably were superimposed on the broad climatic trends recognized in pollen profiles and deep-sea cores. Expansion intervals lasted up to 900 yr and contraction intervals up to 1750 yr. Dates of glacial maxima indicate that the major Holocene intervals of expansion peaked at about 200–330, 2800, and 5300 calendar yr BP, suggesting a recurrence of major glacier activity about each 2500 yr. If projected further into the past, this Holocene pattern predicts that alternating glacier expansion-contraction intervals should have been superimposed on the Late-Wisconsin glaciation, with glacier readvances peaking about 7800, 10,300, 12,800, and 15,300 calendar yr BP. These major readvances should have been separated by intervals of general recession, some of which might have been punctuated by short-lived advances. Furthermore, the time scales of Holocene events and their Late-Wisconsin analogues should be comparable. Considering possible errors in C14 dating, this extended Holocene scheme agrees reasonably well with the chronology and magnitude of such Late-Wisconsin events as the Cochrane-Cockburn readvance (8000–8200 C14 yr BP), the Pre-Boreal interstadial, the Fennoscandian readvances during the Younger Dryas stadial (10,850-10,050 varve yr BP), the Alleröd interstadial (11,800-10,900 C14 yr BP), the Port Huron readvance (12,700–13,000 C14 yr BP), the Cary/Port Huron interstadial (centered about 13,300 C14 yr BP), and the Cary stadial (14,000–15,000 C14 yr BP). Moreover, comparison of presumed analogues such as the Little Ice Age and the Younger Dryas, or the Alleröd and the Roman Empire-Middle Ages warm interval, show marked similarities. These results suggest that a recurring pattern of minor climatic variations, with a dominant overprint of cold intervals peaking about each 2500 yr, was superimposed on long-term Holocene and Late-Wisconsin climatic trends. Should this pattern continue to repeat itself, the Little Ice Age will be succeeded within the next few centuries by a long interval of milder climates similar to those of the Roman Empire and Middle Ages. Short-term atmospheric C14 variations measured from tree rings correlate closely with Holocene glacier and tree-line fluctuations during the last 7000 yr. Such a correspondence, firstly, suggests that the record of short-term C14 variations may be an empirical indicator of paleoclimates and, secondly, points to a possible cause of Holocene climatic variations. The most prominent explanation of short-term C14 variations involves modulation of the galactic cosmic-ray flux by varying solar corpuscular activity. If this explanation proves valid and if the solar constant can be shown to vary with corpuscular output, it would suggest that Holocene glacier and climatic fluctuations, because of their close correlation with short-term C14 variations, were caused by varying solar activity. By extension, this would imply a similar cause for Late-Wisconsin climatic fluctuations such as the Alleröd and Younger Dryas.
2. Hammer, Claus U., Henrik B. Clausen, and Willi Dansgaard. “Greenland ice sheet evidence of post-glacial volcanism and its climatic impact.” Nature 288.5788 (1980): 230. Acidity profiles along well dated Greenland ice cores reveal large volcanic eruptions in the Northern Hemisphere during the past 10,000 yr. Comparison with a temperature index shows that clustered eruptions have a considerable cooling effect on climate, which further complicates climatic predictions.
3. O’Brien, S. R., (Mayewski). “Complexity of Holocene climate as reconstructed from a Greenland ice core.” Science 270.5244 (1995): 1962-1964.  Glaciochemical time series developed from Summit, Greenland, indicate that the chemical composition of the atmosphere was dynamic during the Holocene epoch. Concentrations of sea salt and terrestrial dusts increased in Summit snow during the periods 0 to 600, 2400 to 3100, 5000 to 6100, 7800 to 8800, and more than 11,300 years ago. The most recent increase, and also the most abrupt, coincides with the Little Ice Age. These changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods, and that temperatures in the mid to high northern latitudes were potentially the coldest since the Younger Dryas event.
4. Angelakis, Andreas N., and Stylianos V. Spyridakis. “The status of water resources in Minoan times: A preliminary study.” Diachronic Climatic Impacts on Water Resources. Springer, Berlin, Heidelberg, 1996. 161-191.A well-known passage in Homer’s Odyssey, probably based on an ancient ritual myth, tells the story of Demeter, the Greek corn-goddess and Iasion, the son of Zeus by Electra, daughter of Atlas. The latter was the guardian of the pillars of heaven (Odyssey, 1.53), the Titan who holds the sky up (Hesiod, Theogony, 517) and is, thereby, identified with water and rainfall. [FULL TEXT DOWNLOAD .
5. Alley, Richard B., (Mayewski)  “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.
6. 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.
7. Roberts, Neil, et al. “The age and causes of Mid-Late Holocene environmental change in southwest Turkey.” Third Millennium BC climate change and old world collapse. Springer, Berlin, Heidelberg, 1997. 409-429.  Proxy records such as lake sediment sequences provide important data on abrupt environmental changes in the past, but establishing their specific causes from the palaeoenvironmental record can be problematic. Pollen diagrams from southwest Turkey show a mid-late Holocene pollen assemblage zone, designated as the Beyşehir Occupation phase, the onset of which has been 14C dated to ca. 3000 BP (ca. 1250 BC). A second millennium BC date for the start of the Beyşehir Occupation phase can now be confirmed as a result of the discovery of volcanic tephra from the Minoan eruption of Santorini (Thera) in lake sediment cores from the region. Palaeoecological analyses on sediment cores from Gölhisar gölü, a shallow montane lake, indicate that tephra deposition was followed by a sustained response in the aquatic ecosystem, in the form of increased algal productivity. The onset of pollen changes marking the beginning of the Beyşehir Occupation phase was not, on the other hand, precisely coincident with the tephra layer, but rather occurred at least a century later at this site. Despite the paucity of archaeological evidence for Late Bronze Age settlement in the Oro-Mediterranean region of southwest Turkey, it would appear that the second millennium BC saw the start of a period of major human impact on the landscape which continued until the late first millennium AD. The Santorini ash represents an important time-synchronous, stratigraphic marker horizon, but does not appear to have been the immediate cause of the onset of the Beyş ehir Occupation phase.
8. Bond, Gerard, et al. “Persistent solar influence on North Atlantic climate during the Holocene.” science 294.5549 (2001): 2130-2136.  Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic’s “1500-year” cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.
9. Stenni, Barbara, et al. “Eight centuries of volcanic signal and climate change at Talos Dome (East Antarctica).” Journal of Geophysical Research: Atmospheres 107.D9 (2002): ACL-3.  During the 1996 Programma Nazionale di Ricerche in Antartide‐International Trans‐Antarctic Scientific Expedition traverse, two firn cores were retrieved from the Talos Dome area (East Antarctica) at elevations of 2316 m (TD, 89 m long) and 2246 m (ST556, 19 m long). Cores were dated by using seasonal variations in non‐sea‐salt (nss) SO42− concentrations coupled with the recognition of tritium marker level (1965–1966) and nss SO42− spikes due to the most important volcanic events in the past (Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Kuwae 1452, Unknown 1259). The number of annual layers recognized in the TD and ST556 cores was 779 and 97, respectively. The δD record obtained from the TD core has been compared with other East Antarctic isotope ice core records (Dome C EPICA, South Pole, Taylor Dome). These records suggest cooler climate conditions between the middle of 16th and the beginning of 19th centuries, which might be related to the Little Ice Age (LIA) cold period. Because of the high degree of geographical variability, the strongest LIA cooling was not temporally synchronous over East Antarctica, and the analyzed records do not provide a coherent picture for East Antarctica. The accumulation rate record presented for the TD core shows a decrease during part of the LIA followed by an increment of about 11% in accumulation during the 20th century. At the ST556 site, the accumulation rate observed during the 20th century was quite stable.
10. Mayewski, Paul A. (aka Ice Man). “Holocene climate variability.” Quaternary research 62.3 (2004): 243-255. Although the dramatic climate disruptions of the last glacial period have received considerable attention, relatively little has been directed toward climate variability in the Holocene (11,500 cal yr B.P. to the present). Examination of 50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000″8000, 6000″5000, 4200″3800, 3500″2500, 1200″1000, and 600″150 cal yr B.P. Most of the climate change events in these globally distributed records are characterized by polar cooling, tropical aridity, and major atmospheric circulation changes, although in the most recent interval (600″150 cal yr B.P.), polar cooling was accompanied by increased moisture in some parts of the tropics. Several intervals coincide with major disruptions of civilization, illustrating the human significance of Holocene climate variability.
11. Magny, Michel. “Holocene climate variability as reflected by mid-European lake-level fluctuations and its probable impact on prehistoric human settlements.” Quaternary international113.1 (2004): 65-79.  A data set of 180 radiocarbon, tree-ring and archaeological dates obtained from sediment sequences of 26 lakes in the Jura mountains, the northern French Pre-Alps and the Swiss Plateau was used to construct a Holocene mid-European lake-level record. The dates do not indicate a random distribution over the Holocene, but form clusters suggesting an alternation of lower and higher, climatically driven lake-level phases. They provide evidence of a rather unstable Holocene climate punctuated by 15 phases of higher lake-level: 11 250–11 050, 10 300–10 000, 9550–9150, 8300–8050, 7550–7250, 6350–5900, 5650–5200, 4850–4800, 4150–3950, 3500–3100, 2750–2350, 1800–1700, 1300–1100, 750–650 cal. BP and after 1394 AD. A comparison of this mid-European lake-level record with the GISP2-Polar Circulation Index (PCI) record, the North Atlantic ice-rafting debris (IRD) events and the ¹⁴C record suggests teleconnections in a complex cryosphere-ocean-atmosphere system. Correlations between the GISP2-PCI, the mid-European lake-level, the North Atlantic IRD, and the residual ¹⁴C records, suggest that changes in the solar activity played a major role in Holocene climate oscillations over the North Atlantic area.
12. Alley, Richard B., and Anna Maria Ágústsdóttir. “The 8k event: cause and consequences of a major Holocene abrupt climate change.” Quaternary Science Reviews 24.10-11 (2005): 1123-1149.  A prominent, abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern-hemisphere regions especially in wintertime, in response to a very large outburst flood that freshened the North Atlantic. Changes were much larger than typical climate variability before and after the event, with anomalies up to many degrees contributing to major displacement of vegetative patterns. This “8k” event provides a clear case of cause and effect in the paleoclimatic realm, and so offers an excellent opportunity for model testing. The response to North Atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following North Atlantic freshening, and so greatly strengthens the case that those older events also reflect North Atlantic changes. The North Atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming-caused ice-melt and hydrologic-cycle intensification at high latitudes lead to major changes in North Atlantic circulation. Few model experiments have directly addressed the 8k event, and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies, so much work remains to be done.
13. Chew, Sing C. “From Harappa to Mesopotamia and Egypt to Mycenae: Dark Ages, Political-Economic Declines, and Environmental/Climatic Changes 2200 BC–700 BC.” The Historical Evolution of World-Systems. Palgrave Macmillan, New York, 2005. 52-74.  Considerations of hegemonic decline as a world historical process most often attempt to account for decline and collapse of complex institutions in terms of social, political, and economic processes (Gills and Frank 1992). As we increasingly question whether there are physical–environmental limits that would affect the reproduction of world-systems, political, economic, and social dimensions might not be sufficient to account for hegemonic declines. Consideration of environmental and climatological factors needs to be combined with socioeconomic relations in our understanding of hegemonic declines and shifts. This approach assumes that the humans seek to transform nature in an expansive manner, and ceaselessly amass surpluses. There are certain long periods in world history that exhibit large economic and social crises and hegemonic decline. Such long periods of economic and social distress are here termed dark ages.
14. Gorokhovich, Yuri. “Abandonment of Minoan palaces on Crete in relation to the earthquake induced changes in groundwater supply.” Journal of Archaeological Science 32.2 (2005): 217-222. Mysterious abandonment of palaces on Crete during the Late Minoan period was always a challenging problem for archeologists and geologists. Various hypotheses explained this event by effects of tsunamis, earthquakes or climatic changes that were caused by the volcanic eruption of the Santorini volcano. While each of them or their possible combination contributed to the abandonment of palaces and following Late Minoan crisis, there is another possible cause that appeared as a result of studies within the last 20–30 years. This cause is depletion of groundwater supply caused by persistent earthquake activity that took place during the Bronze Age. This explanation is supported by field observations and numerous studies of similar phenomena in other locations.
15. Wanner, Heinz, et al. “Mid-to Late Holocene climate change: an overview.” Quaternary Science Reviews 27.19-20 (2008): 1791-1828.  The last 6000 years are of particular interest to the understanding of the Earth System because the boundary conditions of the climate system did not change dramatically (in comparison to larger glacial–interglacial changes), and because abundant, detailed regional palaeoclimatic proxy records cover this period. We use selected proxy-based reconstructions of different climate variables, together with state-of-the-art time series of natural forcings (orbital variations, solar activity variations, large tropical volcanic eruptions, land cover and greenhouse gases), underpinned by results from General Circulation Models (GCMs) and Earth System Models of Intermediate Complexity (EMICs), to establish a comprehensive explanatory framework for climate changes from the Mid-Holocene (MH) to pre-industrial time. The redistribution of solar energy, due to orbital forcing on a millennial timescale, was the cause of a progressive southward shift of the Northern Hemisphere (NH) summer position of the Intertropical Convergence Zone (ITCZ). This was accompanied by a pronounced weakening of the monsoon systems in Africa and Asia and increasing dryness and desertification on both continents. The associated summertime cooling of the NH, combined with changing temperature gradients in the world oceans, likely led to an increasing amplitude of the El Niño Southern Oscillation (ENSO) and, possibly, increasingly negative North Atlantic Oscillation (NAO) indices up to the beginning of the last millennium. On decadal to multi-century timescales, a worldwide coincidence between solar irradiance minima, tropical volcanic eruptions and decadal to multi-century scale cooling events was not found. However, reconstructions show that widespread decadal to multi-century scale cooling events, accompanied by advances of mountain glaciers, occurred in the NH (e.g., in Scandinavia and the European Alps). This occurred namely during the Little Ice Age (LIA) between AD ∼1350 and 1850, when the lower summer insolation in the NH, due to orbital forcing, coincided with solar activity minima and several strong tropical volcanic eruptions. The role of orbital forcing in the NH cooling, the southward ITCZ shift and the desertification of the Sahara are supported by numerous model simulations. Other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics, but there is also evidence that changes in the ocean heat transport took place during the LIA at high northern latitudes, with possible additional implications for climates of the Southern Hemisphere (SH).
16. ? Scafetta, Nicola. “Empirical evidence for a celestial origin of the climate oscillations and its implications.” Journal of Atmospheric and Solar-Terrestrial Physics 72.13 (2010): 951-970.  We investigate whether or not the decadal and multi-decadal climate oscillations have an astronomical origin. Several global surface temperature records since 1850 and records deduced from the orbits of the planets present very similar power spectra. Eleven frequencies with period between 5 and 100 years closely correspond in the two records. Among them, large climate oscillations with peak-to-trough amplitude of about 0.1 and 0.25°C, and periods of about 20 and 60 years, respectively, are synchronized to the orbital periods of Jupiter and Saturn. Schwabe and Hale solar cycles are also visible in the temperature records. A 9.1-year cycle is synchronized to the Moon’s orbital cycles. A phenomenological model based on these astronomical cycles can be used to well reconstruct the temperature oscillations since 1850 and to make partial forecasts for the 21st century. It is found that at least 60% of the global warming observed since 1970 has been induced by the combined effect of the above natural climate oscillations. The partial forecast indicates that climate may stabilize or cool until 2030–2040. Possible physical mechanisms are qualitatively discussed with an emphasis on the phenomenon of collective synchronization of coupled oscillators.
17. Tsonis, A. A., et al. “Climate change and the demise of Minoan civilization.” Climate of the Past 6.4 (2010): 525-530.  Climate change has been implicated in the success and downfall of several ancient civilizations. Here we present a synthesis of historical, climatic, and geological evidence that supports the hypothesis that climate change may have been responsible for the slow demise of Minoan civilization. Using proxy ENSO and precipitation reconstruction data in the period 1650–1980 we present empirical and quantitative evidence that El Nino causes drier conditions in the area of Crete. This result is supported by modern data analysis as well as by model simulations. Though not very strong, the ENSO-Mediterranean drying signal appears to be robust, and its overall effect was accentuated by a series of unusually strong and long-lasting El Nino events during the time of the Minoan decline. Indeed, a change in the dynamics of the El Nino/Southern Oscillation (ENSO) system occurred around 3000 BC, which culminated in a series of strong and frequent El Nino events starting at about 1450 BC and lasting for several centuries. This stressful climatic trend, associated with the gradual demise of the Minoans, is argued to be an important force acting in the downfall of this classic and long-lived civilization.  FULL TEXT DOWNLOAD
18. Wanner, Heinz, et al. “Structure and origin of Holocene cold events.” Quaternary Science Reviews 30.21-22 (2011): 3109-3123. The present interglacial, the Holocene, spans the period of the last 11,700 years. It has sustained the growth and development of modern society. The millennial-scale decreasing solar insolation in the Northern Hemisphere summer lead to Northern Hemisphere cooling, a southern shift of the Intertropical Convergence Zone (ITCZ) and a weakening of the Northern Hemisphere summer monsoon systems. On the multidecadal to multicentury-scale, periods of more stable and warmer climate were interrupted by several cold relapses, at least in the Northern Hemisphere extra-tropical area. Based on carefully selected 10,000-year-long time series of temperature and humidity/precipitation, as well as reconstructions of glacier advances, the spatiotemporal pattern of six cold relapses during the last 10,000 years was analysed and presented in form of a Holocene Climate Atlas (HOCLAT; see http://www.oeschger.unibe.ch/research/projects/holocene_atlas/). A clear cyclicity was not found, and the spatiotemporal variability of temperature and humidity/precipitation during the six specific cold events (8200, 6300, 4700, 2700, 1550 and 550 years BP) was very high. Different dynamical processes such as meltwater flux into the North Atlantic, low solar activity, explosive volcanic eruptions, and fluctuations of the thermohaline circulation likely played a major role. In addition, internal dynamics in the North Atlantic and Pacific area (including their complex interaction) were likely involved. AUTHOR’S NOTES: {Based on temperature, humidity and glacier data, we analyze Holocene cold events. During the Holocene a clear cyclicity between warm and cold periods was not found.  Single cold relapses are subject to different dynamical processes. The six analyzed cold events show different spatial structures.}
19. Humlum, Ole, Jan-Erik Solheim, and Kjell Stordahl. “Identifying natural contributions to late Holocene climate change.” Global and Planetary Change 79.1-2 (2011): 145-156.  Analytic climate models have provided the means to predict potential impacts on future climate by anthropogenic changes in atmospheric composition. However, future climate development will not only be influenced by anthropogenic changes, but also by natural variations. The knowledge on such natural variations and their detailed character, however, still remains incomplete. Here we present a new technique to identify the character of natural climate variations, and from this, to produce testable forecast of future climate. By means of Fourier and wavelet analyses climate series are decomposed into time–frequency space, to extract information on periodic signals embedded in the data series and their amplitude and variation over time. We chose to exemplify the potential of this technique by analysing two climate series, the Svalbard (78°N) surface air temperature series 1912–2010, and the last 4000 years of the reconstructed GISP2 surface temperature series from central Greenland. By this we are able to identify several cyclic climate variations which appear persistent on the time scales investigated. Finally, we demonstrate how such persistent natural variations can be used for hindcasting and forecasting climate. Our main focus is on identifying the character (timing, period, amplitude) of such recurrent natural climate variations, but we also comment on the likely physical explanations for some of the identified cyclic climate variations. The causes of millennial climate changes remain poorly understood, and this issue remains important for understanding causes for natural climate variability over decadal- and decennial time scales. We argue that Fourier and wavelet approaches like ours may contribute towards improved understanding of the role of such recurrent natural climate variations in the future climate development.
20. Drake, Brandon L. “The influence of climatic change on the Late Bronze Age Collapse and the Greek Dark Ages.” Journal of Archaeological Science 39.6 (2012): 1862-1870.  Between the 13th and 11th centuries BCE, most Greek Bronze Age Palatial centers were destroyed and/or abandoned. The following centuries were typified by low population levels. Data from oxygen-isotope speleothems, stable carbon isotopes, alkenone-derived seasurface temperatures, and changes in warm-species dinocysts and formanifera in the Mediterranean indicate that the Early Iron Age was more arid than the preceding Bronze Age. A sharp increase in Northern Hemisphere temperatures preceded the collapse of Palatial centers, a sharp decrease occurred during their abandonment. Mediterranean Seasurface temperatures cooled rapidly during the Late Bronze Age, limiting freshwater flux into the atmosphere and thus reducing precipitation over land. These climatic changes could have affected Palatial centers that were dependent upon high levels of agricultural productivity. Declines in agricultural production would have made higher-density populations in Palatial centers unsustainable. The ‘Greek Dark Ages’ that followed occurred during prolonged arid conditions that lasted until the Roman Warm Period.

CHAOS THEORY IN CLIMATE SCIENCE: A BIBLIOGRAPHY

1. Zeng, Xubin, Roger A. Pielke, and R. Eykholt. “Chaos theory and its applications to the atmosphere.” Bulletin of the American Meteorological Society 74.4 (1993): 631-644.  A brief overview of chaos theory is presented, including bifurcations, routes to turbulence, and methods for characterizing chaos. The paper divides chaos applications in atmospheric sciences into three categories: new ideas and insights inspired by chaos, analysis of observational data, and analysis of output from numerical models. Based on the review of chaos theory and the classification of chaos applications, suggestions for future work are given.
2. Marotzke, Jochem. “Abrupt climate change and thermohaline circulation: Mechanisms and predictability.” Proceedings of the National Academy of Sciences 97.4 (2000): 1347-1350.  The ocean’s thermohaline circulation has long been recognized as potentially unstable and has consequently been invoked as a potential cause of abrupt climate change on all timescales of decades and longer. However, fundamental aspects of thermohaline circulation changes remain poorly understood. [LINK TO FULL TEXT PDF]
3. Rial, Jose A., and C. A. Anaclerio. “Understanding nonlinear responses of the climate system to orbital forcing.” Quaternary Science Reviews 19.17-18 (2000): 1709-1722.  Frequency modulation (FM) of the orbital eccentricity forcing may be one important source of the nonlinearities observed in δ¹⁸O time series from deep-sea sediment cores (J.H. Rial (1999a) Pacemaking the lce Ages by frequency modulation of Earth’s orbital eccentricity. Science 285, 564–568). Here we present further evidence of frequency modulation found in data from the Vostok ice core. Analyses of the 430,000-year long, orbitally untuned, time series of CO₂, deuterium, aerosol and methane, suggest frequency modulation of the 41 kyr (0.0244 kyr⁻¹) obliquity forcing by the 413 kyr-eccentricity signal and its harmonics. Conventional and higher-order spectral analyses show that two distinct spectral peaks at ∼29 kyr (0.034 kyr⁻¹) and ∼69 kyr (0.014 kyr⁻¹) and other, smaller peaks surrounding the 41 kyr obliquity peak are harmonically (nonlinearly) related and likely to be FM-generated sidebands of the obliquity signal. All peaks can be closely matched by the spectrum of an appropriately built theoretical FM signal. A preliminary model, based on the classic logistic growth delay differential equation, reproduces the longer period FM effect and the familiar multiply peaked spectra of the eccentricity band. Since the FM effect appears to be a common feature in climate response, finding out its cause may help understand climate dynamics and global climate change.
4. Ashkenazy, Yosef, et al. “Nonlinearity and multifractality of climate change in the past 420,000 years.” Geophysical research letters 30.22 (2003).  Evidence of past climate variations are stored in polar ice caps and indicate glacial‐interglacial cycles of ∼100 kyr. Using advanced scaling techniques we study the long‐range correlation properties of temperature proxy records of four ice cores from Antarctica and Greenland. These series are long‐range correlated in the time scales of 1–100 kyr. We show that these time series are nonlinear for time scales of 1–100 kyr as expressed by temporal long‐range correlations of magnitudes of temperature increments and by a broad multifractal spectrum. Our results suggest that temperature increments appear in clusters of big and small increments—a big (positive or negative) climate change is most likely followed by a big (positive or negative) climate change and a small climate change is most likely followed by a small climate change.
5. Rial, Jose A. “Abrupt climate change: chaos and order at orbital and millennial scales.” Global and Planetary Change 41.2 (2004): 95-109.  Successful prediction of future global climate is critically dependent on understanding its complex history, some of which is displayed in paleoclimate time series extracted from deep-sea sediment and ice cores. These recordings exhibit frequent episodes of abrupt climate change believed to be the result of nonlinear response of the climate system to internal or external forcing, yet, neither the physical mechanisms nor the nature of the nonlinearities involved are well understood. At the orbital (10⁴–10⁵ years) and millennial scales, abrupt climate change appears as sudden, rapid warming events, each followed by periods of slow cooling. The sequence often forms a distinctive saw-tooth shaped time series, epitomized by the deep-sea records of the last million years and the Dansgaard–Oeschger (D/O) oscillations of the last glacial. Here I introduce a simplified mathematical model consisting of a novel arrangement of coupled nonlinear differential equations that appears to capture some important physics of climate change at Milankovitch and millennial scales, closely reproducing the saw-tooth shape of the deep-sea sediment and ice core time series, the relatively abrupt mid-Pleistocene climate switch, and the intriguing D/O oscillations. Named LODE for its use of the logistic-delayed differential equation, the model combines simplicity in the formulation (two equations, small number of adjustable parameters) and sufficient complexity in the dynamics (infinite-dimensional nonlinear delay differential equation) to accurately simulate details of climate change other simplified models cannot. Close agreement with available data suggests that the D/O oscillations are frequency modulated by the third harmonic of the precession forcing, and by the precession itself, but the entrained response is intermittent, mixed with intervals of noise, which corresponds well with the idea that the climate operates at the edge between chaos and order. LODE also predicts a persistent ∼1.5 ky oscillation that results from the frequency modulated regional climate oscillation.
6. Huybers, Peter, and Carl Wunsch. “Obliquity pacing of the late Pleistocene glacial terminations.” Nature 434.7032 (2005): 491.  The 100,000-year timescale in the glacial/interglacial cycles of the late Pleistocene epoch (the past ∼700,000 years) is commonly attributed to control by variations in the Earth’s orbit¹. This hypothesis has inspired models that depend on the Earth’s obliquity (∼ 40,000 yr; ∼40 kyr), orbital eccentricity (∼ 100 kyr) and precessional (∼ 20 kyr) fluctuations^2,3,4,5, with the emphasis usually on eccentricity and precessional forcing. According to a contrasting hypothesis, the glacial cycles arise primarily because of random internal climate variability^6,7,8. Taking these two perspectives together, there are currently more than thirty different models of the seven late-Pleistocene glacial cycles⁹. Here we present a statistical test of the orbital forcing hypothesis, focusing on the rapid deglaciation events known as terminations^10,11. According to our analysis, the null hypothesis that glacial terminations are independent of obliquity can be rejected at the 5% significance level, whereas the corresponding null hypotheses for eccentricity and precession cannot be rejected. The simplest inference consistent with the test results is that the ice sheets terminated every second or third obliquity cycle at times of high obliquity, similar to the original proposal by Milankovitch¹². We also present simple stochastic and deterministic models that describe the timing of the late-Pleistocene glacial terminations purely in terms of obliquity forcing.
7. Tziperman, Eli, Carl Wunsch. “Consequences of pacing the Pleistocene 100 kyr ice ages by nonlinear phase locking to Milankovitch forcing.” Paleoceanography 21.4 (2006).:    The consequences of the hypothesis that Milankovitch forcing affects the phase (e.g., termination times) of the 100 kyr glacial cycles via a mechanism known as “nonlinear phase locking” are examined. Phase locking provides a mechanism by which Milankovitch forcing can act as the “pacemaker” of the glacial cycles. Nonlinear phase locking can determine the timing of the major deglaciations, nearly independently of the specific mechanism or model that is responsible for these cycles as long as this mechanism is suitably nonlinear. A consequence of this is that the fit of a certain model output to the observed ice volume record cannot be used as an indication that the glacial mechanism in this model is necessarily correct. Phase locking to obliquity and possibly precession variations is distinct from mechanisms relying on a linear or nonlinear amplification of the eccentricity forcing. Nonlinear phase locking may determine the phase of the glacial cycles even in the presence of noise in the climate system and can be effective at setting glacial termination times even when the precession and obliquity bands account only for a small portion of the total power of an ice volume record. Nonlinear phase locking can also result in the observed “quantization” of the glacial period into multiples of the obliquity or precession periods.
8. Eisenman, Ian, Norbert Untersteiner, and J. S. Wettlaufer. “On the reliability of simulated Arctic sea ice in global climate models.” Geophysical Research Letters 34.10 (2007).  While most of the global climate models (GCMs) currently being evaluated for the IPCC Fourth Assessment Report simulate present‐day Arctic sea ice in reasonably good agreement with observations, the intermodel differences in simulated Arctic cloud cover are large and produce significant differences in downwelling longwave radiation. Using the standard thermodynamic models of sea ice, we find that the GCM‐generated spread in longwave radiation produces equilibrium ice thicknesses that range from 1 to more than 10 meters. However, equilibrium ice thickness is an extremely sensitive function of the ice albedo, allowing errors in simulated cloud cover to be compensated by tuning of the ice albedo. This analysis suggests that the results of current GCMs cannot be relied upon at face value for credible predictions of future Arctic sea ice.
9. Frank, Patrick, and John McCarthy. “A climate of belief.” Skeptic 14.1 (2008): 22-30. The claim that anthropogenic CO2 is responsible for the current warming of Earth climate is scientifically insupportable because climate models are unreliable by Patrick Frank “He who refuses to do arithmetic is doomed to talk nonsense.” — John McCarthy “The latest scientific data confirm that the earth’s climate is rapidly changing. … The cause? A thickening layer of carbon dioxide pollution, mostly from power plants and automobiles, that traps heat in the atmosphere. … *A+verage U.S. temperatures could rise another 3 to 9 degrees by the end of the century … Sea levels will rise, *and h+eat waves will be more frequent and more intense. Droughts and wildfires will occur more often. Disease-carrying mosquitoes will expand their range. And species will be pushed to extinction.” So says the National Resources Defense Council,2 with agreement by the Sierra Club,3 Greenpeace,4 National Geographic,5 the US National Academy of Sciences,6 and the US Congressional House leadership.7 Concurrent views are widespread,8 as a visit to the internet or any good bookstore will verify. Since at least the 1995 Second Assessment Report, the UN Intergovernmental Panel on Climate Change (IPCC) has been making increasingly assured statements that human-produced carbon dioxide (CO2) is influencing the climate, and is the chief cause of the global warming trend in evidence since about 1900. The current level of atmospheric CO2 is about 390 parts per million by volume (ppmv), or 0.039% by volume of the atmosphere, and in 1900 was about 295 ppmv. If the 20th century trend continues unabated, by about 2050 atmospheric CO2 will have doubled to about 600 ppmv. This is the basis for the usual “doubled CO2” scenario. Doubled CO2 is a bench-mark for climate scientists in evaluating greenhouse warming. Earth receives about 342 watts per square meter (W/m2 ) of incoming solar energy, and all of this energy eventually finds its way back out into space. However, CO2 and other greenhouse gasses, most notably water vapor, absorb some of the outgoing energy and warm the atmosphere. This is the greenhouse effect. Without it Earth’s average surface temperature would be a frigid -19°C (-2.2 F). With it, the surface warms to about +14°C (57 F) overall, making Earth habitable.9 With more CO2, more outgoing radiant energy is absorbed, changing the thermal dynamics of
   the atmosphere. All the extra greenhouse gasses that have entered the atmosphere since 1900, including CO2, equate to an extra 2.7 W/m2 of energy absorption by the atmosphere.10 This is the worrisome greenhouse effect. On February 2, 2007, the IPCC released the Working Group I (WGI) “Summary for Policymakers” (SPM) report on Earth climate,11 which is an executive summary of the science supporting the predictions quoted above. The full “Fourth Assessment Report” (4AR) came out in sections during 2007.  [LINK TO FULL TEXT PDF]
10. Huybers, Peter John. “Pleistocene glacial variability as a chaotic response to obliquity forcing.” (2009).  The mid-Pleistocene Transition from 40 ky to ~100 ky glacial cycles is generally characterized as a singular transition attributable to scouring of continental regolith or a long-term decrease in atmospheric CO2 concentrations. Here an alternative hypothesis is suggested, that Pleistocene glacial variability is chaotic and that transitions from 40 ky to ~100 ky modes of variability occur spontaneously. This alternate view is consistent with the presence of ~80 ky glacial cycles during the early Pleistocene and the lack of evidence for a change in climate forcing during the mid-Pleistocene. A simple model illustrates this chaotic scenario. When forced at a 40 ky period the model chaotically transitions between small 40 ky glacial cycles and larger 80 and 120 ky cycles which, on average, give the ~100 ky variability.
11. Dima, Mihai, and Gerrit Lohmann. “Conceptual model for millennial climate variability: a possible combined solar-thermohaline circulation origin for the~ 1,500-year cycle.” Climate Dynamics 32.2-3 (2009): 301-311.  Dansgaard-Oeschger and Heinrich events are the most pronounced climatic changes over the last 120,000 years. Although many of their properties were derived from climate reconstructions, the associated physical mechanisms are not yet fully understood. These events are paced by a ~1,500-year periodicity whose origin remains unclear. In a conceptual model approach, we show that this millennial variability can originate from rectification of an external (solar) forcing, and suggest that the thermohaline circulation, through a threshold response, could be the rectifier. We argue that internal threshold response of the thermohaline circulation (THC) to solar forcing is more likely to produce the observed DO cycles than amplification of weak direct ~1,500-year forcing of unknown origin, by THC. One consequence of our concept is that the millennial variability is viewed as a derived mode without physical processes on its characteristic time scale. Rather, the mode results from the linear representation in the Fourier space of nonlinearly transformed fundamental modes.
12. Dijkstra, Henk A. Nonlinear climate dynamics. Cambridge University Press, 2013.  

EARLY HOLOCENE SEA LEVEL RISE & 8.2K EVENT

1. Hori, Kazuaki, and Yoshiki Saito. “An early Holocene sea‐level jump and delta initiation.” Geophysical Research Letters 34.18 (2007).  Early Holocene sea‐level change controlled the evolution of classic coastal depositional systems. Radiocarbon‐dated borehole cores obtained from three incised‐valley‐fill systems in Asia (Changjiang, Song Hong, and Kiso River) record very similar depositional histories, especially between about 9000 and 8500 cal BP. Sedimentary facies changes from estuarine sand and mud to shelf or prodelta mud suggest that the marine influence in the incised valleys increased during this period. In addition, large decreases in sediment accumulation rates occurred. A sea‐level jump causes an estuarine system and its depocenter to move rapidly landward. It is possible that the final collapse of the Laurentide Ice Sheet, accompanied by catastrophic drainage of glacial lakes, at approximately 8500 cal BP caused such a jump. The jump was followed immediately by a period of decelerated sea‐level rise that promoted delta initiation.
2. Vink, Annemiek, et al. “Holocene relative sea-level change, isostatic subsidence and the radial viscosity structure of the mantle of northwest Europe (Belgium, the Netherlands, Germany, southern North Sea).” Quaternary Science Reviews26.25-28 (2007): 3249-3275.  A comprehensive observational database of Holocene relative sea-level (RSL) index points from northwest Europe (Belgium, the Netherlands, northwest Germany, southern North Sea) has been compiled in order to compare and reassess the data collected from the different countries/regions and by different workers on a common time–depth scale. RSL rise varies in magnitude and form between these regions, revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity. It clearly contains a non-linear, glacio- and/or hydro-isostatic subsidence component, which is only small on the Belgian coastal plain but increases significantly to a value of ca 7.5 m relative to Belgium since 8 cal. ka BP along the northwest German coast. The subsidence is at least in part related to the Post-Glacial collapse of the so-called peripheral forebulge which developed around the Fennoscandian centre of ice loading during the Last Glacial Maximum. The RSL data have been compared to geodynamic Earth models in order to infer the radial viscosity structure of the Earth’s mantle underneath NW Europe (lithosphere thickness, upper- and lower-mantle viscosity), and conversely to predict RSL in regions where we have only few observational data (e.g. in the southern North Sea). A very broad range of Earth parameters fit the Belgian RSL data, suggesting that glacial isostatic adjustment (GIA) only had a minor effect on Belgian crustal dynamics during and after the Last Ice Age. In contrast, a narrow range of Earth parameters define the southern North Sea region, reflecting the greater influence of GIA on these deeper/older samples. Modelled RSL data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow, WNW–ESE trending band connecting the German federal state of Lower Saxony with the Dogger Bank area in the southern North Sea. Identification of the effects of local-scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea-level index points based on model-data comparisons is possible but is still complicated by the relatively large range of Earth model parameters fitting each RSL curve, emphasizing the need for more high-quality observational data.
3. Kendall, Roblyn A., et al. “The sea-level fingerprint of the 8.2 ka climate event.” Geology 36.5 (2008): 423-426.  The 8.2 ka cooling event was an abrupt, widespread climate instability. There is general consensus that the episode was likely initiated by a catastrophic outflow of proglacial Lakes Agassiz and Ojibway through the Hudson Strait, with subsequent disruption of the Atlantic meridional overturning circulation. However, the total discharge and flux during the 8.2 ka event remain uncertain. We compute the sea-level signature, or “fingerprint,” associated with the drainage of Lakes Agassiz and Ojibway, as well as the expected sea-level signal over the same time period due to glacial isostatic adjustment (GIA) in response to the Late Pleistocene deglaciation. Our analysis demonstrates that sites relatively close to the lakes, including the West and Gulf Coasts of the United States, have small signals due to the lake release and potentially large GIA signals, and thus they may not be optimal field sites for constraining the outflow volume. Other sites, such as the east coast of South America and western Africa, have significantly larger signals associated with the lake release and are thus better choices in this regard.
4. Hijma, Marc P., and Kim M. Cohen. “Timing and magnitude of the sea-level jump preluding the 8200 yr event.” Geology 38.3 (2010): 275-278.  Evidence from terrestrial, glacial, and global climate model reconstructions suggests that a sea-level jump caused by meltwater release was associated with the triggering of the 8.2 ka cooling event. However, there has been no direct measurement of this jump using precise sea-level data. In addition, the chronology of the meltwater pulse is based on marine data with limited dating accuracy. The most plausible mechanism for triggering the cooling event is the sudden, possibly multistaged drainage of the Laurentide proglacial Lakes Agassiz and Ojibway through the Hudson Strait into the North Atlantic ca. 8470 ± 300 yr ago. Here we show with detailed sea-level data from Rotterdam, Netherlands, that the sea-level rise commenced 8450 ± 44 yr ago. Our timing considerably narrows the existing age of this drainage event and provides support for the hypothesis of a double-staged lake drainage. The jump in sea level reached a local magnitude of 2.11 ± 0.89 m within 200 yr, in addition to the ongoing background relative sea-level rise (1.95 ± 0.74 m). This magnitude, observed at considerable distance from the release site, points to a global-averaged eustatic sea-level jump that is double the size of previous estimates (3.0 ± 1.2 m versus 0.4–1.4 m). The discrepancy suggests either a coeval Antarctic contribution or, more likely, a previous underestimate of the total American lake drainage.
5. Bard, Edouard, Bruno Hamelin, and Doriane Delanghe-Sabatier. “Deglacial meltwater pulse 1B and Younger Dryas sea levels revisited with boreholes at Tahiti.” Science327.5970 (2010): 1235-1237.  Reconstructing sea-level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets. The resolution of the few sea-level records covering the critical time interval between 14,000 and 9,000 YBP calendar years before the present is still insufficient to draw conclusions about sea-level changes associated with the Younger Dryas cold event and the meltwater pulse 1B (MWP-1B). We used the uranium-thorium method to date shallow-living corals from three new cores drilled onshore in the Tahiti barrier reef. No significant discontinuity can be detected in the sea-level rise during the MWP-1B period. The new Tahiti sea-level record shows that the sea-level rise slowed down during the Younger Dryas before accelerating again during the Holocene.
6. Smith, D. E., et al. “The early Holocene sea level rise.” Quaternary Science Reviews 30.15-16 (2011): 1846-1860.  The causes, anatomy and consequences of the early Holocene sea level rise (EHSLR) are reviewed. The rise, of ca 60m, took place over most of the Earth as the volume of the oceans increased during deglaciation and is dated at 11,650–7000 cal. BP. The EHSLR was largely driven by meltwater release from decaying ice masses and the break up of coastal ice streams. The patterns of ice sheet decay and the evidence for meltwater pulses are reviewed, and it is argued that the EHSLR was a factor in the ca 8470 BP flood from Lake Agassiz-Ojibway. Patterns of relative sea level changes are examined and it is argued that in addition to regional variations, temporal changes are indicated. The impact of the EHSLR on climate is reviewed and it is maintained that the event was a factor in the 8200 BP cooling event, as well as in changes in ocean current patterns and their resultant effects. The EHSLR may also have enhanced volcanic activity, but no clear evidence of a causal link with submarine sliding on continental slopes and shelves can yet be demonstrated. The rise probably influenced rates and patterns of human migrations and cultural changes. It is concluded that the EHSLR was a major event of global significance, knowledge of which is relevant to an understanding of the impacts of global climate change in the future. Highlights:  1. Reviews the early Holocene sea level rise of 11650–7000 cal. BP. 2. Argues that the rise was involved in the discharge of Lake Agassiz-Ojibway and the 8200-year cooling event. 3. Shows that he rise influenced climate by increasing sea areas, in turn affecting human migration. 4. Suggests that the rise increased volcanic activity, but that its effects on submarine sliding are uncertain. 5. Argues that study of the rise helps throw light on the effects of future sea level changes in a global warming world.
7. Hijma, Marc P., and Kim M. Cohen. “Holocene transgression of the Rhine river mouth area, The Netherlands/Southern North Sea: palaeogeography and sequence stratigraphy.” Sedimentology 58.6 (2011): 1453-1485.  This study presents a detailed reconstruction of the palaeogeography of the Rhine valley (western Netherlands) during the Holocene transgression with systems tracts placed in a precise sea‐level context. This approach permits comparison of actual versus conceptual boundaries of the lowstand, transgressive and highstand systems tracts. The inland position of the highstand Rhine river mouth on a wide, low‐gradient continental shelf meant that base‐level changes were the dominant control on sedimentation for a relatively short period of the last glacial cycle. Systems in such inland positions predominantly record changes in the balance between river discharge and sediment load, and preserve excellent records of climatic changes or other catchment‐induced forcing. It is shown here that the transgressive systems tract‐part of the coastal prism formed in three stages: (i) the millennium before 8·45 ka bp, when the area was dominated by fluvial environments with extensive wetlands; (ii) the millennium after 8·45 ka, characterized by strong erosion, increasing tidal amplitudes and bay‐head delta development; and (iii) the period between 7·5 and 6·3 ka bp when the Rhine avulsed multiple times and the maximum flooding surface formed. The diachroneity of the transgressive surface is strongly suppressed because of a pulse of accelerated sea‐level rise at 8·45 ka bp. That event not only had a strong effect on preservation, but has circum‐oceanic stratigraphical relevance as it divides the early and middle Holocene parts of coastal successions worldwide. The palaeogeographical reconstruction offers a unique full spatial–temporal view on the coastal and fluvial dynamics of a major river mouth under brief rapid forced transgression. This reconstruction is of relevance for Holocene and ancient transgressive systems worldwide, and for next‐century natural coasts that are predicted to experience a 1 m sea‐level rise.
8. Hijma, Marc P., et al. “Pleistocene Rhine–Thames landscapes: geological background for hominin occupation of the southern North Sea region.” Journal of Quaternary Science 27.1 (2012): 17-39.  This paper links research questions in Quaternary geology with those in Palaeolithic archaeology. A detailed geological reconstruction of The Netherlands’ south‐west offshore area provides a stratigraphical context for archaeological and palaeontological finds. Progressive environmental developments have left a strong imprint on the area’s Palaeolithic record. We highlight aspects of landscape evolution and related taphonomical changes, visualized in maps for critical periods of the Pleistocene in the wider southern North Sea region. The Middle Pleistocene record is divided into two palaeogeographical stages: the pre‐Anglian/Elsterian stage, during which a wide land bridge existed between England and Belgium even during marine highstands; and the Anglian/Elsterian to Saalian interglacial, with a narrower land bridge, lowered by proglacial erosion but not yet fully eroded. The Late Pleistocene landscape was very different, with the land bridge fully dissected by an axial Rhine–Thames valley, eroded deep enough to fully connect the English Channel and the North Sea during periods of highstand. This tripartite staging implies great differences in (i) possible migration routes of herds of herbivores as well as hominins preying upon them, (ii) the erosion base of axial and tributary rivers causing an increase in the availability of flint raw materials and (iii) conditions for loess accumulation in northern France and Belgium and the resulting preservation of Middle Palaeolithic sites.
9. Törnqvist, Torbjörn E., and Marc P. Hijma. “Links between early Holocene ice-sheet decay, sea-level rise and abrupt climate change.” Nature Geoscience 5.9 (2012): 601.  The beginning of the current interglacial period, the Holocene epoch, was a critical part of the transition from glacial to interglacial climate conditions. This period, between about 12,000 and 7,000 years ago, was marked by the continued retreat of the ice sheets that had expanded through polar and temperate regions during the preceding glacial. This meltdown led to a dramatic rise in sea level, punctuated by short-lived jumps associated with catastrophic ice-sheet collapses. Tracking down which ice sheet produced specific sea-level jumps has been challenging, but two events between 8,500 and 8,200 years ago have been linked to the final drainage of glacial Lake Agassiz in north-central North America. The release of the water from this ice-dammed lake into the ocean is recorded by sea-level jumps in the Mississippi and Rhine-Meuse deltas of approximately 0.4 and 2.1 metres, respectively. These sea-level jumps can be related to an abrupt cooling in the Northern Hemisphere known as the 8.2 kyr event, and it has been suggested that the freshwater release from Lake Agassiz into the North Atlantic was sufficient to perturb the North Atlantic meridional overturning circulation. As sea-level rise on the order of decimetres to metres can now be detected with confidence and linked to climate records, it is becoming apparent that abrupt climate change during the early Holocene associated with perturbations in North Atlantic circulation required sustained freshwater release into the ocean.
10. Sturt, Fraser, Duncan Garrow, and Sarah Bradley. “New models of North West European Holocene palaeogeography and inundation.” Journal of Archaeological Science 40.11 (2013): 3963-3976. Highlights: New Palaeogeographic models of North West Europe from 11,000 BP to present day at 500 year intervals. Calculated rates for Holocene inundation across North West Europe. High rates of change do not necessarily mean catastrophic impacts. Understanding rates of change and their social implications requires a multi-scalar, multidisciplinary approach to the past.Abstract: This paper presents new 500 year interval palaeogeographic models for Britain, Ireland and the North West French coast from 11000 cal. BP to present. These models are used to calculate the varying rates of inundation for different geographical zones over the study period. This allows for consideration of the differential impact that Holocene sea-level rise had across space and time, and on past societies. In turn, consideration of the limitations of the models helps to foreground profitable areas for future research.