Using Patterns of Recurring Climate Cycles to Predict Future Climate Changes D.J

CHAPTER 21 Using Patterns of Recurring Climate Cycles to Predict Future Climate Changes D.J. Easterbrook Western Washington University, Bellingham, WA, United States

OUTLINE

1. Introduction 395 4. Correlation of Temperature Cycles and the Paciﬁc Decadal Oscillation 405 2. The Past is the Key to the Future: Lessons From Past Global Climate Changes 396 5. The Atlantic Multidecadal Oscillation 407 2.1 Past Climate Changes 396 6. Where Is Climate Headed During the Coming 2.2 Magnitude and Rate of Abrupt Climate Changes 396 Century? 407 2.3 Holocene Climate Changes (10,000 Years Ago 6.1 IPCC Predictions 407 to Present) 398 6.2 Predictions Based on Past Cyclic Climate 2.3.1 The Roman Warm Period 398 Patterns 407 2.3.2 Dark Ages Cool Period 398 2.3.3 Medieval Warm Period (900e1300 AD) 400 References 410 2.3.4 The Little Ice Age 401 2.3.5 Climate Changes During the Past Century 403 3. Signiﬁcance of Past Global Climate Changes 404

1. INTRODUCTION

Global warming that occurred from 1978 to about 1998 pushed climate change into the forefront of potential concern. Every day the news media is ﬁlled with dire predictions of impending disastersdcatastrophic melting of the Antarctic and Greenland ice sheets, drowning of major cities from sea level rise, drowning of major portions of countries, droughts, severe water shortages, no more snow, more extreme weather events (hurricanes, tor- nadoes), etc. With no unequivocal, cause-and-effect, tangible, physical evidence that increasing CO2 caused this most recent global warming, adherents of this ideology have had to rely on computer models that have proven to be unreliable. Abundant, physical, geologic evidence from the past provides a record of former periods of recurrent global warming and cooling that were far more intense than recent warming and cooling. These geologic records provide clear evidence of global warming and cooling that could not have been caused by increased CO2. Thus, we can use these records to project global climate into the future, ie, the past is the key to the future.

Evidence-Based Climate Science, Second Edition http://dx.doi.org/10.1016/B978-0-12-804588-6.00021-5 395 Copyright © 2016 Elsevier Inc. All rights reserved. 396 21. USING PATTERNS OF RECURRING CLIMATE CYCLES TO PREDICT FUTURE CLIMATE CHANGES 2. THE PAST IS THE KEY TO THE FUTURE: LESSONS FROM PAST GLOBAL CLIMATE CHANGES

2.1 Past Climate Changes

Those who advocate CO2 as the cause of global warming have stated that never before in the Earth’s history has climate changed as rapidly as in the past century, and that proves global warming is being caused by anthropogenic CO2. Statements such as these are easily refutable by the geologic record. Fig. 21.1 shows temperature changes recorded by oxygen isotope ratios from the GISP2 ice core from the Greenland Ice Sheet. The global warming experienced during the past century pales into insigniﬁcance when compared to the magnitude of the profound climate reversals over the past 15,000 years. The GISP2 Greenland ice core isotope data have proven to be a great source of climatic data from the geologic past. Paleo-temperatures for more than 100,000 years have been determined from nuclear accelerator measurements of thousands of oxygen isotope ratios (16O/18O) (Grootes and Stuiver, 1997), and these data have become a world standard. Oxygen isotope ratios are a measure of paleo-temperatures at the time snow fell that was later converted to glacial ice. The age of such temperatures can be accurately measured from annual layers of accumulation of rock debris marking each summer’s melting of ice and concentration of rock debris on the glacier. Paleo-temperatures from the GISP2 ice core were also reconstructed using ice core temperatures (Fig. 21.2; Cuffy and Clow, 1997; Alley, 2000). These also show exceptionally high rates of warming and cooling near the end of the Pleistocene. The oxygen isotope and paleo-temperature data clearly show remarkable swings in climate over the past 100,000 years. In just the past 500 years, Greenland warming/cooling temperatures ﬂuctuated back and forth about 40 times, with changes every 25e30 years (27 years on the average). None of these changes could have been caused by changes in atmospheric CO2 because they predate the large CO2 emissions that began about 1945. Nor can the e warming of 1915 45 be related to CO2, because it predates the soaring emissions after 1945. Thirty years of global e cooling (1945 77) occurred during the big post-1945 increase in CO2 emissions.

2.2 Magnitude and Rate of Abrupt Climate Changes But what about the magnitude and rates of climates change? How do past temperature oscillations compare with recent global warming (1977e98) or with warming periods over the past millennia? The answer to the question of magnitude and rates of climate change can be found in the d18O and ice core temperature data (Steffensen et al., 2008). Temperature changes in the GISP2 core over the past 25,000 years are shown in Figs. 21.1 and 21.2. The temperature curve in Fig. 21.2 is a portion of the Cuffy and Clow (1997) original curve. The horizontal axis is time and the vertical axis is temperature, based on ice core borehole temperature data. Details are discussed in their paper. Places where the curve becomes nearly vertical signify times of very rapid temperature change. Keep in mind that these are temperatures in Greenland, not global temperatures. However, correlation of the ice core temperatures with

FIGURE 21.1 Oxygen isotope ratios from the GISP2 ice core, Greenland. Note the extremely sharp rises in temperature (red) at about 14,500 years and 11,500 years, which had much greater magnitude and rate of rise than the past century. Plotted from data by Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in Greenland snow and ice with 103 to 105eyear time resolution. Journal of Geophysical Research 102, 26455e26470.

IX. CLIMATE PREDICTIONS 2. THE PAST IS THE KEY TO THE FUTURE: LESSONS FROM PAST GLOBAL CLIMATE CHANGES 397

FIGURE 21.2 Greenland temperatures over the past 25,000 years recorded in the GISP2 ice core. Strong, abrupt warming is shown by nearly vertical rise of temperatures, strong cooling by nearly vertical drop of temperatures. Modified from Cuffey, K.M., Clow, G.D., 1997. Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition. Journal of Geophysical Research 102, 26383e26396. worldwide glacial fluctuations and correlation of modern Greenland temperatures with global temperatures con- firms that the ice core record does indeed follow global temperature trends and is an excellent proxy for global temperature changes. For example, the portions of the curve from about 25,000 to 15,000 represent the last Ice Age (the Pleistocene), when huge ice sheets, thousands of feet thick, covered North America, northern Europe, and northern Russia, and alpine glaciers readvanced far downvalley. Some of the more remarkable sudden climatic warming periods are listed later in this section and in Fig. 21.3. The numbers in Fig. 21.3 correspond to the temperature curves in Fig. 21.2. How do the magnitude and rates of change of modern global warming/cooling compare to warming/cooling events over the past 15,000 years? We can compare the warming and cooling in the past century to approximate 100-year periods in the past 25,000 years. The scale of the curve does not allow enough accuracy to pick out exactly 100-year episodes directly from the curve, but that can be done from the annual dust layers in ice core data. Thus, not all of the periods noted here are exactly 100 years. Some are slightly more, some are slightly less, but they are close enough to allow comparison of magnitude and rates with the past century. 1. Temperature changes recorded in the GISP2 ice core from the Greenland Ice Sheet (Figs. 21.1 and 21.2) show that the global warming experienced during the past century pales into insignificance when compared to the magnitude of profound ice sheets that covered Canada and the northern United States, all of Scandinavia, and much of northern Europe and Russia.

0 1 2 3 4 5 6 7 8 9 1011 12 13 1415 16 17

FIGURE 21.3 Magnitudes of the largest warming/cooling events over the past 25,000 years. Temperatures on the vertical axis are rise or fall of temperatures in about a century. Each column represents the rise or fall of temperature shown in Fig. 21.2. Event number 1 is about 24,000 years ago and event number 15 is about 11,000 years old. The sudden warming about 14,000 years ago caused massive melting of these ice sheets at extraordinary rates.

IX. CLIMATE PREDICTIONS 398 21. USING PATTERNS OF RECURRING CLIMATE CYCLES TO PREDICT FUTURE CLIMATE CHANGES 2. Shortly thereafter, temperatures dropped abruptly about 10 C (20 F) and temperatures then remained cold for several thousand years. 3. About 13,000 years ago, global temperatures plunged sharply (w12 C; w21 F) and a 1300-year cold period, the Younger Dryas, began. 4. 11,500 years ago, global temperatures rose sharply (w12 C; w21 F), marking the end of the Younger Dryas cold period and the end of the Pleistocene Ice Age. The end of the Younger Dryas cold period warmed by 5 C(9F) over 30e40 years and as much as 8 C (14 F) over 40 years. Fig. 21.2 shows comparisons of the largest magnitudes of warming/cooling events per century over the past 15,000 years. At least three warming events were 20e24 times the magnitude of warming over the past century and four were 6e9 times the magnitude of warming over the past century. The magnitude of the only modern warm- e ing that might possibly have been caused by CO2 (1978 98) is insigniﬁcant compared to the earlier periods of warming.

2.3 Holocene Climate Changes (10,000 Years Ago to Present) Almost all of the past 10,000 years have been warmer than the present. Figs. 21.4 and 21.5 show temperatures from the GISP2 Greenland ice core. With the exception of a brief cool period about 8200 years ago, almost all of the entire period from 10,500 to 1500 years ago was signiﬁcantly warmer than the present. About 8200 years ago, the post-Ice Age interglacial warm period was interrupted by sudden global cooling that lasted for a few centuries (Figs. 21.4e21.6). During this time, alpine glaciers advanced and built moraines. The warming that followed the cool period was also abrupt. Neither the abrupt climatic cooling nor the warming that followed was preceded by atmospheric CO2 changes. As shown by oxygen isotope data from the GISP2 ice core, historical accounts, and various other data, the last 2000 years of the late Holocene was characterized by alternating warm and cold periods (Fig. 21.7).

2.3.1 The Roman Warm Period The Roman Warm Period shows up prominently in the GISP2 ice core (Fig. 21.7) between about 1500 and 1800 years ago. During that time, Romans wrote of grapes and olives growing farther north in Italy that had been previously possible and of little snow or ice (Singer and Avery, 2007).

2.3.2 Dark Ages Cool Period The Dark Ages Cool Period, which began about 1500 years ago, marks the end of 8500 years of Holocene warming and the beginning of late Holocene cold periods (Fig. 21.7). This cool period shows up conspicuously in the GISP2 ice core and in historic accounts. The Romans wrote that the Tiber River froze and snow remained on the ground for long periods (Singer and Avery, 2007).

FIGURE 21.4 Greenland GISP2 oxygen isotope curve for the past 10,000 years. The vertical axis is d18O, which is a temperature proxy. The red areas represent temperatures several degrees warmer than present. Blue areas are cooler times. Note the abrupt, shorteterm, cooling 8200 years ago and cooling from about 1500 to present. Plotted from data by Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in Greenland snow and ice with 103 to 105eyear time resolution. Journal of Geophysical Research 102, 26455e26470.

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FIGURE 21.5 Greenland GISP2 temperature reconstruction for the past 10,000 years based on ice core temperatures. The paleo-temperature reconstruction is essentially the same as shown by the d18O curve (Fig. 21.4). Modiﬁed from Cuffey, K.M., Clow, G.D., 1997. Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition. Journal of Geophysical Research 102, 26383e26396.

FIGURE 21.6 The 8200-year BP sudden climate change, recorded in oxygen isotope ratios in the GISP2 ice core, lasted about 200 years. Plotted from data by Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in Greenland snow and ice with 103 to 105eyear time resolution. Journal of Geophysical Research 102, 26455e26470.

FIGURE 21.7 Greenland GISP2 oxygen isotope ratios for the past 5000 years. Red areas are warm periods and blue areas are cool periods. Virtually all of the past 5000 years was warmer than present until about 1500 years ago. Plotted from data by Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in Greenland snow and ice with 103 to 105eyear time resolution. Journal of Geophysical Research 102, 26455e26470.

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2.3.3 Medieval Warm Period (900e1300 AD) The Medieval Warm Period (MWP) is the most contentious of the late Holocene climatic oscillations because of claims by the Intergovernmental Panel on Climate Change (IPCC) and CO2 alarmists that it didn’t really happen, ie, the basis for the infamous “hockey stick” assertion of no climate changes until CO2 increase after 1950. Oxygen isotope data from the GISP2 Greenland ice core clearly show a prominent MWP (Fig. 21.8) between 900 and 1300 AD. It was followed by global cooling and the beginning of the Little Ice Age. The MWP is also conspicuous on reconstruction of sea surface temperature near Iceland (Fig. 21.9; Sicre et al., 2008). As shown by numerous studies using a wide variety of methods, the MWP was a period of global warming. One example among many is the study of tree rings in China (Fig. 21.10; Liu et al., 2011). Historical accounts conﬁrm the worldwide occurrence of the MWP. It was a time of warm climate from about 900 AD to 1300 AD. Its effects were evident in Europe, where grain crops ﬂourished, alpine tree lines rose, many new cities arose, and the population more than doubled. The Vikings took advantage of the climatic amelioration to colo- nize Greenland, and wine grapes were grown as far north as England, where growing grapes is now not feasible, and about 500 km north of present vineyards in France and Germany. Grapes are presently grown in Germany up to el- evations of about 560 m, but from about 1100 AD to 1300 AD., vineyards extended up to 780 m, implying temperatures warmer by about 1.0e1.4 C. Wheat and oats were grown around Trondheim, Norway, suggesting climates about 1 C warmer than present (Fagan, 2000). Elsewhere in the world, prolonged droughts affected the southwestern United States and Alaska warmed. Sed- iments in central Japan record warmer temperatures. Sea surface temperatures in the Sargasso Sea were approxi- mately 1 C warmer than today (Keigwin, 1996), and the climate in equatorial east Africa was drier from 1000 AD to 1270 AD. An ice core from the eastern Antarctic Peninsula shows warmer temperatures during this period.

FIGURE 21.8 Oxygen isotope curve from the GISP2 Greenland ice core. (Red ¼ warm, blue ¼ cool.) Plotted from data by Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in Greenland snow and ice with 103 to 105eyear time resolution. Journal of Geophysical Research 102, 26455e26470 data.

FIGURE 21.9 Summer sea surface temperatures near Iceland (Sicre et al., 2008).

IX. CLIMATE PREDICTIONS 2. THE PAST IS THE KEY TO THE FUTURE: LESSONS FROM PAST GLOBAL CLIMATE CHANGES 401

FIGURE 21.10 Temperature reconstruction from tree rings in China. (Red ¼ warm, blue ¼ cool.) Modiﬁed from Liu, Y., Cai, Q.F., Song, H.M., et al., 2011. Amplitudes, rates, periodicities and causes of temperature variations in the past 2485 years and future trends over the central-eastern Tibetan Plateau. Chinese Science Bulletin 56, 2986e2994.

Oxygen isotope studies in Greenland, Ireland, Germany, Switzerland, Tibet, China, New Zealand, and elsewhere, plus tree-ring data from many sites around the world, all confirm the existence of a global MWP. Soon and Baliunas (2003) found that 92% of 112 studies showed physical evidence of the MWP, only 2 showed no evidence, and 21 of 22 studies in the Southern Hemisphere showed evidence of Medieval warming. Evidence of the MWP at specific sites is summarized in Fagan (2007) and Singer and Avery (2007). Evidence that the MWP was a global event is so widespread that one wonders why Mann et al. (1998) ignored it. Over a period of many decades, several thousand papers were published establishing the MWP from about 900 ADto 1300 AD. Thus, it came as quite a surprise when Mann et al. (1998), on the basis of a single tree-ring study, concluded that neither the MWP nor the Little Ice Age actually happened and that assertion became the official po- sition of the 2001 Intergovernmental Panel on Climate Change (IPCC). The IPCC 3rd report (Climate Change, 2001) totally ignored the several 1000 publications detailing the global climate changes during the MWP and the LIA and used the Mann et al. single tree-ring study as the basis for the now-famous assertion that “Our civilization has never experienced any environmental shift remotely similar to this. Today’s climate pattern has existed throughout the entire history of human civilization” (Gore, 2007). This claim was used as the main evidence that increasing atmospheric CO2 was causing global warming, and so, as revealed in the “Climategate” scandal, advocates of the CO2 warming theory were very concerned about the strength of data showing that the MWP was warmer than the 20th century and had occurred naturally, long before atmospheric CO2 began to increase. The Mann et al. “hockey stick” temperature curve was at so at odds with thousands of published papers, one can only wonder how a single tree-ring study could purport to prevail over such a huge amount of data. McIntyre and McKitrick (2003) and McKitrick and McIntyre (2005) evaluated the data in the Mann paper and concluded that the Mann curve was invalid “due to collation errors, unjustifiable truncation or extrapolation of source data, obsolete data, geographical location errors, incorrect calculation of principal components and other quality con- trol defects”. Thus, the “hockey stick” concept of global climate change is now widely considered totally invalid and an embarrassment to the IPCC.

2.3.4 The Little Ice Age At the end of the MWP w1300 AD, temperatures dropped sharply and the colder climate that ensued for several centuries is known as the Little Ice Age (LIA). The cooling was devastating. Temperatures of the cold winters and cool, rainy summers were too low for growing of cereal crops, resulting in widespread famine and disease (Fagan, 2000; Grove, 2004). Glaciers in Greenland advanced and pack ice extended southward in the North Atlantic. Glaciers expanded worldwide. Temperature changes during the LIA are well shown in various paleo-temperature data (Figs. 21.7e21.10). The population of Europe had become dependent on cereal grains as a food supply during the MWP, and when the colder climate, early snows, violent storms, and recurrent ﬂooding swept Europe, massive crop failures occurred. Three years of torrential rains that began in 1315 led to the Great Famine of 1315e17. The Thames River in London froze over, the growing season was signiﬁcantly shortened, crops failed repeatedly, and wine production dropped sharply. Winters during the LIA were bitterly cold in many parts of the world. Advance of glaciers in the Swiss Alps in the mid-17th century (Fig. 21.11) gradually encroached on farms and buried entire villages. The Thames River and ca- nals and rivers of the Netherlands frequently froze over during the winter (Fig. 21.12). New York Harbor froze in the winter of 1780 and people could walk from Manhattan to Staten Island. Sea ice surrounding Iceland extended for miles in every direction, closing many harbors. The population of Iceland decreased by half and the Viking colonies

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FIGURE 21.11 Advance of the Rhone glacier during the Little Ice Age.

FIGURE 21.12 Cold conditions in Europe during the Little Ice Age.

in Greenland died out in the 1300s because they could no longer grow enough food there. In parts of China, warm weather crops that had been grown for centuries were abandoned. In North America, early European settlers experienced exceptionally severe winters. Global temperatures have ﬂuctuated about 1 F per century since the cooling of the LIA, but the warming has not been continuous. Numerous w30-year warming periods have been interspersed with w30-year cooling periods. Oxygen isotope data dating back to 1480 AD from the GISP2 ice core show about 40 periods of warming/cooling (Fig. 21.13). The average time span of each warm/cool period is about 27 years. As shown by Fig. 21.13, the LIA was not a single period of global cooling, but rather multiple cold periods sepa- rated by warm periods beginning about 1300 AD and continuing into the 20th century. One of the strongest periods of cooling occurred during the Maunder Solar Minimum from 1650 AD to 1700 AD (Maunder, 1894, 1922; Eddy, 1976, 1977). Other notable cool intervals were the Dalton Solar Minimum (1790e1820 AD), the 1890 to 1915 cool period, and the 1945 to 1977 cool interval. Numerous others also occurred. The importance of these climate ﬂuctuations is that they show long-standing evidence of cool/warm cycles over many centuries when CO2 could not possibly have been the cause.

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FIGURE 21.13 Oxygen isotope curve from the GISP2 Greenland ice core showing the warm/cool oscillation of temperatures over the past 500 years. The average length of each warm/cool cycle was 27 years. The cool periods correspond to solar minima.

During each warm cycle, glaciers retreated, and during each cool cycle, glaciers advanced. However, because each warm cycle was slightly warmer than the previous one, and each cool cycle not quite as cool as the previous one, glacier termini have progressively receded upvalley from their LIA maximums.

2.3.5 Climate Changes During the Past Century The climate has changed five times since 1850 (Fig. 21.14). The 1850e80 warm period was comparable to the two warm intervals that occurred in the 20th century. Atmo- spheric temperature measurements, glacier fluctuations, and oxygen isotope data from Greenland ice cores record a cool period from about 1880 to about 1915. Glaciers advanced, some nearly to the terminal positions reached during the LIA. Many cold temperature records in North America were set during this period. Global temperatures rose steadily in the 1920s, 1930s, and early 1940s. By the mid-1940s, global temperatures were about 0.5 C (0.9 F) warmer than they had been at the turn of the century. More high-temperature records for the century were recorded in the 1930s than in any other decade of the 20th century. Global temperatures began to cool in the mid-1940s at the point when CO2 emissions began to soar. Many of the world’s glaciers advanced during this time, and recovered a good deal of the ice lost during the 1915e45 warm period. Although CO2 emissions soared during this interval, he climate cooled, just the opposite of what should have happened if CO2 caused global warming. The global cooling that prevailed from 1945 to 1977 ended abruptly in 1977 when the Pacific Ocean shifted from its cool mode to its warm mode, and global temperatures began to rise, initiating two decades of global warming. The year 1977 has been called the year of the “Great Climate Shift.” During the ensuing warm period from 1978 to w2000, alpine glaciers retreated and Arctic sea ice diminished. The abruptness of the shift in Pacific sea-surface temperatures and corresponding change from global cooling to global warming in 1977 is highly significant and strongly

FIGURE 21.14 Global temperatures since 1850. Six global climate changes have occurred since 1850, three periods of warming and three periods of cooling. The 1850e80 and 1915e45 warming intervals were of similar magnitude and intensity to the 1977e99 warming but occurred without any signiﬁcant change in CO2.

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FIGURE 21.15 The abrupt 1977 climate change from cooling to warming occurred with no relationship to CO2.

suggests a cause-and-effect relationship. The rise of atmospheric CO2, which accelerated after 1945, shows no sudden change that could account for the “Great Climate Shift” (Fig. 21.15).

3. SIGNIFICANCE OF PAST GLOBAL CLIMATE CHANGES

The most striking thing about climate changes in the late Pleistocene is the large magnitude of the changes over very short periods of time (w20 F/ century). These are vastly greater than any climate changes that occurred in the past few centuries. Carbon dioxide always lags temperature and, thus, cannot have anything to do with causing these dramatic climate changes. Nor can these climate changes be caused by orbital changes of the Earth (Milankovitch cycles) because orbital changes occur far too slowly to account for such multiple, abrupt changes. As shown by the data above, the pattern of multiple climate changes in the geologic past reveals repeated warm/ cool cycles. What this means is that these recurring cycles can be projected into the future to predict possible forth- coming climates. A critical aspect of this method is how consistent the warm/cool cycles have been in the geologic past. Since 1850, six climate changes have occurred, three warm periods and three cool periods (Fig. 21.14), averaging 30 years in length. Forty warm/cool cycles averaging 27 years each have occurred since 1480 AD (Fig. 21.13). Eighty warm/ cool cycles averaging 28 years appear in the GISP2 ice core record over the past 1200 years (Fig. 21.16).

FIGURE 21.16 GISP2 oxygen ice core curve showing oscillating pattern of warm/cool periods. Each warm/cool cycle lasts an average of 28 years, the same as the PDO. Plotted from data by Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in Greenland snow and ice with 103 to 105eyear time resolution. Journal of Geophysical Research 102, 26455e26470.

IX. CLIMATE PREDICTIONS 4. CORRELATION OF TEMPERATURE CYCLES AND THE PACIFIC DECADAL OSCILLATION 405

The pattern of warm/cool cycles, averaging 27e30 years, appears to have been consistent over the past 1200 years. Thus, we can project this pattern into the future to predict what the climate will most likely be.

4. CORRELATION OF TEMPERATURE CYCLES AND THE PACIFIC DECADAL OSCILLATION

The Pacific Decadal Oscillation (PDO) refers to cyclical variations in sea surface temperatures in the Pacific Ocean. The PDO index is defined as the leading principal component of North Pacific monthly sea surface temperature variability (poleward of 20N for the 1900e93 period). A summary of the PDO is given in D’Aleo and Easterbrook (2011 and this volume). It was discovered in the mid-1990s by fisheries scientists studying the relationship between Alaska salmon runs, Pacific Ocean temperatures, and climate. Hare (1996) and Mantua et al. (1997) found that cyclical variations in salmon and other fisheries correlated with warm/cool changes in Pacific Ocean temperatures that followed a regular pattern. Each warm PDO phase lasted about 25e30 years and then switched to the cool mode for 25e30 years. Fig. 21.17 shows the cold and warm modes of the PDO. During a typical PDO cold mode, cool sea surface temperatures extend from the equator northward along the coast of North America into the Gulf of Alaska. During a typical PDO warm mode, warm sea surface temperatures extend from the equator northward along the coast of North America into the Gulf of Alaska. Fig. 21.18 shows the PDO from 1900 to 2015. The PDO was cool from 1890 to 1915, warm from 1915 to 1945, cool from 1945 to 1977, warm from 1977 to w2000, and cool from 2001 to 2016. Global temperatures are tied directly to sea-surface temperatures. When sea-surface temperatures are cool (cool- phase PDO), global climate cools. When sea-surface temperatures are warm (warm-phase PDO), the global climate warms, regardless of any changes in atmospheric CO2 (Easterbrook, 2005, 2008a,b). Fig. 21.19 shows the correlation between the PDO, advance and retreat of glaciers on Mt. Baker, Washington, and global climate. When the PDO is positive (warm), glaciers retreat and the global climate warms. When the PDO is negative (cool), glaciers advance, and the global climate warms. During the past century, global climates have consisted of two cool periods (1880e1915 and 1945e77) and two warm periods (1915e45 and 1977e2000). In 1977, the PDO switched abruptly from its cool mode, where it had been since about 1945, into its warm mode and global climate shifted from cool to warm. This rapid switch from cool to warm has become to known as “the Great Pacific Climatic Shift” because it happened in just 1 year. Atmo- spheric CO2 showed no unusual changes across this sudden climate shift (Fig. 21.15), and thus was clearly not responsible for it. Similarly, the global warming of 1915e45 could not have been caused by increased atmospheric

FIGURE 21.17 In 1945, the PDO (Paciﬁc Decadal Oscil- PDO COLD MODE (1945-77) PDO WARM MODE (1977-98) lation) switched from its warm mode to its cool mode and global climate cooled from then until 1977, despite the soaring of CO2 emissions. In 1977, the PDO switched back from its cool mode to its warm mode, initiating what is regarded as “global warming” (from 1977 to w2000).

Great Pacific Climate Shift

PDO index: 1900 -January 2008 2 4

0 0

–2

–4 1900 1920 1940 1960 1980 –2 Year 1900 1920 1940 1960 1980 2000

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FIGURE 21.18 PDO from 1900 to 2015 showing warm and cool periods. Modiﬁed from Spencer and JISAO, University of Washington.

FIGURE 21.19 PDO, global temperature, and glacier advance and retreat.

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CO2 because that time preceded the rapid rise of CO2 emissions after 1945. When CO2 began to increase rapidly after e 1945, 30 years of global cooling ensued (1945 77), just the opposite of what should have happened if CO2 causes global warming. Each time this has occurred in the past century, global temperatures have remained cool for about 30 years. Thus, the current cool PDO not only explains the absence of any global warming for the past 18½ years, but also assures that cool temperatures will continue for several more decades (Easterbrook, 2001, 2006a,b, 2007, 2008c).

5. THE ATLANTIC MULTIDECADAL OSCILLATION

The Atlantic Ocean also has multidecadal warm and cool modes with periods of about 30 years, much like the PDO. With the Atlantic Multidecadal Oscillation (AMO), during warm phases, the Atlantic is warm in the tropical North Atlantic and far North Atlantic and relatively cool in the central area. During cool phases, the tropical area and far North Atlantic are cool and the central ocean is warm. For a more detailed discussion, see D’Aleo and Easterbrook (2010, 2011 and this volume).

6. WHERE IS CLIMATE HEADED DURING THE COMING CENTURY?

6.1 IPCC Predictions What does the century have in store for global climates? According to the IPCC, the Earth is in store for climatic catastrophe this century. Computer models predict global warming of as much as 5e6 C (10e11 F) by 2100, predicated on the assumption that global warming is caused by increasing atmospheric CO2 and that CO2 will continue to rise. According to the IPCC (IPCC-AR4, 2007), the ramiﬁcations of such an increase in global warming would be far reaching, even catastrophic in some areas. They predicted that by now the Arctic Ocean would be completely free of sea ice; the Greenland Ice Sheet would melt; alpine glaciers would retreat rapidly, resulting in decreased water supply in areas that depend on snowmelt; melting of Greenland and Antarctic ice would cause sea level to rise sharply, drowning major cities and ﬂooding low coastal areas; crops would fail, resulting in widespread food shortages for people in agriculturally marginal areas; wheat/grain belts would have to shift northward; droughts would become increasingly severe in dry areas; environmental impacts would be severe, resulting in extinction of some species and drastic population decreases in other. All of these disasters are predicated on computer models that assume rising atmospheric CO2 will cause catastrophic warming. Computer models predictions have been around long enough now that their earlier predictions can be checked against what really happened. Fig. 21.20 shows a comparison of 90 computer model predictions and actual surface and satellite temperature measurements. The computer models failed miserably to come even close to accurate predictions.

6.2 Predictions Based on Past Cyclic Climate Patterns In 2000, I used past warming and cooling cycles over the past 1200 years and historical PDO cycles to accurately predict the end of the 1977e2000 warm period and predicted 25e30 years of global cooling. How well has this prediction (Easterbrook, 2001) compared with actual temperature measurements since then? Fig. 21.22 shows a slight cooling trend in satellite (RSS) temperatures since 2000. Fig. 21.23 shows a slight cooling trend in HADCRUT surface temperature measurements. Fig. 21.24 shows a slight cooling trend in NOAA surface measurements in the United States. In contrast, computer models predicted up to 1 C of global warming per decade. In light of evidence of global cooling since 2000, how can NOAA and NASA contend that virtually every year recently is the hottest ever recorded? Chapter 2 documents the wholesale corruption of surface temperature data, showing that NASA and NOAA data are no longer credible. Only the satellite data is uncorrupted and it shows no global warming for the past 18½ years. The patterns of two kinds of data may be used to predict future climate: recurring cycles of global temperature and recurring PDO cycles. In 1999, the PDO abruptly switched from its warm mode to its cool mode and the 1978 to 1998 warm period ended, succeeded by slight cooling from 2000 to 2015. As shown in Fig. 21.21, the recurring pattern of the PDO for the past century has been alternating warm/cool periods having a duration averaging

IX. CLIMATE PREDICTIONS 408 21. USING PATTERNS OF RECURRING CLIMATE CYCLES TO PREDICT FUTURE CLIMATE CHANGES

FIGURE 21.20 Comparison of computer model temperature predictions and actual temperature measurements. The models failed dismally. Modiﬁed from Spencer.

FIGURE 21.21 PDO from 1900 projected to 2035. Extending the long-term cyclic trend suggests global cooling until 2035.

25e30 years. Now that the PDO has shifted into its cool phase, if we project the previous cool period (1945e77) into the future, we should have global cooling for 25e30 years (Fig. 21.21). The recurring pattern of temperature changes can also be used to predict future climates. Fig. 21.25 shows the HADCRT3 global surface temperature for the past century. This record can be extended 1200 years into the past 6. WHERE IS CLIMATE HEADED DURING THE COMING CENTURY? 409

FIGURE 21.22 Satellite temperatures (RSS) from 2000 to 2015 showing a slight cooling trend.

FIGURE 21.23 HADCRUT surface temperature measurements from 2000 to 2012.

using GISP2 Greenland ice core data (Fig. 21.16). These data show recurring warm/cool intervals lasting 25e30 years, so if we project the same pattern into the future, we should have global cooling for the next three decades. There have been two cycles of global cooling in the past century: 1890 to 1915 and 1945 to 1977. Because HADCRUT has essentially erased the 1945e77 cooling, the 1890e1915 cooling has been grafted onto Fig. 21.25 as the most likely prediction of future global climate. The qualitative prediction of global cooling for the next three decades is straightforward, based on projection of the recurring cycles of PDO and global temperatures (Figs. 21.21 and 21.25). However, quantifying this prediction is more difﬁcult because, going back in time, each of the cool periods was more intense than those that followed. Thus if the coming cool period resembles the 1890e1915 cool phase, we will have the magnitude of cooling shown on the projected temperatures in Fig. 21.25. However, the sun has just entered a Grand Solar Minimum, so if cooling resembles the last time this happened (the Dalton Solar Minimum), cooling will be more intense than that shown on Fig. 21.25. The cooling might even resemble that of the Maunder Solar Minimum, and much colder temperatures could prevail (Easterbrook, 2010; Easterbrook et al., 2013). We have no way to predict just how intense the coming cooling will be, so time will tell.

IX. CLIMATE PREDICTIONS 410 21. USING PATTERNS OF RECURRING CLIMATE CYCLES TO PREDICT FUTURE CLIMATE CHANGES

FIGURE 21.24 NOAA temperature measurements from 2005 to 2014 in the United States show a cooling trend.

FIGURE 21.25 Projected climate for the century based on recurring climatic patterns over the past 1200 years. The projected cooling is based on repeating of the 1880 to 1915 cool period over the next three decades.

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IX. CLIMATE PREDICTIONS