Little Ice Age (Regional - Asia: China) – Summary

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In an attempt to rewrite climatic history, certain scientists have claimed that the Little Ice Age and Medieval Warm Period were neither global in extent nor strong enough where they did occur to have a discernable influence on mean global air temperature.  By doing so, they have made the putative dramatic warming of the latter part of the 20th century appear highly unusual, which they equate with anthropogenic-induced, which they associate with the historical rise in the air's CO2 content, which gives them a pretense to call for huge reductions in the use of fossil fuels, which we believe to be unwarranted.  Hence, we continually search the emerging scientific literature for evidence that the Little Ice Age and Medieval Warm Period were truly significant global events.  This summary reports what we have learned over the past few years about the Little Ice Age in China.

Hong et al. (2000) developed a 6000-year high-resolution ð¹⁸O record from cellulose deposited in a peat bog in the Jilin Province of China from which they inferred the temperature history of that location over the past six millennia.  In comparing this record with a previously-derived ð¹⁴C tree-ring record of the intensity of solar activity, they found "a remarkable, nearly one to one, correspondence between the changes of atmospheric ð¹⁴C and the variation in ð¹⁸O of the peat cellulose," implying that the climate changes they observed had been "forced mainly by solar variability."  One of these solar-induced regimes, as they describe it, was "an obvious warm period represented by the high ð¹⁸O from around AD 1100 to 1200, which may correspond to the Medieval Warm Epoch of Europe," while the regime that followed it was the cooler Little Ice Age, which was also likely induced by the sun.

In a somewhat similar study, Xu et al. (2002) examined plant cellulose ð¹⁸O variations in cores retrieved from peat deposits west of Hongyuan County at the northeastern edge of the Qinghai-Tibetan Plateau.  Following the demise of the Roman Warm Period, they detected three consistently cold events centered at approximately AD 500, 700 and 900, during the Dark Ages Cold Period.  Then, from AD 1100-1300, they report that "the ð¹⁸O of Hongyuan peat cellulose increased, consistent with that of Jinchuan peat cellulose and corresponding to the 'Medieval Warm Period'."  Finally, they note that "the periods AD 1370-1400, 1550-1610, [and] 1780-1880 recorded three cold events, corresponding to the 'Little Ice Age'."

Chen et al. (2000) studied sediment cores from Erhai Lake on the Yun-Gui Plateau, reconstructing a temperature history of that region for the 700-year period 1290-1990.  The two coldest intervals of this period occurred during the 14th century and from about 1550 to 1800.  Of the latter cold period, Chen et al. say it "may be the imprint left of the Little Ice Age."  And to be sure we get the point, they repeat this statement twice more.  Hence, it would be safe to say that Chen et al. do not subscribe to the climate-alarmist claim that the Little Ice Age was confined to countries bordering the North Atlantic basin.  Also, their statement that "the global warming at the beginning of this century continued until the 1940s" does not bode well for the climate-alarmist claim of "unprecedented" warming over the latter part of the 20th century.

Reporting on a second study of lake sediments that were extracted from Lake Chen Co in the Yamzhog Yum Co drainage basin of southern Tibet in the delta of the Kaluxiong River, Zhu et al. (2003) state that "the 'Middle Ages Warm-period' (around ca. 1120-1370 AD) was demonstrated by recent studies in China (Zhang, 1993)," and for this same time period, they say their newest data reveal "a warm-humid stage."  This period was followed by what they call "an intensively cold stage during ca. 1550-1690 AD, a cold-humid stage from ca. 1690-1900 AD and a warm-dry stage since ca. 1900 AD."  However, Zhu et al. note that the warm period of the past century, which followed the Little Ice Age, was not as warm as the earlier 250-year warm period of the Middle Ages.

Also working with lake sediment data were Zhang et al. (2004), who developed a salinity history of Qinghai Lake (the largest inland saline lake in China) for the period AD 1100-2000 using ostracod shell-length information derived from a 114-cm sediment core and a relationship between ostracod shell-length and salinity that was developed by Yin et al. (2001) from data gathered from fifty lakes of different salinities scattered across the Tibetan Plateau.  They report that "low salinity during 1160-1290 AD showed the humid climate condition [of] the Medieval Warm Period in this area, while the high salinity during 1410-1540 AD, 1610-1670 AD and 1770-1850 AD [corresponded with] the three cold pulses of the Little Ice Age with a dry climate condition," where the evidence for the occurrence of these warm and cold intervals comes from the climate change studies of Yao et al. (1990) and Wang (2001).

In another study of Qinghai Lake, Ji et al. (2005) used reflectance spectroscopy on a sediment core to obtain a continuous high-resolution proxy record of the Asian monsoon over the past 18,000 years.  Their data indicated that monsoonal moisture since the late glacial period was subject to "continual and cyclic variations," among which was a "very abrupt onset and termination" of a 2,000-yr dry spell that started about 4200 yr BP and ended around 2300 yr BP.  Other variations included the well-known centennial-scale cold and dry spells of the Dark Ages Cold Period and Little Ice Age, which lasted from 2100 yr BP to 1800 yr BP and 780 yr BP to 400 yr BP, respectively.  Sandwiched between them was the warmer and wetter Medieval Warm Period, while preceding the Dark Ages Cold Period was the Roman Warm Period.  Time series analysis of the sediment record revealed statistically significant periodicities (above the 95% level) of 123, 163, 200 and 293 yr, the 200-yr periodicity of which corresponds well with the de Vries or Suess solar cycle and implies that change in solar activity is an important trigger for some of the cyclic environmental changes at Qinghai Lake.

Working in Inner Mongolia, Jin et al. (2004) analyzed percent organic carbon and Rb/Sr ratios in a sediment core extracted from the deepest part of Daihai Lake, which is located "in the transitional zone between semi-arid and semi-humid conditions that is sensitive to East Asian monsoon variability."  They report that both data sets "support two distinct Little Ice Age cooling events centered at ~850 yr BP and ~150 yr BP," as well as "the Medieval Warm Period between 1200 and 900 yr BP," which they say "was warmer than the present, with higher chemical weathering than at present," additionally citing the study of Jin et al. (2002) to this effect.

In tropical South China, Chu et al. (2002) studied the geochemistry of sediments recovered from seven cores taken from three locations in Lake Huguangyan on the low-lying Leizhou Peninsula, assisted by additional information relative to the presence of snow, sleet, frost and frozen rivers over the past 1000 years obtained from historical documents.  They report that "cold winter events over the past 1000 years in tropical South China are concentrated in three time intervals during the Little Ice Age at c. AD 1480-1550, 1670-1730 and 1830-1900," noting that this distribution of cold events agrees well with results obtained from phenological studies (flowering seasons of peach, apricot, clove, etc.) that depict cold intervals at AD 1470-1520, 1620-1720 and 1840-1890 (Chu, 1973).  In addition, they report that "recent publications based on the phenological phenomena, distribution patterns of subtropical plants and cold events (Wang and Gong, 2000; Man, 1998; Wu and Dang, 1998; Zhang, 1994) argue for a warm period from the beginning of the tenth century AD to the late thirteenth century AD," as their own data also suggest.  Their data further indicate that floods were quite common during the Little Ice Age, while two major dry periods occurred during the Medieval Warm Period; and they say that "local historical chronicles support these data and suggest that the climate of tropical South China was dry during the 'Mediaeval Warm Period' and wet during the 'Little Ice Age'."

Turning to other types of palaeoclimate information, Qian and Zhu (2002) analyzed several data sets related to Holocene climate change in China, one of which was an 1100-year record of annual calcite accumulation derived by Qin et al. (1999) from a stalagmite found in Shihua Cave, Beijing.  The sequence of laminae thickness in this stalagmite, which provides a history of the hydrologic balance of the surrounding area, revealed the existence of a relatively wet Medieval Warm Period running from approximately AD 940 to 1200 and a relatively dry Little Ice Age that was most strongly expressed between 1400 and 1800.  One of the driving forces behind their study was "the question of whether warming similar to the recent occurred before the Little Ice Age."  Their analysis of the Beijing stalagmite data indicated that most of the AD 940 to 1200 period was indeed equivalent to the most outstanding portions of the 20th century with respect to moisture availability, suggesting that the temperatures of that earlier period may well have been equivalent too.

In another study of a stalagmite, this one from Jingdong Cave about 90 km northeast of Beijing, Ma et al. (2003) assessed the climatic history of the past 3000 years at 100-year intervals on the basis of ð¹⁸O data, the Mg/Sr ratio, and the solid-liquid distribution coefficient of Mg.  Between 200 and 500 years ago (aBP), they report that "air temperature was about 1.2°C lower than that of the present, corresponding to the Little Ice Age in Europe."  Earlier, between 1000 and 1300 aBP, there was an equally aberrant but warm period that peaked at about 1100 aBP, which they say "corresponded to the Medieval Warm Period (AD 900-1300) in Europe."  This period of peak warmth was in turn preceded by what has come to be called the Dark Ages Cold period, which was preceded by the Roman Warm Period.

Further south, Paulsen et al. (2003) used high-resolution records of ð¹³C and ð¹⁸O in a stalagmite from Buddha Cave (33°40'N, 109°05'E) to infer changes in climate in central China for the last 1270 years in terms of warmer, colder, wetter and drier conditions.  Among the climatic episodes evident in their data were "those corresponding to the Medieval Warm Period, Little Ice Age and 20th-century warming, lending support to the global extent of these events."  Specifically, their record begins in the depths of the Dark Ages Cold Period, which ends about AD 965 with the commencement of the Medieval Warm Period, which continues to approximately 1475, whereupon the Little Ice Age sets in and holds sway until about 1825, after which the warming responsible for the Modern Warm Period begins.

Moving from caves to deserts, Jin et al. (2004) analyzed magnetic susceptibility (related to summer monsoon intensity), organic matter (related to vegetation coverage and biomass), and granularity (related to wind speed) associated with samples of "six aeolian sand layers overlapping six sandy paleosol layers" that comprise "an uninterrupted and whole stratigraphic profile" of the Hunshandake Desert in the eastern part of Inner Mongolia.  They report that power spectrum analysis of the magnetic susceptibility data revealed two periodicities, one of 1465 years that "approximates to the 1450-year period of the North Atlantic Ice floating event and to the arid-humid cycle of 1450-1470 years in Arabia (Pinegina et al., 2003; Sirocko et al., 1996)."  With respect to the most recent 1800-year segment of this pervasive oscillation, they say that "cold events occurred in many regions of China during 240-800 AD (Yang et al., 2002)," which cool interval comprised the Dark Ages Cold Period, after which a "warming event happened in Daihai Lake in the southern part of the study region during 1.2-0.9 kaBP (Jin et al., 2002), and most of the China region had warming event records during 800-1400 AD (Yang et al., 2002) ... which indicated that this was the Medieval Warm Period."  Then, between AD 1300 and 1800, Jin et al. say their data recorded the last cold event of their study, and that "the extreme of this cold event took place at about 400 aBP, corresponding to the Little Ice Age cold event."  Last of all, they state that "the arid events of the study area coincided with the cold events in [the] North Atlantic and arid events in middle to low latitudinal zones, which indicated that the periodical change of Holocene climate in Hunshandake Desert has global significance."

In another comprehensive study, Yang et al. (2002) used nine separate proxy climate records derived from peat, lake sediment, ice core, tree ring and other proxy sources to compile a single weighted temperature history for all of China spanning the past two millennia.  This record revealed five distinct climate epochs: a warm stage from AD 0 to 240 (the latter part of the Roman Warm Period), a cold interval between AD 240 and 800 (the Dark Ages Cold Period), a return to warm conditions from AD 800-1400 (which included the Medieval Warm Period between AD 800 and 1100), a cool interval between 1400 and 1820 (the Little Ice Age), and the current warm regime (the Modern Warm Period), which has so far not been the warmest of the three warm periods, that distinction being held by the Roman Warm Period during the second and third centuries AD.

Working with even more data, i.e., 200 different sets of phenological and meteorological records extracted from a number of historical sources, many of which are described by Gong and Chen (1980), Man (1990, 2004), Sheng (1990) and Wen and Wen (1996), Ge et al.(2003) produced a 2000-year history of winter half-year temperature (October to April) for the region of China bounded by latitudes 27 and 40°N and longitudes 107 and 120°E.  This work revealed that "from the beginning of the Christian era," as they describe it, "climate became cooler at a rate of 0.17°C per century," which correlates well with the fact that this is the period of time when the planet slipped out of the Roman Warm Period and entered into the Dark Ages Cold Period.  Around the AD 490s, for example, they note that "temperature reached about 1°C lower than that of the present (the 1951-80 mean)."  Then, they say "temperature entered a warm epoch from the AD 570s to 1310s with a warming trend of 0.04°C per century; the peak warming was about 0.3-0.6°C higher than present for 30-year periods, but over 0.9°C warmer on a 10-year basis."  Finally, "after the AD 1310s," Ge et al. report that "temperature decreased rapidly at a rate of 0.10°C per century; the mean temperatures of the four cold troughs were 0.6-0.9°C lower than the present, with the coldest value 1.1°C lower."  This, of course, was the Little Ice Age, from which the world appears to be still in processes of recovering.

In a follow-up study, Ge et al. (2004) say "it is important to study the temperature change during the past 2000 years for understanding the issues such as the greenhouse effect and global warming induced by human activities," stating additionally that "China has advantages in reconstructing historical climate change for its abundant documented historical records and other natural evidence obtained from tree rings, lake sediments, ice cores, and stalagmites."  Within this context, their most fundamental and important finding was the discovery of "an about 1350-year periodicity in the historical temperature change," which revealed a number of multi-century warm and cold periods.  Preceding the Modern Warm Period, for example, was the Little Ice Age, which "in China," in their words, "began in the early 14th century (the 1320s) and ended in the beginning of the 20th century (the 1910s)."  It included four cold stages and three short warming phases.  The Little Ice Age, in turn, was preceded by the Medieval Warm Period, which Ge et al. say "began in the 930s and ended in the 1310s."  It was composed of two warm stages, each of over 100 years duration, and a shorter intervening cold stage.  Further back in time, they found a cold period from the 780s to the 920s and a warm period from the 570s to the 770s, which was in turn preceded by a cold period from the 210s to the 560s, which they say "was the only one comparable with [the] Little Ice Age for the past 2000 years."  This cold spell, of course, was the Dark Ages Cold Period that followed on the heels of the Roman Warm Period.

In light of these several observations, it is clear that the Little Ice Age was manifest in China as a cold node of the millennial-scale oscillation of climate that brought this vast region, as well as most of the rest of the world, the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Modern Warm Period, which suggests there is nothing unusual about the planet's current state of warmth and, therefore, that there is no need to invoke the historical increase in the air's CO2 content as its cause.

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Last updated 19 October 2005