DDS014-「Disastrous climate change and the history of China」

〔註：這篇論文是我多年來，悉心研究「中國歷史」與「氣候變遷」的一些心得，為求審慎負責並便予更多的國際同好、學者、專家分享，謹以英文期刊論文的格式書寫。對於習於中文的讀者，我將於往後的「部落格」文中，以「科普」的方式另予重新整理陳述，敬請期待並不吝惠予指正。〕

David D. Sheu 

Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, Republic of China

daviddsheu@gmail.com

  

Abstract

Disastrous climate change accompanying prolonged droughts has been considered to play a key role in the collapse of human societies and ancient civilizations.  By using well-documented historic records and superimposing the years of the rises and falls of all dynasties in Chinese history on the reported temperature anomaly trend during the past two millennia, I show that the successive change of dynasties in Chinese history is no exception to this causative link and the entire history of China can be viewed as a series of devastating climate oscillations in China.  When temperatures plunged sharply from the norm, the long-lived dynasties were all overthrown by rebellions, mostly peasants, fleeing their homelands in search of food sources and shelters when large-scale famine and chaos occurred under such devastating climate conditions.  The shorter-lived dynasties, which represent the most turbulent periods in Chinese history, also all coincided with recurrent severe droughts when temperatures dropped and consistently remained well below the mean during prolonged cold episodes.  The case of China revealed in this study thus provides a real example of the potential threat of disastrous climate change to current and future societal stability and human civilizations.

Introduction

The potential impact of continuing increases in atmospheric CO₂ on the future climate has been a subject of intensive studies at different levels (IPCC, 2007). The abrupt and disastrous changes in climate accompanying prolonged droughts have been shown to play key roles in the downfall of ancient Akkadian, Andean, Mesopotamian and Mayan societies and civilizations (Weiss et al., 1993; Hodell et al., 1995; Binford et al., 1997; Cullen, et al., 2000; deMenocal, 2001; Weiss and Bradley, 2001; Hauq et al., 2003). The recorded history of China spans more than 2800 years, and the years of the rises and falls of all dynasties in Chinese history are well documented in chronological order (Feng, 2003; Kuo, 2003). Furthermore, China retains a variety of instrumental meteorological information sources, including the Local Chronicles, the Official Weather Reports and the Official Historical Documents, which can be used to identify extreme climatic events and help establish semi-quantitatively the overall climate variability in China (Wang and Zhang, 1988; Zhang and Crowley, 1989; Zhang, 1991; Song, 2000; Qian and Zhu, 2002; Ge et al., 2003; Qian et al., 2003).  Studies of paleoclimate proxy records derived from ice cores, tree rings, lake sediments, peat cellulose and laminated stalagmites provide further evidence of climate variations in China during the preceding 2-3 millennia (Lin et al., 1995; Sun et al., 1998; Sun, 2000; Wang and Gong, 2000; Wang et al., 2001; Hong et al., 2001; Yang et al., 2002; Paulsen et al., 2003; Tan et al., 2003; Xu, 2003; Yang et al., 2004).

Most of these studies however emphasize only climate fluctuations (mainly cold vs. warm temperatures and/or drought vs. flood) and broad temperature variation trend in China with scant attention to the impact of recurrent disastrous climates on the rise and fall of all dynasties throughout the full history of China. Here I use historic documents and superimpose the years of the rise and fall of each dynasty in Chinese history on the reconstructed “weighted” temperature anomaly trend (Yang et al., 2002) in China during the last two millennia to show that the successive changes of dynasties in Chinese history are, with no exceptions, coherent with a series of disastrous climate events in China, and that the entire history of China can be compiled in the context of disastrous climate changes in China.

Prehistory of China (pre-Qin dynasty)

A sketch of the important historic and climate-mediated events during the ancient Chinese history from 0 to 3,000 BC is presented chronologically in Figure 1. From 4,500 to 3,000 BP, the region along the bank of Huanghe (Yellow River) continued basking in the mild weather, and the first Chinese Kingdom, i.e., Huang-Te, was founded in 2,697 BC (the year generally regarded as the commencing year of Chinese history) (Feng, 2003; Kuo, 2003). After some 600 years of turmoil, the first dynasty of the Chinese empire, i.e. the Xia dynasty, was established in 2,070 BC. During this period, Chinese characters evolved from the earliest forms of hieroglyphs to modern words. The first year documented by the Official Almanac was dated in 841 BC during the Western Zhou dynasty, and the famous ancient chronicle, the Autumn-Spring, began documenting historical records from 722 BC during the Eastern Zhou dynasty (Kuo, 2003). The entire history of China has been well documented in script since then, and the years of the rise and fall of all successive dynasties have been dated in chronological order. Studies of fossil pollens reveal that, from 1,000 to 770 BC, during a cold period classified as the first Chinese Little Ice Age (CLIA I) by paleoclimatologists, the temperature in China plunged ~1.0 ^oC below average and many areas, including Yangtze and Han rivers, became deeply frozen (Liu, 1994). A rapidly deteriorating climate was evidenced by extended and repeated droughts (from 858 BC to 722 BC), and widespread crop failure and food shortage due to damage by huge swarms of locusts were first reported in 707 BC (Kuo, 2003). These factors led to prolonged violence from devastated peasants and invasion by the nomadic tribes from the north (Hong et al., 2001; Yang et al., 2002), forcing the Western Zhou dynasty to move eastward and ultimately succeed to the Eastern Zhou dynasty in 771 BC. According to historic records, the Eastern Zhou dynasty consisted of two distinct periods: the Spring and Autumn Annals (771-475 BC) and the Warring States Periods (475-221 BC). Historical documents further reveal that the climate was generally warm and wet during the Spring and Autumn Annals. However, towards the end of the period, the mild climate was punctuated by severe droughts. Such hostile climate led to further intense conflicts among various kingdoms and regional warlords and the Spring and Autumn Annals was ultimately succeeded by the Warring States Periods.

Dynastic changes in Chinese history (from the Qin to the Qing dynasty)

The fluctuating climate continued as the Qin dynasty rose to form the first unified Chinese empire in 221 BC. Due to the continuously worsening climate and widespread famine across the county, the Qin dynasty lasted merely 15 years despite its dictatorial rule and was overthrown by rebellions led respectively by Chenshan and Wukuang (Liu, 1994; Feng, 2003; Kuo, 2003). This was the first uprising of devastated peasants (209 BC) against the ruling empire documented in Chinese history (Fig. 1). During the Western Han (206 BC-AD 25) and the Eastern Han (AD 25-AD 221) dynasties, in addition to severe droughts and freezing temperatures, the Chinese empire suffered from invasions of various nomadic tribes along the northern border. The domestic turmoil and diplomatic wrangling together led to the end of the Western Han (AD 25) and the Eastern Han (AD 221) dynasties. Historical documents clearly record a large-scale famine (the Ginzhou famine) occurring in AD 17 until the uprising of the Lulin-Chimei rebellion that ousted the Western Han emperor in AD 25 (Kuo, 2003). From AD 109 to 194, severe weather conditions continued and the Eastern Han dynasty was overthrown by a 20-year rebellion, Huang-Jin, from AD 184 to 204. The Eastern Han dynasty collapsed in AD 221 (Fig. 2).

In this study, I superimpose the years of the rises and falls of all dynasties since the Eastern Han on the “weighted” temperature anomaly trend in China during the past two millennia as reconstructed by (Yang et al., 2002) (Fig. 2). The composite trend is thought to best represent the overall temperature variations in China because it is constructed by combining multiple paleoclimate proxy records obtained from ice cores, tree rings, lake sediments and historical documents, and takes into account the uneven spatial and temporal distribution of proxy records. As depicted, temperatures in China were above the mean between AD 0-250 with two peaks—one occurring around AD 25 and the other in AD 100-250—then decreased rapidly and stayed mostly below the mean until AD 600. From AD 600 to 1400, temperatures in China are characterized by decadal to centennial variability around the mean but the climate was noticeably punctuated with several severe cold periods centered around AD 900, 1150, and 1300. From AD 1400 to 1920, China entered the so-called Little Ice Age period, with prominent cold peaks around AD 1500, 1650 and 1850. Since the AD 1920s, temperatures have been rising rapidly. The rapid transitions between cold and warm periods over the past 2000 years that are revealed by this anomaly trend broadly match the winter half-year temperature fluctuations in the middle and lower reaches of the Yellow and Yangtze Rivers reconstructed by Ge et al. (2003) using phenological cold/warm events recorded in Chinese historical documents.

Figure 2 (above) further shows that, without exception, all major dynasties collapsed and were overthrown by rebellions during times when temperatures dropped sharply, namely, the Western Han dynasty (202 BC- AD 25) by the Lulin-Zhimei rebellion (AD 21-25), the Eastern Han dynasty (AD 25-220) by the Huang-Jin rebellion (AD 184-204), the Tang dynasty (AD 617-907) by the Huang-Chao rebellion (AD 867-884), the Yuan dynasty (AD 1279-1367) by the Hong-Jin rebellion (AD 1351-1367) and the Ming dynasty (AD 1367-1644) by the Zhang and Li (AD 1630-1644) rebellions. It also shows that the short-lived dynasties from 221 to 617 AD, including the Three Kingdoms (AD 221-263), Wei (AD 263-280), Western Jin (AD 280-316) and Eastern Jin (AD 316-417), Northern and Southern Dynasties (AD 417-589), Sui (AD 589-617) and the Five Dynasties and Ten Kingdoms (AD 907-960)—the most turbulent periods in Chinese history—all coincided with severe droughts and cold episodes when temperatures were well below the mean. The pronounced cold spells during the Northern and Southern Dynasties (AD 417-589), the late Tang dynasty and the mid-Ming dynasty are revealed by the 2,650-year stalagmite record from Shihua Cave, Beijing, China (Tan et al., 2003). The prolonged cold phases during the Ming and early Qing dynasties with the three prominent cold peaks (Fig. 2) are commonly referred to the Chinese Little Ice Age IV to VI (CLIA IV-VI) (Liu, 1994; Lin et al., 1995; Wang et al., 2001; Qian and Zhu, 2002) that occurred between fifteenth and nineteenth century. The three cold peaks shown in Figure 2 are also identified in the 1,270-year high-resolution d¹⁸O stalagmite record from Buddha Cave, China (Paulsen et al., 2003).

A conceptual model for understanding the dynastic changes

Figure 3 depicts a conceptual model for helping explain how severe climate variability could have affected prehistoric China and the dynastic changes in modern Chinese history. The model emphasizes the importance of the physiography of China (Zhang and Crowley, 1989; Sun et al., 1998; Sun, 2000). The present-day China borders span 74^oE to 135^oE and 18^oN to 53^oN, covering a vast land mass of ~9.6 x 10⁶ km² that stretches over 5,200 km from east to west and over 5,500 km from north to south. Two-thirds of the total land area is occupied by high mountain ranges, hills, plateaus and deserts in the north and west, while eastern and southern China is predominated by lowlands and plains. Because of China’s extensive territory and complex geomorphology, the climate in China is highly variable and diversified.  With the additional effect of alternating dry and wet monsoons, the climate in China can be divided diagonally from northeast to southwest into two highly contrasting patterns: the western and northwestern part of the country is dominated by dry, cold weather, while eastern and southeastern China is mostly wet and warm. The climatic divide in China preordains the dynastic succession from the west to the east (e.g., the Western Zhou to the Eastern Zhou, the Western Han to the Eastern Han, and the Western Jin to the Eastern Jin dynasties) and from the north to the south (e.g., the Northern Song to the Southern Song dynasties). This is owing to the fact that when the climate starts to deteriorate, it always begins from the northern and western parts of China, then spreads southeastwardly across the entire country.

The contrasting climate patterns have also led the ancient Chinese to develop two distinct living styles and types of settlements, namely (1) the agriculture-oriented Han race that nurtured ancient Chinese civilization around the middle reach of the Huang He (Yellow River) in the central part of China and established the first Chinese empire (i.e., the Xia dynasty) in 2,070 BC, and (2) the nomadic tribes that occupied and roamed the northern and western parts of China. When the climate was mild, the nomadic tribes settled separately from and at peace with the Han race. Once the climate deteriorated, however, the nomads were forced to cross borders to invade the Chinese empire for food sources and shelters. The conflicts between nomadic tribes and the Chinese empire have pervaded Chinese history, including the most famous example that lasted nearly 120 yr (AD 316 to 436) of the attacks by the five major nomadic tribes (the Shung-Ru, Shang-Bei, Jei, Dee and Zharng) along the northern border of the Eastern Jin dynasty (Feng, 2003; Kuo, 2003). Additional examples of invasions by nomads include those by Zhi-Dan and Ru-Jen during the Northern Song dynasty and by the Mongolians during the late Ming dynasty (Liu, 1994). The endless confrontation is evidenced by the construction of the Great Wall, which was intended to be used for protecting the northern borders of the Chinese empire from invasion by nomads and had a history of more than 2,200 yr of construction from individual, small defensive fortifications built in the 6th century BC to its present-day length of over 6,700 km in the AD 16th century during the Ming dynasty (Fig. 1).

As can be seen in Figure 2, all of these turbulences coincide with the most devastating climates in Chinese history. The rapidly deteriorating climate conditions have resulted in widespread crop failures and subsequent large-scale famines in the homeland ruled by Chinese emperors, and consequently effectuated war and conflict between the Han race and various nomadic tribes along the northern and western borders. Indeed, the wars, starvation and epidemics led to the two worst demographic disasters in Chinese history during the Yuan dynasty (13th-14th century) and the late Ming dynasty (AD 1620-1650), in which the population declined sharply by 50% (~55 million decline) and 43% (~70 million decline), respectively (Zhang et al., 2007). During these critical periods of time, as long as someone (e.g., the leaders of rebellions) advocated violence to challenge the sovereign of the ruling emperor, the massive number of refugees would quickly join together as rebellions and jeopardize the governance of the Chinese empire. The turmoil would further worsen the political stability of an empire already plagued by corruption, persecution and incapable rule.  In the end, the ruling emperor would be disposed of and replaced by a new dynasty. Such cause-and-effect repeats throughout the entire history of China. It thus appears that riots instigated by rebellions and invasions by nomads, both mediated largely by disastrous climate changes, are two major causes responsible for successive changes of dynasties in Chinese history and that disastrous climate change plays a key role in the shaping of the history of China.

Conclusion

Upon close examination of Chinese history in conjunction with associated climate oscillations, the succession of dynastic regimes throughout the history of China should be viewed from a global perspective to provide a better understanding of the potential threat of climate change to current and future societal stability and human civilization. This study shows that the entire history of China can be compiled in accordance with the associated series of disastrous climate changes in China.  More specifically, this study shows that the link between climate change and the rise and fall of each dynasty from Western Zhou (771 BC) to Ming (AD 1,644) through the history of China is not correlative but rather causative, as each dynasty was demolished by a rebellion arising due to severe climate changes.

We live in a shrinking world. Any regional geopolitical instability due to hostile climate changes may heighten a nation’s level of tension with neighboring countries as well as pose a threat to the lives and welfare of humankind. Although we are living in an era that is very different from ancient times and modern advancement of science and technology has advanced our flexibility to respond to climate changes, lessons can still be learned from the climate-mediated rise and fall of dynasties occurring throughout the history of China.

Acknowledgements

I thank S. W. Wang, D. Zhang and A. E. Sheu for constructive discussion and providing valuable references and W. P. Hou for preparing figures. This manuscript was benefited greatly by the critical reviews and comments by D. J. Meltzer and M. Williams.  I am also indebted greatly to the late C. C. Biq and T. S. Liu for their moral support and inspiration.

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Figure Captions

Fig. 1. Important historic and climate-mediated events during the ancient Chinese history from 0 to 3000 BC.

Fig. 2. The correlation between the dynastic changes in Chinese history and the reconstructed temperature anomaly trend in China during the last two millennia (see details in text). The temperature anomaly trend is redrawn from Yang et al. (2002).  Bold vertical dash lines mark the years of the beginning and the end of each major dynasty, whereas thin dotted lines denote the short-lived dynasties, the Three Kingdoms (AD 221-263), Wei (AD 263-280), Western (AD 280-316) and Eastern (AD 316-417) Jin, Northern and Southern Dynasty (AD 417-589), and Sui (AD 589-617), in chronological order. Separation of the Song dynasty into the Northern and Southern Song in AD 1,127 is also marked by a thin dotted line. FDTK stands for the Five Dynasties and Ten Kingdoms (AD 907-960). The zero horizontal line (thin dashed) is the mean temperature anomaly trend of the reconstructed series. Names and durations of rebellions that lead to the fall of each dynasty are shown on the top of the panel. Also shown are the durations of the three major cold episodes known as Chinese Little Ice Ages (CLIA IV to VI).

Fig. 3. The conceptual model used in this study for understanding the role of severe climate fluctuations in ancient Chinese civilization and the collapse of each dynasty throughout the entire history of China.