The Social Impacts of Climate Change in China over the Past 2000 Years

The basic characteristics of Chinese physical geography and historical socio-economic development in China are introduced in this chapter. China is distinguished by a prominent monsoonal climate in the east of the country, a continental arid climate in the northwest and a highland cold climate on the Qinghai-Tibet Plateau. During the last several thousand years, Chinese society was built on massive agricultural production, by which the huge numbers of people it supported. It has followed a unique spiral of development in terms of production, population, economy and politics. Due to the close relationship between agriculture and social development of China,  abundant researches have been conducted on historical climate change impacts over the past hundred year.

According to the temperature and wet/dry sequences synthesized reconstructed from the regional high-resolution paleoclimatic sequences based on the proxies of abundant and well-dated documentary records and natural archives, the basic characteristics of climate change over the past 2 000 years in China is summarized. On the centennial scale, there were 4 warm periods and 3 cold periods, but regional differences existed among the 5 sub-regions. In the Eastern China, wet/dry changes showed decadal, multi-decadal and centennial oscillations, while the drought/flood spatial patterns were different between the centennial warm periods and the cold periods. The wet/dry changes in the Northwest China and the Qinghai-Tibet Plateau were different from that in the Eastern China.

China is a country that has great potential for the research of impacts of past climate change. To study the process and mechanism of the impacts of historical climate change on social economy in China, a concept model and methodologies for reconstructing social-economic sequences were developed. The historical climate change impacts in China could be attributed as a food security issue. Using the concepts of food security, resilience, vulnerability and adaptation, a food security based concept model was designed to illustrate the impact-response processes of historical climate transmitted in the subsystems of production, economy, population and society. A gradation methodology on the base of semantic differential was developed for converting the historical literal records about social and economic descriptions to graded sequences. The methods of gradation and frequency could be used to reconstruct the historical social-economic sequences with the same time resolution, duration, and continuity as the climate sequences to represent the subsystems of agricultural production, population, economy, society in the history of China.

The impact of climate change on agricultural production is integral to understanding the impacts of historical climate change on society and the economy of China. The semantic differential method was used to reconstruct the grain grade sequence with a 10-year resolution from 210 BCE to 1910 CE in China. A positive correlation between the winter half-year temperature departure and the grain yield was found. The bumper harvest stages corresponded to the warm periods, and poor harvest stages corresponded to the cold periods. In both warm and cold periods, the grain yield grades assumed a trend of convergence with the temperature increase. The sensitivity of grain yield to temperature change became weakened over the past 2000 years.

The semantic differential method was used to reconstruct the economic and fiscal sequences with a 10-year resolution from 220 BCE to 1910 CE in China based on 1091 macroeconomic items and 1101 fiscal items of direct and proffered evidence from Chinese economic and fiscal history books written by leading contemporary scholars. It is found that both macroeconomic and fiscal fluctuations during 220 BCE–1910 CE in China displayed cyclical changes following climate change. A warm and wet climate was beneficial to economic development, and a combined cold-dry climatic scenario would greatly increase the possibility of economic or fiscal crisis. There were several common periodicities and associations at those common periodicities among climate change, macro economy and fiscal balance.

Famine and uprisings, sensetive to climate change, had serious social impacts in ancient China. Based on historical literature records, a famine index sequence and a frequency sequence of peasant uprisings were constructed. There are 826 years with records of famine in the total of 2 117 years from the Western Han Dynasty to the Qing Dynasty. A total of 4 186 famine events have been recorded in total. Famine was most severe in the Yuan, Qing, Ming and Song dynasties. There were 468 large-scale peasant uprisings of national significance in historical China. In the Sui, Eastern Han, Yuan and Ming dynasties, there were more frequent peasant uprisings. The changes of the famine index and temperature anomalies over the past 2000 years are significantly negatively correlated, while the correlations between famine index and dry-wet index are not significant. Most of the decades with the high frequency of famine events were within the cold periods or the warm-cold transition periods. On the other side, at the 90-year timescale, the frequency of peasant uprisings correlated negatively with both temperature anomalies and dry-wet index. It is very notable that peasant uprisings were less frequent during the warm periods, while they were more frequent during the cold periods.

“Nomadic pastoralism” and “sedentary farming” are two main modes of economic production and social life in ancient China, forming two different types of civilizations named nomadic and sedentary. The ethnic relations between sedentary and nomadic groups written by “war” and “peace”, under the background of climate change, were an important part of the history of Chinese civilization. Based on historical literature records, the sequences of war and peace-making events between sedentary farming and nomadic pastoral groups were constructed. There are 832 wars from the Western Han Dynasty to the Qing Dynasty. Dynastic statistics reveal that the frequency of nomadic-sedentary wars during the Eastern Han, Western Jin, Eastern Jin, Song, and Ming dynasties far exceeded the average level. From 210 BCE to 1910 CE, a total of 504 peace-making events were recorded. The frequency of peace-making events was much higher than average in the Northern and Southern Dynasties, Sui, Five Dynasties and Ten Kingdoms, Northern Song and Qing dynasties. Wars occurred more frequently during the warm phases and less frequently in cold phases and the frequency was positively correlated with temperature anomalies. While the frequency of peace-making events was negatively correlated with temperature anomalies, contrary to the trend of more wars in warm phases and fewer in cold phases.

The relationship between climate change and historical rhythms in China has long been discussed.  Based on semantic differential method, a quantitative sequence of the social vicissitudes over the past 2000 years with a 10-year resolution was reconstructed by using 1586 items of direct and proffered evidence from 29 Chinese history books. Social vicissitudes have clear cyclical features on multiple time scales, and temperature change displayed more significant effects on them in the long-time scale, while precipitation change displayed more significant effects in the short-time scale. Social rise mostly occurred in the centennial-scale warm periods, whereas social decline mostly occurred in the centennial-scale cold periods. 

As an agriculture-oriented society, the traditional China had been strongly impacted by climate change. The issue about how climate change impact the social development in the history of China was discussed in the perspective of social-ecological resilience. The general characteristics of the impacts of historical climate change could be summed as, negative in the cold periods and positive in the warm periods. Adaptation could not only help people to avoid the harmful impacts of climate change, but also is a chance for creating new social-ecological resilience to keep Chinese civilization development continually.