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The present study aims to compare quantitatively the similarities and differences of transmission processes extending from climate change to grain harvests and economies (macro-economy and fiscal balance) between the Han (206 BC–AD 220) and Tang (AD 618–907) dynasties of China. It is found that both the Han and Tang periods displayed close positive correlations among temperature, grain harvest, macro-economy and fiscal balance and conveyed a positive feedback–oriented transmission pattern with the upgrade of climatic impact level from grain harvest to economic system. Compared with the Han period, the overall linkages among indicators weakened during the Tang period, particularly for the correlation between grain harvest and fiscal balance. The mean temperature during the Tang period was slightly higher but had greater multidecadal variability, coinciding with better performance (and less variations) of macro-economy and fiscal balance (particularly for cold units) and higher variations of grain harvest. It displayed relatively little difference for the main pathways that could be interpreted as climatic impacts during the warm units between the Han and Tang periods, and both approximately 33% of the decades for warm units (100%) ending with fiscal balance/surplus were more likely to be associated with the impacts of temperature change. The difference mainly lies in cold units in the links of ‘cold → poor harvest’ and ‘poor harvest → macro-economic depression’ through the pathway of ‘cold → poor harvest → macro-economic depression/normal economy → fiscal deficiency’. Overall, macro-economy and fiscal system of the Tang period displayed less sensitivity to temperature change and agriculture production in cold period. Those patterns might be related with the unique socio-economic situations such as agricultural fragmentation, southward shift of economic resource and tax system reform during the later Tang Dynasty.

The social impact of past climate change is one of the key areas of study relating to global climate change, particularly its ability to provide valuable lessons for dealing with ongoing challenges of global climate change. Drawing on the abundant historical literature, many recent studies have examined the social impacts of climate change in China during the past 2000 years. This paper reviews the main progress of these studies in three parts. First, a concept model based on the food security in relation to global climate change has been constructed, which can then be used to interpret impact-response processes of climate change in the history of China. Second, we derive a methodology for quantifying the impact of historical climate change, drawing on a series of 4 key social and economic sequences at a 10-year resolution. These have been reconstructed based on the semantic differential method over the past 2000 years in China. Third, using a variety of statistical analyses, we update the understanding of climate impacts throughout the history of China. The overall impacts of climate were negative in the cold periods and positive in the warm periods, at decadal to centennial scales during Chinese history. However, the impacts seemed a mixed blessing both in the cold or warm periods. The social-economic development and population growth in warm periods would intensify the natural resource shortage and disequilibria in the human-environment system, especially when encountering abrupt climate changes. Adaptation to adverse climate change could not only help people to avoid hardship whilst maximizing profits, but also expanded the capabilities for the continual development of Chinese civilization.

The relation between climate change and historical rhythms has long been discussed; however, this type of study still faces the lack of high-resolution data of long-term socio-economic processes. In this study, we collected 1101 items of direct and proffered evidence from 24 Chinese fiscal and economic history books written by leading contemporary scholars. By analysing the semantics of words, we reconstructed a 2130-year-long fiscal sequence with decadal resolution to express the phase transition of fiscal soundness for approximately 21 dynasties in China. Our reconstruction shows four relatively sufficient stages and three relatively deficient stages, with several secondary stages lasting 60 or 160 years on average within each large stage, from 220 bc to ad 1910. Then, the fiscal association with climate change was analysed. The results show that the fiscal crisis was more likely to occur in cold-dry climatic scenarios. Both temperature and precipitation displayed more significant effects on the fiscal fluctuation within the long term, particularly for temperature. In short, fiscal decline had a 10-year lag in response to decreasing precipitation, whereas influence of decreasing temperature on the fiscal balance might be through amplifying already deteriorating fiscal conditions. Regional differences existed in the influence of precipitation on the fiscal balance. The precipitation in the Northern China Plain and in the Jiang-Huai area had more significant effects on the fluctuation of the dynastic fiscal balance than on that in the Jiang-Nan area. In particular, the dynastic finance was more sensitive to the change in the precipitation in the Northern China Plain because of its special geographical, economic and social backgrounds.

Historical case studies of climate change impacts and the resulting social responses can provide analogies for better understanding the impacts of current and future climate changes. Around the turn of the 19th century, the climate of the North China Plain experienced a shift from a relatively warm stage in the 18th century to a colder stage in the 19th century, which was characterised by a much colder climate and more frequent and severe floods and droughts. Historical information about refugees, social disorder, grain transportation, and disaster relief on the North China Plain in 1780–1819 is collected from the Veritable Records of the Qing Dynasty (a collection of official records). The mechanism of climate change affecting the food security of the society, as indicated by the development of a refugee problem around the turn of the 19th century, is analyzed by examining the social vulnerability. There are four basic findings: (1) In the 40 years from 1780–1819, the society on the North China Plain was unstable and characterised by a significant deterioration of the refugee situation. The number of refugees increased markedly, and their behaviour became increasingly violent. In the 1780s, most of the disaster victims chose to stay at their residences waiting for relief. From 1790 to 1800, hundreds of thousands of refugees migrated to northeast China. In the 1810s, the frequency of farmer rebellions increased sharply. (2) The increase in instability corresponded to the climatic cooling over the same time period. The increased instability was a result of the negative impacts of climate change accumulating and transmitting to the social level. (3) For food security, a precondition for the negative impacts of climate change on human society was the vulnerability of the regional socioeconomic system, which had a high sensitivity and low capacity to respond. This vulnerability could be described by the following three observations: ① The regional balance of supply and demand for food was in a critical state, which led to a high sensitivity and dramatic reduction in yield that was caused by climate change; ② the capacity for disaster relief efforts by the government was too low to meet the needs of crisis management; ③ the capacity for refugees’ resettlement in eastern Inner Mongolia and northeast China, which both border the North China Plain, was severely restricted by climatic conditions or the quarantine policy. (4) It is estimated that climate change caused the social vulnerability to reach a critical level approximately 20 years earlier on the North China Plain.