A quantitative analysis of the relationship between climate change and war along the Silk Road regions during the Little Ice Age

The Silk Road passes through China, Central Asia and the Middle East, where they are also sensitive to climate change in history. However, in the current research, there is little analysis and comparison of the characteristics of climate change and war in these three regions, especially the lack of related quantitative approach. Therefore, in this paper we collected the climatic reconstruction data in the Northern Hemisphere and historical war data in the three regions during 1400~1800 A.D., which belongs to the Little Ice Age, the coldest period over the last millennium. In addition, the data on population size of the above regions were retrieved for facilitating the comparison of the relationship between climate change and human society in different regions along the Silk Road. Then, several statistical methods, such as(partial) correlation analysis, regression analysis as well as Granger causality analysis, were employed to analyze and examine the "climate-war" nexus. The results show that there are more wars in China and Central Asia during climate cooling owing to cooling-led ecological-environmental degradation; in the Middle East, due to its location at lower latitude, it is less affected by climate cooling, whereas drought induced by rising temperature usually corresponds to more wars. Besides, climate change may be overlaid with population pressure in the Middle East and Central Asia, and both may synergistically have an effect on the outbreak of war. In summary, the different quantitative results of the three regions reflect the different climatic impacts and social responses along the Silk Road under the background of traditional societies dominated by agriculture and animal husbandry, which remind us to pay more attention to the climate sensitivity in different regions. Furthermore, the findings of this study reveal the potential threat possibly brought by contemporary global warming and provide historical quantitative evidence for better understanding and tackling the issue of climate security around the world.