Chinese researchers have found a startling correlation between peaks of warfare in China and cold phases.

Zhang reviewed warfare data from 899 wars in eastern China between 1000 and 1911

warfare frequency in eastern China, and the southern part in particular, significantly correlated with temperature oscillations. In fact, almost all peaks of warfare and dynastic changes coincided with cold phases. Zhang speculates that in times of such ecological stress, warfare could be the ultimate means of redistributing resources.

shortages of essential resources, such as fresh water, agricultural land, energy sources and minerals may trigger more armed conflicts among human societies