The idea that much of China’s civil turmoil has been the result of weather-related calamities such as floods, droughts and locust plagues has been around for some time. However, the new study, by a team of Chinese and European scientists led by Zhibin Zhang of the Chinese Academy of Sciences in Beijing, is the first to systematically tie climate to social upheavals such as war and the collapse of dynasties.

The team found that the collapse of the Han, Tang, Northern and Southern Song, and Ming dynasties were all closely associated with low temperatures or a rapid decline in temperature. Although they found that floods and droughts were more common during these cold periods, the factors that were most likely to be associated with wars and dynastic break-ups were soaring rice prices and locust infestations.

They suggest that food shortages caused by reduced growing seasons would have led to civil unrest and pushed the nomads in the north to invade the Chinese-speaking southern regions. ‘When the climate worsens beyond what the available technology and economic system can compensate for, people are forced to move or starve,’ they write in a paper that appeared in the Proceedings of the Royal Society B.

September 2010