Between 1000 and 1911, notes University of Hong Kong Earth scientist David Zhang, eastern China witnessed 899 wars.
A study by Zhang's team published in Human Ecology classified the conflict level of successive decades over nine centuries as 'very high' :more than 30 wars, ' high ':15-30 wars, or 'low' ; less than 15 wars.
Eastern China is where most of the country's food is grown. Over the same period, the climate data for the Northern Hemisphere Zhang et al. adduce show six major cycles of warm and cold phases. Chinese crop and livestock production dropped significantly during the cold phases.
All four decades of very high conflict, and most periods of high conflict, coincided with cold phases, they found. Warfare generally lagged 10-30 years behind the start of a cold phase.
"In situations of ecological stress, warfare could become the ultimate means of redistributing shrinking resources,"--
Zhang, D. D., Zhang, J., Lee, H. F. & He, Y.-Q. Hum. Ecol.
(2007). You can read a precis in Nature. Don't be surprised if the usual suspects on K-Street try to bend the hypothesis to fit The Warring States Period and the overthrow of the Mao dynasty.