Quantifying the Influence of Climate on Human Conflict - Hsiang 0913.pdf - meta-analysis of 60 studies. Graphs below tell the story. Some come from studies further down the page, some from other studies. Below, SD = standard deviation.
Rainfall changes (mostly drying) are drivers in panels D, G, H & K below, temperature for the other 8.
Dotted lines come at 1,000 year intervals.
2,600 years of European history
China graph spans 2070 BC - 1450 AD. Titanium count is proxy for strength of winter monsoon winds & rain.
Section Map: Costs, Wars, Migrate +