Is there a link between the weather and human conflict?

Nature : In a paper published online in Science, researchers look at whether human conflict can be affected by changes in climate. Solomon Hsiang of the University of California, Berkeley, and colleagues looked at data from 60 studies that cover six continents and some 12 000 years of human history. They found that for each one standard deviation change in climate toward warmer temperatures or more extreme rainfall, “the frequency of interpersonal violence rises 4% and the frequency of intergroup conflict rises 14%.” If true, such a link would present yet another downside to global warming. Critics point out, however, that the researchers neglected to explain the exact causal mechanism between climate and conflict and that many more variables need to be taken into account.