Climate change will probably trigger more human conflict, according to an article in the journal Science.
An examination of 60 separate studies, including one stretching back to 10,000 B.C., found that individuals, groups and nations are “substantially” more likely to become involved in physical conflict in hot weather and heavy rain.
Climate change is expected to drive up temperatures in many regions, which will “systematically increase the risk of many types of conflict” ranging from barroom brawls and rape to civil wars and international disputes, according to the article.
“The strongest evidence is that high temperatures really matter,” said Solomon Hsiang, one of the study’s authors. “A few degrees warmer is always worse.”
Higher temperatures affect people through a combination of geographical, sociological and physiological factors, he said.
Harsh weather may destroy crops and cause food shortages. Heavy rainfall may induce flooding that leads to land disputes. And in one study, police officers in a simulation were more likely to unholster their guns as the training room grew warmer.
“The officers said they felt more threatened when they were in the hot room,” said Hsiang, a public policy professor at the University of California, Berkeley, who co-authored the study while a researcher at Princeton University. “Imagine you’re in a country, there are some protesters, and some policemen who are supposed to be maintaining order. Their response to that protest may change based on environmental conditions.”
The study found that the rate of interpersonal violence, including assaults and rapes, increases 4 percent for every “standard deviation change in climate toward warmer temperatures or more extreme rainfall.” Intergroup conflict rises 14 percent.
One standard deviation is comparable to a 0.4-degree Celsius (0.6-degree Fahrenheit) increase in temperature in an African nation for a month, or a 3-degree C boost in a U.S. county for a month. Many areas on the planet are on pace to warm 2 to 4 standard deviations by 2050.
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