Warming planet = more violence, study shows

WASHINGTON -- It's a hot day; sweat soaks your forehead, and you just want to get back to your air-conditioned home, so of course you're going to be angry if the car in front of you doesn't move when the traffic light turns green. Honk! Honk!

When the temperature rises, so does aggression -- and that can lead to large-scale consequences, considering that climate change is turning up the heat over the entire planet.

A new study in the journal Science shows that shifts in climate historically have been associated with violent conflicts, among both individuals and groups, and that current warming patterns could significantly increase the abundance of human conflict by midcentury.

Researchers' meta-analysis of 60 studies suggest that, consistent with links between conflict and climate shifts in the past, the risk of intergroup conflict around much of the planet would be amplified by 50% in 2050.

"It does change how we think about the value of avoiding climate change," said Solomon Hsiang, lead study author and researcher at the University of California, Berkeley. "It makes us think that avoiding climate change is actually something we should be willing to invest more in."

Future populations will hopefully also be able to figure out ways to adapt to these climate events, such that the predicted increase in violence will become less likely. Large-scale changes in technologies or political institutions may also alter the risk of violence in the future, Hsiang said.

Research on the topic of climate change and violence has been exploding onto the scene in recent years, study authors noted, with 78% of the studies included in this analysis having been published since 2009. Hsiang and colleagues incorporated research on civilizations dating back as far as 10,000 B.C. and across all major world regions.

Studies both in laboratory settings and of "natural" human situations have found a connection between heat and violence (PDF), the study said. Higher temperatures have been linked to both innocuous hostile behaviors, such as horn-honking while driving, and more serious behaviors such as domestic violence within households, assault and rape. Police officers are also more likely to use force at higher temperatures, studies have found.

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