It's a lot easier to lose your cool when it's hot outside. Just wait until your car's air conditioning is broken and a vehicle in front of you at a fresh green light doesn't move. Honk honk!
Sociologists and those who study crime have long noticed that interpersonal conflict and violence rises on very hot days and nights, as anyone who’s seen Do The Right Thing will tell you. But a new study suggests there is a surprisingly strong link between climate change and conflict on a range of scales—from violent crime between individuals, to wars, and even the collapse of civilizations.
The study, published recently in the journal Science, is the first quantitative assessment of all relevant research examining how climate change affects human conflict, said co-study author and University of California-Berkeley researcher Marshall Burke.
In reviewing 60 studies "that reliably infer causal associations between climate variables and conflict outcomes," the authors found that nearly all showed a strong link between the two. And 27 of the 27 studies that looked at the effect of hotter temperatures found they likely cause more conflict, Burke said. "That's extremely unlikely to happen by chance," he said. In both cases, the authors are referring to all types of conflicts measured, between individuals, groups and nations.
In total, the expected increase in temperature and intense storms from present day until 2050 could cause conflicts between ethnic groups and nations to rise by as much as 56 percent, and interpersonal violence to climb up to 16 percent, according to the study.
In the past, climate change has sparked trouble in a variety of ways.
For example, prolonged drought likely played a big role in the collapse of the Akkadian Empire some time shortly after 2,200 B.C. Unusual heat in 1992 was linked with high levels of domestic violence in Australia. And both droughts and floods occured at the same time as a number of peasant rebellions that roiled China between 1470 and 1900, according to the study.
Since the study was first published in August, it has received some criticism.
One of the more common gripes was that Burke and colleagues confused climate with weather. Whereas weather is best described as atmospheric conditions over a short period of time, climate is how the atmosphere behaves over long periods of time: Climate is what you expect, weather is what you get. Burke maintained that the conclusions of the paper are nonetheless valid, since "the relationship between climate variables and conflict shows up at a variety of time scales, from hourly changes in temperature to century-scale changes in temperature and rainfall."
Others asked whether it were possible to come to such broad conclusions based on different types of climate change and different types of conflict. Burke said the study shows that disruptive climate events tend to cause predictable conflict at both individual and group levels, and the historical record shows examples of how people have reacted to similar situations in the past. .
On the heels of the latest report from the Intergovernmental Panel on Climate Change, which states it's "extremely likely" that human activities have caused the bulk of the global warming since 1950, Burke’s study provides another reason to act now to mitigate climate change.
"The costs of inaction are probably higher than we previously thought: "Our results suggest that rates of human conflict could rise relative to a world without climate change," Burke said.
“Given how costly conflict has been to economic productivity and human livelihoods, these results suggest larger benefits to taking action today to stem future temperature rise."