Along with rising sea levels and global insecurity, climate change is producing yet another unforeseen consequence—rising violence, from road rage to civil war, a new report finds.
A working paper released Thursday by the National Bureau of Economic Research, which conducted a meta-analysis of 55 separate reports on global warming and conflict in a variety of settings, found that "deviations from moderate temperatures and precipitation patterns systematically increase the risk of conflict, often substantially, with average effects that are highly statistically significant."
The paper looked at a vast range of violence perpetrated by both individuals and groups. The studies reviewed instances of road rage, domestic abuse, assault, rape, and murder alongside geopolitical conflicts like "riots, ethnic violence, land invasions, gang violence, civil war and other forms of political instability, such as coups."
The researchers measured the records of violence against climate variables such as rainfall, drought, and temperature increases.
One standard deviation towards warmer temperatures increased the frequency of intergroup conflict by more than 11 percent.
Stanford researcher Marshall Burke, one of the paper’s authors, explained to the Washington Post that "for a degree Celsius of temperature increase (1.8 degrees Fahrenheit)... there could be a 20 percent increase in civil conflict in Africa."
The Post continues:
[A]cross 19 studies, Burke and his colleagues found 24 separate estimates of the relationship between temperature changes and various kinds of conflict outcomes, and in every case, that relationship was positive. "The probability of getting 24 positive values if there was in fact no relationship between temperature and conflict ... is less than 1 in 100 million," Burke said in an e-mail. "It's like flipping a coin 24 times and getting heads each time."
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The paper echoes similar findings from another meta-analysis published in Science in August 2013 by researchers from Princeton University and University of California Berkeley, which found a link between climate change and precipitation and a rise in interpersonal violence, institutional breakdown, and inter-group violence, such as war.
Solomon Hsiang, Princeton professor and one of that study's lead authors, told the Atlantic that there could be several causes behind the phenomenon:
Climate change causes migration, and as big populations move, they might confront existing residents in a battle for resources and land. It can also alter physical environments in a way that predisposes people to confrontation, or—particularly in earlier eras—might have caused people to wrongly attribute environmental conditions to the actions of their enemies. Other studies have shown that hot temperatures make us more hostile psychologically.
The Post continues:
It is important to underscore that the temperature-violence relationship is not deterministic. In their meta-analysis, Burke and his colleagues liken the situation to "the rise in car accident rates during rainy days"—the rain ups the risk of accidents overall, but each accident is still contingent on the individual situation and choices (and mistakes) of the drivers involved.
In May, the Institute for Policy Research and Development pointed to Nigeria—which had just been rocked by the kidnapping of more than 200 schoolgirls by the militant group Boko Haram—as an example of a country where increasing instability could be linked to climate change.
"[P]oor responses to climatic shifts create shortages of resources such as land and water," IPRD executive director Dr. Nafeez Ahmed wrote in the Guardian. "Shortages are followed by negative secondary impacts, such as more sickness, hunger, and joblessness. Poor responses to these, in turn, open the door to conflict."
But while the results of Thursday’s paper are only statistical, Burke told the Post, they are still real: "We believe there is overwhelming evidence of a strong relationship between changes in temperature in particular, and various types of human conflicts."