El Niño years bring with them warmer temperatures, atypical precipitation patterns—and violence, according to a study published Wednesday (August 24) in Nature.
Heat has been linked to violent behaviors among individuals, and researchers have previously suggested that global climate changes may be at fault for specific outbreaks of violence, war, and civil unrest. But thus far, the evidence for such claims has been lacking.
Examining data on organized political violence in the tropics from 1950 to 2004, Solomon Hsiang and his colleagues found that hostility was more common during El Niño years than La Niña years, estimating that the El Niño/Southern Oscillation (ENSO) could have influenced as many as 20 percent of civil conflicts in affected regions in the last 60 years. The authors hypothesize one cause for this relationship might be that the climate pattern instigates conflicts that would have occurred at a later date.
"More and more of the evidence is pointing toward a strong link between adverse weather or adverse climate and political violence in the world's poor regions," Edward Miguel, an economist at the University of California, Berkeley, who was not involved in this study, told ScienceNOW. "This is an important piece of evidence in that debate."
Because ENSO events can be predicted up to two years ahead of time, the researchers propose that the “findings may improve global preparedness for some conflicts and their associated humanitarian crises,” they wrote. More research is required, however, to understand how other sources of climate change may similarly influence political order.