Peru’s civil war started in an El Ni単o year (Image: Enrique Castro-Menoivil/Reuters/Corbis)
THE Peruvian highlands were hit hard by El Ni単o in 1982, and crops were destroyed. The same year, guerrilla attacks by the Shining Path movement erupted into a civil war that would last 20 years. Random coincidence? Possibly not.
The first study to link global climate patterns to the onset of civil conflict places El Ni単o on a par with factors like poverty and social exclusion.
, a researcher in international affairs at Princeton University, and colleagues looked at data on conflicts between 1950 and 2004 that killed more than 25 people in a year. They compared El Ni単o years, which happen roughly every five years, with La Ni単a years. El Ni単o tends to bring hotter, drier conditions and La Ni単a cooler ones to tropical countries, but both have less of an influence on temperate countries.
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The analysis included 175 countries and 234 conflicts, over half of which caused more than 1000 deaths. It found that the risk of conflict in tropical countries rose from 3 per cent during La Ni単a years to 6 per cent during El Ni単o years. The effect was absent from countries only weakly affected by these climate cycles (Nature, ).
“I was surprised by the strength of the effect,” says of the Peace Research Institute Oslo in Norway. “Doubling of risk is a large increase, about on a par with poverty and ethno-political exclusion.”
“Doubling the risk of conflict is a large increase, about on a par with poverty and ethno-political exclusion”
Buhaug has been sceptical of similar studies, and though he finds the statistics convincing, he says he is puzzled, as the study offers no explanation for how El Ni単o might exert an influence over stressed human societies.
Hsiang’s team found that El Ni単o appeared to have an immediate effect in their analysis, conflicts erupted within months of the onset of El Ni単o events but the correlation was independent of local weather events like drought, which can bring famine and increased tension.
Hsiang cannot yet explain what is causing the link. One possibility is that international markets spread climate signals around the world. For instance, widespread drought in an El Ni単o year could cause global food prices to rise.
But as Andrew Solow of the Woods Hole Oceanographic Institution in Massachusetts points out, “People do not start wars simply because they are hot.” And until we know what it is about El Ni単o that increases the likelihood of conflict, it will be impossible to say whether this means we should expect more unrest due to climate change.
