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Does Climate Change Cause Civil War?

by Michael Levi
September 7, 2010

I’m back after a few weeks mostly away from New York. That means it’s time to get back to blogging.

A  relationship between climate change and armed confict is frequently invoked in policy debates. But does it exist? A paper in the Proceedings of the National Academy of Sciences published last October claimed to have found an empirical relationship between climate change (specifically temperature and precipitation) and civil conflict in sub-Saharan Africa. A new paper, published online today in the same journal, hits back hard, arguing that the original result was an artifact of sloppy modeling. It argues, in particular, that the original paper used an inappropriate definition for civil war, and failed to control for standard variables like ethno-political exclusion, macroeconomic fundamentals, and the collapse of the Cold War security system. (Nature has more on the debate between the authors.)

I come away the same as I was before reading both papers: unconvinced by either side. The failure of the original paper to use an appropriate definition for civil wars, and to properly control for non-climate variables, is a severe problem. But the new critique completely ignores the central idea underlying the original work. The authors of that paper hypothesized that climate change would affect conflict through its negative impact on economic performance.  (Climate change is projected to hurt agricultural productivity, which, in turn, is economically damaging.) By controlling for economic performace, though, the new paper eliminates this as a possible explanation for civil war. What the new paper is really examining is whether non-economic impacts of climate change cause civil conflict. Its answer – “no” – is interesting, but it does not contradict the paper that it claims to bury.

Indeed the original paper includes the following comment, which, perhaps unsurprisingly, the new paper fails to note:

“Because economic welfare is the single factor most consistently associated with conflict incidence in both cross-country and within-country studies, it appears likely that the variation in agricultural performance is the central mechanism liking warming to conflict in Africa.”

Ultimately, if we want to understand whether climate change drives civil conflict, it will be necessary to separate climate-driven economic change from other sources of economic change, control for the latter, and then see what comes out. This is hard to do. Until then, both of the climate-and-conflict-in-Africa studies are inconclusive.

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