8.25.2011

An association between the global climate and civil conflict

Yesterday, a paper that I wrote with Kyle Meng and Mark Cane was published in the journal Nature:

Civil conflicts are associated with the global climate 

Credit: Nature/S. Hsiang
Abstract: It has been proposed that changes in global climate have been responsible for episodes of widespread violence and even the collapse of civilizations. Yet previous studies have not shown that violence can be attributed to the global climate, only that random weather events might be correlated with conflict in some cases. Here we directly associate planetary-scale climate changes with global patterns of civil conflict by examining the dominant interannual mode of the modern climate, the El Niño/Southern Oscillation (ENSO). Historians have argued that ENSO may have driven global patterns of civil conflict in the distant past, a hypothesis that we extend to the modern era and test quantitatively. Using data from 1950 to 2004, we show that the probability of new civil conflicts arising throughout the tropics doubles during El Niño years relative to La Niña years. This result, which indicates that ENSO may have had a role in 21% of all civil conflicts since 1950, is the first demonstration that the stability of modern societies relates strongly to the global climate.

Updates

  • The original article is un-pay-walled here.  
  • A short summary that I wrote for Earth Magazine is here.
  • I present the results in a 30 min non-technical talk to policy-makers at the Woodrow Wilson Center here (starting at 43:00).


Additional Nature materials: Andrew Solow's News & Views pieceNature Podcast, Nature NewsEditorial


I was planning on finishing a lengthly blog post describing what we found, but this week was more overwhelming than expected so it will have to wait until next week (see updates above).  However, since we've spent time time talking with the media about the project, I suppose I can free-ride on the coverage that it's getting and send interested readers to articles in The Economist, NPRThe Washington PostScience, BBCScientific AmericanSlate and other news sites.

For folks interested in additional material, Kyle has posted the replication code on his website (it's also posted as a file under Supplementary Materials on the Nature site, but Kyle's site doesn't require a subscription).

Google Earth: ENSO teleconnections
I've also posted this Google Earth file which let's you look at the data we used to make the cover image (above), although it doesn't look as "nice" because the data in the cover image is smoothed for aesthetic reasons.

Below is a video I made using slides from the talks I've given in academic seminars.  It let's you see the impact that ENSO has on surface temperatures around the world.  If you want to take a closer look, you can download a PDF "flipbook" of these images (10M file).


Finally, some related links on this blog that I will reference with more structure sometime next week:

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