Folks at the Woodrow Wilson Center asked for my thoughts on the recent issue of the JPR (earlier comments here and here). I sent them this comment.
Basically, the quantitative empirical findings in the issue support all the existing findings in the literature. There are some new data sets and associated results. But overall, the stylized facts remain unchanged (eg. see here for results and many links).
The editor of the special issue, Nils Peter Gleditsch, has argued that the findings in the issue indicate that climate is irrelevant for conflict in his intro:
However, to date there is little evidence that the meteorological or agricultural conditions associated with climate change are actually a major source of violence.
and his conclusion:
The study of the relationship between climate change and conflict has advanced noticeably in the past four years. Several recent summaries conclude that so far there is not yet much evidence for climate change as an important driver of conflict [Sol: some of my thoughts on the summary he is referencing are here]. Although environmental change may under certain circumstances increase the risk of violent conflict, the existing evidence indicates that this is not generally the case.but these statements are not supported by the results actually presented in his Special Issue. Below is the breakdown of empirical papers in the issue, which I describe in my NewSecurityBeat comment (yes, I read every single paper carefully and examined the data and code for most of them). Of the ten quantitative empirical papers, eight asked whether climatological variables influenced the risk of conflict. Seven of these eight papers found an association. If Gleditsch viewed the quality of all these papers to be high (which I assume he does, since he approved them all for publication), I do not see how they collectively point to the conclusion that climatological variables are unimportant.
Marshall Burke and I are in the middle of doing a careful review of the quantitative literature (this post is actually taking me away from working on one of our tables) and the JPR findings are generally in line with the results from a much larger body of literature. Stay tuned.