One reason for so little consistency in the climate change and conflict literature could be research design, according to a paper by Jonas Nordkvelle, Siri Aas Rustad, and Monika Salmivalli in Climatic Change. “The innovation in this paper is that we explore how climate variability can be used as a randomized variable, and let this guide our design choices,” they write. Comparing unusually wet and dry periods across months in “area-month sets” for parts of Nigeria, Kenya, Uganda, Darfur, and India, they find that both departures from the norm affect conflict in different ways. Unusually wet periods that last longer than a year increased the chances the conflict, while drought tended to have an effect only in the short term. “Possibly, there needs to be some resource abundance for communal conflicts to ‘pay off’ (long, unusually wet periods), while droughts that destroy harvests (short, unusually dry periods) pull resource-scarce groups into violence,” they write. A recent history of conflict related to drought also increased the chances for future conflict. Nordkvelle et al. caution, however, that these results should only be understood to apply to communal conflicts, not state-based conflicts like civil war.

[This description originally appeared on New Security Beat, the blog of the Environmental Change and Security Program.]