Trends and triggers redux: Climate change, rainfall, and interstate conflict

Given freshwater is crucial to sustaining life and forecasted to decline in relative abundance under most climate change scenarios, there is concern changing precipitation patterns will be a cause of future interstate conflict. In theorizing the impact of climate change for interstate conflict, we distinguish between trends (long-term means) that may affect the baseline probability of conflict, and triggers (short-term deviations) that may affect the probability of conflict in the short run. We jointly model the effects of mean precipitation scarcity and variability (trends) and year-to-year changes in precipitation (triggers) on militarized interstate disputes between states. We find higher long-run variability in precipitation and lower mean levels of precipitation in dyads are associated with the outbreak of militarized interstate disputes (MIDs). Contra neo-Malthusian expectations, however, we find joint precipitation scarcity - defined as both countries experiencing below mean rainfall in the same year - has a conflict-dampening effect. These findings push the literature in a direction that more closely aligns our modeling of human impacts with our understanding of the physical impacts of climate change.