Droughts are already making conflict more likely. As the world gets hotter, mayhem could spread. Green campaigners and eager headline-writers sometimes oversimplify the link between global warming and war. It is never the sole cause. But several studies suggest that, by increasing the frequency and intensity of extreme weather events, including floods and droughts, it makes conflict likelier than it would otherwise be. In a meta-analysis carried out in the early 2010s, Solomon Hsiang, Lab co-director, then at Princeton University, and Marshall Burke, then at the University of California, Berkeley, found “strong support” for a causal link between climate change and conflict (encompassing everything from interpersonal to large-scale violence). They even tried to quantify the relationship, claiming that each rise in temperature or extreme rainfall by one standard variation increased the frequency of interpersonal violence by 4% and intergroup conflict by 14%.