Linking global climate to civil conflicts

About

Scientists and writers have previously suspected that strong climatic or environmental change can trigger conflict, and even cause societies to fall. Some scholars have used proxy measures for climate change—like tree rings or titanium sediments in the ocean—to match extreme climatic events with the collapse of ancient civilizations, including the Maya, Angkor in Cambodia, and Mesopotamia’s Akkadian empire. 

It’s possible that climate changes can still have a strong effect on societies even in the modern era, despite the fact that we may be more insulated from the effects of weather. 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. We examined planetary-scale climate changes and global patterns of civil conflict to determine if there is an association between the two events.

Approach

Historians have argued that the El Niño Southern Oscillation (ENSO or El Niño) may have driven global patterns of civil conflict in the distant past, a hypothesis that we extended to the modern era and tested quantitatively. Using global climate data and the “Onset and Duration of Intrastate Conflict” data set from 1950 to 2004, we compared societies around the world with themselves when they are exposed to different states of the global climate. For practical purposes, a society observed during a La Niña is the ‘control’ for that same society observed during an El Niño ‘treatment.’ We sharpened this comparison by separating the world into two groups of countries: those whose climate is strongly coupled to ENSO and those weakly affected by ENSO.

Key Findings

We found 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.