Civil conflicts are associated with the global climate

• Published in: Nature (London) 2011-08, Vol.476 (7361), p.438-441
• Main Authors: Hsiang, Solomon M., Meng, Kyle C., Cane, Mark A.
• Format: Article
• Language: English
• Subjects: 704/106; 704/844; Bgi / Prodig; Climate change; Climatology; Conflict (Psychology); El Nino; El Nino-Southern Oscillation - history; Environmental problems; Experiments; Female; Global climate; History, 20th Century; History, 21st Century; Human ecology and demography; Humanities and Social Sciences; Humans; Influence; Internationality; La Nina; letter; Male; multidisciplinary; Physical geography; Rain; Risk; Science; Science (multidisciplinary); Society; Socioeconomic Factors - history; Sociology; Southern Oscillation; Studies; Temperature; Time Factors; Tropical Climate; Tropical environments; Urbanization - history; Variables; Violence - history; Violence - statistics & numerical data; Warfare
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature10311

Climate and conflict hot spots Historians and scientists have long theorized that the global climate and global patterns of violence might be connected, but this idea has never been directly tested with data. Now a new analysis examines whether civil conflicts might be linked to the El Niño-Southern Oscillation (ENSO), the dominant mode of interannual variability in the modern global climate. Using data on tropical countries collected between 1950 and 2004, the study finds that the probability of new civil conflicts breaking out in El Niño years is double that seen in cooler La Niña years. Overall, these findings suggest that the ENSO may have played a part in initiating 21% of all civil conflicts since 1950. This study represents the first demonstration that the stability of modern societies is associated with the global climate. It has been proposed that changes in global climate have been responsible for episodes of widespread violence and even the collapse of civilizations 1 , 2 . 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 3 , 4 , 5 , 6 , 7 . Here we directly associate planetary-scale climate changes with global patterns of civil conflict by examining the dominant interannual mode of the modern climate 8 , 9 , 10 , the El Niño/Southern Oscillation (ENSO). Historians have argued that ENSO may have driven global patterns of civil conflict in the distant past 11 , 12 , 13 , a hypothesis that we extend to the modern era and test quantitatively. Using data from 1950 to 2004, we show 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.