Positive correlation between the North Atlantic Oscillation and violent conflicts in Europe

Violent conflicts were more prevalent in historical Europe during colder periods, caused by food scarcity. Up to now, however, cold periods have not been attributed to planetary-scale atmospheric circulation, and thus no relationship between circulation and violence in Europe has been established. In this study, we took an innovative step in exploring the association between the NAO and violent conflicts in Europe in 1400-1995. Our results show that the NAO was positively cor related with violent conflicts, particularly in southern Europe and the Mediterranean-the region in which an NAO-induced desiccation effect is experienced. Results hold up even with different measures of violent conflict. Nevertheless, the NAO-conflict correlation has weakened since the Industrial Revolution. Our result is the first demonstration that the NAO affected social stability in pre-industrial societies. This knowledge is crucial in examining violent conflicts in northwestern Africa, a region affected by the NAO, as well as being highly agricultural.