Climate has been a major driver of armed conflict in Africa, research shows - and future warming is likely to increase the number of deaths from war. US researchers found that across the continent, conflict was about 50% more likely in unusually warm years. Writing in Proceedings of the National Academy of Sciences (PNAS), they suggest strife arises when the food supply is scarce in warm conditions. Climatic factors have been cited as a reason for several recent conflicts. One is the fighting in Darfur in Sudan that according to UN figures has killed 200,000 people and forced two million more from their homes. Previous research has shown an association between lack of rain and conflict, but this is thought to be the first clear evidence of a temperature link. The researchers used databases of temperatures across sub-Saharan Africa for the period between 1981 and 2002, and looked for correlations between above average warmth and civil conflict in the same country that left at least 1,000 people dead. Warm years increased the likelihood of conflict by about 50% - and food seems to be the reason why. "Studies show that crop yields in the region are really sensitive to small shifts in temperature, even of half a degree (Celsius) or so," research leader Marshall Burke, from the University of California at Berkeley, told BBC News. "If the sub-Saharan climate continues to warm and little is done to help its countries better adapt to high temperatures, the human costs are likely to be staggering." Conflicting outcomes If temperatures rise across the continent as computer models project, future conflicts are likely to become more common, researchers suggest.