By Richard Black
Environment correspondent, BBC News website
Climate has been cited as a factor behind civil conflict in Darfur
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."
If temperatures rise across the continent as computer models project, future conflicts are likely to become more common, researchers suggest.
Northwestern Kenya's drought has brought conflict between pastoralists
Their study shows an increase of about 50% over the next 20 years.
When projections of social trends such as population increase and economic development were included in their model of a future Africa, temperature rise still emerged as a likely major cause of increasing armed conflict.
"We were very surprised to find that when you put things like economic growth and better governance into the mix, the temperature effect remains strong," said Dr Burke.
At next month's UN climate summit in Copenhagen, governments are due to debate how much money to put into helping African countries prepare for and adapt to impacts of climate change.
"Our findings provide strong impetus to ramp up investments in African adaptation to climate change by such steps as developing crop varieties less sensitive to extreme heat and promoting insurance plans to help protect farmers from adverse effects of the hotter climate," said Dr Burke.
Nana Poku, Professor of African Studies at the UK's Bradford University, suggested that it also pointed up the need to improve mechanisms for avoiding and resolving conflict in the continent.
"I think it strengthens the argument for ensuring we compensate the developing world for climate change, especially Africa, and to begin looking at how we link environmental issues to governance," he said.
"If the argument is that the trend towards rising temperatures will increase conflict, then yes we need to do something around climate change, but more fundamentally we need to resolve the conflicts in the first place."