History shows climate changes led to war

HONG KONG (Reuters) - Global warming is one of the most significant threats facing humankind, researchers warned, as they unveiled a study showing how climate changes in the past led to famine, wars and population declines.

The world's growing population may be unable to adequately adapt to ecological changes brought about by the expected rise in global temperatures, scientists in China, Hong Kong, the United States and Britain wrote in the journal Proceedings of the National Academy of Sciences.

"The warmer temperatures are probably good for a while, but beyond some level plants will be stressed," said Peter Brecke, associate professor in the Georgia Institute of Technology's Sam Nunn School of International Affairs.

"With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water."

Trawling through history and working out correlative patterns, the team found that temperature declines were followed by wars, famines and population reductions.

The researchers examined the time period between 1400 and 1900, or the Little Ice Age, which recorded the lowest average global temperatures around 1450, 1650 and 1820, each separated by slight warming intervals.

"When such ecological situations occur, people tend to move to another place. Such mass movement leads to war, like in the 13th century, when the Mongolians suffered a drought and they invaded China," David Zhang, geography professor at the University of Hong Kong, said in an interview on Thursday.

"Or the Manchurians who moved into central China in 17th century because conditions in the northeast were terrible during the cooling period," he said.

"Epidemics may not be directly linked to temperature (change), but it is a consequence of migration, which creates chances for disease to spread."