Here's a new potential threat of climate change: the human body will not be able to adapt to higher temperatures, and half the Earth's land surface will become uninhabitable.

Parts of China, India and the eastern US could all become too warm in summer for people to lose heat by sweating - rendering such areas effectively uninhabitable.

Steven Sherwood, a climate expert at Yale University, told a global warming conference in Copenhagen that people will not be able to adapt to a much warmer climate as well as previously thought.

The physiological limits of the human body will begin to render places impossible to support human life if the average global temperature rises by 7C on pre-industrial levels, he said.