Severe global warming will render half of world's inhabited areas unliveable, expert warns

Parts of China, India and the eastern US could all become too warm in summer for people to lose heat by sweating, expert warns
David Adam, guardian.co.uk 12 Mar 09;

Severe global warming could make half the world's inhabited areas literally too hot to live in, a US scientist warned today.

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.

"There will be some places on Earth where it would simply be impossible to lose heat," Sherwood said. "This is quite imaginable if we continue burning fossil fuels. I don't see any reason why we wouldn't end up there."

The 2007 report from the Intergovernmental Panel on Climate Change (IPCC) said that average temperatures could rise by 6C this century if greenhouse gas emissions continue to rise at current rates. Scientists at the Copenhagen Climate Congress this week said the IPCC may have underestimated the scale of the problem, and that emissions since 2000 have risen much faster than expected.

Sherwood told the conference: "Seven degrees would begin to create zones of uninhabitability due to unsurvivable peak heat stresses and 10C would expand such zones far enough to encompass a majority of today's population."

He said air temperature measurements were a poor guide to the true impact of global warming on people. A better assessment is "wet bulb" temperature, which combines temperature and humidity. "A warming of only a few degrees will cause large parts of the globe to experience peak wetbulb temperatures that never occur today."