"This map shows the maximum wet-bulb temperatures reached in a climate model from a high carbon dioxide emissions future climate scenario with a global-mean temperature 12 degrees Celsius (21 degrees Fahrenheit) warmer than 2007. The white land areas exceed the wet-bulb limit at which researchers calculated humans would experience a potentially lethal level of heat stress. (Credit: Purdue University graphic/Matthew Huber)"
"Whole countries would intermittently be subject to severe heat stress requiring large-scale adaptation efforts," Huber said. "One can imagine that such efforts, for example the wider adoption of air conditioning, would cause the power requirements to soar, and the affordability of such approaches is in question for much of the Third World that would bear the brunt of these impacts. In addition, the livestock on which we rely would still be exposed, and it would make any form of outside work hazardous."
"Steven Sherwood, the professor at the Climate Change Research Centre at the University of New South Wales, Australia, who is the paper's lead author, said prolonged wet-bulb temperatures above 95 degrees would be intolerable after a matter of hours."
"The wet-bulb limit is basically the point at which one would overheat even if they were naked in the shade, soaking wet and standing in front of a large fan," Sherwood said. "Although we are very unlikely to reach such temperatures this century, they could happen in the next."
"These temperatures haven't been seen during the existence of hominids, but they did occur about 50 million years ago, and it is a legitimate possibility that the Earth could see such temperatures again," Huber said..."