Climate change could make much of the world too hot for human habitation within just three centuries
Scientists from Australia's University of New South Wales and Purdue University in the United States found that rising temperatures in some places could mean humans would be unable to adapt or survive.
"It would begin to occur with global-mean warming of about seven degrees Celsius (13 Fahrenheit), calling the habitability of some regions into question," the researchers said in a paper.
"With 11-12 degrees Celsius warming, such regions would spread to encompass the majority of the human population as currently distributed."
Researcher Professor Steven Sherwood said there was no chance of the earth heating up to seven degrees this century, but there was a serious risk that the continued burning of fossil fuels could create the problem by 2300.
"There's something like a 50/50 chance of that over the long term," he said.
The study -- which examined climate change over a longer period than most other research -- looked at the "heat stress" produced by combining the impact of rising temperatures and increased humidity.
Sherwood said climate change research had been "short-sighted" not to probe the long-term consequences of the impact of greenhouse gases blamed for global warming.