Scenario 2300: Half the Earth Too Hot to Live in

A worst-case scenario of global warming, in which temperatures would soar some 21 degrees, is that much of the world may simply become too hot for humans to live in, according to new research published last week in the Proceedings of the National Academy of Sciences. The research suggests that without action to cut greenhouse gas emissions, average temperatures could rise as much as 10 to 12% by 2300.

AAP Report in The Age (11 May 2010):

HALF the Earth could become too hot for human habitation in less than 300 years, Australian scientists warn.

New research by the University of NSW has forecast the effect of climate change over the next three centuries, a longer time scale than that considered in many similar studies.

The research suggests that without action to cut greenhouse gas emissions, average temperatures could rise as much as 10 to 12 per cent by 2300.

The research, produced in partnership with Purdue University, in the US, is published today in the American scientific journal Proceedings of the National Academy of Sciences.

”Much of the climate change debate has been about whether the world will succeed in keeping global warming to the relatively safe level of only 2 degrees Celsius by 2100,” said Professor Tony McMichael, from the Australian National University, in an accompanying paper published in the journal.

”But climate change will not stop in 2100 and, under realistic scenarios out to 2300, we may be faced with temperature increases of 12 degrees or even more.”

Professor McMichael said that if this were to happen, then current worries about sea level rises, occasional heatwaves and bushfires, biodiversity loss and agricultural difficulties would ”pale into insignificance” compared to the global impacts.

Such a temperature rise would pose a ”considerable threat to the survival of our species”, he said, because ”as much as half the currently inhabited globe may simply become too hot for people to live there”.

Professor McMichael and co-author Associate Professor Keith Dear, also from ANU, described the study as ”important and necessary” because there was a need to refocus government attention on the health impacts of global temperature rise.

There was also a real possibility that much of the existing climate modelling had underestimated the rate of global temperature rise, they said.

Dr Dear said scientific authorities on the issue, such as the United Nations Intergovernmental Panel on Climate Change (IPCC), had struck a cautious tone in forecasting future temperature rise and its impact.

”In presenting its warnings about the future, the IPCC is very careful to be conservative, using mild language and low estimates of impacts,” Dr Dear said.

”This is appropriate for a scientific body, but world governments, including our own, should be honest with us about the full range of potential dangers posed by uncontrolled emissions and the extremes of climate change that would inevitably result.”

Source: www.theage.com.au

By Doyle Rice for USA Today (10 May 2010):

Report: Climate change could render much of world uninhabitable

A worst-case scenario of global warming, in which temperatures would soar some 21 degrees, is that much of the world may simply become too hot for humans to live in, according to new research published last week in the Proceedings of the National Academy of Sciences.

“We found that … a 21-degree warming would put half of the world’s population in an uninhabitable environment,”says study co-author Matthew Huber of Purdue University.

While the Intergovernmental Panel on Climate Change found that the result of business-as-usual warming would be 7 degrees by 2100, eventual warming over several centuries of 25 degrees is feasible, says Huber.

The new research calculated the highest tolerable “wet-bulb” temperature that humans can withstand.

“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,” says study lead author Steven Sherwood of the University of New South Wales in Sydney.

The researchers found that humans and most mammals experience a potentially lethal level of heat stress at a “wet-bulb” temperature above 95 degrees sustained for six hours or more.

(The more familiar air temperature is known as the “dry-bulb” temperature; wet bulb temperatures can be used along with the dry bulb temperature to calculate humidity.)

Researchers say that while wet-bulb temperatures of 95 degrees never happen now, they would begin to occur with global-average warming of about 12 degrees, calling the habitability of some regions into question.

“We show that even modest global warming could therefore expose large fractions of the population to unprecedented heat stress, and that with severe warming this would become intolerable,” the authors write.

“If warmings of 10 degrees C (18 degrees F) were really to occur in next three centuries, the area of land likely rendered uninhabitable by heat stress would dwarf that affected by rising sea level. Heat stress thus deserves more attention as a climate-change impact.”

Source: www.content.usatoday.com