A joint research conducted by the Purdue University and the University of New South Wales, Australia has calculated the highest “wet-bulb” temperature that can be tolerated by humans and revealed that this temperature limit could be surpassed if greenhouse gases continue to be emitted at the present rate.
Wet-bulb temperature is similar to the feeling of wet skin being exposed to air in motion
Atmospheric humidity is an additional factor that is considered while measuring wet-bulb temperature which is done by covering the bulb of a standard thermometer with a wet cloth and ventilating it completely.
Researcher and Professor of Earth and Atmospheric Sciences at Purdue University, Matthew Huber said that most mammals including humans have an internal body temperature of around 98.6 degree Fahrenheit. If such mammals are subjected to a wet-bulb temperature higher than 95 degrees Fahrenheit for more than six hours, then they will feel a level of heat stress that can be dangerous.
The occurrence of very high wet bulb temperatures is less in the present scenario, though there exist places on the planet where temperatures exceed 100 degrees. Such hot places have very less humidity, such as the “dry heat” present in Arizona. The absence of humidity allows the body to cool itself by perspiring and stay comfortable.
The study was unable to predict the likelihood of excessive wet-bulb temperatures, but it pointed out its impact. Entire nations might face high heat stress levels and mass adaptation measures would be necessary. A 12 degree rise in temperature could lead to excess wet-bulb temperature in certain regions whereas a 21 degree temperature rise could lead to half the people in the world living in uninhabitable heat conditions.
The research was funded by the National Science Foundation and conducted by Matthew Huber along with Professor Steven Sherwood, who is employed at University of New South Wales’ Climate Change Research Centre. The climate modeling was done by Huber on supercomputers owned by Purdue University’s central IT organization, Information Technology at Purdue (ITaP). Steven Sherwood was in charge of calculating different wet-bulb temperatures. The results of the research will appear as a paper in the May 6 issue of the journal Proceedings of the National Academy of Sciences.