Many millions of people in densely-populated South Asia will face extreme increases in both heat and humidity by the end of the century if global warming is allowed to reach the levels in high-end projections, according to a paper last week in the journal Science Advances.
“Human beings, like any other animals, have their physical limits,” the Washington Post explains. “Above certain temperature and humidity thresholds, the body can no longer function properly and will eventually die. Greater levels of humidity in the air can make higher temperatures even more dangerous because the moisture in the air inhibits the body’s ability to cool itself by sweating.”
The research team behind the study said the results point to severe vulnerability for populations that have had the least responsibility for bringing about the climate crisis.
“These are people who did not contribute to the root cause of the problem,” said co-author and MIT hydrologist Elfatih Eltahir. “The accumulated emissions have been contributed primarily by the rich fraction of the world’s population.”
The study looked specifically at “wet bulb” temperatures, a combined index of air temperature and humidity. It shows that, depending on humidity, temperatures as low as 35°C/95°F can be lethal in just a few hours. The threshold can be reached “through a variety of different combinations of air temperature and humidity—for instance, an air temperature of about 115°F with relative humidity of 50%, or an air temperature of about 100°F with relative humidity of 85%,” the Post notes.
Matthew Huber, the Purdue University climate scientist who co-authored the 2010 paper that first flagged the risk of wet bulb temperatures, stressed that the dire outcomes described in the most recent study are not locked in. “There is nothing inevitable about this hot, wet future with killer heat waves,” he said. “Even modest efforts to transition to a lower emissions future may avert this scenario.”
Last month, the Asian Development Bank and the Potsdam Institute for Climate Research projected up to a 6.0°C temperature increase for parts of Asia and the Pacific by 2100, leading to “drastic changes in the region’s weather systems, agriculture and fisheries, biodiversity, trade, and urban development,” Eco-Business reported. “The living conditions that result in the tropics would make it almost impossible for people to live outside, prompting migration on a massive scale.”