The combined effects of increased heat and humidity will affect more northeastern India in the world near the turn of the century, according to a global study. Although humidity can greatly magnify the effects of heat, most climate projections tend to neglect this major factor that could make things worse. The new study, published in the journal Environmental Research Letters, projects that in the coming decades the effects of high humidity in many areas will increase dramatically. While hundreds of millions of people would suffer worldwide, the area most affected in terms of human impact is likely to be densely populated in northeastern India, the researchers said.
“The conditions we are talking about basically never happen now, people in most places have never experienced them,” said lead author Ethan Coffel of Columbia University in New York. “But they are expected to occur near the end of the century,” Coffel said. Using global climate models, the researchers mapped the current and projected “wet bulb” temperatures in the future, reflecting the combined effects of heat and humidity.
The measurement is made by covering a cloth saturated with water on the bulb of a conventional thermometer. The study found that by the 2070s, high-grade wet bulb readings that now occur perhaps once a year could prevail from 100 to 250 days of the year in some parts of the tropics.
Laboratory experiments have shown that wet bulb readings of 32 degrees Celsius are the threshold beyond which many people would have trouble carrying out normal activities abroad. “A lot of people would collapse long before they reached the 32 C wet bulb temperatures, or something close,” said co-author Radley Horton, climate scientist at the Lamont-Doherty Earth Observatory at Columbia University. “They found terrible problems,” Horton said.
The results could be “transformative” for all areas of human effort: “economics, agriculture, military, recreation,” Horton said. The study projects that some parts of the southern Middle East and northern India will even reach 35 degrees Celsius in the last century, equal to the temperature of human skin and the theoretical limit at which people will die in a matter of hours without artificial cooling.
Other areas that are likely to withstand the worst combination of heat and humidity include the southeastern United States. UU., The Amazon, the west and the center of Africa, the Arabian Peninsula and the east of China. Research suggests that humidity can be a breaking point for some areas as temperatures rise. It is projected that warm weather will dry many areas that are now dry, in part by changing precipitation patterns. But for the same reason, as global temperatures rise, the atmosphere may contain more water vapor. That means that chronically humid areas located along coasts or otherwise hooked to wet weather patterns can be more difficult.
And, as many people know, humid heat is more oppressive than the “dry” type. That’s because humans and other mammals cool their bodies by sweating; Sweat evaporates from the skin in the air, taking excess heat with it. It works very well in the desert. But when the air is already full of humidity, think about the windiest days of summer in the city, the evaporation of the skin slows down and finally becomes impossible.
When this cooling process is stopped, one’s core body temperature rises beyond the narrow tolerable range. The results are lethargy, illness and, in the worst conditions, death.