Think temperatures are rising fast? That’s nothing compared with the apparent temperature, or heat index, which is increasing three times faster than the measured temperature, according to a study offering a new way to look at the heat index, with a focus on Texas last summer. The heat index factors in relative humidity to show what the temperature truly feels like. When relative humidity is low, sweat is quickly evaporated, cooling the body. But when relative humidity is high, perspiration is slow to evaporate, making the body feel warmer. It’s important people understand heat index values so they know the risk of overheating. But according to study author David Romps of UC Berkeley, the NOAA’s heat index values are inaccurate, conveying only “a conservative estimate of heat stress,” per a release.
Basically, the heat index model breaks down “at humidities and temperatures that the originator of the index thought would be rarely reached,” according to the release. Previously, relative humidity typically fell when the temperature increased, per Newsweek. But with climate change “the relative humidity remains about constant as the temperature increases, which reduces the effectiveness of sweating to cool the body,” the release notes. Romps and colleague Yi-Chuan Lu came up with a revised heat index based on calculations of all combinations of temperature and humidity. Based on the revised index, the apparent temperature at Houston’s Ellington Airport on July 23 of last year was 167 degrees Fahrenheit, with climate change accounting for 12 degrees.
“It sounds completely insane … approaching something like a setting on the oven,” says Romps, per the release. “It’s beyond the physiological capacity of a young, healthy person to maintain a standard core temperature.” But “we think if you kept your skin wet … you’d still be alive. Definitely not happy. But alive.” In extreme heat, shade and water are “your friends,” Romps says. Park yourself in front of a fan, wet your skin, drink fluids, and you should be OK. But we’re nearing a point where the heat index in Texas might climb high enough to make conditions hyperthermic for all, warns Romps, whose study is published in Environmental Research Letters. He adds that “the obvious thing to do is to cease additional warming, because this is not going to get better unless we stop burning fossil fuels.” (More heat stories.)
Dr. Sarah Adams is a scientist and science communicator who makes complex topics accessible to all. Her articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
