According to a new study, increasing heat and humidity at levels high enough to cause a location to be uninhabitable, are occurring right now all around us.
Meteorologists measure the heat/humidity effect on the so-called “wet bulb” Centigrade scale. In the United States, these readings are often translated into a “heat index”.
Prior studies suggest that even the strongest people cannot carry out normal outdoor activities when the wet bulb hits 32 C, equivalent to a heat index of 132 F. Most others would crumble well before that.
A reading of 35 is considered the theoretical survivability limit. That translates roughly to a heat index of 160 F.
The study identifies thousands of previously rare bouts of extreme heat and humidity in Asia, Africa, Australia, South America and North America, including in the U.S. Gulf Coast region.
Prior climate studies failed to recognize most past incidents because climate researchers usually look at averages of heat and humidity measured over several hours at a time.
Researchers instead drilled directly into hourly data from 7,877 individual weather stations, allowing them to pinpoint shorter-lived bouts affecting smaller areas.
The outbreaks have so far been confined to localized areas and lasted just hours, but they are increasing in frequency and intensity, say the authors.
Lead author Colin Raymond, who did the research at Columbia University’s Lamont-Doherty Earth Observatory, said, “Previous studies projected that this would happen several decades from now, but this shows it’s happening right now. The times these events last will increase, and the areas they affect will grow in direct correlation with global warming.”
Analyzing data from weather stations from 1979 to 2017, the authors found that extreme heat/humidity combinations doubled over the study period.
The southeastern United States saw extreme conditions dozens of times, mainly near the Gulf Coast in east Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle. The worst spots: New Orleans and Biloxi, Miss. Such conditions also reached inland into Arkansas and along the southeastern coastal plain.
The number of readings of 31- previously believed to occur only rarely – totaled around 1,000.
Readings of 33 – previously thought to be almost nonexistent – totaled around 80.