Needed: Alert systems for the growing threat of humid heat

livemint.com:

The June that just ended was the Earth’s hottest recorded—ever. And the first week of July saw the trend continue. Surging summer temperatures made me wonder: Just how much heat can the human body stand? Deaths from heat are common, and as the world heats up, may become more so if we don’t develop a plan for extreme heat days, like the kind of warning system that comes before a major storm.

In 2019, about 469,000 people worldwide died from overheating, according to a 2021 paper in The Lancet. Heat is called a silent killer, said Ollie Jay, director of the Heat and Health Research Incubator at University of Sydney. It doesn’t make for dramatic TV footage the way tsunamis, tornados and floods do.

Whether heat can kill depends on humidity, wind velocity and direct exposure to sunlight as well as a person’s level of exertion, body size and clothes. In the US, temperatures of even 42° Celsius have resulted in fatalities. In California, a couple, their baby daughter and family dog died in 2021 while hiking after the mercury hit 41.7° C.

The parents had brought what seemed like ample water. When they set out, the temperature was only in the 20s. They had planned to be home before the heat set in.

But the hike started downhill. Getting back to their car required a climb up in direct sunlight. They never made it.

Heat can kill because our bodies are made of cells contained with membranes that can melt. While we think of ourselves as warm-blooded animals, biologists would call us homeothermic—we need to maintain a core temperature within a narrow range around 36.6° C. It can get up to about 40° C for a short time without permanent damage.