Deadly combination of global warming: heat and humidity

Above a wet bulb temperature of 35 Celsius, the body cannot cool down, because the sweat on the skin can no longer evaporate. Prolonged exposure to such conditions can be fatal, even for healthy people. Lower but still high wet bulb temperatures can affect health and productivity in other ways.

Ms. Zhang warned that the health effect of her study was uncertain, as she and her colleagues only looked at the height of wet bulb temperatures, not how often extremes would be reached or how long they lasted. “In-depth knowledge of the health impact of the intensity, frequency and duration of high wet bulb temperatures is required,” she said.

The study was published in the journal Nature Geosciences.

The 1.5 degree warming target was the lower of two set by the 2015 Paris Agreement between nations to tackle climate change. But the world has already warmed by about 1 degree since 1900, and the ability to stay below target is slowly wiping out as nations’ emission reductions, both achieved and promised, are far from being. up to what is needed.

A growing body of research has revealed that global warming has so far had an increasing impact on human health indirectly due to drought and crop failure, extreme storms and flooding, the increased spread of certain diseases transmitted by insects and other effects.

But heat also has direct effects on the human body. Even relatively dry heat can be enough to kill people, as evidenced by the toll of heat waves in recent years. And the combination of heat and high humidity has already reached dangerous levels in some parts of the world.

A study last year that looked at weather data found two sites in the tropics that have already had numerous occurrences of wet bulb temperatures above 35 degrees, and many sites, including some along the coast. southeastern United States, which had TW readings. from 31 to 33 degrees. But in most cases, the extreme conditions only lasted an hour or two.

The effects of heat and humidity are worse for women, the elderly and people with chronic conditions like diabetes and hypertension, said Glen Kenny, professor of physiology at the University of Ottawa who studies how the body copes with heat stress.