The danger of heat was underestimated: climatologists warned of serious risks in the heat

Climatologists from the University of California, Berkeley, investigated the impact of extremely high

The study found that the heat index understates thereal perception of temperature at 10 °C in extreme cases, when human sweating cannot cope with the increase in temperature.

The heat index was developed in 1979physicist Robert Steadman, who wrote simple equations to calculate what he called the relative "hotness" of warm and humid as well as hot and dry conditions during the summer. This index, which takes into account air temperature and relative humidity, is used by meteorologists to calculate the "felt" temperature on warm days.

Sweating and redness when the blood is forheat dissipation is removed to the capillaries located close to the skin, are the main ways of human adaptation to hot temperatures, the authors explain. It is these effects that the heat index evaluates. The higher the index, the more stress the human body is exposed to.

Modified heat index - perceivedtemperature at various temperatures and air humidity. Temperature is in °F. 80°F = 26.6°C, 86°F = 30°C, 104°F = 40°C. A "perceived temperature" above 130°F (54°C) is considered dangerous. Image: David Romps, Yi-Chuan Lu, UC Berkeley

The main problem with Steadman's equations is thatthey were calculated based on normal conditions and extrapolated for higher temperatures and humidity, the scientists explain. The model works in most cases, but breaks down when people sweat so much that sweat puddles form on the skin. In such situations, the heat index is calculated for a condition with relative humidity above 100%, which is physically impossible.

Climatologists have adjusted the temperature index fromtaking into account physiological limitations and human response to extreme conditions. The study showed that dangerous conditions for humans begin with lower temperatures than previously thought. For example, at 100% humidity, the human body is exposed to high risks already at a temperature of 30 ° C, since the body in such conditions “feels” 60 ° C. A similar effect is exerted by a temperature of 35 ° C at a humidity of 65%.

Underestimation of the perceived temperature inexisting index. Temperature is in °F. 80°F = 26.6°C, 86°F = 30°C, 104°F = 40°C. -20°F difference = -11°C. Image: David Romps, Yi-Chuan Lu, UC Berkeley

The researchers note that in the pastextreme conditions were rare and could be ignored. But in conditions of climate change with a large number of heat waves, it is necessary to properly assess the risks to the body.

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