Modern heat waves appear much hotter than any measurement indicates, warn scientists

Modern heat waves appear much hotter than any measurement indicates, warn scientists

Modern heat waves appear much hotter than any measurement indicates, warn scientists

The heat index measurement, calculated by meteorologists to indicate how hot it is, underestimates the temperature people perceive on the hottest days, a new study reveals.

Climate scientists, including those at the University of California (UC) Berkeley in the US, say that the apparent temperature perceived by individuals is sometimes over 20°F.

Humans adapt to hot temperatures by sweating and flushing, a natural process in which blood is diverted to capillaries near the skin to dissipate heat.

The heat index, the researchers say, is a measure of how the body handles heat when humidity is high, and sweating becomes less effective at cooling us down.

While the measure was adopted as an indicator of people’s comfort, the scientists say, the index remained undefined for many extreme conditions that are now becoming increasingly common due to climate change.

They say the accurate indication of people’s comfort using the measurement stops when people sweat so much that sweat accumulates on the skin.

The findings, recently published in the journal Environment Research Letters, have implications for those who suffer from hot flashes.

When the heat index is high, the human body is more stressed during heat waves than public health officials often realize, the researchers warn.

A heat index above 103 can be dangerous and above 125 can be extremely dangerous, scientists say.

The new study expanded the old model to accurately represent apparent temperature for regimes outside those previously calculated.

“Most of the time, the heat index that the National Weather Service is providing is the right value. It’s only in these extreme cases that they’re getting the wrong number,” David Romps, a professor of earth and planetary sciences at UC Berkeley, said in a statement.

“What matters is when you start mapping the heat index back to physiological states and you realize, oh these people are being stressed with a very high skin blood flow condition where the body is getting close to running out of tricks. to compensate for this kind of heat and humidity. So we’re closer to that limit than we thought we were before,” said Romps, co-author of the study.

In the new research, the scientists applied the extended heat index to the top 100 heat waves that occurred between 1984 and 2020.

They found that seven of the 10 most physiologically stressful heat waves in the U.S. during that period were in the Midwest — primarily Illinois, Iowa and Missouri — not the Southeast, as meteorologists assumed.

Citing an example of one of the conclusions drawn from the study, the scientists say the maximum heat index reported during the July 1995 Chicago heat wave, which killed at least 465 people, was 135°F when it actually looked like 154 °F.

Doctors say that the body usually starts going crazy when the skin temperature rises to equal the body’s core temperature of around 98.6°F.

After that point, the core temperature starts to rise and the maximum sustainable core temperature is around 107°F – the threshold for heat death.

For the healthiest individuals, the researchers say, this threshold is reached at a heat index of 200°F.

Although the then-reported heat index at Chicago’s Midway Airport of 124°F only implied a 90% increase in skin blood flow, the new study suggests that people in the shade would have experienced blood flow to the skin that was 170 percent above normal to adapt to very high temperature and humidity per wash.

“Diverting blood to the skin stresses the system because you are pulling blood that would otherwise be sent to internal organs and sending it to the skin to try to raise the temperature of the skin. The rough calculation used by the NWS, and widely adopted, inadvertently minimizes the health risks of severe heat waves,” Romps said.

“But now that we have this model of human thermoregulation that works under these conditions, what does that really mean for the future habitability of the US and the planet as a whole? There are some scary things we are seeing,” she added.

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