In Earth's hottest spots, heat is testing the limits of human survival - The Washington Post

At Earth's hottest spots, heat is testing the limits of human survival - The Washington Post

As the Northern Hemisphere approaches summer’s peak, heat is testing the limits of human survival in Earth’s hottest spots — and demonstrating the extremes that are increasingly possible and probable against the backdrop of accelerating global warming.

Persian Gulf International Airport in Iran reported a heat index of 152°F (66.7°C) today at 12:30 pm.— Colin McCarthy (@US_Stormwatch)

Those are intolerable conditions for human/animal life. pic.twitter.com/R3RJ9pf4DC July 16, 2023

Such conditions are more than enough to overwhelm the body’s ability to regulate its internal temperature, experts said, and offer a glimpse of dangers only expected to become more prevalent as global warming increases extremes in heat and humidity.

“We know these extreme temperatures are killing people right now,” said Cascade Tuholske, an assistant professor at Montana State University.
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Here’s what extreme heat does to the body, and how some parts of the world could become too hot for humans to survive.

precautions you can take. There are

foods you can eat (and should avoid) to help keep cool. Here’s

how to know if it’s too hot to exercise, or

too hot to take your dog for a walk.

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Without the help of air conditioning, fans or shade, the body only has its own cooling system to withstand heat. Some body heat can escape through convection and radiation, though that is only effective if the air temperature is lower than body temperature.

Otherwise, sweating is the only way to cool down, transferring heat from the body to the air as it turns from a liquid to a vapor. But that, too, has its limits.

“Sweating is only effective in cooling our bodies if it evaporates,” said Larry Kenney, a professor at Pennsylvania State University who studies physiological responses to heat. Sweat that pools on the skin or drips off “represents dehydration, without any cooling effect,” he said.

Research has shown the human body loses its ability to cool itself via sweating at 95 degrees (35 degrees Celsius) on a scale known as the wet bulb global temperature, which factors in a combination of temperature, humidity, wind speed, sun angle and cloud cover.

A study Kenney published last year estimates that bar to be even lower, closer to 88 degrees (31 degrees Celsius) even for young and healthy people, based on observations of volunteer test subjects in a weather-controlled chamber.

At that point, exposure to such heat and humidity can strain the heart and cause body temperatures to rise unabatedly, Kenney said. That’s why extreme heat is most dangerous for older people and those with heart conditions.

On Sunday at the Persian Gulf International Airport in Iran, air temperatures exceeded 100 degrees, and the air was nearly saturated with humidity. That translated to a wet bulb temperature of 92.7 degrees (33.7 degrees Celsius), according to data and a wet bulb conversion calculator from the National Weather Service.

The heat and humidity were so intense, they translated to a heat index value that was literally off the charts. The heat index is designed to max out at about 136 degrees, but on Sunday it surpassed 150 degrees on the Persian Gulf.

Well beyond the Middle East, wet bulb temperatures were approaching dangerous levels. Across the southwestern and southeastern United States, wet bulb temperatures hovered in the upper 80s to around 90 degrees on Monday, according to Weather Service data.

Research published in 2020 found that dangerously high wet bulb temperatures are occurring far more frequently — more than twice as often since 1979.

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Look up your city to see extreme heat risks near you.

This year, the extreme conditions are occurring alongside a large surge in global heat. It is the product of a resurgent planet-warming El Niño climate pattern on top of greenhouse gas-driven warming.

The planet experienced record warmth in June, and the trend also extends to Earth’s oceans.

The waters around Florida, where residents used to steamy conditions are experiencing record heat and humidity this year, have surged close to 100 degrees Fahrenheit. That means, Tuholske added, that not even a dip in the ocean can provide relief from the heat.

“The summer of 2023 is proving to be one of the hottest, if not the hottest and most dangerous,” Tuholske said.

🌡️ Extreme levels of heat are affecting large parts of the Northern Hemisphere— Met Office (@metoffice)

⚠️ Exceptionally high temperatures are breaking records in places and dangerously hot weather will continue in many areas during the next week pic.twitter.com/zebYqdZXGH July 17, 2023

More on extreme heat

Our warming climate: In the Southern U.S., a sweltering heat wave isn’t moving anytime soon. At Earth’s hottest spots, heat is testing the limits of human survival. It’s not just you ⁠— summers in the U.S. are getting hotter. Look up your city to see your extreme heat risk with our tracker. Take a look at what extreme heat does to the human body.

How to stay safe: It’s better to prepare for extreme heat before you’re in it. Here’s our guide to bracing for a heat wave, tips for staying cool even if you don’t have air conditioning, and what to know about animal safety during extreme heat. Traveling during a heat wave isn’t ideal, but here’s what to do if you are.

Understanding the science: Sprawling zones of high pressure called heat domes fuel heat waves. Here’s how they work. You can also read more about the link between weather disasters and climate change, and how leaders in the U.S. and Europe are responding to heat.