When it comes to heat, the human body is remarkably resilient—moisture is what makes it difficult to cool down. And humidity, driven in part by climate change, is increasing.
The measurement of the mixture of heat and humidity is called “wet bulb temperature”, which is determined by turning Wet wick around thermometer bulb. Scientists use this scale to find out which areas of the world may become very dangerous to humans.
Rarely heard of, wet bulb temperature reflects not only heat but also the amount of water in the air. The higher this number It is difficult for sweat to evaporate and cool the body.
At a certain threshold of heat and humidity, “you can no longer be able to sweat fast enough to prevent overheating,” said Radley Horton, a professor at Columbia University’s Lamont-Doherty Earth Observatory.
Scientists have found that Mexico, Central America, the Persian Gulf, India, Pakistan and Southeast Asia are all heading toward this threshold before the turn of the century.
“The risks of moist heat are greatly underestimated today and will increase significantly in the future,” Horton said. “As sites around the world have previously experienced rare or unprecedented extremes with increasing frequency, we risk that our previous message about the dangers of extreme heat – already insufficient – will fall short of the target.”
You might think that getting close to the beach would be a great way to enjoy the ocean breeze and relax. But Horton said the proximity of the water in harsh conditions It could make things worse. As higher temperatures cause water to evaporate, it adds moisture to the air.
“If you are sitting in a city along the Persian Gulf,” he said, “the sea breeze can be a deadly breeze.”
To understand why the temperature and humidity in these places are so high for humans to bear, you first need to understand how the body cools itself.
The wet bulb temperature that defines the upper limit of what the human body can tolerate is 95 degrees Fahrenheit (35 degrees Celsius). But any temperature above 86 degrees Fahrenheit (30 degrees Celsius) can be dangerous and deadly. Horton and other scientists note that paper 2020 These temperatures are occurring with increasing frequency in parts of the world. To put things into perspective, the hottest wet bulb temperature ever recorded in the Washington area, known for its unbearably humid summer, was 87.2 degrees (30.7 degrees Celsius).
“Overall, extreme moist heat has more than doubled since 1979,” the study authors wrote.
Scientists say these conditions are reaching that lethal threshold in places like South Asia and the Middle East and could regularly exceed it by 2075.
Horton and colleagues found that parts of the United Arab Emirates and Pakistan have each crossed the 95-degree mark for an hour or two more than three times since 1987.
Also on the Gulf Coast of California, in the Mexican state of Sonora, scientists are seeing a “very significant” increase in wet-bulb temperature and air temperatures, Teresa Cavazos, a senior researcher in the Department of Physical Oceanography in Ensenada, said. Center for Scientific Research and Higher Education.
During the summer, temperatures in parts of the bay can reach 86 to 87.8 degrees Fahrenheit (30 to 31 degrees Celsius), causing the water to evaporate more quickly. The combination of warmer waters and increasing heat trends in Sonora is causing wet-bulb temperatures to reach dangerous levels.
“Just an increase of one or two degrees Celsius can be the tipping point for changing the effect,” Cavazos said.
The extreme heat leads to difficult living conditions, especially for communities that lack the resources to provide relief.
Why do some survive while others die
Even below these thresholds, cooling is hard work on the body. Efforts to combat the effects of heat put stress on your heart and kidneys. With extreme heat, people’s organs can begin to fail. If you have pre-existing conditions, they most likely are.
In heat waves, many deaths occur due to health problems exacerbated by harsh conditions.
“It’s very clear during a heat wave, that more people are dying from heat stroke,” said Zachary Schlader, an assistant professor at Indiana University Bloomington who focuses on heat stress and the human body. But even more Dies of heart disease. The body responds [to heat] This way you can make the member weak.”
During heat waves there are some simple ways to take care of your body.
Protecting yourself from this stress is closely related to your social and economic status and resources.
“The poorest are the most vulnerable, and they are already suffering,” Cavazos said, noting that Sonora relies on agriculture, which means many people have to work physically in the dangerous heat.
In regions like the Persian Gulf, extreme heat is the new normal: Qatar has adapted so extensively to the climate that it outdoor air conditioning. But not everyone has access to outdoor air conditioning, including those who build the facilities that contain it. When the wealthy country began building stadiums to host the 2022 World Cup, it faced an uproar over its treatment of the workers who build stadiums.
In 2019, the United Nations warned During the four hottest months of the year, outdoor workers in Qatar were working under “significant occupational heat stress conditions”.
Qatar imposed in May systems Increase the number of hours prohibiting outdoor work to 10 a.m. and 3:30 p.m. during the hottest months of the year, with any work prohibited if the wet bulb temperature is above approximately 89 degrees Fahrenheit.
Just surviving in these conditions depends on your place in society and what that provides: access to air conditioning, insulated homes, jobs that don’t require much physical exertion in the sun and the policies in place to protect you from dangerous conditions.
“We as humans have learned to adapt,” Cavazos said. “The problem is the cost. Some will not survive.”