When W. Larry Kenney, a professor of physiology at Pennsylvania State University, began studying how extreme heat harms humans, his research focused on workers at the disaster-stricken Three Mile Island nuclear power plant, where temperatures can reach as high as 165 degrees Fahrenheit. could rise.
In the decades that followed, Dr. Kenney studied how heat stress affects a range of people in intense environments: soccer players, soldiers in protective suits, runners in the Sahara.
Recently, however, his research has focused on a more mundane subject: ordinary people. doing everyday things. While climate change is ruining the planet.
Heat advisories and extreme heat warnings went into effect Monday across much of the eastern United States after a weekend of record heat in the southwestern United States. The heat will move further northeast in the coming days, according to the National Weather Service, into the upper Mississippi Valley, the western Great Lakes and the Ohio Valley.
With severe heatwaves now hitting parts of the world with terrifying regularity, scientists are delving into the ways living in a hotter world will sicken us and kill us. The aim is to gain a better understanding of how many more people will suffer from heat-related illnesses, and how frequent and severe their suffering will be. And to understand how to better protect the most vulnerable.
One thing is certain, scientists say: The heatwaves of the past two decades are not good predictors of the risks we will face in the coming decades. The link between greenhouse gas emissions and blistering temperatures is already so clear that some researchers say there will soon be no point in trying to determine whether today’s most extreme heatwaves could have happened two centuries ago, before humans could destroy the planet. started to warm up. None of them could have that.
And if global warming isn’t curbed, the hottest heat wave many people have ever experienced will simply be their new summer norm, said Matthew Huber, a climate scientist at Purdue University. “It’s not going to be something you can escape.”
Which is harder for scientists to pin down, said Dr. Huber, is how these climate changes will affect human health and well-being on a large scale, particularly in the developing world, where huge numbers of people are already suffering, but good data is scarce. Heat stress is the product of so many factors – humidity, sun, wind, hydration, clothing, physical fitness – and causes such a range of damage that it is difficult to project future effects with any precision.
There haven’t been enough studies either, said Dr. Huber, about living full-time in a warmer world, rather than just experiencing the occasional scorching summer. “We don’t know the long-term consequences of getting up every day, working three hours in near-death heat, sweating like crazy and then going home,” he said.
The growing urgency of these issues is attracting researchers such as Dr. Kenney, who didn’t always consider themselves climate scientists. For a recent study, he and his colleagues placed young, healthy men and women in specially designed rooms, where they pedaled an exercise bike at low intensity. Then the researchers turned up the heat and humidity.
They found that their subjects overheated dangerously at much lower “wet bulb” temperatures — a measure that explains both heat and stuffiness — than they’d expected based on previous theoretical estimates by climate scientists.
In fact, under steam bath conditions, our bodies absorb heat from the environment faster than we can sweat to cool ourselves. And “unfortunately for humans, we don’t pump out much more sweat to keep up,” said Dr. kenney.
Heat is climate change at its most devastatingly intimate, devastating not just landscapes and ecosystems and infrastructure, but the depths of individual human bodies.
Heat’s victims often die alone, in their own home. Aside from heatstroke, it can cause cardiovascular collapse and kidney failure. It damages our organs and cells, even our DNA. Its damage increases in the very old and the very young, and in people with high blood pressure, asthma, multiple sclerosis and other conditions.
When the mercury is high, we are not as effective at work. Our thinking and motor functions are affected. Excessive heat is also associated with increased crime, anxiety, depression and suicide.
The toll on the body can be strikingly personal. George Havenith, director of the Environmental Ergonomics Research Center at Loughborough University in England, recalled an experiment years ago involving a large group of test subjects. They wore the same clothes and did the same job for an hour, in 95 degrees heat and 80 percent humidity. But by the end, their body temperatures ranged from 100 degrees to 102.6 degrees Fahrenheit.
“A lot of the work we do is trying to understand why one person ends up on one end of the spectrum and another on the other,” he said.
Vidhya Venugopal, professor of environmental health at Sri Ramachandra University in Chennai, India, has been studying the effects of heat on workers in steel mills, car plants and brick kilns in India for years. Many of them suffer from kidney stones caused by severe dehydration.
She remembers a meeting from ten years ago. She met a steel worker who had worked 8 to 12 hours a day near a furnace for 20 years. When she asked him how old he was, he said 38 to 40.
She was sure she had misunderstood. His hair was half white. His face had shrunk. He didn’t look younger than 55.
So she asked how old his child was and how old he was when he got married. The math is checked out.
“It was a turning point for us,” said Dr. venugopal. “Then we started thinking: heat ages people.”
Adelaide M. Lusambili, a researcher at Aga Khan University in Kenya, studies the effects of heat on pregnant women and newborns in Kilifi County, on the coast of Kenya. In communities there, women collect water for their families, which can mean walking long hours in the sun, even when pregnant. Studies have linked heat exposure to preterm births and underweight babies.
The most heartbreaking stories, said Dr. Lusambili, are from women who suffered after childbirth. Some walked long distances with their day-old chicks on their backs, causing blisters on their bodies and mouths for the babies and making breastfeeding difficult.
It’s all been enough, she said, to make her wonder whether climate change is reversing the progress Africa has made in reducing newborn and child deaths.
Given the number of people who don’t have access to air conditioners, which themselves are making the planet hotter by consuming massive amounts of electricity, societies need to find more sustainable means of defense, said Ollie Jay, a professor of heat and health at the University of Sydney.
dr. Jay has studied the body’s reactions to sitting near an electric fan, wearing wet clothes, and sponging with water. For one project, he recreated a Bangladeshi garment factory in his lab to test low-cost ways to keep workers safe, including green roofs, electric fans and scheduled water cuts.
Humans have some ability to acclimate to warm environments. Our heart rate goes down; more blood is pumped with each beat. More sweat glands are activated. But scientists primarily understand how our bodies adapt to heat in controlled lab environments, not in the real world, where many people can dive in and out of air-conditioned homes and cars, said Dr. jay.
And even in the lab, inducing such changes requires people to be exposed to uncomfortable stress for hours each day for weeks, said Dr. Jay, who has done just that with his subjects.
“It’s not particularly pleasant,” he said. Hardly a practical solution to living in a stifling future – or, for people in some places, an increasingly oppressive present. More profound changes in the body’s adaptability will only occur on the timescale of human evolution.
dr. Venugopal becomes frustrated when asked about her research on Indian workers: “India is a hot country, so who cares?”
No one asks what the problem is with a fever, but heat stroke puts the body in a similar state.
“That’s human physiology,” said Dr. venugopal. “You can’t change that.”