A body adapted to the heat knows how to sweat.
To keep the internal organs cool, the blood flows to the skin at a higher speed. There is more sweat and it becomes more diluted to reduce electrolyte loss (a major problem with dehydration). The body slows down its metabolism and heart rate for a lower core temperature and basically uses less oxygen.
But it takes weeks of constant heat exposure to build up all that tolerance. We’re at our best when the heat doesn’t surprise us. A summer athlete may be familiar with this process called acclimatization: the key is to take it slow while also hydrating and taking breaks to cool off.
Climate change is making safe, slow adaptation to the heat much more difficult, upending what we would normally expect as the seasons change. Summers are getting longer and more intense, encroaching on winter and lasting well into autumn.
Large parts of Asia have been hit particularly hard in the past two weeks. Axios reported how heat records fell across China, India, Bangladesh and Thailand as areas surpassed 100 degrees Fahrenheit (40 degrees Celsius). 13 people have died from heat stroke in India. Thailand recorded a new all-time temperature record this month. And more than a dozen Chinese provinces broke new heat records.
It has been exactly a year since Pakistan and India last experienced similarly shocking temperatures; Last May, half the US population faced an historic heatwave of 20 to 30 degrees Fahrenheit above average. Temperatures this spring across the US are already reaching historic highs in the 1990s.
Although late summer can bring more extreme temperatures, these early heatwaves are taking a particularly dangerous toll. “It’s well documented that there is higher mortality earlier in the season because people are not used to the higher temperatures,” said Kristie Ebi, professor of global health at the University of Washington, author of the interstate’s sixth assessment Committee on Climate Change (IPCC).
Another public health researcher, Professor Patrick Kinney of Boston University, explained that acclimatization can also help to understand why heat deaths vary so much across regions.
“In the northern parts of the United States, like Boston or New York or Chicago, it doesn’t have to get that hot before you see people dying on hot summer days. On the other hand, if you go to Atlanta or Houston, it has to get a lot hotter before mortality goes up,” he said.
Being unprepared for the heat can be worse than the heat itself. Acclimatization gives us a clue as to why it is so dangerous. But we have a lot more control to ensure we are helping those most vulnerable to adapt and adapt.
Elderly people, outdoor workers and people taking certain medications are at risk from the early season heat
A wealth of research shows that heat waves can have higher mortality in early summer than later in the season. It changes how we think about heat by considering its year-round effects and not just the longest and most extreme exposures.
The same earlier-is-worse trend can apply to a given event: even in a prolonged heatwave, there is more mortality at the beginning than at the end.
There are a few in-game explanations. One theory is that the most vulnerable populations (older adults and those with chronic conditions) will succumb to the higher temperatures early in the season, leaving less vulnerable people in the more intense heatwaves a few months later.
A second explanation is the acclimatization effect, as humans need time to get used to heat. How much time it takes a person to adjust physiologically depends on this. “People acclimate at different rates depending on their age, their physiology, or the previous exposures they’ve had,” Ebi said.
A long list of populations are particularly vulnerable to heat, including adults over 65, children under the age of 1, people taking certain prescription medications, those with certain chronic illnesses, outdoor and farm workers, the homeless and pregnant women. Dehydration, heat illness and death are risks for the more susceptible individuals, and studies have linked exposure to high heat in the last trimester to lower birth weights in babies.
Climate change makes it harder for us to adapt
Climate change is throwing off conventional expectations of when the heat will become too much.
One of the problems is that the nights are much hotter than they used to be. The ability to cool off at night is one of the most important factors in preventing heat illness. But hot nights disturb sleep and put a strain on the body.
“Since records began in 1895, summer nighttime low temperatures have generally been warming at nearly twice the rate of US afternoon high temperatures, and the 10 warmest summer minimum temperatures have all occurred since 2002,” according to the National Oceanic and Atmospheric Administration.
There is also a difference between moist and dry heat. Humidity makes it feel hotter, so areas used to dealing with dry heat may not be adapted to different conditions.
Places typically accustomed to dry heat, such as Southern California, are expected to experience more humidity. Warmer air can hold more moisture – about 7 percent more per degree Celsius – and the higher surface temperatures also mean more water evaporates. This not only leads to large precipitation events, but to more uncomfortable temperatures overall.
Finally, the world is experiencing more weather-related whiplash, including wild temperature swings. The relationship between whiplash and climate change is harder to establish, but some studies suggest it could shift air movements around the North Pole, causing the polar vortex to wobble and more cold air to flow south (toward the US). It helps explain why parts of the US experienced unusually cold winter storms.
Climate change has shattered any sense that heat vulnerability follows a pattern confined to July and August. Experts like Ebi argue that this requires a rethink of heat risks throughout the year so we can better prepare for the heat and help the most vulnerable at the times when it is most needed.
Early heat is more dangerous in areas with poorly adapted infrastructure
The way we adapt to the pre-season heat isn’t just about physiological changes in our bodies. Behavior also makes a difference, as do policies and infrastructure to help people deal with it.
Those of us who are not used to the heat can compensate in other ways, e.g. B. by running the air conditioning earlier or by cooling off by water or in the shade. Green landscaping, white surfaces, and breathable clothing can also help us adapt.
But access to all of these resources is another matter, and we see tremendous disparities based on income, race, geography, and politics.
“A heat wave is partly a natural phenomenon, but there are policy decisions that have been made over decades and centuries that have deprived low-income people of color of vital resources, infrastructure, disaster preparedness and green amenities,” said Michael Méndez, an assistant professor of environmental policy and planning at the University of California Irvine. “And it’s no surprise that when a disaster strikes, the hardest hit communities are the least prepared.”
Trees are a prime example of this disparity. Historically marked communities still have significantly less tree cover (estimated at 21 percentage points less in one paper) than areas that have not faced racial discrimination. Green spaces mitigate the effects of heat waves: not only do they provide shade, they also lower the temperature, especially compared to the radiant heat emitted by concrete.
Schools are also unevenly equipped for the heat. In 58 countries, each additional day with temperatures above 80 degrees Fahrenheit lowered children’s test scores, a study published in the journal Nature Human Behavior found. When researchers broke down the data for the US, they found a strong impact of heat on black and Hispanic students, noting that they were less likely to have access to air conditioning at home and at school.
The US still has few policies to help protect people from the most extreme summer heat. Federal and state programs to help people focus their energy bills more on the winter months than the summer, so some low-income customers don’t turn on the air-conditioning to keep their bills affordable.
Many states also lack policies that prevent utility companies from turning off electricity when there is an unpaid bill during the summer months. Outdoor workers also have poorly enforced protections: In general, the Centers for Disease Control and Prevention (CDC) recommends that outdoor workers work only a small portion of the day and take frequent breaks and drink plenty of water while they work over a period of two years build tolerance weeks. Some states like California have standards for education, water, and shade, but abuses abound, especially in the agricultural sector.
“Agribusiness workers have a mortality rate 35 times higher than non-agricultural workers, and we also see this especially among Latin American rural and migrant workers who are in conditions of reduced labor protections,” Méndez said.
The Department of Labor’s Occupational Safety and Health Administration (OSHA) is making slow progress on draft heat standards to protect outdoor workers, which are several years away from being enacted.
Even heat-related protections, such as cooling centers, energy bill assistance and prevention of blackouts, are not focused on the important pre-season when people are least used to the hot temperatures. These types of initiatives, where they exist, typically don’t kick in until after a certain date or when temperatures are above 95 degrees Fahrenheit, which is well above the threshold that some vulnerable populations can handle. Coping with heat risk requires far more investment in heat preparedness much earlier in the year.
“We barely have enough resources to deal with what’s happening right now,” said Keith Ladd, a professor of urban planning at the University of Arizona. “With climate change, we’re seeing increased frequency, intensity and duration of heat waves, so we need to adjust our response.”
Update April 19 11:40 am: This story was originally published on April 14th and has been updated to include information about the heatwaves in China, India, Bangladesh and Thailand.
Help us celebrate nine years of Vox
Since Vox launched in 2014, our audience has supported our mission in so many meaningful ways. More than 80,000 people have responded to requests to support our reporting. Countless teachers have told us how they use our work in their classrooms. And in the three years since we started the Vox Contributions program, tens of thousands of people have contributed to keep our unique work free. We are committed to keeping our work free to all who need it because we believe quality explanatory journalism is a public good. We cannot rely solely on advertisements. Help us keep Vox free for the next nine years by giving a gift today?