Climate change could triple U.S. heat deaths by mid-century, experts warn

If global warming is left largely unchecked, the number of Americans who succumb to extreme heat will triple by mid-century, new projections estimate.

These deaths could affect poor and minority Americans much more than the white and better-off, according to a team led by Dr. Sameed Khatana of the University of Pennsylvania.

Rising temperatures will lead to a slight dip in deaths due to extreme cold, his team found, but triple-digit heat waves will more than offset that.

“Overall extreme temperature–related deaths were projected to more than double or triple depending on the [carbon] emissions increase scenario analyzed,” Khatana’s team reported Sept. 20 in the journal JAMA Network Open.

A study published just last month found that U.S. heat-related deaths have risen sharply and steadily from 2016 through 2023.

“Heat-related illnesses, like heat exhaustion or heat stroke, happen when the body is not able to properly cool itself,” according to the U.S. Centers for Disease Control and Prevention.

“While the body normally cools itself by sweating, during extreme heat, this might not be enough. In these cases, a person’s body temperature rises faster than it can cool itself down. This can cause damage to the brain and other vital organs.”

In the new study, the UPenn team used data on all counties in the United States for past trends in deaths linked to extreme heat and cold.

They then turned to “temperature projections from 20 climate models,” plus projections on changes in population, “to estimate extreme temperature–related deaths for 2036 to 2065.”

Those projections relied on two models of what might happen to the planet’s climate over the next few decades.

One projection assumed lower carbon emissions, “due to successful implementation of many currently proposed emissions control,” such as a switch away from fossil fuels to renewable sources of energy, the researchers said.

The other projection assumed a continuation of “fossil fuel–reliant socioeconomic development, with a larger increase in emissions.”

The result: In the first scenario, where rates of global warming were somewhat curbed, U.S. annual deaths linked to extreme temperatures (mostly heat) rose from about an average of 8,249 seen today to 19,348 annually by the middle of the century.

That’s still more than a doubling of the death rate.

However, in the second, worst-case scenario, deaths will more than triple by mid-century, to an average of 26,574, Khatana’s group said.

Race and ethnicity will make a big difference as to who might die on extremely hot days.

While the risk of extreme-temperature deaths are projected to rise by about 71% among white Americans by mid-century, the rise in risk for Black Americans will jump by 395.7% and the risk to Hispanic Americans by 537.5%, the researchers calculated.

“Many individuals from ethnic and racial minority groups reside in neighborhoods that have lower access to air conditioning, a higher urban heat island effect, reduced green space exposure, greater exposure to traffic-related air pollution, and a higher likelihood of winter power outages, which increase their vulnerability to extreme temperatures,” Khatana and colleagues explained.

Of course, the use of air conditioning may increase, but “even areas with nearly universal air conditioning access, such as the southern U.S., were found to have a high burden of extreme heat and temperature-related deaths,” the team noted.

But climate change will deliver other threats to health, one expert noted.

Dr. Cioe-Peña, vice president for Northwell Health’s Center for Global Health, stressed that climate change is no longer a distant threat, pointing to the undeniable increase in extreme weather events, record-breaking temperatures and the spread of mosquito-borne illnesses like malaria and dengue fever into new areas as proof.

“We’re going to see [these diseases] in places that we haven’t seen them before,” he warned. “Malaria in Florida, dengue on the West Coast. But we’re also going to see them moving farther north than they ever have before.”

He also noted that the United States is facing a “perfect storm” of soaring temperatures and a surge in vulnerable aging baby boomers. With 10,000 boomers turning 65 every day, the health care system is bracing for a demographic shift unlike any other, he said.

“They always say that extreme weather events affect the extremely old…disproportionately,” Cioe-Peña said. “And we’re now seeing kind of a top-heavy graph in the age distribution in the United States as the baby boomers age.”

This is particularly concerning because seniors are uniquely vulnerable to heat. They have a harder time regulating their body temperature, are less likely to recognize the signs of heatstroke and are more susceptible to dehydration and heat-related illnesses, he noted.

Still, intervening now may help prevent thousands of deaths in years to come, the study researchers said.

“Along with efforts to reduce greenhouse gas emissions, efforts to mitigate the adverse outcomes of extreme temperatures for population health are needed,” they wrote.

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