Nearly 62,000 people died heat-related deaths last year during Europe’s hottest summer on record, a new study has found — more heartbreaking evidence that heat is a silent killer, and its victims are vastly under-counted.
The study, published Monday in the journal Nature Medicine, found that 61,672 died in Europe from heat-related illness between May 30 and September 4 last year. Italy was the hardest-hit country, with around 18,000 deaths, followed by Spain with just over 11,000 and Germany with around 8,000.
Researchers also found the extreme heat disproportionately harmed the elderly and women. Of the nearly 62,000 deaths analyzed, heat-related mortality rate was 63% higher in women than in men. Age was also an important factor, with the death toll increasing significantly for people aged 65 and over.
“It’s a very big number,” Joan Ballester, an epidemiologist at ISGlobal and the lead author of the study, told CNN.
Eurostat, which is Europe’s statistical office, attempted to quantify the heat wave’s death toll last year by tallying excess deaths — or how many people died more than a typical summer. But Ballester, who lives in Spain and sweated through last year’s heat wave, said the study published Monday was the first to analyze how many deaths last summer were specifically caused by heat.
Researchers analyzed temperature and mortality data between 2015 and 2022 for 35 European countries — representing a total population of 543 million people — and used it to create epidemiological models to calculate heat-related deaths.
“For me, I’m an epidemiologist, so I know what to expect and (the number of deaths) is not surprising, but for the general population, it’s very likely that this is astonishing,” he said.
View this interactive content on CNN.comThe region has seen this script before — an unprecedented heat wave resulted in more than 70,000 excess deaths in the summer of 2003. That heat wave was an “exceptionally rare event,” the study’s scientists said, even when accounting for the human-caused climate crisis.
The 2003 heat wave was a wake-up call, researchers said. It showed Europe at the time lacked the kind of preparedness to prevent a mass casualty event from heat, and it exposed the fragile nature of the region’s health system, Ballester said, particularly as weather extremes become more frequent and intense.
But the study’s findings show that even Europe’s current prevention plans are still not enough to keep up with the breakneck pace at which dangerous heat waves are occurring and putting even more lives at risk.
“The fact that more than 61,600 people in Europe died of heat stress in the summer of 2022, even though, unlike in 2003, many countries already had active prevention plans in place, suggests that adaptation strategies currently available may still be insufficient,” said Hicham Achebak, a co-author of the study and researcher at ISGlobal.
While the numbers may have been worse without the region’s current heat prevention plans, the authors warn that the world is only going to get hotter — and that without effective adaptation plans in place, Europe could face more than 68,000 premature deaths each summer by 2030, and over 94,000 by 2040.
“The acceleration of warming observed over the last 10 years underlines the urgent need to reassess and substantially strengthen prevention plans,” Achebak said.
Lessons for the US
Monday’s study shows how serious a health risk extreme heat can be. In the US, heat kills more Americans than any other weather-related disaster, and the climate crisis has been making these extreme events more deadly. Heat deaths have outpaced hurricane deaths in the country by more than 8-to-1 over the past decade, according to data tracked by the National Weather Service.
Yet the United States’ heat mortality numbers would suggest that far fewer people are dying from heat than in Europe. According to data from the Centers for Disease Control and Prevention, around 700 people die heat-related deaths each year.
David S. Jones, a physician and historian at Harvard University, said there are a couple explanations as to why US statistics seem low: the US could be underreporting its numbers, or heat is more lethal in Europe due to the lack of air conditioning — or it could be a combination of the two.
Jones, who is not involved with Monday’s study, said just 5% of households in France have air conditioning, for example, compared to nearly 90% in the US.
“There’s also reason to believe that places that are more often exposed to heat, like the American South, are actually less vulnerable to heat than in places like the Northeast US or in Chicago or Europe,” Jones said.
“But it comes back to this question of, well, is Europe just reporting more accurately than the US is?” he said. “There’s been people who have been frustrated with the quality of US health data across the board, not just heat, but everything else, for decades.”
John Balbus, the acting director of the Office of Climate Change and Health Equity at the US Department of Health and Human Services, said the number is lower because the CDC estimates heat-related deaths based on death certificates which list heat as the primary or contributing cause of death, whereas academic institutions, such as ISGlobal, use statistical models for their estimates.
A 2020 study found that heat-related deaths were being underestimated in 297 of the country’s most populous counties. Researchers said mortality records tend to neglect other potentially heat-related causes of death, like heart attacks.
But there are other ways of getting at how many people in the US are being harmed by increasingly frequent heat waves. Balbus noted the CDC does track the number of people who show up to emergency rooms for heat-related illnesses.
The Biden administration is working on short-term solutions for heat, Balbus said, like more effective advisories and getting air conditioners into the hands of low-income families.
But they also have an eye on the longterm through recent legislation: planting more trees and green space in urban areas, which cools the surrounding air; offering communities support for reflective streets and roofs; and working to modernize building codes so they trap less heat.
Still, Balbus said, as temperatures continue to climb, more funding should be dedicated to studying and tracking the health impacts of the climate crisis.
“We’re doing the best we can with the resources we have,” Balbus said. “And we could do more with more capacity, but it’s something that has scientific challenges, and it requires support.”
Correction: An earlier version of this story misstated the way CDC calculates heat-related deaths. The agency's estimate includes death certificates that list heat as a primary or contributing factor of death.