Study Estimates Summer Heat Killed About 50,000 People in Europe’s Cities

Record heat across Europe this summer killed an estimated 50,000 people in the continent’s cities, and about two-thirds of those deaths would not have happened without human-caused climate change, according to a new study by researchers at Imperial College London and the London School of Hygiene and Tropical Medicine.

The team modeled heat-related deaths by age group in 854 European cities during the repeated heat waves of June, July and August. They estimated 50,391 deaths from hot weather, of which 32,619 were attributable to the extra warming caused by burning coal, oil and gas. The findings are due to appear in the journal Nature Health.

By the researchers’ own earlier tallies, that makes this the deadliest summer on record for those cities, about 71 percent higher than the previous worst, 2022, when they estimated about 29,500 heat deaths. The share of heat deaths attributable to warming has also grown, from under half in the early 2000s to about 65 percent this summer.

The figures are estimates rather than counts, and the researchers say they are likely too low. Heat rarely appears on death certificates, even when it pushes someone with heart disease or lung cancer past their limits, so the team relied on established statistical relationships between temperature and mortality in each city. The study left out a deadly heat wave in May, and the cities covered hold only about 40 percent of Europe’s population; the authors cautioned that their results cannot simply be scaled up to include towns and rural areas.

To separate natural variation from the effect of warming, the scientists compared the actual summer with computer simulations of a climate without human influence, a method used in several earlier peer-reviewed studies. Outside experts consulted by reporters described the approach as state of the art. Howard Frumkin, a former director of the National Center for Environmental Health in the United States, who was not involved, said that hotter summers and better attribution tools together are producing larger and more accurate counts.

The burden fell most heavily on the old. People 85 and older made up about half of the deaths, but the study also estimated that more than 800 people between 20 and 44 died from the heat. Italy, France, Spain and Germany recorded the largest totals, and Naples was the hardest-hit city, with an estimated 815 heat deaths per million people.

About a third of the deaths occurred during an especially intense spell from June 17 to July 1, when temperatures ran about 5.3 degrees Celsius, or 9.5 degrees Fahrenheit, above normal. Clair Barnes, the lead author, said much of western and northern Europe was built for a cooler climate and is poorly equipped for the temperatures warming now brings.

Europe is the fastest-warming continent, about 2.5 degrees Celsius hotter than in preindustrial times, Barnes said. Euronews, reporting in September on data from the European Union’s Copernicus climate service, said western Europe had just had its hottest summer on record, breaking the mark set in 2003.