Heatwave killed three times more people due to climate change

The heatwave that swept across Europe between June 23 and July 2 caused 2,300 deaths in 12 European cities.

Of these, 1,500—or 65%—would not have occurred if climate change had not intensified the heatwave. This is according to a report from the World Weather Attribution group, published this week. It is the first rapid study to estimate the number of deaths linked to climate change during a heatwave, conducted by scientists from Imperial College London and the London School of Hygiene & Tropical Medicine. Previously, such research took months.

Madrid (108 out of 118 climate-related deaths) is the worst-affected city in relative terms: more than 90% of deaths linked to excessive heat are attributable to climate change. In detail, during this period, climate change caused 317 deaths due to excessive heat in Milan, 286 in Barcelona, and 235 in Paris. This is, for example, more than the floods in Valencia in 2024 (224 deaths).

Invisible Deaths

“Once again, the heatwave is an ‘invisible killer of invisible people,'” commented Alexandre Florentin, Paris councilor and author of the “Paris at 50°C” report, on LinkedIn. “Heatwaves are a silent killer because deaths occur mainly in homes and hospitals, far from public view, and are rarely reported,” confirmed Pierre Masselot of the London School of Hygiene and Tropical Medicine (LSHTM), one of the authors of the study, quoted by the media outlet Climate Home News. “While a handful of deaths have been reported in Spain, France, and Italy, thousands more have died due to the scorching temperatures, and their deaths will not be recorded as heat-related,” he added.

Heat does not kill directly, but rather exacerbates existing health problems. People aged 65 and over accounted for 88% of deaths during the early summer heatwave. In France, consultations Emergency visits for heat-related illnesses peaked on July 1st, the height of the recent heatwave, according to the French Public Health Agency, with nearly 600 emergency room visits. During the recent orange alert period—even red around July 1st in some departments—the symptoms mainly affected elderly patients. A good half of heat-related emergency room visits (51%) were among those over 75.
2 to 4°C warmer

According to the World Weather Attribution report;

The early summer heatwave was between 2 and 4°C warmer than it would have been without climate change. June 2025 will therefore rank as the hottest June ever recorded in Western Europe, according to the European Copernicus climate service. Locally, temperatures regularly exceeded 40°C and reached as high as 46°C in Spain and Portugal, and as high as 48°C in “feels like temperature” (Universal Thermal Climate Index) north of Lisbon.

June 30th, a new monthly daily record, was “one of the hottest summer days ever recorded” on the continent. Spain recorded 24 tropical nights, where the temperature did not drop below 20°C, 18 more than a normal June, and some Mediterranean coastal areas experienced 10 to 15 of them instead of the usual zero in June, Copernicus points out. Experts warn that temperatures linked to heat waves will continue to rise and that the future death toll will likely be higher, as long as we continue to burn fossil fuels.