Climate change tripled European heatwave deaths in June, study finds

Climate change tripled the death toll from a European heatwave in late June, killing an estimated 2,300 people across 12 major cities, according to early analysis released by scientists studying the impact of planetary heating on extreme weather events.

Researchers from the World Weather Attribution group attributed 1,500 of the deaths to climate breakdown during the 10-day period between 23 June and 2 July, when temperatures soared across Europe. The analysis used established epidemiological methods but has not yet undergone peer review.

Milan recorded the highest absolute death toll with 317 out of 499 heat deaths attributed to climate breakdown, followed by Paris and Barcelona. London experienced 273 heat deaths, with researchers attributing 171 to human influence on climate.

Older populations most affected

The study found 88% of climate-driven deaths occurred among people over 65, with older populations showing highest mortality rates. Scientists described extreme heat as an “underappreciated” threat, noting most victims died privately in homes and hospitals with limited media coverage.

Researchers used epidemiological models to estimate heat-related mortality in cities including Paris, London, Madrid and Rome, comparing actual death tolls with hypothetical scenarios without human-caused planetary heating through fossil fuel burning and nature destruction.

The study found climate breakdown pushed temperatures in some cities up to 4C higher, resulting in 1,500 additional deaths. This exceeded death tolls from other recent weather disasters worsened by fossil fuel pollution, including 224 deaths in Spanish floods in 2024 and 243 deaths across north-west Europe in 2021 floods.

Record Mediterranean temperatures

The EU’s Copernicus Earth observation service reported last month as the third hottest June globally, with an “exceptional” marine heatwave developing in the western Mediterranean. Average daily sea surface temperatures reached record highs of 27C for the region in June.

Copernicus recorded increased “tropical nights” where temperatures remained above 20C, preventing adequate rest. Parts of Spain experienced 24 tropical nights last month, 18 above the June average.

“In a warming world, heatwaves are likely to become more frequent, more intense and impact more people across Europe,” said Samantha Burgess, deputy director of the Copernicus climate change service.

Analysis by Mercator Ocean found nearly two-thirds of the Mediterranean experienced marine heatwaves classified as strong or worse, representing the greatest extent ever recorded. High temperatures disrupt fish populations and kill marine vegetation.

Previous studies estimate approximately 44,000 annual heat deaths across Europe. The 2,300 deaths from a single heatwave in 12 cities suggests potentially dangerous conditions this summer, researchers warned.