Study attributes roughly two-thirds of Europe's 2025 summer heat deaths to human-caused warming
Researchers say about 16,500 additional deaths occurred across 854 cities during the 2025 summer, with more than 1,100 in the United Kingdom
A multi-institution analysis released Tuesday found that climate change was responsible for roughly 68% of the estimated 24,400 heat-related deaths across 854 European cities during the summer of 2025 — about 16,500 excess deaths compared with a summer without human-driven warming. The study identified more than 1,100 deaths in the United Kingdom attributable to rising temperatures and said older people bore the overwhelming share of the burden.
The research, led by scientists at Imperial College London and collaborating institutions, examined mortality during several intense heatwaves this summer and compared observed conditions with modeled counterfactuals that exclude human-caused warming. The authors said Europe experienced multiple episodes of extreme heat, including a July 21–27 heatwave that produced temperatures up to 6°C above average in parts of southeastern Europe and was associated with an estimated 950 deaths during that week alone.
The study reported 4,597 deaths attributable to climate change in Italy, 2,841 in Spain, 1,477 in Germany, 1,444 in France, 1,147 in the United Kingdom, 1,064 in Romania, 808 in Greece, 552 in Bulgaria and 268 in Croatia. Capitals with the highest death rates per capita were Rome, Athens and Bucharest, the researchers said. People aged 65 and older accounted for about 85% of the additional deaths, and 41% were over age 85.
Researchers highlighted several individual workplace and public deaths reported during the summer, including a 51-year-old street cleaner in Barcelona and a 47-year-old construction worker in San Lazzaro di Savena, Italy, underscoring the risk to outdoor workers who continued to labor during temperatures above 40°C in some regions.
"Heatwaves are silent killers," said Dr. Garyfallos Konstantinoudis, a lecturer at the Grantham Institute — Climate Change and the Environment at Imperial College London, adding that most heat deaths occur in homes and hospitals where existing health conditions are aggravated and that heat is seldom recorded on death certificates. Friederike Otto, professor in climate science at Imperial's Centre for Environmental Policy, said the fatalities illustrate the consequences of continued fossil fuel use. "If we had not continued to burn fossil fuels over the last decades, most of the estimated 16,600 people in Europe wouldn't have died this summer," she said.
Other researchers noted that heat-health warning systems and adaptation measures are in place across much of Europe, but that those interventions have not prevented high mortality in recent summers. Dr. Malcolm Mistry, assistant professor at the London School of Hygiene & Tropical Medicine, said well-developed warning systems exist but that the health burden from heat has remained high despite warnings issued by meteorological and public health authorities.
The study urged both adaptation and mitigation: recommended measures include flexible working schedules, adjustments to school calendars, increased urban green space and expanded access to cooling such as air conditioning, together with improved public health infrastructure. Researchers warned, however, that such measures have limited capacity to offset the scale of risk unless greenhouse gas emissions are sharply reduced.
Europe has warmed faster than most other continents, the authors noted, meaning summers will continue to grow hotter until fossil fuel use is curtailed and replaced by low-carbon energy sources. The report said that across the continent this summer, climate change accounted for approximately two-thirds of heat-related deaths, reinforcing warnings from public health officials and climate scientists that extreme heat already poses a major and growing risk to human life.
The findings add to a growing body of research linking recent extreme-heat events to human-driven climate change and provide a mortality estimate for the summer of 2025. Policymakers and public-health authorities face decisions about strengthening heat adaptation measures while pursuing emissions reductions to limit further increases in heat-related mortality in coming years.