Climate change causes three times more heat deaths in Europe

Europe's cities suffered from oppressive heat this summer – temperatures of up to 46 degrees Celsius were recorded in Spain and Portugal, and over 50 degrees Celsius in Turkey. For young and healthy people, extreme temperatures are usually only unpleasant. But for older and vulnerable individuals, they can be life-threatening.

Due to climate change, there were three times more heat-related deaths this summer than would otherwise have been expected. Around 16,500 deaths, or almost 70 percent of all heat-related deaths, were attributable to rising temperatures alone. This was the result of a model by Imperial College London and the London School of Hygiene & Tropical Medicine . "Extreme heat is the deadliest type of weather, and the officially recorded number of heat-related deaths is significantly underestimated," the researchers write. They therefore conducted more precise calculations.

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To do this, they analyzed data from 854 European cities to first estimate how many people are likely to have died this summer due to extreme heat. They also used figures to estimate how much temperatures are likely to have changed due to human influence. They assumed that the 1.3-degree warming compared to the pre-industrial era was primarily due to the burning of fossil fuels. Finally, by calculating how many people would have died had temperatures been 1.3 degrees Celsius lower, they were able to derive how many deaths are attributable to the human contribution to climate change.

The summer of 2025 was the fourth warmest on record. Temperatures from June to August 2025 were 0.9 degrees Celsius above the 1990-2020 average, according to the study. "This means a significantly increased risk of death for vulnerable individuals, such as those over 65 and those with underlying health conditions, as well as an increased risk of overheating in enclosed spaces," the study states.

Looking at European capitals, the study shows that Rome, Athens, and Bucharest experienced the greatest excess heat-related mortality this summer. The largest proportion of heat-related deaths attributable to climate change, however, occurred in Stockholm, Madrid, and Bratislava. According to the model, there were 423 heat-related deaths in Madrid, of which 387 (93 percent) were attributable to climate change. This is explained by the fact that mortality increases sharply during particularly high temperatures.

In Stockholm, however, only an estimated 31 people died from the heat. Of these heat-related deaths, 30, or 97 percent, were attributable to climate change. This means that without climate change, only one person in all of Stockholm would have died from heat this summer, as extreme heat is not usually experienced there.

For Berlin, the modeling revealed a total of 219 heat-related deaths, of which 140, or 66 percent, are likely attributable to climate change. The population of the other German cities examined is approximately 23.4 million. Among these 23.4 million residents, there were an estimated 2,445 heat-related deaths, of which 1,477 (60 percent) were due to climate change.

The study did not examine which factors other than temperatures influenced heat mortality in cities. However, the study identified important roles in the age structure of the population, as well as air pollution and the extent to which cities were adapted to rising temperatures.

"Cities are particularly vulnerable to heat because large amounts of concrete and asphalt surfaces trap and store heat, while transportation and energy consumption generate additional heat," the publication states. Green spaces and water are effective measures to reduce the heat storage effect of cities. They can serve as "lifelines" for residents during heatwaves, the authors write. This is especially true for the socioeconomically disadvantaged segments of the population who live in densely populated neighborhoods and are less likely to have air conditioning.

As a further measure, health systems and social institutions would need to adapt to the challenges posed by increasing heat, and working conditions and activities would need to be adapted during periods of severe heat.

The researchers also point out that 70 percent of people in Europe live in cities, and that this will rise to 80 percent by 2050. At the same time, Europe's population is aging, creating more vulnerable people. With an expected warming of another two degrees Celsius, 163 million Europeans would be exposed to unprecedentedly high summer temperatures in 2050. That will be twice as many as today. This will not only lead to more heat-related deaths, but heat will also lead to more hospital admissions and a worsening of chronic diseases, especially among older people and those with lower incomes, the study continues.

So far, Europe has been only "moderately" prepared for the increasing heat. The study's findings are consistent with data the researchers had already published at the beginning of the summer . This initial modeling only determined the number of heat-related deaths in twelve European cities and only during the first heat wave of the summer. Even then, estimates had shown that the number of heat-related deaths had tripled due to climate change.

While cities could adapt by planting more trees, reducing space for cars, and caring for the most vulnerable, the authors said when presenting the first study. However, even then, they called for addressing the root cause of climate change, emphasizing the role of fossil fuels as the "primary trigger" of climate change.