More than 50,000 people are estimated to have died from extreme heat across European cities and towns this summer, researchers reported Friday, marking the deadliest heat season in the continent’s recent history. The findings, published in two studies in the journal Nature Health, attribute the surge in fatalities primarily to climate change driven by the burning of fossil fuels.

Scientists from Imperial College London analyzed heat-related mortality across 854 urban areas in 30 countries, including the 27 European Union member states as well as Britain, Norway, and Switzerland. These cities and towns collectively represent roughly 40 percent of the population in the examined countries. The studies utilized a complex methodology factoring in demographics, socioeconomic status, and health system availability to estimate deaths indirectly linked to heat. Unlike official government figures—which typically account only for deaths directly attributed to heatstroke—this research includes fatalities from cardiovascular and respiratory conditions exacerbated by prolonged high temperatures.

This summer’s heatwave was shaped by several sustained “heat dome” weather systems, which trapped extreme temperatures over large swaths of Europe. The additional warming caused by greenhouse gas emissions intensified these heat events beyond what would have occurred in preindustrial times. “Even in a preindustrial climate, for some of these heat waves, we would have expected to see high mortality,” said Clair Barnes, lead author and climate specialist at Imperial College London. “But that mortality has been pushed substantially higher by the human-caused warming, primarily from the burning of fossil fuels.”

The death toll of approximately 50,400 this year far exceeds previous peaks, including 29,480 fatalities in 2022 and 28,462 during the infamous 2003 heatwave, which raised early warning about Europe’s vulnerability to climate change. The intense heat this year also contributed to historic wildfires in France and Spain, forcing the evacuation of 300,000 people.

The researchers used climate models to simulate this summer’s temperatures in a hypothetical scenario without human-induced warming. Comparing estimated mortality rates between the actual and modeled climates highlighted that the record-breaking death toll is mainly due to the severity and duration of the heat episodes, rather than demographic shifts such as population growth or urbanization.

Garyfallos Konstantinoudis, a co-author on the studies, emphasized that the spike in heat-related deaths could not be explained by changes in the number or age of urban residents. The unprecedented heatwaves exposed millions to hazardous outdoor conditions, straining health systems throughout Europe.

In response to rising heat risks, public health agencies in several nations—including Britain, France, Germany, and Spain—have begun issuing real-time estimates and warnings during the summer months. These measures indicate growing awareness of the need to mitigate heat-related health impacts amid ongoing climate change.