According to a major study published in Nature Health and conducted jointly by Imperial College London and the London School of Hygiene & Tropical Medicine, successive heat waves killed more than 50,000 people.
A Record Summer Mortality
This unprecedented death toll directly implicates human-caused climate disruption. The researchers analyzed the impact of extreme temperatures from June through August across 854 urban areas in 30 countries, including the European Union, the United Kingdom, Switzerland, and Norway. The conclusions are definitive: of the 50,391 heat-related deaths, nearly two‑thirds (32,619 fatalities) are attributable to the impact of human activities on the climate. The episodes of intense heat were especially devastating, with nearly a third of the fatalities recorded in the period from June 17 to July 1. That figure far surpasses previous summer mortality records logged in the century. For comparison, the historic heatwaves of 2003 and 2022 caused 28,400 and 29,480 deaths, respectively.
The rapid worsening of the phenomenon is striking: the share of victims due to climate change in 2026 alone surpasses the total mortality observed during any prior summer since 2000. Southern and Central European countries bore the heaviest toll, notably Italy, France, Spain, Germany, and the United Kingdom. For the study’s lead author, Clair Barnes, a climatologist at Imperial College London, this summer was “the worst ever recorded in Europe for heat-related mortality. These figures are a brutal reminder that our hotter and more extreme summers are taking an ever greater toll on public health.”
A Toll That Is Still Underestimated
While people aged 85 and older accounted for nearly half of the deaths, these repeated heatwaves did not spare younger populations either. The Nature Health study led by two British institutions counted more than 6,000 victims under 65. Experts also note that heat often acts invisibly, worsening pre-existing conditions without being listed on death certificates, with amplification from isolation and poverty.
For the study’s authors, this dramatic toll could still be underestimated—the analysis focused exclusively on urban populations in 854 metropolitan areas. In the face of these alarming projections, scientists are calling for an urgent response. They argue that the study shows climate change “has already significantly increased heat-related mortality in European cities, underscoring the need to rapidly cut emissions and implement targeted local adaptation.”
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