Record-breaking heat in Europe this summer killed an estimated 50,391 people in the continent's cities, and nearly two-thirds of those deaths would not have happened without human-caused climate change, according to a new study by researchers at Imperial College London and the London School of Hygiene & Tropical Medicine.
The study, published in the journal Nature Health, modelled heat-related deaths across 854 cities in 30 countries — the European Union's 27 members plus the United Kingdom, Norway and Switzerland — home to about 173 million people. Between June and August, repeated heat waves pushed temperatures far above normal. The researchers estimate that 32,619 of the deaths were caused by the extra heat attributable to the burning of coal, oil and gas.
The toll makes 2026 the deadliest European summer for heat in the team's records, which run back to 2000, and it was 71 percent higher than the previous deadliest summer, 2022, when the same researchers estimated 29,480 deaths. The authors caution that this summer's figures are underestimates: the analysis excludes a deadly heat wave in May and covers only city populations, roughly 40 percent of Europe's total.
The oldest bore the brunt
About a third of the deaths occurred during a single intense heat wave from June 17 to July 1, when temperatures ran 9.5 degrees Fahrenheit (5.3 degrees Celsius) above normal, said co-author Garyfallos Konstantinoudis, a biostatistician at Imperial College London. Some cities recorded temperatures 21.6 F (12 C) above normal.
Age did most of the damage. People aged 85 and over account for an estimated 22,502 of the deaths — about 45 percent of the total — and those aged 75 and over for nearly three-quarters. Working-age adults were not spared: the model attributes roughly 6,000 deaths to people aged 20 to 64.
"Much of Western and Northern Europe, our infrastructure is just not designed to cope with the sort of temperatures that we are seeing now because of the effects of human-caused warming," said lead author Clair Barnes, a climate scientist at Imperial College London. "Until we kick the fossil fuel habit, we will continue to see increasingly hot and dangerous summers."
How the estimate works — and why it matters
These are modelled "excess deaths" — deaths above what would statistically be expected — rather than a count of death certificates listing heat as the cause. The researchers compared this summer's temperatures with a simulated climate without human-caused warming, then applied established research linking heat to daily mortality. Earlier estimates using the same method have broadly matched later figures published by national health authorities.
Heat is often called a silent killer because most of its victims die at home or in hospital from heart, lung or kidney conditions that extreme temperatures aggravate, rather than from heatstroke itself. The study's practical message is about adaptation as much as emissions: heat-health warning systems, cooling centres, shaded public space, building standards and checks on elderly residents living alone are among the measures public health experts say can cut the toll in future summers. Insurers, too, are paying attention, as extreme heat drives a growing share of weather-related claims and losses.
What happens next
The findings land as European governments review their heat action plans after the summer and ahead of international climate negotiations, where adaptation funding — money to protect populations from impacts already under way — is a central dispute. Scientists behind the study argue that without both faster emissions cuts and serious investment in heat protection, each successive record summer will keep resetting the mortality benchmark that 2026 has just set.
Reporting based on the Associated Press and the Nature Health study.