FILE – A tourist drinks water on a hot day at the beach in Barcelona, Spain, July 2, 2025. (AP Photo/Emilio Morenatti, File)

The heat waves that baked Europe this summer were likely the continent’s deadliest on record, and climate change was primarily responsible, researchers at Imperial College London and the London School of Hygiene & Tropical Medicine found in two recent peer-reviewed studies.

About 50,000 more people died in European cities between June and August than would have if temperatures had not been abnormally hot, researchers estimate. The figures are 71% higher than in 2022, the second-deadliest year, which researchers said is likely due to just how widespread and extreme the heat domes were across Europe this summer.

Of those estimated additional deaths, about two-thirds would not have occurred if the climate were not warming, the researchers calculated. The papers were accepted for publication in the journal Nature Health, and one published earlier this month.

The findings “clearly highlight the danger from human-caused warming and the need for rapid emissions reductions,” said Clair Barnes, a statistician and climate change researcher at Imperial College London, who is a lead author of the studies.

The researchers analyzed weather data from 854 urban areas in Europe, covering a total population of about 173 million. Using 26 years of data, climate models, population data and a previously peer-reviewed method to link mortality to heat, researchers calculated how many more deaths likely occurred due to the heat than would’ve without the high temperatures.

The research comes on the heels of a United Nations climate report out this week, which found that the planet is on track to warm 2.6 degrees Celsius above preindustrial levels during this century – assuming countries stick to their climate action plans – and that the previous global target to not overshoot 1.5 degrees of warming “has been lost.”

Determining how many people’s deaths are at least partially caused by heat is notoriously difficult for public health authorities to untangle, earning it the nickname of a “silent killer.” Heat can cause heat stroke, but it can also contribute to death by heart attack, stroke, cardiovascular disease and other conditions.

“Whenever the human body is exposed to extremes of temperature, but particularly heat, it puts the body under stress,” said Andrew Hartle, an intensive care consultant at the Imperial College Healthcare NHS Trust, who did not contribute to the new research. The body has coping strategies, he said, but “eventually, your ability to control your temperature fails.”

But even when it’s very likely that heat played a role in a death, other causes often take the blame on death certificates. For example, if the medical examiner evaluates the body long after the internal core temperature has fallen, heat may not be listed as a factor.

Recognizing the gap in data, some European health authorities also calculated heat-related death estimates this summer with their own models. In France, for example, the nation’s public health agency Santé publique estimated about 5,800 excess deaths during the late June heat wave. (The Nature Health study estimates about 7,300 heat-related deaths in France’s urban areas across the whole summer.)