They found that more than 50,000 heat-related excess deaths occurred in those cities this summer, with around 32,000 attributable to climate change driving up temperatures. 

The studies also showed how exceptionally deadly this year’s summer proved. Between 2000 and 2025, the first paper found a total of 430,000 heat-related deaths, with around half caused by climate change. The 2026 figures eclipsed the previous records of 29,000 deaths in 2022 and 28,000 in 2003.

Almost a third of this summer’s heat-related deaths occurred during Europe’s late June heat wave that smashed several temperature records. 

And while the elderly were the worst-affected population group, the death toll of this summer included around 6,000 people under the age of 65. 

“The burden was greater among older adults. People aged 85 and over accounted for roughly half of the estimated deaths,” said Garyfallos Konstantinoudis, study co-author and assistant professor at Imperial College. 

“However, heat-related mortality was not limited to the older populations,” he added. “Even among younger adults, people aged between 20 and 44, we estimated more than 800 excess deaths.”