A groundbreaking new analysis has provided the most direct link yet between human-caused climate change and immediate loss of life, concluding that global warming made the recent deadly heatwave across Europe significantly hotter and tripled the resulting death toll.
The rapid attribution study, conducted by leading climate scientists from the World Weather Attribution group, including researchers at Imperial College London and the London School of Hygiene & Tropical Medicine, represents a landmark shift in understanding the real-time, fatal consequences of climate change.
The research focused on the extreme heatwave that swept across the continent between June 23 and July 2, 2025. It found that the burning of fossil fuels made the event between 1°C and 4°C (1.8°F to 7.2°F) hotter than it would have been in a world without human-induced warming. Cities like London experienced the most dramatic increase, nearing the 4°C mark.
For the first time, scientists combined meteorological data with established epidemiological models to calculate the direct human cost. Their analysis of 12 major European cities, including Paris, Madrid, Rome, and London, estimated that a total of 2,300 people died due to the heat.
Crucially, the study concluded that approximately 1,500 of these deaths—or 65%—would not have occurred without the additional heat intensity created by climate change.
Dr. Friederike Otto, a climate scientist at Imperial College London and co-author of the study, stated the findings bluntly: “Those 1,500 people have only died because of climate change. They would not have died if it would not have been for our burning of oil, coal, and gas.”
The study underscores the immense vulnerability of certain populations. People aged 65 and over were disproportionately affected, accounting for an estimated 88% of the excess deaths.
Ben Clarke, another author from Imperial College, highlighted the danger in what might seem like small temperature shifts. “The influence of climate change has pushed it up by several degrees, and what that does is it brings certain groups of people more into dangerous territory,” he said. "For some people, it's still warm, fine weather, but for a huge sector of the population, it's more dangerous." The study serves as a stark warning that heatwaves, often called "silent killers," are becoming more frequent, more intense, and demonstrably more lethal due to the ongoing climate crisis.
