A severe heatwave that gripped Western Europe from June 23 to July 2, 2025, is estimated to have caused at least 2,300 deaths across 12 major cities, including London, Paris, Milan, and Madrid. Scientific analysis attributes approximately 1,500 of those deaths to anthropogenic climate change, underscoring the direct impact of rising global temperatures on human health.

Researchers from Imperial College London and the London School of Hygiene and Tropical Medicine employed rapid epidemiological models to compare real-world mortality data with a hypothetical scenario without human-induced warming. This method revealed that many deaths occurred in conditions significantly worsened by climate-driven temperature increases, by as much as 4°C in certain cities.

Milan recorded the highest number of fatalities, with 499 deaths, 317 of which were directly tied to global warming. In London, 273 people died due to the heat, and 171 of those cases were attributed to climate factors. Paris and Barcelona showed similar patterns. Elderly populations were disproportionately affected, with about 88% of climate-linked deaths occurring in people over 65.

The heatwave set new climate records. June 2025 was the hottest ever recorded in Western Europe and the third hottest globally, according to the EU’s Copernicus Climate Change Service. Mediterranean Sea surface temperatures also reached unprecedented levels, intensifying the heat’s impact on the inland regions.

Unlike wildfires or floods, heatwaves are often underreported and misunderstood. Most deaths occur in private residences or care facilities, making heat a “silent killer” that escapes headlines but leaves a profound health toll.

Experts emphasize that these impacts are preventable. Solutions include investing in public cooling centers, especially in low-income or elderly-dense neighborhoods, and upgrading ventilation systems in hospitals and eldercare facilities. Municipalities can also implement urban cooling strategies, such as increasing tree cover, reflective roofing, and installing misting systems in public areas.

Without substantial adaptation and mitigation efforts, such lethal heat events will become more frequent and severe as climate change continues to intensify extreme weather across Europe. The research paints a stark picture: climate inaction is now directly costing lives.