The record-shattering heat that gripped western and central Europe in late June was rendered at least 100 times more probable for night-time temperatures and roughly 10 times more probable for daytime peaks by human-caused climate change, according to a rapid attribution study by the World Weather Attribution (WWA) group. Compared with the climate of June 1976, the same event would have been 3.5°C cooler during the day and 2.4°C cooler at night; even against the deadly 2003 heatwave, the analysis found the current episode would have been about 2°C cooler by day and 1.3°C cooler by night. The researchers described the heat as the most severe ever recorded in the region and the most intense humid-heat event documented there.

The study, which has not yet undergone external peer review but employs a methodology already validated by the scientific community, drew on observed and forecast temperature data for the hottest three-day period across a swathe of Europe trapped under a persistent heat dome. That blocking high-pressure system drew hot air from the Sahara and compressed it at altitude, producing daytime highs above 40°C in multiple countries and night-time lows that stayed above 20°C for more than a week in parts of France. The scientists calculated that the probability of such an event has “changed immensely” over the past 50 years, during which the planet has warmed by 1.1°C. They explicitly ruled out any role for the natural El Niño cycle in this particular heatwave.

Health impacts began to surface as the heatwave unfolded. The WWA analysis noted that 45% of 854 cities across 30 European countries had already broken or were expected to break their records for wet-bulb globe temperature—a measure of heat stress that accounts for humidity and the body’s ability to cool itself through sweating. In France, authorities reported 40 drowning deaths as people sought relief in water, and the government banned alcohol consumption in red-alert zones to ease pressure on emergency services. A researcher at the Red Cross Red Crescent Climate Centre observed that many people “live, work, and study in places that are not designed for the temperatures we are now experiencing.” The World Health Organization has previously documented more than 200,000 heat-related deaths across Europe in a four-year period.

Viewed from London, Imperial College researchers stressed that the speed of change is startling, with heat records falling in consecutive months. UN climate change executive secretary Simon Stiell called the science “very clear” and urged a faster shift to clean energy, noting that no nation can afford business as usual. Europe remains the world’s fastest-warming continent, heating at twice the global average rate since the 1980s, according to the EU’s Copernicus Climate Change Service. The WWA study, released while the heatwave was still in progress, adds a quantitative layer to the growing body of evidence linking specific extreme events to fossil-fuel emissions. The next factual milestone will be the final, peer-reviewed version of the analysis, but the immediate focus remains on managing the ongoing heat stress and the policy response it is likely to intensify.