Human-caused climate change significantly intensified recent European heatwaves, making temperatures in many cities up to 4 degrees Celsius hotter, scientists announced on Wednesday. This surge in temperatures pushed conditions into deadly territory for thousands of vulnerable individuals. A rapid study, conducted by over a dozen researchers from five European institutions, concluded that this likely led to a substantially higher number of heat-related deaths than would have occurred without the influence of global warming.
Between late June and early July, temperatures across many European countries soared well above 40°C (104°F) as the first heatwave of the summer shattered records and triggered widespread health warnings. The EU’s climate monitor, Copernicus, confirmed on Wednesday that it was the hottest June on record in western Europe, where some schools and tourist sites were temporarily closed due to the soaring mercury.
To determine the role of climate change, scientists compared the intensity of the heatwave with what it would have been in a world unaffected by human-induced warming from fossil fuel combustion. Utilizing historical weather data, they concluded that the heatwave “would have been 2-4°C cooler” without human-induced climate change in all but one of the 12 cities analyzed.
These added degrees substantially elevated the risk in these cities, which collectively have a population exceeding 30 million and include major capitals such as Paris, London, and Madrid. Ben Clarke, a researcher from Imperial College London, which co-led the study with the London School of Hygiene and Tropical Medicine, explained: “What that does is it brings certain groups of people into more dangerous territory.” He told reporters, “For some people it’s still warm, fine weather. But for now a huge sector of the population, it’s more dangerous.”
Life and Death Implications
For the first time, the study also sought to estimate the death toll from the heatwave within the 12 cities examined, and how many could be directly attributed to climate change. Children and adults are seen cooling off and enjoying water games at a water fountain in the Andre-Citroen public park in Paris, France, on June 29, 2025, as a heatwave impacts southern Europe. — AFP
Based on peer-reviewed scientific methods and established research on heat and mortality, the study concluded that the heatwave likely caused approximately 2,300 deaths between June 23 and July 2 across the 12 cities. However, researchers estimated that about 1,500, or roughly two-thirds, of these deaths would not have occurred had climate change not driven temperatures to such dangerous highs.
The authors, from research institutions in the UK, Netherlands, Denmark, and Switzerland, emphasized that this estimate represents only a snapshot of the broader heatwave, as official death counts are not yet available.
Heatwaves pose particular dangers to the elderly, the sick, young children, outdoor workers, and anyone exposed to high temperatures for prolonged periods without adequate relief. The health impact is exacerbated in urban environments, where paved surfaces and buildings absorb heat, making cities significantly hotter than surrounding areas. Copernicus noted that large parts of southern Europe experienced “tropical nights” during the heatwave, where overnight temperatures remained too high to allow the body to recover.
“An increase in heatwave temperature of just two or four degrees can mean the difference between life and death for thousands of people,” stated Garyfallos Konstantinoudis, a lecturer at Imperial College London. He explained to reporters, “This is why heatwaves are known as silent killers. Most heat-related deaths occur in homes and hospitals out of public view and are rarely reported.” Authorities anticipate that it could take weeks to compile a more definitive death toll from the recent heatwave, but similar events have claimed tens of thousands of lives in Europe during previous summers.
