A recent study has estimated that climate change tripled the number of heat-related deaths in European cities during the heatwaves of June 2025, including 171 excess heat-related deaths in London.
Scientists have issued warnings that global warming, primarily due to burning fossil fuels and deforestation, intensified the recent extreme heat. This follows a significant heatwave that swept across much of Europe in late June and early July, with temperatures exceeding 40C in France, Germany, Italy, Portugal and Spain.
The UK has also experienced two heatwaves so far in 2025, with the Met Office forecasting a third one this week. Temperatures are predicted to hit 33C in parts of southern England, with highs of 30C expected across the UK.
In anticipation of the forecasted heatwave, the UK Health Security Agency (UKHSA) has issued heat-health alerts for six regions in England. The yellow alert will be effective from 10am today (Wednesday, July 9) until 10am on Tuesday, July 15, reports the Manchester Evening News.
The new study is the first quick analysis to estimate the number of deaths linked to climate change during a heatwave. Researchers from the World Weather Attribution found that the recent heatwaves were up to 4C hotter across cities compared to a world without climate change.
Researchers have discovered that human-induced global warming was to blame for approximately 65 per cent of the fatalities during heatwaves across 12 cities, including London, Paris, Madrid, Barcelona and Rome. They cautioned that their findings only provide a glimpse into the actual number of deaths, which could be in the tens of thousands.
Dr Ben Clarke, from the Centre for Environmental Policy at Imperial College London, commented on the silent yet deadly nature of heatwaves: “Heatwaves don’t leave a trail of destruction like wildfires or storms. Their impacts are mostly invisible, but quietly devastating – a change of just 2 or 3C can mean the difference between life and death for thousands of people. Our study shows how dangerous climate change already is with just 1.3C of warming. However, we could reach 3C this century, unless countries speed up the transition from fossil fuels to renewable energy.”
Clarke also highlighted the consequences of more severe heatwaves: “That would bring fiercer heatwaves to Europe, causing more deaths and placing greater pressure on health systems.”
The research focused on a 10-day period from June 23 to July 2, when a “heat dome” over Europe trapped hot dry air, leading to an intense heatwave. This extreme weather caused schools to shut down in parts of France, outdoor work to be restricted during the day in Italy, and set off health alerts in numerous countries.
Utilising existing research on the correlation between high temperatures and daily mortality rates in urban areas, scientists estimated the toll of excess deaths attributable to heatwaves. They compared these figures against a “counterfactual” scenario, which projected death counts if such extreme heat had occurred without the influence of climate change.
The investigation, spearheaded by experts at Imperial College London and the London School of Hygiene and Tropical Medicine (LSHTM), concluded that out of an estimated 2,300 fatalities during the heatwaves, approximately 1,500 were due to the effects of climate change – effectively tripling the death toll as a result of global warming.
The analysis attributed climate change to causing an additional 171 deaths in London, 317 in Madrid, and 235 in Paris.
Dr Pierre Masselot, a research fellow at LSHTM, warned: “At the rate the world is warming, heatwaves are not going away and we have to prepare for their public health impacts. Cities can adapt by planting trees, reducing the space given to cars and caring for the most vulnerable. But ultimately, the best way to avoid dire consequences is to aggressively reduce greenhouse gases emissions.”
The study also pointed out that the majority of these heat-related deaths occurred among the elderly, underscoring the heightened danger that older individuals in Europe face from increasingly prolonged, intense, and frequent heatwaves.
The UKHSA’s heat-health alerts caution that individuals aged 65 and over, or those with health conditions, face an increased risk of death due to soaring temperatures. The agency recommends avoiding the sun during its peak hours, between 11am and 3pm, maintaining a cool home environment by shutting windows and curtains in sun-facing rooms, and ensuring adequate hydration by drinking plenty of fluids.
Looking for more from MyLondon? Subscribe to our daily newsletters here for the latest and greatest updates from across London.
