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An analysis published by Imperial’s Grantham Institute and LSHTM looks at summer heat deaths driven by climate change across Europe.
Dr Chris Huntingford, Climate Modeller, UK Centre for Ecology & Hydrology (UKCEH), said:
“There are two critical factors that imply, for European heat extremes, we need to be mindful of much more than just considering the impact of limiting global temperature rise, such as at two degrees. First, various feedbacks in the climate system imply that warming is increasing faster over most land locations than the global average. Second, for many locations across Europe, and for reasons not yet fully understood, the hottest days are accelerating, warming even faster than the average local temperature rise. These two amplifying processes imply that the temperatures of the most extreme hottest days in much of Europe are rising far faster than background global warming. This additional acceleration of extremely hot days has likely contributed to the high number of heat-related European deaths that this new report robustly attributes to the rise of atmospheric greenhouse gases. The report also provides a very valuable constraint on climate-health models designed to project changed mortality rates in response to heat extremes, enhancing their predictive capability for any future climate change.
Dr Madeleine Thomson, Head of Climate Impacts & Adaptation at Wellcome, said:
“Extreme heat kills – and these new data show that no city in Europe is immune. Climate change is driving up temperatures, and with them, not just deaths but serious illnesses including heart attacks, kidney disease, miscarriages, and mental health crises.”
“If we don’t act now, the toll will rise. We must urgently phase out fossil fuels and implement policies that protect those most at risk from increasingly deadly heatwaves.”
Dr Raquel Nunes, Associate Professor in Health and Environment, University of Warwick, said:
“The increasing frequency, intensity and duration of heatwaves are dangerous new reality we need to adapt to. This study highlights the importance of mitigation and adaptation for future heat-health outcomes. There is an urgent need to shift from reactive to anticipatory strategies. Heatwaves increase the vulnerability of populations, particularly older adults, children, and those with pre-existing health conditions. Those living in urban areas are at particular risk due to the urban heat island effect. This is specially concerning as the built environment, health infrastructure, and social norms remain largely maladapted to extreme heat.”
Dr Akshay Deoras, Research Scientist, National Centre for Atmospheric Science, University of Reading, said:
“Human-induced climate change is no longer a distant or abstract threat. It is already costing thousands of lives every summer. This new study reinforces what climate scientists have been warning for years: the link between global warming and extreme heat is undeniable, and the consequences are lethal.
“What makes this finding even more alarming is that the methods used in these attribution studies are scientifically robust, yet conservative. The models used are known to underestimate the rate of warming in many parts of Europe, meaning the actual death toll could be even higher. These are not speculative projections; they are data-backed conclusions grounded in rigorous science, with clear acknowledgment of limitations and uncertainties. None of this changes the fundamental message that the world is already too hot for too many people.
“The study also highlights that heat does not kill equally. Older populations are affected the most, with more than 80% of the excess heat-related deaths occurring among people aged over 65. It is a tragic reality that those who contributed least to the climate crisis are now suffering the most. While today’s emissions continue to rise, it is the older generation, many already in fragile health, who are paying the highest price for our collective inaction.
“The implications for public health are stark and immediate. Every fraction of a degree we fail to prevent will result in more lives lost, particularly among the most vulnerable. The longer we delay meaningful action, the more extreme heat becomes a silent and seasonal killer. But it does not have to be this way. Rapid reductions in greenhouse gas emissions and improved adaptation practices can still prevent thousands of deaths in the years to come. What we choose to do today will determine whether this becomes the new normal or a turning point toward a safer, more resilient future.”
Dr Karsten Haustein, Climate Scientist, Leipzig University, said:
“After last week’s study that linked emissions of carbon majors to individual heat waves in a systematic way [1], this analysis provides another step forward to systemise attribution science. Taking the collective expertise of several health experts on board, the study connects excess deaths to this summer’s heat waves across Europe. The team finds that almost 70% of the over 24,000 heat related deaths during the summer of 2025 in Europe – which was the 4th hottest on record – are attributable to human-induced climate change. Rome and Athens had the highest death toll. The study authors highlight that each tenth of a degree of additional warming can cause unprecedented surges of death, a threat which is only exacerbated by Europe’s rapidly ageing population.”
Prof Richard Allan, Professor of Climate Science, University of Reading, said:
“It’s impossible to know for sure if inhaling car fumes or experiencing excessive heat over a summer caused an individual’s death but these very real risks can be mistakenly perceived as less important than more dramatic events like terrorism or natural disasters.
“The report has combined multiple lines of evidence to robustly estimate how deadly the summer heat was to the people across European cities. It scrutinises the heightened exposure to the dangerous conditions compared to a world without the unnatural warming that has emerged, as well as painting a statistical picture of how many more deaths occurred that would have been expected for the time of year and region.
“This underscores the danger of silent killers like heatwaves, and the only way to limit the worsening risk to people and animals from rising global temperatures is to rapidly cut greenhouse gas emissions across all sectors of society.”
‘Summer heat deaths in 854 European cities more than tripled due to climate change’ by Barnes et al. is an unpublished analysis conducted by Imperial’s Grantham Institute and LSHTM. The embargo lifted at 05:00 AM UK Time Wednesday 17th September 2025.
Declared interests
Dr Chris Huntingford: None
Dr Madeleine Thomson: None
Dr Raquel Nunes: None
Dr Akshay Deoras: None
Dr Karsten Haustein: None
Prof Richard Allan: None