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A study published in Nature Medicine estimates heat and cold related deaths in Europe as a result of climate change.
Dr Garyfallos Konstantinoudis, Lecturer at the Grantham Institute – Climate Change and the Environment, Imperial College London, said:
Is this good quality research? Are the conclusions backed up by solid data?
“The study is of high quality, offering a thorough assessment of future scenarios regarding net changes in temperature-related mortality, factoring in various climate, demographic, and adaptation scenarios. Its conclusions are strongly supported by solid data. However, it’s important to note that the applicability of these results is primarily limited to European urban settings.”
What does this study add to our understanding of heat/cold deaths after climate change? Was there doubt before now that on balance deaths would increase in Europe with warmer temperatures?
“Previous estimates based on historical data have suggested that for every heat-related death, there are roughly 10 cold-related deaths. This raises important questions about the net impact of temperature changes due to anthropogenic climate change. This new study underscores a crucial point: without any adaptation to temperature, projections suggest that temperature-related deaths are likely to increase overall, with heat-related deaths surpassing cold-related ones. A related study in Europe also highlighted the significance of mitigation efforts in shaping this net effect, noting that in the most extreme scenarios, mitigation could lead to a positive outcome, balancing the impact of temperature change (https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00150-9/fulltext).”
What does the study tell us about excess heat deaths even under relatively optimistic scenarios?
“In the most optimistic scenario—warming is kept below 2°C—while assuming no adaptation to heat, heat-related deaths are projected to outnumber cold-related deaths by 12 per 100,000 person years in 2050-2054. By the end of the century, this gap is expected to widen, with heat-related deaths potentially exceeding cold-related deaths by 50 per 100,000 person years.
“It is clear a hotter world is a more dangerous world. With every fraction of a degree of warming, we will also face increased spread of mosquito-transmitted disease and more intense extreme weather, among other threats to human health.”
Dr Luke Parsons, Applied Climate Modeling Scientist, Global Science, The Nature Conservancy, said:
“I appreciate that this study used different temperature-mortality relationships for different age groups, because we know that different age groups in different locations can respond differently to temperature extremes.
“Additionally, these researchers derived local temperature-mortality relationships and did not extrapolate spatially to grossly different geographies- for example, many studies have tried to estimate global temperature-related mortality changes under warming, but we these studies often lack data for most of Africa (outside of South Africa) and many other countries, so studies often have to make very broad assumptions about how people will react to temperatures without concrete local health data to validate form relationships.
“Despite these strengths, something I worry about that I didn’t see addressed in this paper:
“As this study highlighted several years ago (https://iopscience.iop.org/article/10.1088/1748-9326/10/6/064016):
“Heat waves are often associated with increases in deaths, but many studies also find increased deaths in cold times of year, concluding that cold season deaths are due to colder temperatures; therefore, as the globe warms and the cold season becomes warmer, we should see decreases in deaths. However, a variety of other factors could lead to cold-season deaths (such as respiratory infections during the cold season)- if we are indeed over-counting cold-season deaths and their potential reductions in a warmer world, the net impacts of increasing temperatures could result in even larger numbers of early deaths than studies like this estimate. However, we also don’t know how humans will react to the heat- as far as I can tell, these studies don’t take into account migration (for example, do people leave exceedingly hot areas in southern Europe in a warmer world?) or other possible factors- although they do try to account for potential adaptation.
“Additionally, as the authors acknowledge, the health data are aggregated to the city level, and within cities, people can respond quite differently in disparate neighborhoods to temperature extremes depending on social networks, income, housing, and other factors. We have this problem with health data in the US often as well- to keep data anonymous, it is often aggregated, but then we lose really important local information about how more and less vulnerable areas within cities are being impacted by climate change.”
Dr Matthew Maley, Lecturer in Environmental Ergonomics at Loughborough University, said:
Is this good quality research? Are the conclusions backed up by solid data?
“The study should be commended for accounting for variations in demographics (i.e. age) whilst presenting various future climate change scenarios in various adaptation scenarios.”
What does this study add to our understanding of heat/cold deaths after climate change? Was there doubt before now that on balance deaths would increase in Europe with warmer temperatures?
“This study confirms a consistent trend of increasing heat-related deaths, particularly under high-warming scenarios. The study also extends what we know by including European regions not included in previous studies.”
The study focuses on a relatively low mitigation and adaptation scenario – (SSP3-7.0) – can you comment on this? How likely/unlikely is it considered to be?
“It’s certainly a pessimistic scenario but one that could be our reality given current emission trajectories and failure to achieve our international climate change goals.”
What does the study tell us about excess heat deaths even under relatively optimistic scenarios?
“The more optimistic scenarios (SSP1-2.6 and SSP2-4.5) predict an increase in heat-related deaths, though to a lesser extent than SSP3-7.0. This emphasises that adaptation measures must accompany mitigation efforts to manage heat-related health impacts effectively.”
The study suggests that a significant amount of these deaths could be reduced with adaptation. In the cities where the largest death tolls are predicted (Barcelona, Rome, Naples, Madrid, Milan, Athens), what kinds of adaptation measures would be most effective?
“Effective adaptation measures for these Mediterranean cities could include:
Dr Christopher Callahan, Postdoctoral Scholar in Earth System Science, Stanford University, said:
“This study is an impressive synthesis of heat- and cold-related mortality across Europe. While climate change may reduce cold-related deaths in winter, these results are unambiguous that increased heat-related mortality will outweigh these potential benefits, with an escalating death toll for every degree of global warming.
“One limitation of this study is that their numbers only account for about 40% of the population of the countries analyzed. The total death toll of climate change in these countries is likely substantially greater than these numbers indicate.
“One of the scenarios the authors examine is SSP3-7.0, which is a scenario of relatively high warming. While the most extreme emissions scenarios appear less likely today than previously, we should not discount the potential for very high levels of warming even given current climate policy. Many countries are on track to miss their stated emissions targets, and the rise of the second Trump administration in the United States may impede further progress on emissions reductions.”
Dr Raquel Nunes, Assistant Professor in Health and Environment at the University of Warwick Medical School, said:
“The findings of this study have serious implications for public health. As climate change leads to more extreme heat events, the number of heat-related deaths is expected to rise, putting additional pressure on healthcare systems. Vulnerable groups, such as older adults, those with chronic illnesses, and low-income communities, will be at the highest risk. Without strong adaptation measures, public health systems could struggle to cope with the increased demand for emergency services and hospital admissions.
“To protect public health, governments and policymakers need to invest in early warning systems, public education campaigns, and infrastructure improvements to help individuals stay cool and safe. Health professionals must also be trained to recognise and respond to heat-related illnesses. Additionally, social policies that provide support for vulnerable populations, such as access to cooling centres and affordable healthcare, will be essential in reducing the impact of extreme temperatures.
“This study highlights the urgent need for a coordinated public health response to climate change, focusing on prevention, preparedness, and adaptation to reduce future health risks. A significant proportion of current and future heat-related illnesses and deaths is preventable. What is essential now is the development and implementation of policies and actions aimed at minimising both morbidity and mortality.”
Prof Tim Osborn, Director of the Climatic Research Unit, University of East Anglia (UEA), said:
“Cold weather and hot weather kill tens of thousands of people across Europe every year. Climate change is bringing less severe cold weather but more frequent hot weather, but it isn’t yet known if that means more or fewer people will die from temperature-related deaths in future. The clear finding of this new research is that the net effect of climate change will be more temperature-related deaths in future. Put bluntly, the increase in hot weather will kill more people than the decrease in cold weather will save.”
“While this new study isn’t the final say on the matter, and more research will certainly refine and could still change the overall prediction of future temperature-related deaths, it does break new ground by scrutinizing people’s vulnerability to extreme temperatures by age and by city to a much better level of detail than previous work. This extra level of detail ought to make the new study’s results more reliable.”
“This study also confirms two more general features about climate change. First, the harm from climate change impacts people very unevenly (in this case, with far greater increases in temperature-related deaths predicted for southern Europe than for northern Europe, where milder winters may even reduce the number of deaths). Second, we can greatly reduce the harm from climate change by adaptation — making changes that increase our resilience to extreme weather — but these adaptations are far more successful if we also limit the amount of climate change that we are faced with by accelerating the move away from fossil fuels as our primary energy source.”
Prof Simon Gosling, Professor of Climate Risks & Environmental Modelling at University of Nottingham, said:
“This is a high quality study that uses established modelling methods. It shows an increase in the overall number of deaths from temperature due to future global warming could be avoided if society makes big adaptations to heat. However, we are talking about a really big level of adaptation here – a level where the risk of dying from the heat is half of what it is nowadays. The models aren’t specific about how such a high level of adaptation could be achieved in reality. The way that this might be seen in the real world is through a combination of societal adjustments – in our cities, our homes, public services and work environments. Examples include increasing the amount of green spaces in our cities to help keep them cool, providing cooling centres where people can get relief from the heat, changing our work environments and work policies so that people are at less risk from heat stress at work, and by ensuring the people most vulnerable to heat are cared for and protected. There are some great examples of how this is starting to happen, but it’s a challenge that society has to rise to and achieve at scale, because this study very clearly shows that without high levels of adaptation, we are looking at an overall increase in deaths due to temperature in the future. Reducing global warming is also really important – lowering greenhouse gas emissions will help to significantly lessen the blow on society if we don’t achieve the high levels of adaptation needed to avoid an increase in deaths in the future.”
‘Estimating future heat-related and cold-related mortality under climate change, demographic and adaptation scenarios in 854 European cities’ by Pierre Masselot et al. was published in Nature Medicine at 16:00 UK time on Monday 27 January 2025.
DOI: 10.1038/s41591-024-03452-2
Declared interests
Professor Tim Osborn: No interests to declare.
For all other experts, no reply to our request for DOIs was received.