Forecast: Hotter Days Ahead — and Rising Death Tolls

According to data from the World Meteorological Organization, average annual temperatures in Europe have risen by half a degree over the past thirty years —more than twice the global average. The organization's report indicates that this rise has increased both the frequency and intensity of extreme weather events such as floods, wildfires, and heatwaves, affecting millions of people. During the summer of 2022, temperature records were shattered across the continent, and a study published the following year estimated that this series of heatwaves calimed the lives of more than sixty thousand people.

But these alarming figures tell only part of the story. Researchers note that winter-related mortality in Europe—particularly during years with severe cold spells—has historically been about ten times higher than deaths caused by heat. This ratio is expected to change as average temperatures continue to rise due to global warming. As a result, deaths from extreme heat in Europe are projected to increase, while cold-related fatalities are expected to decline. In a new study published in Nature Medicine, researchers from many European countries collaborated to assess the projected change in overall mortality as the continent grows warmer.

In 2022, a series of heatwaves in Europe led to the deaths of more than sixty thousand people. A family cooling off in front of a fan during the heat | Andocs, Shutterstock

Dying from Heat and Freezing from Cold

The researchers analyzed climate data from 2000 to 2015 across 854 cities. For each city, they constructed a temperature–mortality curve that also accounted for the local age distribution. Using these curves along with population growth forecasts, they built predictive models for each city, to predict excess mortality caused by rising temperatures  by the end of the century. The models were tested under three global climate change scenarios, each reflecting different global energy and socio-economic policies adopted by countries. In these scenarios, the projected rise in global temperatures ranges from 1.5°C in the least pessimistic case to 4°C in the worst-case scenario by century’s end.

In addition, the researchers examined, for each of the three scenarios, the potential impact of interventions that could reduce heat-related mortality—such as significant advancements in air conditioning technology. Since there is no reliable method for calculating the expected decline in mortality, they tested three hypothetical levels of reduction without specifying the mechanisms through which these reductions might be achieved.

Across all three climate scenarios, the study found that without protective measures to shield the public from the dangers of high temperatures, the rise in heat-related deaths will surpass the reduction in cold-related fatalities. Even in the most optimistic scenario—where the temperature increase by the end of the century is limited to around 1.5°C—the model predicts an average of 8,000 additional deaths per year in the cities studied due to global warming.

In the pessimistic scenario, where the average temperature rise reaches 4°C, the number of additional deaths from extreme climate events could climb to as many as 80,000 per year in the cities analyzed. A 10% reduction in the risk of heat-related deaths through effective preventive measures would lower the projected increase in mortality but would not be enough to prevent it. Only a 50% or greater reduction would be sufficient to offset the excess mortality in moderate warming scenarios. In the most severe scenario, a 90% reduction in risk would be required to prevent an overall increase in mortality.

 In the most optimistic climate scenario, the model predicts an average of 8,000 additional deaths per year due to warming. A heatwave hits the Mediterranean basin | Piyaset, Shutterstock

The Wrong Place at the Wrong Time

The findings are not geographically uniform. In Southern Europe, where temperatures are already relatively high and winters are mild, the increase in mortality due to expected warming is projected to be the greatest. Further north, in Eastern and Western European countries, the overall rise in deaths is expected to be smaller.  This projection is consistent with previous studies indicating the Mediterranean region is particularly sensitive to climate change.

The study also found that in some Northern European countries, the reduction in cold-related deaths could initially outweigh the expected increase in heat-related mortality. However, a closer look at the trends reveals that this gap between Northern and Southern Europe narrows over time. In a scenario where temperatures rise by four degrees by the end of the century, even residents of northern cities such as Stockholm and Helsinki are projected to experience an increase in heat-related deaths.

Mortality patterns are shaped not only by the rate of warming but also by factors such as the population’s average age and socio-economic conditions. In the small island nation of Malta, located in the heart of the Mediterranean, the projected increase in mortality is the highest among all countries studied. Among the countries of Eastern Europe, Romania and Bulgaria are expected to see particularly sharp rises in heat-related deaths, while neighboring countries are likely to be less affected—even though their average temperature increases are expected to be similar. In contrast, Ireland is projected to remain notably stable, with none of the scenarios predicting a significant rise in mortality due to warming.

Overall, according to the researchers’ projections, under the most severe scenario, temperature-related mortality across most European cities is expected to rise by approximately 50%, resulting in a total of 2.3 million deaths between 2015 and the end of the century. However, if effective global policies are implemented to limit temperature increases, the projected number of deaths could be reduced to 700,000.

While the study’s estimates are alarming, it’s important to note that they are based on assumptions that are difficult to verify, resulting in a considerable margin of error.  The researchers themselves acknowledge that estimates of heat-related mortality could vary by hundreds of thousands. Moreover, the study does not account for differences between European countries in their climate adaptation policies or socio-economic conditions. Further research is therefore needed to deepen our understanding of the likely consequences of global climate change.

Nonetheless, the stark contrast between the scenarios highlights the urgent need for global action to curb climate change and mitigate its impacts. The study also reinforces the understanding that, while global warming is a worldwide challenge, its impact on human life varies by location and is shaped by factors such as age and socio-economic status.