Heatwaves do discriminate: This new map shows who is most at risk when hot weather strikes Europe

Heatwave warnings are already coming thick and fast across Europe this summer, as experts predict another record-hot year driven by climate change. But it can be hard to gauge how dangerous they are to you in particular.

A new tool seeks to bridge that gap by forecasting how likely you are to die when hot weather hits different places in Europe. The data is based on age and sex.

Around 70,000 people died from heat-related causes during summer 2022 in Europe, according to researchers at the Barcelona Institute for Global Health (ISGlobal). The same team has taken past mortality data and combined it with weather forecasts to create this first-of-its-kind tool, which it hopes will save lives in future.

“Until now, temperature warnings have been solely based on the physical information of weather forecasts, and therefore, they ignore the differences in vulnerability to heat and cold among population groups,” explains Joan Ballester Claramunt, principal investigator of the adaptation group at ISGlobal.

“The problem is that this information is the same for everybody,” he says, “while in reality the impacts are different.”

The Barcelona-based scientists’ system “changes this paradigm” by shifting the focus from meteorology to epidemiology - the study of disease and other public health concerns.

With extreme weather on the rise, they say epidemiological models are essential to developing new, impact-based early warning systems.

Launched online today, Forecaster.health is the first pan-European, publicly available platform to predict the actual mortality risks of temperatures for different demographics.

Who is most at risk during heatwaves?

The Forecaster.health map for 26 June, unfiltered by age or sex, shows that people in western Greece are most at risk from heat today. ISGlobal

Ambient temperatures are associated with over five million premature deaths worldwide every year, with more than 300,000 of these in Western Europe alone, according to ISGlobal.

Our vulnerability to heat is influenced by a number of factors, including sex and age.

“We know, for example, that women are more susceptible to heat than men, and that the risk of death for both heat and cold increases with age,” says Marcos Quijal-Zamorano, researcher at ISGlobal and one of the authors of the system.

Looking ahead to 30 June, for example, Forecaster.health gives an extreme heat warning for women in the Campobasso region of Italy, and a high one for men. The forecast is extreme for both sexes aged 75-84 in the nearby Potenza, but only a low heat warning is issued for those aged 65-74 in this region.

Why are women more at risk of dying in heatwaves?

“I'm not 100 per cent sure that all old women are aware that they have more risk than men. And maybe if they knew it, they might change things,” Ballester tells Euronews Green.

There are a number of factors behind this phenomenon, he explains. Socioeconomics provides some answers: women tend to have lower salaries, therefore have fewer resources like air conditioning to protect themselves. They are more frequently widowed and so more likely to live alone and be isolated from help.

It’s also important to understand that heatwaves typically kill through comorbidities - underlying conditions such as obesity, diabetes, infectious diseases and cancer - on which the heat acts as an additional, fatal stressor.

In men, these comorbidities appear at younger ages - so younger men are actually more vulnerable to heat than younger women. As more women survive and, as a group, have a longer life expectancy, they become more vulnerable in older age.

How can scientists predict heatwave deaths?

Forecaster.health draws on the mortality database of the EU-funded research project EARLY-ADAPT, which currently holds data for 580 regions in 31 European countries.

People can enter the date for which they want to see health predictions within the next two weeks, and filter by population subgroups.

There are real numbers behind this, Ballester explains. The epidemiological models calculate the percentage of deaths attributed to temperature for a given forecast. An extreme warning means that the temperature is predicted to cause more than 20 per cent of the deaths tomorrow.

How can the heatwave mortality map help save lives?

In most countries, heatwave warnings are issued by the meteorological agency, amplified by the media and acted on by public health officials and the public.

The ISGlobal team isn’t seeking to change this system - but the information itself. Understanding how the same temperature kills or impacts people’s health differently enables us to make more informed decisions, says Ballester.

“I'm always thinking about my father, who is 95. And even if he has a son who is an epidemiologist, and I always tell [him about the age difference], he's not aware of the risk that it implies for him.

“So I imagine that for the general population, there is a lot of lack of knowledge about these issues,” he adds. “‘Through the awareness, this tool also aims to change some of these habits.”

“We need to provide warnings adapted to the characteristics of each person,” Ballester believes. If not, “we are not doing our best to prevent deaths.”

The scientists want to build a multi-hazard platform

Eventually, the plan is to develop Forecaster.health into a multi-hazard platform for Europe and the rest of the world.

Over the next few months and years, the researchers will be expanding it in different directions, firstly by adding new countries and smaller regions to the platform once new data is acquired.

The tool is also expected to build new epidemiological models to incorporate health warnings for several air pollutants, such as particulate matter, ozone or nitrogen dioxide.

Finally, the platform will also issue warnings for specific causes of death - such as cardiovascular and respiratory diseases - and for other health outcomes, such as hospital admissions and occupational accidents.

“Our approach crucially depends on the availability of health data to fit our epidemiological models. We are eager to add additional health outcomes for more countries or smaller regions, either from Europe or in other continents, if data is provided to us,” adds Ballester.