Scorching temperatures across Europe have killed tens of thousands of people in recent years. But as fatalities rise, researchers are finding that one group is disproportionately bearing the brunt of extreme heat: those living in poverty. “It’s common sense,” said Julio Díaz Jiménez, an investigative professor at Madrid’s Carlos III health institute. “A heatwave is not the same when you’re in a shared room with three other people and no air conditioning, as when you’re in a villa with access to a pool and air conditioning.” Díaz Jiménez is among a group of researchers who explored how extreme heat had affected 17 districts in Madrid. Their paper, published in 2020, found that heatwaves had an impact on mortality in just three districts – those where household incomes were below average. They followed up with a similar analysis looking at communities across Spain. “And we saw the same thing,” he said. “When it comes to heat and vulnerability, the key factor is income level.” People with lower incomes often struggle to access quality housing, with many living in overcrowded, poorly ventilated homes that offer little respite from the heat. Some struggle to access adequate healthcare, leaving them more likely to suffer from conditions that could be exacerbated by extreme heat, while others work in sectors such as agriculture and construction where they are regularly exposed to high temperatures. Even when air conditioning is available, people with lower incomes are less likely to be able to afford to use them. Earlier this year Save the Children warned that one in three children in Spain were unable to keep cool at home. It said this could have a “hugely detrimental” influence on the mental and physical health of more than 2 million children. The link between heat stress and poverty has long been a talking point across the Atlantic, heightened by findings such as a 2019 joint investigation by National Public Radio and the University of Maryland that documented how low-income neighbourhoods across the US were more likely to be hotter than their wealthier counterparts. But across Europe – a continent that is warming at a much faster rate than other parts of the world – the conversation has been slow to take off, said Yamina Saheb, a lead author of the IPCC report on climate change mitigation. She pointed to research published this month that found that hot weather inflamed by carbon pollution killed nearly 50,000 people across Europe last year. “We need to sound the alarm that this is extremely urgent,” said Saheb, who is also a lecturer at Sciences Po in Paris. “We need to decide that this is the last time that we will have people dying because of the heat in European countries.” Recent years have seen heatwaves across the continent become hotter, longer and more frequent, with 2023 ranking as the hottest year on record. Scientists expect that 2024 will soon take its place. “Global warming is killing people,” Saheb said. “And the question for me is how many people will it take for our policymakers, advocates and experts to realise that summertime energy poverty is a major issue?” For years Saheb has pushed policymakers to recognise access to cooling as a right, a move that would contrast with its current status as a consumer good. “Because when you’re a consumer, it’s related to your income,” she said. “And this is what increases inequalities.” Lower incomes also often mean people have less say over the areas in which they live, leaving them more likely to live in asphalt-dominated areas with fewer trees and green spaces, said Alby Duarte Rocha, a researcher at the Technical University of Berlin. Duarte Rocha was recently part of a team of researchers who looked at 14 major urban areas across Europe. What they found was a constant association, one that held from Berlin to Budapest, where lower-income residents had more difficulty accessing green spaces capable of naturally cooling the heat of the city. Those with higher incomes, in contrast, had above-average access to these spaces. Part of this could be explained by “green gentrification”, said Duarte Rocha, where areas with more vegetation are in higher demand than those that are densely populated and sprawling with concrete. The result, however, is that those with lower incomes are often pushed out of the coolest areas of the city. He called for policymakers and politicians to see cooling as a service to be provided, akin to public transit or street cleaning, with measures ranging from planting trees to installing green building facades rolled out with emphasis on areas that are lacking in these spaces. It would be a small step towards correcting “the epitome of environmental injustice”, he said. “We need to ask ourselves why the groups of people who are least responsible for climate change are often those most affected by its impacts.”