Twenty degrees apart: How urban inequality drives indoor heat in Paris and Barcelona
- Written by Peter Yeung and Natalie Donback
- Edited by Tina Lee
- Illustration by Suryaa Rangarajan
While European cities face record-shattering heat due to climate change, not all residents are affected equally. Indoor heat sensors show scorching temps in areas with lower-income housing, compounded by neglectful urban planning and pollution- a combination that is creating health risks in urban peripheries.
Research collaborators in Paris and Barcelona: Leonardo Sánchez Vargas, Sergio Álvarez Rodríguez, Angela Maria Uribe, Guillaume Perret, Adèle Scheuer-Rothan, Vincent Fratello, Gaelle Meynadier, Horaye Dia, Anne-Sophie Ledos, Freddie Ramos Lopez.
On 14 August, at 4 in the afternoon, the temperature inside Leonardo Sánchez Vargas’ apartment in Barcelona hit a sweltering 36 degrees Celsius. “It was a difficult day,” said Sánchez, who lives with his wife and their two children, aged six and nine, on the top floor of a six-floor building in Nou Barris, a working-class district in the north-west of the city. “We couldn’t sleep much that morning because the heat woke us up very early.”
Their apartment, which belongs to Sánchez’s mother-in-law, is a converted rooftop terrace with badly insulated walls and the living room – turned into a playroom filled with books, drawings, and games for the kids – is full of windows letting in the merciless sun. “In winter and summer, it’s like the two extremes. The insulation isn’t really well done for a permanent home,” said Sánchez, who is a stay-at-home dad while his wife, a trained art historian, currently works as an administrative assistant.
Vargas’ experience is familiar to many people living on the margins of Europe’s cities.
An investigation by Unbias the News has found that residents in low-income areas of Barcelona and Paris are disproportionately suffering from extreme heat in their homes, in part due to substandard housing, difficulties paying for cooling, and lack of green spaces. Temperatures recorded by heat sensors installed in the homes of residents in the summer of 2025 appear to have breached recommended guidelines, in one case exceeding 50°C. These sweltering conditions are creating and exacerbating health issues among vulnerable groups and interventions from local authorities are falling short, even as the death toll mounts.
“It’s the fastest warming continent in the world. Projections show that we are likely to have a severe problem. But we don’t have a harmonized system to tackle heat-related mortality.”
“What we see in Europe is a perfect storm brewing,” said Aleksandra Kazmierczak, an expert in climate change and human health at the European Environment Agency (EEA), an independent EU body. “It’s the fastest warming continent in the world. Projections show that we are likely to have a severe problem. But we don’t have a harmonized system to tackle heat-related mortality.”
Socio-economic factors play an important role in heat exposure, as low-income families often can’t afford cooling and home improvements, but also tend to work more physically demanding jobs, explained Carme Borrell, the head of Barcelona’s public health agency. Eight of the city’s 13 lowest-income neighborhoods are in Nou Barris, far from central Barcelona’s popular tourist attractions and beaches.
Josefa Romero, a retired widow from Nou Barris, had AC until her husband passed away a few years ago. “Without two pensions, I can’t afford it anymore,” she said.
In Verdun, the neighborhood where Sánchez and his family live, the average income is less than 1,000 euros a month, making it one of the most climate vulnerable districts, according to a 2022 study commissioned by the city authorities. While Sánchez’s apartment has air conditioning, it doesn’t work well and the moment it’s turned off the cool air escapes. “It’s like throwing away money, so instead we decided to try to get used to living with the heat,” he said. They can’t afford the 8,000 euros needed to improve the insulation.
Instead, the family spends a lot of time in a nearby park, where they play with water balloons and water guns to cool down. On August 14 – at the peak of the longest and most intense heatwaves in the region’s history – they spent the whole day looking for places to stay cool. August temperatures in Barcelona hit a record 38.9°C, the highest since records began 112 years ago.
No relief
The odds are further stacked against marginalized communities due to the heat-trapping urban environment.
In the northeast of Paris, beyond the Périphérique, a ring road that physically and symbolically demarcates the French capital’s center from its often-maligned suburbs, Aubervilliers presents a very different picture from the rose-tinted images of the City of Light.
Here, in one of the most deprived districts in France, concrete reigns.
Enormous tower blocks, not permitted in inner Paris, loom over the main drag. Nearby, constant, pollution-pumping traffic roars day and night along the eight-lane highway, itself a great mass of tarmac. To the west is a sprawling area almost entirely filled with industrial warehouses.
A study carried out in 2022 and 2023 by authorities in Aubervilliers, which is a separate municipality to the city of Paris, found that there are some “micro neighborhoods” in the municipality with zero green space. While Paris has set the goal of 10 square meters of green space per inhabitant in cities, there are currently only 8.6 square meters and, the study found, just 1.3 square meters in Aubervilliers. There have been efforts to introduce more, yet as Paris expands and the population grows, pressure to build on this hinterland is ramping up. One of Aubervilliers’ few green spaces, the Terre Terre community garden, has already been earmarked for sale to property developers.
“Dense urban areas with lots of concrete create an urban heat island effect – the absorption of solar radiation and then re-radiating of it,” said Kazmierczak of the EEA. “Urban populations, particularly disadvantaged ones, have a constant exposure to heat. It’s very limiting even for young and healthy individuals.”
Research co-created by Unbias the News and citizens in Paris and Barcelona further underlines the debilitating impact of increasingly extreme heat.
All five heat sensors in Aubervilliers regularly logged temperatures in excess of 26°C during a three-week period in August. All of these homes registered indoor temperatures higher than 30°C at some point, but one, which had no window blinds, hit 51.6°C on August 14.
According to data logged by eight heat sensors installed in the homes of residents in the districts of Aubervilliers on the outskirts of Paris and Nou Barris in Barcelona – as well as surveys conducted with some 70 citizens – many are struggling with the impacts of heat on their health and everyday lives.
Although the research is limited and scientists are divided over what constitutes a safe indoor temperature – local factors such as humidity and acclimatization (when locals get used to high temperatures over time) also play a role – a 2018 review by the World Health Organization of multiple studies across the world suggested that long-term exposure to indoor temperatures above 24°C may lead to health risks, including higher blood pressure, cardiovascular problems and even adverse pregnancy outcomes, such as stillbirth or miscarriage. Canadian health authorities, for example, recommend avoiding prolonged exposure to temperatures above 26°C.
All five heat sensors in Aubervilliers regularly logged temperatures in excess of 26°C during a three-week period in August. All of these homes registered indoor temperatures higher than 30°C at some point, but one, which had no window blinds, hit 51.6°C on August 14. In Nou Barris, three heat sensors installed during the last two weeks of August showed indoor peak temperatures of over 30°C and an average of 27.4°C.
Some 85% of 53 survey respondents in Aubervilliers, and 88% of the 17 in Nou Barris, said their homes were “uncomfortably hot” this summer, citing poor insulation and the absence of window blinds, as well as a lack of green space nearby. Residents also reported numerous symptoms, including heat strokes, the swelling of limbs, breathing problems, mental anguish, extreme fatigue, dizziness, heart palpitations, and very often, difficulty sleeping.
Nuria Romanos, a 53-year-old woman on minimum basic income, lives with her sister in a flat without air conditioning in Nou Barris. “We only have fans, but the electricity bill goes up anyways,” she said, adding that she’s going through menopause and suffers from heat flashes on top of the already sweltering temperatures.
As global warming accelerates, conditions appear to be worsening: 64% of respondents in Aubervilliers and 88% in Nou Barris said that this summer’s heat was more intense than in previous years.
In order to cope, people are changing habits, including not moving or going outside during the day’s hottest hours. “The truth is that without air conditioning it’s impossible to do anything [indoors] – whether it’s watching a movie, TV, or just being on the computer, it becomes unbearable,” said 29-year-old Sergio Álvarez Rodríguez who works from his home in Nou Barris. According to data from a heat sensor installed in his apartment after the August heatwave, temperatures reached over 30°C on several occasions.
Dissatisfied with local authorities’ responses to the increasing temperatures, 94% of those in Paris surveyed and 82% in Barcelona said that not enough is being done to protect them from extreme heat.
An urban threat
Today, more than 40,000 Europeans die due to extreme heat each year, but that figure could triple by the end of the century if global temperatures reach 3°C above pre-industrial levels. Scientists say this level of warming remains likely, as global efforts to cut emissions fall well short of international commitments to limit the rise to a maximum of 2°C.
Heat-related deaths will be most frequent in densely populated urban area. A study in January 2025 found that, of the 854 European cities it assessed, Barcelona is set to experience the highest rate of mortality by the end of the century. Separate research published in 2023 found that between 2000 and 2019, Paris – which just recorded its third hottest summer since 1900 – is the most vulnerable capital city in Europe to heatwave-related deaths.
Yet so much of this could be prevented, experts say.
Nathalie Blanc, a professor and director of the Center for Earth Policies at the University of Paris Cité, argues that city and state policy is playing a key role in exacerbating the inequalities linked to extreme heat.
“It’s not only a question of climate change, but also poor buildings, lack of green space, and lack of money for things like air con,” said Blanc, who has studied climate and environmental justice in four areas across Greater Paris, including Aubervilliers. “Extreme heat is not felt equally.”
A study by the French National Institute of Health and Medical Research (INSERM) found that during France’s historic heatwave in August 2003, nearly 15,000 people died due to the heat. Seine-Saint-Denis – which is home to Aubervilliers and has the highest rate of poverty of any regional department in mainland France – recorded the second highest number of deaths.
The Cité Cochennec, a set of 1960s social housing blocks in the north of Aubervilliers, is a microcosm of those stark inequalities.
“It’s a life of dogs here,” said Mourad Chebli, a 58-year-old resident of Tunisian origin, gesturing at pungent, overflowing dustbins, smashed-up cars, and the crumbling façades on the 10-storey blocks that contain 700 homes. “See how it has been left? We have rats the size of rabbits.”
Authorities have for years promised to renovate Cochennec, Chelbi explained, but nothing has been done. Meanwhile, as successive heatwaves struck Paris this summer, setting the city on red alert, residents like he and his wife have had to make their own adaptations.
“The heat was suffocating,” said Chebli, who sometimes sat outdoors until midnight since his apartment was too hot. He invested in a second-hand portable air conditioning unit, but with sky-high electricity prices, he could barely afford to keep it on.
Yet the fast-rising temperatures pose even more serious risks to vulnerable groups such as the elderly, children, pregnant women, and those with pre-existing health issues or living with a disability.
Aida Ribera, a senior researcher focused on aging populations at Barcelona’s Vall d’Hebron Research Institute, said older people are more vulnerable to extreme heat due to a higher prevalence of chronic conditions such as high blood pressure and heart disease, as well as their isolation. “There’s also a whole social and behavioral aspect with older people who live alone,” she said, adding that heat also limits much-needed physical exercise for the elderly.
Michelle Bernard Audrin, a 68-year-old retiree with lymph node cancer who lives alone, fell to the floor of her second-floor apartment in Cochennec a number of times this summer when the heatwave became unbearable.
Her thermometer hit as much as 38°C indoors even when the outdoor temperature was lower, since her home, which has no window blinds or fixed ventilation, is directly exposed to the sun.
“I became dizzy and l lost my balance,” said Audrin, who grew up in Aubervilliers and has lived in the same block since 1985.
Her makeshift solution is to put ice cubes atop a large fan, but that only makes a limited difference.
Audrin, like many others in Cochennec, asked local authorities to move her to better-equipped lodgings.
“But I have had no response,” said Audrin. “I’ll probably end my days here.”
Rising temperatures, caused by man-made climate change, have already claimed a number of lives this summer. In July, a 51-year-old street cleaner died shortly after finishing her shift in Barcelona and more than 1,100 deaths have already been linked to Spain’s August heatwave. In France, the first heatwave of summer 2025 – between 19 June and 6 July – led to nearly 500 deaths, according to estimates. A study by Imperial University London found climate change tripled heat deaths in 12 major European cities, including Paris and Barcelona, during 2025’s first heatwave.
According to Antonio Barrera Escoda, a meteorologist specialized in climate with the Catalan Meteorological Service, one of the biggest issues in Barcelona are so-called tropical nights, when minimum nighttime temperatures remain above 20°C. The body relies on cool nights to recover from daytime heat, but high overnight temperatures disrupt the recovery process, which can cause cardiovascular issues, sleep disturbances, and increase mortality.
Sánchez and his family have developed strategies to get as much sleep as they can during hot nights: taking a cool shower before going to bed, sleeping on top of towels, doing calming breathing exercises, and taking turns sleeping in the one bedroom that has a bit of a draft.
“You can’t entirely adapt 100% to these rapid changes in climate. But undoubtedly, there’s more that can be done to try and avert some of these potentially preventable deaths,” said Andy Haines, a professor of environmental change and public health at the London School of Hygiene and Tropical Medicine.
Urban heat islands
“We don’t have the same resources as Paris. It’s a different reality.”
In recent years, authorities in Barcelona and Paris have belatedly accelerated efforts to protect citizens from extreme heat.
In October 2023, Paris conducted crisis drills to simulate the impact of 50°C heat on the city, including breakdowns of public transport, forced closure of schools and failure of phone networks due to overheating. The “Paris at 50°C” test, which revealed numerous vulnerabilities, has led to further investment into urban reforestation, the construction of public shade spots and mist stations, as well as the expansion of “cool islands” such as museums, churches and parks – now totaling 1,400 – where residents can take shelter. This summer, to much fanfare, three bathing sites were also opened on the River Seine. Under the city’s Heatwave Plan, 10,000 vulnerable residents have also been registered to receive phone checks when heatwaves hit.
But in Aubervilliers, a separate – and much less wealthy – municipality than Paris, funding and support for climate adaptation is almost non-existent by comparison. Here, no mist stations or shade spots have been constructed, admitted Fabien Benoit, the environmental project manager at Aubervilliers City Hall, and the municipality’s Heatwave Plan is just a page long. But in the past year, there have been two projects to re-green spaces in the neighborhood.
“We don’t have the same resources as Paris,” he added. “It’s a different reality.”
In June, Barcelona’s city council presented the new €111 million Heat Plan 2025-2035, which aims to prepare the city for rising temperatures by creating more shaded spaces, improving the emergency response to heatwaves through a 50°C drill based on the one in Paris, and reducing the urban heat island effect by increasing greenery.
According to Irma Ventayol, the councilor in charge of climate change at the city council, “heat is tackled in public spaces through more greenery, more shaded areas, and pavements that help reduce the urban heat island effect, but it also considers how to improve conditions in housing.” The new heat plan also addresses issues such as energy-efficient rehabilitation and the monitoring of vulnerable people, but responsibilities like subsidizing energy bills fall under the central government, she explained.
However, the plan largely counts on expanding a network of climate shelters – the city’s big bet when it comes to adapting to global warming. “[These] offer spaces of thermal comfort for people who cannot maintain it at home,” said Ventayol. There are currently 400 such spaces equipped with air conditioning and free drinking water, including libraries, municipal swimming pools, and civic centers.
Yet, experts say the shelters don’t solve the issue of nighttime heat and they can be hard to access for elderly people with limited mobility.
According to Irma Ventayol, the councilor in charge of climate change at the city council, “heat is tackled in public spaces through more greenery, more shaded areas, and pavements that help reduce the urban heat island effect, but it also considers how to improve conditions in housing.”
When Nou Barris and Aubervilliers residents were asked about what actions they would like from local authorities, they said they’d like to see their electricity bills subsidized, more trees planted and the creation of subsidies for the renovation of building façades and insulation.
When Nou Barris and Aubervilliers residents were asked about what actions they would like from local authorities, they said they’d like to see their electricity bills subsidized, more trees planted and the creation of subsidies for the renovation of building façades and insulation – a policy already encouraged by the European Union – as well as more climate shelters.
To help protect the vulnerable from extreme heat, countries like Japan have introduced subsidies for energy-efficient air conditioners and water utility fees.
Experts say there are a number of other effective solutions that should be used, such as improving urban shade cover, better coordination and data-sharing among city departments and, crucially, reducing carbon footprints.
When it comes to improving housing, they say cross ventilation encouraging airflow and improved isolation of buildings can help decrease reliance on expensive, carbon-emitting air conditioning.
“You can’t just adapt your way out of this crisis, you also have to cut emissions,” said Haines of the LSE. “It’s risky to think of a magic bullet.”
Yet, as rapid heating of the planet becomes harder to ignore, marginalized urban communities like those in Aubervilliers and Nou Barris believe that they are being forgotten by authorities even as they suffer on the frontlines of climate change.
“We’ve been abandoned,” said Audrin, glaring out of her window at the beating afternoon sun.
This reporting was supported by Seek Initiative and Journalismfund Europe. ExactLog heat sensors were provided by iButton to record temperatures in the homes.
About the author:
Peter Yeung is an award-winning freelance journalist based in Paris – a short bike ride from Aubervilliers – who covers climate, migration and human rights, often through a critical, solutions-orientated lens. He specialises in non-extractive, on-the-ground reporting about under-covered issues involving and giving a voice to marginalized groups. He has written for The New York Times, the BBC, The Guardian, the Washington Post and National Geographic, among other publications.
Natalie Donback is an independent journalist based in Barcelona covering climate change, human rights, and politics. Her work has appeared in TIME Magazine, The Guardian, Grist, Rest of World, the BBC, and many other outlets. She was previously an editor and reporter at Devex, covering global health and the humanitarian sector. Her investigative work has received grant support from Journalismfund Europe, Investigative Journalism for Europe, and the Magmatic School of Environmental Journalism.
Does housing effect how people experience heat? Are temperatures the same throughout a city? Is current rate of climate change deadly? Are poorer neighborhoods worse for climat change?
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