A Rising Temperature of Human Suffering
As the super El Niño approaches, cities worldwide are struggling with the effects of extreme heat. In southern India, at least 16 people have died so far this year due to heatstroke. The UK recorded its hottest-ever day for May, with temperatures reaching 35.1°C in southwest London. Japan has seen a sharp increase in heatstroke cases, with 1,803 reported in 2025 compared to 546 in 2024.
For professional tennis players, the heat is not just a challenge but a threat to their lives. At the Roland Garros court, players have been collapsing in the scorching heat, a scene repeated in many cities, where people are struggling to cope with the rising temperatures.
Cities Are Getting Hotter, and We're Not Prepared
Researchers have confirmed that extreme heat is reshaping city life, and we're not equipped to handle it. A study published in the Journal of Advances in Modeling Earth Systems found that most Earth system models fail to capture cities' real impact on the climate because they don't consider traffic-related anthropogenic heat. This oversight has severe consequences.
The study developed a traffic heat flux module that can be incorporated into existing climate models. The module takes into account traffic volumes, vehicle type, speed, road characteristics, and weather conditions. When tested in two urban sites, Toulouse, France, and Manchester, UK, the module showed that traffic heat increases the average annual air temperature by about 0.4°C and 0.25°C, respectively. These small increases may seem insignificant, but they're meaningful in the context of already-hot cities.
Underground Environments Are a Hotspot
A separate study published in Nature Cities focused on the metro systems of Boston, London, and New York. By analyzing social media posts and Google Maps data, the researchers found that underground environments are much hotter than the surface above them. In London, the highest recorded temperature on the Tube was 47°C, exceeding the surface air temperature by 6.8°C.
The researchers used natural language processing to identify thermal complaints on social media and found that for every 1°C rise in outdoor air temperature above 10°C, thermal complaints underground increased by 10% in Boston, 12% in New York, and 27% in London. This is a worrying trend, especially as we approach the summer months.
Cooling Poverty Is a Reality for 600 Million People
A team of researchers from across Europe and the US analyzed a vast dataset of demographic and health survey data to quantify the extent and nature of people's ability to remain thermally safe as climate change worsens. They found that system cooling poverty is widespread and unevenly distributed, affecting almost 600 million people worldwide. South Asia and Sub-Saharan Africa are the regions with the strongest deprivation.
The researchers developed a composite "systematic cooling poverty" index (SCPI) to measure the extent of cooling poverty and found that a country's SCPI score is not directly related to its wealth. Instead, it's influenced by factors such as infrastructure, social inequalities, and access to healthcare.
The Problem Goes Beyond Climate Change
Extreme heat is not just a matter of climate change, but also a reflection of our infrastructure and social priorities. Urban planning decisions, access to public services, and individual responses all play a role in exacerbating the effects of heat. And until we address these underlying issues, we'll struggle to mitigate the impact of extreme heat.
The studies highlighted in this article paint a worrying picture of a world where cities are struggling to cope with the effects of extreme heat. And it's a problem that's only going to worsen with the arrival of 'super El Niño'. We need to increase access to cooling technologies, such as air conditioning, but as a study from Singapore shows, this can have unintended consequences, such as weakening people's motivation to engage in collective climate action.
Investing in urban green spaces is another solution. A team of Chinese researchers found that cities that rapidly invested in urban green spaces in recent decades experienced a significant increase in their maximum cooling intensity. The cooling capacity of urban green spaces is also more impactful when they're dense, tall, and structurally complex.
However, these solutions are not a panacea for the problem of extreme heat. Until we address the underlying issues of infrastructure, social inequalities, and access to public services, we'll struggle to mitigate the effects of extreme heat.
The authors of the SCPI study emphasize that systemic cooling poverty is a complex issue that requires a multifaceted approach. They stress that it's not about whether a person can afford air conditioning but rather how surrounding infrastructure, institutions, and design expose someone to harmful heat and then fail to protect them from heat. This is a challenge that we must address urgently, as the consequences of inaction will be severe.
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