The share of the world’s population exposed to extreme heat is set to double by mid-century if global temperatures rise to 2°C above pre-industrial levels, as pointed out by a new study by the University of Oxford. Based on the science, a warming scenario climate scientists increasingly view as likely.
The study, published in Nature Sustainability, finds that 41 per cent of the global population could be living in extreme heat conditions by 2050, up from around 20 per cent today. That would translate to 3.79 billion people exposed to dangerously high temperatures, with impacts accelerating as the world overshoots the 1.5°C limit set under the Paris Agreement.
The research shows that some of the largest increases in extreme heat exposure will occur in Central Africa, with the Central African Republic, Nigeria, and South Sudan among the most affected countries. Outside Africa, Laos and Brazil are also projected to see significant rises in dangerously hot conditions.
In terms of absolute numbers, the study projects that the largest populations affected by extreme heat will be in India, Nigeria, Indonesia, Bangladesh, Pakistan, and the Philippines, highlighting the disproportionate burden facing the Global South.
Researchers note that many of these regions are already grappling with energy poverty, fragile health systems, and climate-sensitive livelihoods, compounding the risks posed by rising temperatures. Climate researchers say the findings should serve as a warning for governments delaying climate action.
“Overshooting 1.5°C of warming will have an unprecedented impact on everything from education and health to migration and farming,” said Dr Radhika Khosla, Associate Professor at Oxford’s Smith School of Enterprise and the Environment and leader of the Oxford Martin Future of Cooling Programme.
Impacts of Extreme Heat Felt Earlier Than Expected
Crucially, the study finds that most of the increase in cooling demand will occur before the world even reaches 1.5°C of warming, emphasizing the urgency of near-term adaptation.
“To achieve the global goal of net-zero carbon emissions by 2050, we must decarbonise the building sector while developing more effective and resilient adaptation strategies,” said Dr Jesus Lizana, lead author of the study and Associate Professor in Engineering Science at the University of Oxford.
“Our study shows most of the changes in cooling and heating demand occur before reaching the 1.5°C threshold, which will require significant adaptation measures to be implemented early on,” he added.
Lizana warned that many regions may need to rapidly expand access to cooling, including air conditioning, within the next five years, even as temperatures continue rising if warming reaches 2°C.
The projected increase in extreme heat is expected to drive a sharp rise in energy demand for cooling, particularly in low- and middle-income countries, potentially increasing emissions if powered by fossil fuels.
By contrast, demand for heating is projected to decline in colder countries such as Canada and Switzerland, further highlighting the uneven global distribution of climate impacts.
“Net-zero sustainable development remains the only established path to reversing this trend of ever hotter days. Politicians must regain the initiative towards it,” reiterated Dr. Khosla.
How the Study Was Conducted
The researchers assessed future heat exposure using cooling degree days and heating degree days — metrics commonly used to estimate whether cooling or heating is required to maintain safe indoor temperatures.
The analysis relied on the HadAM4 climate model developed by the UK Met Office, run through the volunteer-powered climateprediction.net platform. This approach allowed the team to generate high-resolution projections across different warming levels, from 1°C to 2°C, independent of when those thresholds are reached.
The study also released an open-source global dataset, comprising 30 maps at approximately 60-kilometre resolution, detailing projected heating and cooling demand worldwide.
As countries head toward critical climate negotiations later this decade, including UNFCCC forums, the findings outline a stark reality: the consequences of delayed action will be felt first and worst by populations least responsible for global warming.
For Africa and other climate-vulnerable regions, the study reinforces calls for accelerated mitigation, climate-resilient infrastructure, and equitable access to clean cooling solutions before extreme heat becomes unmanageable.
