Nearly half of the global population could be exposed to extreme heat conditions by 2050 if global temperatures rise by 2°C above pre-industrial levels, according to a new study conducted by researchers from the University of Oxford. Climate scientists say this warming scenario is increasingly likely, with serious consequences for human health, energy systems and economic stability.
Extreme heat exposure likely to double compared to 2010 levels
The study estimates that the share of people living under extreme heat will rise sharply from 23 per cent in 2010, about 1.54 billion people, to 41 per cent by 2050, affecting nearly 3.79 billion individuals worldwide. The largest populations exposed to dangerous heat are projected to be in India, Nigeria, Indonesia, Bangladesh, Pakistan and the Philippines, where rapid urbanisation and population growth will further intensify the risks.
Published in Nature Sustainability the research warns that many of the most severe impacts will be felt much earlier than expected, as global warming crosses the 1.5°C threshold set under the Paris Agreement. According to the researchers, changes in cooling demand are accelerating in the current decade, leaving little time for societies to adapt.
Cooling demand to rise sharply before world reaches 1.5°C warming
Lead author Jesus Lizana, associate professor of engineering science at the University of Oxford, said most changes in heating and cooling needs will occur before temperatures stabilise at higher levels of warming. He noted that millions of homes may require air-conditioning installations within the next few years, even though temperatures are expected to continue rising beyond that point if warming reaches 2°C.
The study measured heating and cooling requirements using heating degree days and cooling degree days, standard indicators used to assess energy needs for maintaining safe indoor temperatures. By analysing climate conditions at 1°C, 1.5°C and 2°C of global warming, the researchers found that increases in cooling demand between 1°C and 1.5°C are more severe than those expected between 1.5°C and 2°C.
Developing countries in Africa and South America are expected to experience the most dramatic increases in dangerously hot days. Nations such as the Central African Republic, Nigeria, South Sudan, Laos and Brazil are already witnessing steep rises in cooling degree days, which could increase per capita cooling demand by more than 500 units, placing additional strain on energy systems.
Cold-climate countries also face rising heat stress
The study also found that countries with traditionally colder climates will see a sharp rise in uncomfortably hot days. As global warming approaches 2°C, such days are expected to increase by 100 per cent in Austria and Canada, 150 per cent in the United Kingdom, Sweden and Finland, and more than 200 per cent in Norway, compared to the 2006–2016 period.
While heating demand in these regions is projected to fall significantly, the built environment may be poorly suited to higher temperatures. Homes and infrastructure designed to retain heat and minimise ventilation could face disproportionate impacts even from moderate warming, the researchers warned.
Calling the findings a wake-up call, Radhika Khosla, associate professor at the Smith School of Enterprise and the Environment and leader of the Oxford Martin Future of Cooling Programme, said exceeding the 1.5°C limit would affect everything from education and health to migration and agriculture. She stressed that accelerating net-zero development pathways remains the only viable way to reverse the trend of ever-hotter days.
The study concludes that rising extreme heat will drive up global energy demand for cooling while reducing heating needs in colder countries, underscoring the urgent need for climate-resilient infrastructure, energy-efficient buildings and sustainable cooling technologies.