Nearly half of world’s population to face extreme heat by 2050: Oxford study

Almost half of the world’s population will be living in extreme heat conditions by 2050 if the world reaches 2°C of global warming above pre-industrial levels, a scenario that climate scientists see as increasingly likely, new research by scientists from University of Oxford showed. 

This means that people experiencing extreme heat conditions will double from 23 per cent (1.54 billion people) in 2010 to 41 per cent (3.79 billion) by 2050, with the largest projected populations affected in India, Nigeria, Indonesia, Bangladesh, Pakistan, and the Philippines. 

In fact, in many regions, most of the impacts will be felt early on as global warming breaches the 1.5°C target set by the Paris Agreement, according to the findings published in Nature Sustainability. 

Most of the changes in cooling and heating demand occur before reaching the 1.5ºC threshold, according to Jesus Lizana, lead author and associate professor of engineering science at the University of Oxford. This, he added, will require significant adaptation measures to be implemented early on.  

“For example, many homes may need air conditioning to be installed in the next five years, but temperatures will continue to rise long after that if we hit 2.0 of global warming,” said Lizana. 

The study’s results are measured in heating degree days (HDD) and cooling degree days (CDD) — metrics commonly used in climate research and weather forecasting to estimate whether cooling or heating is needed to keep people within safe temperatures.

HDDs and CDDs quantify the extent to which daily mean temperatures deviate from a reference temperature threshold over a given period. 
The study generated a global dataset for three global warming levels above pre-industrial conditions — 1.0 °C (based on 2006–2016 observations), 1.5 °C and 2.0 °C — regardless of when these occur, to evaluate the climate change implications for the heating and cooling sector globally. 

The countries experiencing the most significant changes in CDD were predominantly developing nations in Africa and South America. The Central African Republic, Nigeria, South Sudan, Laos and Brazil were seeing the most significant increases in dangerously hot temperatures, according to the report.

There will be a significant rise in area-weighted mean CDDs per country, increasing by 524-560 CDDs, drastically increasing cooling needs per capita, the authors warned. 

“As these shifts in CDDs continue, they are expected to place additional pressure on the socio-economic development of these countries, exacerbating existing challenges and hindering their growth and resilience,” the researchers wrote in the report.

They found that cooling needs were changing faster in the current decade as the world approached a 1.5°C global temperature rise, with CDD increases from 1-1.5 °C surpassing those expected between 1.5°C and 2°C. 

Meanwhile, countries with colder climates will see a much larger relative change in uncomfortably hot days, more than doubling in some cases. As global warming reaches 2°C, uncomfortably hot days will increase by 100 per cent in Austria and Canada, 150 per cent in the United Kingdom, Sweden and Finland, 200 per cent in Norway and 230 per cent, compared to that observed during 2006-2016, when global warming touched 1°C. 

This means that these countries will experience a significant decrease in HDDs, ranging from 554 to 850 HDDs, drastically reducing future heating needs per capita. 

Built environment and infrastructure in these countries were predominantly designed for cold conditions; homes were built to maximise solar gains and minimise ventilation. Thus, even a moderate increase in temperature is likely to have disproportionately severe impacts compared with regions that have greater resources, adaptive capacity and embodied capital to manage heat, the findings showed.  

“Our findings should be a wake-up call,” said Radhika Khosla, associate professor at the Smith School of Enterprise and the Environment and leader of the Oxford Martin Future of Cooling Programme. 

“Overshooting 1.5°C of warming will have an unprecedented impact on everything from education and health to migration and farming. Net zero sustainable development remains the only established path to reversing this trend for ever hotter days. It is imperative politicians regain the initiative towards it,” she said. 

The projected increase in extreme heat will also lead to a significant rise in energy demand for cooling systems and corresponding emissions, while demand for heating in countries like Canada and Switzerland will decrease. 

“Additionally, this rapid shift underscores the need for more resilient, energy efficient building designs and cooling technologies to mitigate the growing reliance on air conditioning systems,” it said.