Limiting global warming to 1.5°C would save billions of people from dangerously hot climate

"Already today, about 60 million people are exposed to dangerously high temperatures, i.e. average temperatures of 29 degrees Celsius or more. If the current course is maintained and policies are pursued that are expected to lead to a warming of 2.7 degrees Celsius, this number could rise to 2 billion people by the end of the century, " says Boris Sakschewski of the Potsdam Institute for Climate Impact Research (PIK), one of the co-authors of the study published in the journal Nature Sustainability.

In the paper, researchers at the University of Exeter, in collaboration with the Earth Commission, examine what global warming means for the number of people living outside a so-called "human climate niche." The researchers locate this climate niche with mean annual temperatures between 13 and 27 degrees Celsius. If this range is exceeded or undershot, for example, illnesses and mortality can increase or migration movements intensify.

According to the study, 9 percent of the world's population (more than 600 million people) have already been displaced from their original climate niche since 1980. Most of these people lived near the cooler peak of the niche - 13 degrees Celsius - and are now in the "middle range" between the two peaks. Conditions are not dangerously hot in the middle range, but tend to be much drier and have not contributed to much population degrowth in the past. Temperatures beyond 27 degrees Celsius, the second peak, are associated with a variety of problems, including lower labor productivity, increased preparation of infectious diseases, or increased mortality, among others.

"For every additional tenth of a degree of global warming, about 140 million additional people will be exposed to critical heat above 29 degrees Celsius. The vast majority of these live in regions with comparatively low per capita emissions, such as India or Nigeria," said PIK researcher Sina Loriani, also a co-author of the study.

The worst of these impacts could be avoided by reducing greenhouse gas emissions and limiting global warming to 1.5 degrees Celsius - then only about 5 percent of the global population would be at risk from dangerous heat exceeding 29 degrees Celsius.