‘74% of population to be hit by 2100’

Seventy-four per cent of the world’s population will be exposed to deadly heatwaves by 2100, if carbon dioxide emissions continue to rise at current rates, a study warns.

Even if emissions are aggressively reduced, the percentage of the world’s human population affected is expected to reach 48%, researchers said. “We are running out of choices for the future. For heatwaves, our options are now between bad or terrible,” said Camilo Mora, associate professor at the University of Hawaii at Manoa in the U.S.

“Many people around the world are already paying the ultimate price of heatwaves, and while models suggest that this is likely to continue, it could be much worse if emissions are not considerably reduced,” said Ms. Mora, lead author of the study published in the journal Nature Climate Change.

The human body can only function within a narrow range of core body temperatures around 37 degrees Celsius.

Heatwaves pose a considerable risk to human life because hot weather, aggravated with high humidity, can raise body temperature, leading to life-threatening conditions.

Threshold identified

A team of researchers led by Ms. Mora conducted an extensive review and found over 1,900 cases of locations worldwide where high ambient temperatures have killed people since 1980. By analysing the climatic conditions of 783 lethal heat episodes for which dates were obtained, researchers identified a threshold beyond which temperatures and humidities become deadly.

The area of the planet where such a threshold is crossed for 20 or more days per year has been increasing and is projected to grow even with dramatic cuts in greenhouse gas emissions, researchers said.

Currently, about 30% of the world’s human population is exposed to such deadly conditions each year.