Climate: Two billion people could be exposed to hazardous heat by 2100

Europe 1 with AFP / Photo credit: ARNAUD LE VU / HANS LUCAS / HANS LUCAS VIA AFP 17:00 pm, May 22, 2023

Policies currently in place to limit global warming will expose more than a fifth of humanity to extreme and potentially deadly heat by the end of the century, researchers warn in a study Monday. The temperature at the Earth's surface is on track for a 2.7°C increase by 2100 compared to the pre-industrial era, which is expected to push more than 2 billion people, or 22% of the world's population by that date, out of the climate comfort zone that has allowed humanity to develop for millennia. according to this study published in Nature Sustainability.

>> READ ALSO - Global warming: how France is preparing for increasingly extreme events

India (600 million), Nigeria (300 million) or Indonesia (100 million) are the countries with the highest number of people who could face deadly heat in this scenario. "This represents a profound remodeling of the habitability of the planet's surface and could potentially lead to a large-scale reorganization of the places where people live," said Tim Lenton of Britain's University of Exeter, lead author of the study.

Respecting the Paris Agreement to limit the consequences

But by limiting warming to 1.5°C, the most ambitious target of the 2015 Paris Agreement, the number of people exposed to these risks would be reduced to less than half a billion people. The world is already experiencing warming close to 1.2°C as a result of human activity, including the use of fossil fuels (coal, oil, gas), with a series of disasters: heat waves, droughts, forest fires...

"The costs of climate change are often expressed in financial terms, but our study highlights the phenomenal human cost of failing to address the climate emergency," Lenton said. "For every 0.1°C warming above current levels, an additional 140 million people will be exposed to hazardous heat," he said.

>> READ ALSO - Drought: the Pyrénées-Orientales in "very severe risk" of fire

The threshold of "hazardous heat" was set in the study at 29°C average annual temperature. Historically, human communities have been densest around average temperatures of 13°C (in temperate zones) and to a lesser extent 27°C (in more tropical climates). The risks are heightened in regions along the Earth's equator: the climate can be deadly at lower temperatures than elsewhere due to humidity, which prevents the human body from cooling itself through sweating.