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The 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, published this Monday, May 22 .
The Earth’s surface temperature is on track for a 2.7C rise 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 this deadline – outside the climatic comfort zone that has allowed humanity to develop for millennia, according to this study published in Nature Sustainability.
A procession of natural disasters
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 reshaping of the habitability of the planet’s surface and could potentially lead to a large-scale reorganization of where people live.“, underlines Tim Lenton, of the British University of Exeter, lead author of the study.
But by limiting warming to 1.5°C, the most ambitious goal 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, in particular the use of fossil fuels (coal, oil, gas), with a procession of disasters: heat waves, droughts, forest…
“Dangerous Heat”
“The costs of climate change are often expressed in financial terms but our study highlights the phenomenal human cost of failure to tackle the climate emergency”says Tim Lenton.“For every 0.1°C of warming above current levels, an additional 140 million people will be exposed to dangerous heat”he points out.
The threshold of “dangerous heat” was set in the study at 29°C of average annual temperature. Historically, human communities have been densest around average temperatures of 13°C (in temperate zones) and to a lesser extent around 27°C (in more tropical climates).
The risks are accentuated in the regions along the earth’s equator: the climate can be deadly there at lower temperatures than elsewhere because of the humidity, which prevents the human body from cooling itself by perspiration.