Current measures to limit global warming will expose more than a fifth of humanity to extreme and potentially life-threatening heat by the end of the century, researchers warned Monday.
The Earth’s surface temperature is projected to rise 2.7 degrees Celsius (4.8 degrees Fahrenheit) above pre-industrial levels by the year 2100, putting more than two billion people – 22 percent of the projected world population – well outside the climate comfort zone in which our Species could thrive for millennia, scientists said reported In sustainability in nature.
The countries with the highest number of people exposed to deadly heat in this scenario are India (600 million), Nigeria (300 million), Indonesia (100 million), and the Philippines and Pakistan (80 million each).
“This is a profound change in the habitability of the planet’s surface and could potentially lead to a large-scale reorganization of human habitats,” said lead author Tim Lenton, Director of the Global Systems Institute at the University of Exeter.
Limiting global warming to the 1.5°C target set in the 2015 Paris Climate Agreement would significantly reduce the number of people at risk to less than half a billion, about five percent of the 9.5 billion people who would die in six or seven Decades are expected to live on the planet now, the findings say.
Warming of just under 1.2°C to date has already amplified the intensity or duration of heatwaves, droughts and wildfires beyond what could have occurred were it not for the carbon pollution caused by burning fossil fuels and forests.
The past eight years have been the hottest on record.
“The cost of global warming is often expressed in financial terms, but our study highlights the phenomenal human cost of not addressing the climate emergency.” called lenton
“For every 0.1°C of warming above current levels, about 140 million more people will be exposed to dangerous heat.”
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The threshold value for “dangerous heat” used in the new findings is a mean annual temperature (MAT) of 29 °C.
Throughout history, human communities have been densest around two different MAT temperatures: 13°C (in temperate zones) and to a lesser extent 27°C (in more tropical climates).
Global warming is Everywhere the thermostat is pushed upbut the risk of ending up in deadly heat is significantly higher in regions already near the 29°C red line.
Studies have shown that sustained high temperatures at or above this threshold are severe associated with higher mortalitydecreased labor productivity and crop yields, and increased conflict and infectious disease.
Just 40 years ago, only 12 million people worldwide were exposed to such extremes.
That number has quintupled today and will continue to grow climb steeper and steeper Over the coming decades, the study revealed.
The risk is accentuated Regions straddling the equatorwhere human population is growing fastest: Tropical climates, even at lower temperatures, can become deadly when high humidity levels prevent the body from sweating to cool itself.
Episodes of extreme humid heat have doubled since 1979.
Those most exposed to extreme heat tend to live in poorer countries with the smallest per capita carbon footprints, the authors say.
According to the World BankIndia emits around two tons of CO on average2 per person each year and Nigerians about half a tonne per year, compared to less than seven tonnes per person in the European Union and 15 in the United States.
Unfulfilled carbon reduction pledges by governments and companies would halt global temperatures rising to – or even below – 2°C and allow hundreds of millions of people to escape catastrophic heat.
But even worse scenarios than the 2.7 °C world that would result from current politics cannot be ruled out, the authors warn.
If past and ongoing emissions trigger the release of natural carbon stores, such as in permafrost, or warm the atmosphere more than expected, temperatures could rise nearly four degrees above mid-19th-century levels, they said.
