Deadly heat: will a significant part of Earth soon become uninhabitable? 💀
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A team of scientists from around the world, led by King's College London, published a study in the journal Nature Reviews Earth & Environment. Their findings are alarming: if global temperatures rise by 2°C compared to pre-industrial levels, about 6% of the Earth's land surface will become too hot for even healthy young adults to survive safely. This represents an area almost as large as the United States!
a) Anthropogenic warming required since the pre-industrial period for the maximum heat index over 30 years to exceed the discomfort threshold for young adults (18-40 years). The hatched areas indicate regions where this threshold is crossed at least once for a warming of 2°C.
b) As in (a), but for the unsurvivable threshold after 6 hours of exposure.
c) As in (a), but for adults over 65 years old.
d) As in (b), but for the unsurvivable threshold for adults over 65 years old.
Older adults will be even more affected: about 35% of the land could become dangerous for them. Last year, the global average temperature already exceeded pre-industrial levels by 1.5°C, a record. If nothing changes, we could reach a 2°C increase by the end of the century.
Dr. Tom Matthews, who led the study, explains that extreme heatwaves could become deadly, even for young adults. Until now, only older adults in the hottest regions were affected, but this could soon extend to everyone.
The study distinguishes two types of heat thresholds:
- "Uncompensable" thresholds: the body can no longer cool itself, and internal temperature rises uncontrollably.
- "Unsurvivable" thresholds: body temperature reaches 42°C (107.6°F) in just six hours, which is extremely dangerous.
Between 1994 and 2023, about 2% of the land exceeded tolerance limits for adults under 60, and over 20% for older adults.
If warming reaches 4 to 5°C, older adults could face uncompensable conditions on 60% of the Earth's land surface. Young adults would also be at risk in the hottest regions, such as the Sahara and South Asia.
Dr. Matthews emphasizes the importance of understanding these risks to better protect vulnerable populations. Since 2000, more than 260,000 heat-related deaths have been recorded, showing how extreme heat is already a threat.
This study was conducted with researchers from several prestigious universities, such as Stanford and Columbia. Their work shows that it is urgent to collaborate to better understand and limit the effects of these heatwaves.
What is an uncompensable heat threshold?
An uncompensable heat threshold is when it gets so hot that our bodies can no longer cool down, even by sweating. Internal temperature then rises uncontrollably, which can quickly become very dangerous, even deadly.
These thresholds depend on age, health, and physical condition. Older adults or those with health problems are the most vulnerable. But even healthy young adults could be at risk if the heat lasts too long.
Understanding these thresholds is essential to implement solutions, such as cooling spaces or warning systems to prevent heatwaves.