An international study led by King’s College London reveals that just a half-degree increase beyond 1.5°C in global warming can make an area the size of the US too hot for humans to live. The risks are especially high for older adults.
A new alarming study led by King’s College London has revealed the grave consequences of continued global warming. Published in Nature Reviews Earth and Environment, the research indicates that a global temperature rise of just 0.5 degrees Celsius more than the 1.5 degrees Celsius benchmark could make a significant swath of the planet too hot for human survival, particularly for older adults.
“Our findings show the potentially deadly consequences if global warming reaches 2°C,” lead author Tom Matthews, a senior lecturer in environmental geography at King’s College London, said in a news release. “Unsurvivable heat thresholds, which so far have only been exceeded briefly for older adults in the hottest regions on Earth, are likely to emerge even for younger adults. In such conditions, prolonged outdoor exposure – even for those in the shade, subject to a strong breeze, and well hydrated – would be expected to cause lethal heatstroke. It represents a step-change in heat-mortality risk.”
The sobering assessment spells out that a rise to 2 degrees Celsius above pre-industrial levels could see around 6% of Earth’s landmass — an area comparable to the size of the United States — hit temperatures too hot for even young, healthy individuals to maintain a safe core body temperature.
For older adults, the threat is even more dire, with more than 35% of the planet’s landmass surpassing critical overheating thresholds.
Unforgiving Heat
The study highlights the distinction between “uncompensable” and “unsurvivable” heat thresholds.
Uncompensable thresholds are where the human body’s core temperature rises uncontrollably, even with cooling measures like hydration and shade.
Unsurvivable thresholds are more severe, where the body’s core temperature reaches 42 degrees Celsius within six hours, leading to fatal heatstroke.
Between 1994 and 2023, these thermal tolerances were breached on about 2% of the global land area for adults under 60, with older adults facing these dangerous conditions on more than 20% of the Earth’s surface.
High-Risk Regions
Certain regions are particularly vulnerable to these extreme heat conditions, notably Saharan Africa and South Asia. The study predicts that at higher levels of warming, such as 4-5 degrees Celsius above preindustrial levels, even younger adults will face these deadly conditions.
“At around 4°C of warming above pre-industrial levels, uncompensable heat for adults would affect about 40% of the global land area, with only the high latitudes, and the cooler regions of the mid-latitudes, remaining unaffected,” added Matthews.
The Human Toll
The report underscores the real human cost of extreme heat.
Since 2000, over 260,000 people have died in the deadliest heat events. Notably, nearly 72,000 deaths occurred in Europe during the 2003 heatwave, around 62,000 during the 2022 European heatwave and approximately 56,000 during the 2010 Russian heatwave.
Interdisciplinary Solutions
Matthews stressed the importance of an interdisciplinary approach to combat these deadly heat events.
“Interdisciplinary work is vital to improving our understanding of unprecedented heat’s deadly potential and how it can be reduced,” he added. “As more of the planet experiences outdoor conditions too hot for our physiology, it will be essential that people have reliable access to cooler environments to shelter from the heat.”
This international research team, which includes experts from the University of California, Stanford University, NASA Goddard Institute for Space Studies, Columbia University and Boston University, highlights the urgent need for climate mitigation and targeted adaptation efforts to protect communities most at risk.
Conclusion
This study signals a clear and urgent need for global action to curb emissions and limit temperature rises. With potentially fatal heatwaves becoming more frequent and widespread, comprehending the magnitude of future heat extremes is essential for minimizing their impact on human health and survival.