An international group of scientists, led by King’s College London, has revealed how continued global warming will lead to more parts of the planet becoming too hot for the human body over the coming decades.
The paper, published in Nature Reviews Earth & Environment, finds that the amount of landmass on our planet that would be too hot for even healthy young humans (18 to 60-year-olds) to keep a safe core body temperature will approximately triple (to 6%)—an area almost the size of the US—if global warming reaches 2°C above the preindustrial average.
Under these conditions, they also warn that the area of land where the over 60s will be at risk will increase to about 35%.
Last year was the first calendar year with a global mean temperature of more than 1.5°C above the preindustrial average, and at current rates of warming, 2°C could be reached by mid to late century.
Dr. Tom Matthews, lead author and Senior Lecturer in Environmental Geography at King’s College London said “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 “.
For higher warming levels of 4–5°C above preindustrial, older adults could experience uncompensable heat across around 60% of the Earth’s surface during extreme events. At this level of warming, unsurvivable heat would also begin to emerge as a threat to younger adults in the hottest subtropical regions.
“At around 4°C of warming above preindustrial 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.
The three deadliest heat events of the 21st Century collectively caused nearly 200,000 deaths, including about 72,000 across Europe during 2003, another 62,000 across Europe in 2022, and the Russian heat wave of 2010, which killed around 56,000.