A study published in Nature Sustainability reveals that more than two billion people – 22% of the estimated global population – could face lethal heat by the end of the century if current efforts to limit global warming fail.
The planet’s surface temperature is projected to increase by 2.7°C compared to preindustrial levels by 2100, putting more than a fifth of humanity in danger of extreme heat. The countries with the most people exposed to fatal heat in this scenario are India, Nigeria, Indonesia, Pakistan, and the Philippines.
The research shows that keeping global warming below the Paris climate agreement goal of 1.5°C would significantly lower the number of people at risk to less than half a billion, or 5% of the expected global population. However, just under 1.2°C warming so far has already intensified the frequency and severity of heatwaves, droughts, and wildfires beyond what would have happened without carbon pollution from burning fossil fuels and forests.
The study warns that if past and ongoing emissions trigger the release of natural carbon sources, such as in permafrost, or heat up the atmosphere more than expected, temperatures could rise nearly 4°C above mid-19th century levels.
Lead author Tim Lenton, director of the Global Systems Institute at the University of Exeter, said that the study “underscores the enormous human cost of not addressing the climate crisis.” He added that “for every 0.1°C of warming above current levels, about 140 million more people will be exposed to dangerous heat.” The risk is higher in regions near the equator, where human populations are growing fastest.
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