Rising global temperatures have led to an alarming increase in heat stress across multiple countries, including Mexico, Kenya, and Italy. A recent study has revealed that these regions, among others, are experiencing longer durations of intense heat than in the past, with some areas facing unprecedented levels of heat stress.
According to a new study published in Nature Climate Change, the frequency and severity of heat stress days, extreme temperatures, and tropical nights have surged over the last 60 years due to the ongoing warming of the planet. This trend is largely attributed to the combustion of fossil fuels such as coal, oil, and gas. The researchers utilized “feels-like” temperatures, beyond just actual temperatures, to better assess the human impact. This involves factors such as humidity, wind speed, and temperature, analyzed using the Universal Thermal Climate Index.
The combination of heat and humidity poses significant dangers to human health since humidity affects sweat evaporation, a key cooling mechanism. Humid heat waves tend to be more lethal than dry ones, as they impede the body’s ability to cool itself effectively.
Expanding Heat Stress Across the Globe
Prior research has highlighted the influence of human-driven climate change on rising global temperatures. For instance, people worldwide experienced an average of 41 extra days of dangerous heat in 2024, with projections indicating nearly two additional months of extremely hot days annually by century’s end. This study further explores heat stress at three intensity levels: strong (≥32°C or 89.6°F), very strong (≥38°C or 100.4°F), and extreme (≥46°C or 114.8°F).
Notably, regions like Southern Africa, Eastern Africa, Mexico, and Central America may witness up to 50 more days of strong heat stress each year compared to the 1970s. In Southern Europe, including Spain, Italy, Greece, and Turkey, some areas could experience up to 40 additional strong heat stress days annually. Meanwhile, parts of the United States, particularly Texas and Florida, are seeing an increase in very strong heat stress days.
Rebecca Emerton, the study’s lead author and a senior scientist at the European Centre for Medium-Range Weather Forecasts, pointed out the surprising expansion of heat stress into regions where it was historically uncommon. She noted, “to see heat stress not only intensifying in those places that we already consider as being hot or used to experiencing heat waves … but also to see this, we call it, expanding footprint of heat stress expanding into regions where it’s historically been rare or non-existent.”
Furthermore, the study found that the feels-like temperatures during the ten warmest nights each year have increased faster than the ten warmest days. This suggests that people may not be adequately recovering from daytime heat, particularly during tropical nights, defined as those with minimum temperatures of 20°C (68°F).
Currently, one billion more people face at least one day of extreme heat stress each year compared to the 1970s.
Addressing the Future of Heat Stress
The study underscores the urgent need for actions to mitigate future warming and implement adaptation strategies. Climate scientist Jennifer Francis from the Woodwell Climate Research Center emphasized the study’s importance, stating it “adds stark details about increasing dangers to billions of humans” by showing that rising temperatures and humidity levels make high temperatures more lethal.
Emerton advocates for the establishment of effective measures such as heat health action plans, early warning systems, and comprehensive climate risk assessments to address the growing challenge of heat stress.
Original Story at fortune.com