Recent research reveals that countries like Mexico, Kenya, and Italy are experiencing significantly longer periods of heat stress compared to several decades ago. Some regions that historically did not experience such stress are now feeling the effects. As the planet warms, due to the burning of fossil fuels like coal, oil, and gas, extreme feels-like temperatures, heat stress days, and tropical nights have all increased in frequency and severity over the last six decades, according to a study published in the journal Nature Climate Change.
The researchers focused on the feels-like temperatures to assess the impact on individuals. This approach goes beyond just studying temperature, incorporating factors such as humidity and wind speed to evaluate heat stress on human bodies. The Universal Thermal Climate Index was employed to analyze these factors and model human responses to environmental conditions.
“The combination of heat and humidity poses dangers, as humidity affects sweat evaporation, a key cooling mechanism. Humid heat waves can be more fatal than dry ones,” the study highlights.
Regions that were already warm are experiencing increasing heat stress. Past studies have highlighted how climate change, driven by human activities, has caused global temperatures to soar. One study notes that by 2024, people globally experienced an average of 41 extra days of dangerous heat. Estimates predict that the world might add nearly two months of superhot days each year by the century’s end.
In Southern Africa, parts of Namibia and Angola, as well as Eastern Africa, including areas like Tanzania, Kenya, and Uganda, could face around 50 more days of strong heat stress annually compared to the 1970s. Southern Spain, Italy, Greece, and Turkey might experience up to 40 additional days. Southern Europe sees nearly a month more strong heat stress days than decades ago. In the United States, many regions are experiencing at least 15 additional days of strong heat stress, with southern areas witnessing 25 more days of very strong heat stress.
“The expansion of heat stress to areas where it was previously rare or non-existent is striking,” said lead author Rebecca Emerton from the European Centre for Medium-Range Weather Forecasts.
The study notes that feels-like temperatures on the ten warmest nights each year have increased by 0.32 degrees Celsius per decade, faster than the ten warmest days. Tropical nights, defined as having minimum temperatures of 20 degrees Celsius, mean people might not recover from daytime heat.
Now, an additional billion people face at least one day of extreme heat stress annually compared to the 1970s. The future impact depends on action. Jennifer Francis, a climate scientist not involved in the study, emphasized, “This research shows not only rising temperature but also increased humidity, which makes high temperatures deadlier.”
Emerton stresses the need for mitigation strategies, such as heat health plans, early warning systems, and climate risk assessments, to manage future warming.
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