Dangerous 'Heat Stress' Has Surged Worldwide, Study Shows

Humanity's exposure to dangerous heat stress has surged dramatically over the past half-century, driven by climate change, according to a study released Monday. This finding comes as Europe endures a punishing heatwave, highlighting the escalating global threat.

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On every continent, strong to extreme heat stress is now more frequent.

Heat stress, a hazardous buildup of body heat caused by high temperatures and humidity, is a leading weather-related killer. The study, published in Nature Climate Change, tracked heat stress levels globally from the 1970s to 2024. Researchers found that "on every continent, strong to extreme heat stress is now more frequent."

In the 1970s, approximately 16 percent of the global population experienced at least one day of extreme heat stress, defined by a "feels-like" temperature of at least 46 degrees Celsius (115 degrees Fahrenheit). Fifty years later, this figure has climbed to 22 percent. Lead author Rebecca Emerton of the European Centre for Medium-Range Weather Forecasts noted that this increase represents roughly one billion additional people facing extreme heat stress compared to the 1970s.

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But that's an extra approximately one billion people that are seeing at least some extreme heat stress now that wouldn't have done in the 1970s.

The study utilized the Universal Thermal Climate Index (UTCI) to measure the "feels-like" temperature, incorporating factors like humidity, wind, and radiation. The research indicates that human-driven global warming is causing heat stress events to become more frequent, severe, and prolonged. Some countries, including Spain, Portugal, Italy, and France, are now experiencing "feels-like" temperatures up to five degrees Celsius hotter than in the 1970s. The study also noted the global rise of unrelentingly hot nights, where temperatures do not drop below 20 degrees Celsius, posing significant health risks, particularly for vulnerable populations.

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you can't get any relief, and your body can't cool down, that becomes very dangerous for people's health, particularly for vulnerable people