Extreme heat waves have been sweeping Europe, Asia, and North America, forcing millions of people to scorching conditions with temperatures and humidity much beyond average for lengthy periods of time. On July 16, 2023, Death Valley recorded a blistering temperature of 128 degrees Fahrenheit (53.3 degrees Celsius), nearly surpassing the world's hottest day on record.
With additional hot days forecast, Phoenix set a record heat streak of 19 consecutive days above 110 °F (43.3 °C), accompanied by nights that never went below 90 °F (32.2 °C). According to Science Times, the hottest week on record occurred in early July.
A pedestrian shelters from the sun with a handheld fan as she walks past a mural by the artists Maria Ginzburg and Gaetano Matrella, downtown Rome, on July 19, 2023, amid a heat wave in Italy.
How Much Heat Can the Body Take?
Studies have shown that as climate change intensifies, heat waves are becoming more extreme, lasting longer, and occurring more frequently. This heightened heat has raised concerns among people about when it will become too hot for normal daily activities, even for young, healthy adults. While temperature readings on thermometers are one aspect of the issue, humidity also plays a crucial role.
A 2021 study by researchers from the Pennsylvania State University focused on the combination of heat and humidity, measured as "wet-bulb temperature," which poses a significant risk to human health.
According to an article in the Conversation that the researchers wrote, the current understanding is that a wet-bulb temperature of 95 °F (35 °C) would be the upper safety limit, beyond which the human body can no longer effectively cool itself by sweating to maintain a stable core temperature.
However, recent tests in laboratory settings have indicated an even greater cause for concern, as the dangerous combination of heat and humidity can become hazardous at lower levels than previously believed.
Scientists and observers are increasingly alarmed by the rising frequency of extreme heat events accompanied by high humidity, which poses severe threats to human well-being and highlights the urgency of addressing climate change.
READ ALSO: El Niño Warning: World Should Brace For Higher Global Temperatures, New Record Heat Levels, UN Says
Heat Plus Humidity
Researchers conducted controlled experiments at Penn State University's Noll Laboratory to determine the point at which combinations of temperature and humidity become harmful to even young, healthy individuals.
As per the article, participants swallowed telemetry pills to monitor their core temperature while sitting in an environmental chamber, simulating everyday activities. The critical environmental limit, where the core temperature starts to rise continuously, indicates when heat-related illnesses become a significant risk with prolonged exposure.
The upper environmental limit, where the body struggles to maintain a stable core temperature, is lower than previously theorized. In the experiments with healthy young men and women, the critical environmental limit was found to be around 87°F (31°C) at humidity levels above 50%. This corresponds to 87°F at 100% humidity or 100°F (38°C) at 60% humidity.
When the body overheats, the heart works harder to pump blood to the skin for heat dissipation, and sweating leads to a loss of body fluids. Prolonged exposure to high heat and humidity can result in life-threatening heat stroke, necessitating immediate cooling and medical intervention.
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