Title: Humid Heat Already Exceeding Human Tolerance in Some Regions | American Association for the Advancement of Science
Headings: Humid Heat Already Exceeding Human Tolerance in Some Regions
Humid Heat Already Exceeding Human Tolerance in Some Regions
Content: Without the opportunity to cool off, people can suffer from elevated heart rate, high blood pressure and even organ failure and death. Wet-bulb temperature is a measure of heat and humidity that expresses how human bodies will experience the temperature. It is so named because it is calculated by wrapping the bulb of a thermometer in a wet cloth. In low humidity, water will evaporate from the cloth, carrying away heat and cooling the thermometer in the same way sweat cools the human body. In these conditions, the wet-bulb temperature will be lower than the air temperature. In high humidity — when the air is more saturated with water vapor — the water cannot evaporate as easily so the cloth stays hot. If the wet cloth cannot cool below the air temperature, neither can human skin. "Physiologically," Raymond said, "there's a point when heat and humidity will become not just uncomfortable, but actually impossible to acclimate to." In 2010, scientists Steven C. Sherwood and Matthew Huber suggested that a person in perfect health, at total rest, in full shade and with unlimited water will still overheat if heat and humidity combine to stop sweat from cooling their skin below 35°C (95°F). Since these ideal conditions are rarely realized, even lower wet-bulb temperatures are dangerous.