With climate change causing temperatures to rise across the world, extreme heat is increasingly becoming a threat to health. the human body is resilient, but it can’t handle so much. So what’s the hottest temperature people can handle?
The answer is simple: a wet bulb temperature of 95 degrees Fahrenheit (35 degrees Celsius), according to a 2020 study in the journal Scientists progress. The temperature of the wet thermometer is not the same as that of the air Temperature you might see a report from your local forecaster or your favorite weather app. On the contrary, a wet temperature is measured by a thermometer covered with a cloth dampened with water, and it takes into account both heat and humidity. This last point is important because with more water in the air, it is more difficult for sweat to evaporate from the body and cool a person.
If the humidity is low but the temperature is high, or vice versa, the wet bulb temperature is unlikely to be near the tipping point of the human body, said Colin Raymond, postdoctoral researcher at NASA’s Jet Propulsion Laboratory who study extreme heat. But when the humidity and temperature are very high, the temperature of the wet thermometer can reach dangerous levels. For example, when the air temperature is 115 F (46.1 C) and the relative humidity is 30%, the temperature of the wet thermometer is only about 87 F (30.5 C). ). But when the air temperature is 102 F (38.9 C) and the relative humidity is 77%, the wet bulb temperature is around 95 F (35 C).
Related: Why is humidity so uncomfortable?
The reason people cannot survive high heat and humidity is that they can no longer regulate their internal temperature. “If the temperature of the wet bulb exceeds the temperature of the human body, you can still sweat, but you will not be able to cool your body to the temperature it needs to function physiologically,” Raymond told Live Science.
At this point the body becomes hyperthermic – above 104 F (40C). This can lead to symptoms such as a rapid heartbeat, change in mental state, lack of sweating, fainting and coma, depending on the doctor. National Institutes of Health.
A humid temperature of 95 F will not, however, cause immediate death; it probably takes around 3 hours for that heat to get overwhelming, Raymond said. There is no way to know for sure the exact duration, he said, but studies have attempted to estimate it by immersing human participants in tanks of hot water and removing them when their temperature is over. body began to increase uncontrollably. There is also no way to confirm that 95 F is the exact temperature of the wet thermometer that cannot survive; Raymond estimated that the actual number is in the range of 93.2 F to 97.7 F (34 C to 36.5 C).
While no one can live above about 95 ° F wet bulb temperature, lower temperatures can also be fatal. Exercise and direct exposure to the sun make it easier to overheat. Older people; people with certain health problems, such as obesity; and the people who take antipsychotics also cannot regulate their temperature, so it is easier for the heat to kill them. This is why people sometimes die in a heat that does not reach a humid temperature of 95 F.
Fortunately, air conditioning can save people from unbearable heat. But, of course, not everyone has access to it, and even in places where many people are air-conditioned, the power grid can be unreliable, Raymond said.
Few places have reached a humid temperature of 95 F in recorded history, according to the Science Advances study. Since the late 1980s and 1990s, the hot spots have been the Indus River Valley of central and northern Pakistan and the southern shore of the Persian Gulf. “There are places that are already starting to feel these conditions for an hour or two,” Raymond said. “And with global warming, it will only become more frequent. Places that are at risk of experiencing these temperatures over the next 30 to 50 years include northwestern Mexico, northern India, Southeast Asia and West Africa, a- he added.
“Unfortunately, with climate change already locked in, we will continue to warm up a bit, even if we stop broadcasting greenhouse gas today, ”Raymond said. “I think it is inevitable that the places I have mentioned will struggle with this problem for the foreseeable future, and I hope other places will not be added to this list.
Originally posted on Live Science.