WITH the rising effects of climate change, heat waves have become more severe and intolerable around the world, posing dangerous health issues such as heat exhaustion, heat strokes, severe dehydration, and heat cramps which could even be fatal.
Many places around the world have registered record-breaking high temperatures this year such as India, the UK, and the US. According to a study published last year in The Lancet, just under half a million deaths a year are estimated to be due to excess heat.
The question that arises is “When is the heat too hot to be tolerable?”. The answer lies beyond the temperatures reported in news headlines which actually do not tell the whole story.
[ihc-hide-content ihc_mb_type=”block” ihc_mb_who=”unreg” ihc_mb_template=”3″ ]Humidity plays a crucial role in determining how we experience heat. The measurement of heat coupled with humidity is known as the “wet-bulb temperature”. Wet-bulb temperature is the lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure.
The term wet- bulb temperature originated from the technique the measurement is taken, which is by wrapping a wet muslin cloth around the bulb of the thermometer. This technique analyses to what degree the temperature is reduced compared to the dry temperature.
You might wonder, how is humidity factored into the way we experience heat? We all know that humans sweat during high temperatures to cool off their bodies and maintain optimal temperatures. As the water in sweat evaporates into the surrounding, it releases heat from the body. However, when the surrounding is highly humid, in other words, saturated with water vapour, water in sweat is unable to escape into the surrounding space and no longer has the ability to cool our bodies.
The critical wet-bulb temperature for humans, the point at which a fit and healthy person could survive for only six hours, is considered to be 35℃, approximately equivalent to an air temperature of 40℃ with a relative humidity of 75%.
When this wet bulb temperature is exceeded, sweat can’t evaporate into the surrounding, which means we are not able to cool down our bodies and will eventually die. Wet-bulb temperatures in Malaysia currently range from about 16℃ up to 28℃.
Science Advances Journal reported in 2020 that the lethal combination of heat and humidity is alarming because the challenge posed by it is more intense and increasingly severe than what was formerly analysed.
It was found that some coastal subtropical locations have already experienced a wet-bulb temperature of 35℃, although only for a few hours. Global warming will drive the frequency and the areas affected reaching the threshold wet-bulb temperature to significantly increase.
The term “wet-bulb temperature” that was little known outside meteorology circles is now gaining popularity among the public as the effects of humid heat is crucial to be factored in, in assessing the risk to human health in preparation for the expected extreme weather pattern due to global warming.
So in the future, you might want to check the wet-bulb temperature before leaving home!
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