HUMIDITY AND HEATWAVE

May 9, 2022

The recent IPCC report AR6 has emphasised that humidity is also very important while estimating the physiological stress that extreme heat puts on the human body.

Why is humidity such a critical factor while measuring heat exposure?

Humans lose heat generated within their body by producing sweat that evaporates on the skin.
The cooling effect of this evaporation is essential in maintaining a stable body temperature.
As humidity rises, sweat does not evaporate —just like clothes take a long time to dry in humid locations – and makes it difficult to regulate body temperature. This is why we feel more discomfort in humid places.
The humidity required to reach wet bulb temperatures in excess of 35°C over land is exceedingly difficult to achieve for a variety of reasons.

Wet bulb temperature

In the recent IPCC report AR6, instead of the “dry bulb” temperature that is usually measured using a regular thermometer, an alternative metric known as the “wet bulb temperature” has been used to measure exposure to extreme heat.
The report mentions that sustained exposures to wet bulb temperatures above 35°C are fatal, while sustained exposures to wet bulb temperatures above 32°C are dangerous for intense physical activity.

Source : Indian Express