It is understood that climate change will lead to increased humidity, but why should we care? The reason is that heat stress, which is set to become a prominent and pressing issue as global temperatures rise, is compounded by humidity.
Materials provided by The Earth Institute at Columbia University explain that it is more difficult to cool down in a muggy hot environment than a dry one because increased humidity means more moisture in the air; this prevents sweat from evaporating off the skin (an essential method that allows mammals to cool down).
There is a certain small range of internal temperatures which the body can endure. Outside of this organs begin to fail, leading to lethargy, sickness and even death due to heat stress.
Taking both heat and humidity into account, a “wet bulb” temperature, after which everyday activities become difficult, has been calculated as 32℃. After this, the fatal “wet bulb” temperature has been estimated at 35℃. At this value, without intervention, people will die within hours.
Incidents of wet bulb temperatures on Earth are extremely rare at the moment, however, they are predicted to become more frequent in the future. At the moment high wet bulb temperatures occur possibly once a year, however, by 2070 this could rise to as frequent as 100-250 days a year in regions of the tropics.
How destructive high temperatures will be will depends on many factors including population density, wealth and surrounding infrastructure. On the 31st July 2015, Bandar Mahshahr in Iran experienced a wet bulb reading close to 35℃. By staying inside air conditioned buildings and cars, the effects were reduced. However, these are luxuries that many do not have and if such high wet bulb readings were to hit more susceptible areas the results could be catastrophic.
It was therefore argued as vital that the effect of humidity is factored in to future climate change predictions so that the necessary preparatory steps can be taken to prevent disaster.