It’s not just heat that threatens our future, but humidity, experts say

In the fight against global warming, the focus tends to be on the air temperature, often dismissing humidity levels. However, experts say increasing levels of humidity can also pose a risk to human lives.

Heat is dangerous. But when extreme heat is combined with high humidity, the health risks multiply, according to Climate Central.

In fact, a 2020 study stated that humans would not be able to withstand the extreme conditions that are approaching. The study titled "Heat and humidity too severe for human tolerance", was published in the journal ‘Science’.

The study showed that the maximum wet bulb temperature that humans can tolerate is 35ºC (95ºF).

The wet bulb reflects the amount of moisture in the air and more accurately indicates hot conditions that affect comfort and the body's cooling capacity.

When the relative humidity of the air is 50%, this corresponds to approximately 45ºC (113ºF). In other words, as humidity increases, temperature also increases.

This measurement is more accurate because, in humid environments, the evaporation of sweat is difficult, making it more difficult for the body to maintain its internal temperature.

Despite humans having an advanced thermoregulation system, extreme heat still represents one of the greatest natural risks, causing tens of thousands of deaths in the deadliest events of this century.

Photo: Unsplash - Nathan-Dumlao

Furthermore, the authors of the 2020 study also highlighted that the combined effects of heat and humidity go beyond direct impacts on health, affecting people's performance in various activities and causing broad economic impacts.

In other words, no amount of shade and cool water can alleviate the impact of heat and humidity when the temperature limit is reached. And under continuous exposure, the risk is imminent.

The study explained that to maintain a normal core temperature of 36.8°C (98.3ºF), the skin needs to be around 35°C (95ºF) to release body heat. When the air temperature passes this limit, the body can only cool down through sweat.

Photo: Unsplash - Huum

The big problem is that if the wet bulb temperature exceeds 35°C (95ºF), this cooling method no longer works.

According to the article, climate models predict that wet bulb temperatures of 35°C (95ºF) will occur from the middle of the 21st century, but data from weather stations show that some subtropical coastal areas have already recorded this level.

Furthermore, according to the authors, the frequency of extreme humid heat has more than doubled since 1979. The occurrence of temperatures slightly below the critical point, between 32ºC (89.6ºF) and 35ºC (95ºF) has tripled in the last 40 years.

Another relevant factor is that ideal conditions for rest, shade and hydration are almost never present, increasing the risks. Regions affected by devastating heatwaves in Europe in 2003 or Russia in 2010, for example, recorded wet bulb temperature values of up to 28°C (82.4ºF).

The results indicate that, depending on the emissions scenario, air temperatures could regularly exceed 35°C (95ºF) in parts of South Asia and the Middle East by the end of the 21st century.

South Asia’s annual monsoon brings hot and humid air on to the land. And even though the projected extremes are higher in the Gulf in the Middle East, they mostly occur over the gulf itself, the study showed, rather than on land as in South Asia.

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