Earth Already Experiencing Heat and Humidity Too Severe for Human Tolerance
Sat, December 3, 2022

Earth Already Experiencing Heat and Humidity Too Severe for Human Tolerance


For hundreds of thousands of years, humans have had a surprising ability to adapt to environmental changes.  / Photo by Soloviova Liudmyla via Shutterstock


For hundreds of thousands of years, humans have had a surprising ability to adapt to environmental changes. While they face many challenges as they evolve, they met these challenges and learn to adapt to environmentally dynamic settings. They could live in forested surroundings, arid grasslands, or the icy Arctic. But humans also have a limit for survivability. If the humidity and temperatures rise high enough, they can pose a health hazard even to a healthy person in full shade and with unlimited access to water.


Understanding the wet-bulb temperature (TW)

In a study that appeared in journal Science Advances, authors Colin Raymond from the Department of Earth and Environmental Sciences at Columbia University, New York and colleagues shared that some parts of the planet are already experiencing heat and humidity too severe for human tolerance.

They explained the concept of wet-bulb temperature (TW), a measure that combines humidity and air temperature. Once it reaches 35 degrees Celsius or 95 degrees Fahrenheit, it already marks our upper physiological limit.

Based on their climate models, parts of the Persian Gulf, some Mexican locales, and the Indian subcontinent have already recorded 35°C TW. Some cities have also reached brief periods of heat and humidity beyond human tolerance. Raymond said that everyone can acclimate to heat and humidity but there is a certain point where we cannot just cool ourselves through sweating regardless of how healthy we are. “It’s like sitting in a steam room,” he said.


The 2003 European heatwave

The moment the natural cooling mechanism of the body is impaired, it can lead to heatstroke or organ failure. Fatal health impacts are observed with prolonged exposure to extreme humid heat or less-oppressive temperatures. The study cited the deadly heatwave that happened in Europe in 2003. A factor in the death toll was the absence of air conditioning in places that are not used to such heat. It shows that at least 35,000 people died as a result of the heatwave that scorched the continent. Back then, the nonprofit environmental organization Earth Policy Institute warned that “more extreme weather events lie ahead.”


Fatal health impacts are observed with prolonged exposure to extreme humid heat or less-oppressive temperatures.  / Photo by FocusStocker via Shutterstock


Studying temperature data of over 7,000 weather stations

Raymond and his team studied the temperature data from 1979 of over 7,000 weather stations in the world. They discovered that the severity of extreme humid heat is increasing and it now happens twice as often as it did 40 years ago. Considering that there are only a few weather stations in some places, such as in Pakistan, there may be higher TW values out there, Raymond added.

Knowing such a trend is important as it helps build the weather station data, which is now the most direct evidence we have, opined climate scientist Elfatih Eltahir from the Massachusetts Institute of Technology. Eltahir is not involved in the new study.

Often, the highest extremes lasted for an hour or two so they didn’t hit the limit of human physiological tolerance. These conditions are concentrated in South Asia, the coastal southwest North America, and in the coastal Middle East, near high sea surface temperature (SSTs) and intense continental health that both lead to the occurrence of extreme humid heat. The study further stated that low-level winds during the afternoon and midday hours can cause rapid dew point temperature (Td) - the temperature to which air must be cooled to become saturated with water vapor – increases in semiarid and arid coastal areas.

However, the highest extremes that previously lasted within the 1-to 2-hours’ duration may begin to cover larger areas and last longer, leading to a warmer future.


Effect of the heatwave on the economy

Economic analyst Kimberly Amadeo, who was also not involved in the new research, shared that heatwaves affect the economy. This is because it likely affects individuals who live or work outdoors. The US Bureau of Labor Statistics shows that more than 15 million people in the country have jobs that require them to be outdoors at some point.



In 2014, a total of 14,710,000 employees in the leisure and hospitality industry worked outdoors and their numbers are projected to grow to 15,651,200 in 2024. Moreover, 6,138,4000 people in the construction industry worked outdoors in 2014 and that number is projected to reach 6,928,800 in 2040. Other selected industries mentioned in the BLS survey are transportation and warehousing (4,640,300 outdoor work in 2014 and 4,776,900 for 2040 forecast), agriculture, forestry, fishing, and hunting (2,138,300 in 2014 and 2,027,700 for 2024), mining, quarrying, and oil and gas extraction (843,800 in 2014 and 924,000 for 2024), and utilities (553,000 in 2014 and 505,100 for 2024).

Outdoor work also often involves doing physically demanding tasks, including digging and lifting. Because of this, some outdoor workers incur illnesses or occupational injuries at a higher rate than an average worker.

For instance, the incidence rate for nonfatal occupational injuries and illnesses among line installers and repairers stood at 293.0, among light truck or delivery services drivers 298.0 incidence rate, construction laborers 256.0, tree trimmers and pruners 214.1, landscaping and groundskeeping workers 157.2, logging workers 133.2, and recreation workers 119.6. Those who are working outdoors said that among the perks not staying in the office for 8 hours is that they enjoy nature, open-air, and getting exercise. All of these help outweigh the challenges that their careers present.

As climate changes, though, heat waves are poised to get more intense and last longer. This may mean heat exhaustion and related illness for farmworkers, construction crews, and delivery personnel who are not as immune to the economic blows of climate change.



Annual heat wave index

In the US, the heatwave index reached the highest in 1936 at 125.5. The index defines a heatwave as a period lasting at least four days with an average temperature that would only be expected to occur once a decade. In 2010, US’ annual heatwave index was 14.9, 28.5 in 2011, 25.0 in 2012, 8.8 in 2013, 3.9 in 2014, and 12.9 in 2015, according to Our World in Data, a scientific online publication that focuses on large global problems.

The new study highlights the need to reduce greenhouse emissions now to also stop global warming, preventing wet-bulb temperatures higher than the 35 degrees C limit from happening. There is a need for us to put serious thought into how we could slow down the Earth’s warming.