American researchers conducted an experiment that showed that the threshold of human endurance to high temperature and humidity can be much lower than assumed. In the context of successive heatwaves and the steady increase in the global average temperature, the research seems particularly important.
Heat waves, which are becoming longer and more intense each year, can adversely affect the human body. Prolonged and frequent exposure to high temperature can cause overheating, dizziness, exhaustion, circulatory disorders, in extreme cases, cause a stroke, coma and even lead to death. Heat is especially dangerous for children, the elderly and the sick, but also a young, healthy person can experience serious ailments.
The limit of surviving in the heat
The scientific community has been convinced for years that the limit of human survival is 35 degrees Celsius at 100% humidity or 46 degrees C at 50 percent humidity. These are basically theoretical conditions, as such values are very rarely really exceeded in nature. But it has happened, and it has been reported several times in South Asia and the Gulf region. “Never before have such extreme conditions lasted more than two hours, and therefore there have been no mass deaths of people,” said Colin Raymond of the Jet Propulsion Laboratory. NASA (NASA Jet Propulsion Laboratory) in an interview with AFP.
However, according to the latest research, our endurance threshold may be much lower and it is influenced by many factors (such as the aforementioned age and health, but also social and economic factors). It is estimated that in the summer of 2022, over 61,000 people died in Europe due to the heat, and yet – although the temperature can be very high – 100% humidity is rare on our continent.
How the limit of dangerous temperature was studied
In a scientific experiment, researchers from Pennsylvania State University in the United States determined the limit of dangerous temperature using a method called a wet bulb. They put a damp cloth over the thermometer and exposed it to the air. This made it possible to measure how quickly water – imitating sweat on the skin – evaporates from the fabric.
Then, to test the veracity of the obtained results, they measured the temperature of the internal organs of young, healthy people placed in a thermal chamber with 100% humidity. It turned out that the participants of the experiment reached the critical limit – when their body was unable to stop the temperature of internal organs from increasing further – at 30.6 degrees Celsius, well below the previously assumed 35 degrees C.
It should be noted that these values concerned young and healthy people who did not exercise during the study, but remained relatively at rest. Most of the fatalities during heatwaves in Europe and South Asia occurred at much lower temperature and humidity levels.
Impact of climate change
Scientists have warned that as global temperatures rise, dangerous conditions that occur when high humidity meets heat are becoming more common. ‘The combination of these two factors has at least doubled in the last 40 years and is linked to man-made climate change,’ said Colin Raymond.
His research predicts temperatures of 35 degrees Celsius with 100 percent humidity will be “regularly exceeded” in several places around the world in the coming years if the Earth warms 2.5 degrees Celsius above pre-industrial levels.
(Let’s be clear that, according to the decision of specialists compiling the Report of the Intergovernmental Panel on Climate Change – IPCC – averages from 1850-1900 are now considered representative of the “pre-industrial period”. However, there is no shortage of scientists who suggest that these time frames should be undo.)
PAP, ScienceAlert, tvnmeteo.pl
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