Image source, AFP/Getty Images
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- Author, Nidale Abou Mrad
- Author's title, World BBC service
Climate change is intensifying and increasing the probability of heat waves, already measure that temperatures rise with summer in the northern hemisphere, much of Europe and areas of the United States and the Asian northeast experience much higher temperatures than usual.
This entails various health risks, especially for vulnerable populations such as elders, children and people with pre -existing diseases.
In Spain, on Saturday there was a new 46 ° C heat record in the town of El Granado, according to the Spanish National Meteorological Service, which also indicated that this month is on its way to the most hot June ever registered.
But the figures can be misleading: high temperatures are not perceived the same, nor are they so dangerous, in dry countries with low humidity (such as Canada Center) that in wet and embarrassing climates (as in the Persian Gulf area).
This is where wet bulb temperatures come into play, as a way to measure the potentially lethal heat and humidity combination. But what are they and how do they work?
What are moist bulb temperatures?
Everyone knows the word “temperature”, which is what the thermometer on the air temperature indicates.
The humid bulb temperature measures the effect of a combination of heat and humidity (the amount of humidity or water vapor present in the air).
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How is it measured?
In its simplest version, a bulb thermometer is taken (the glass thermometer with which most of us grew) and wrapped in cotton.
Then it is sprayed with water until it moistened it.
This indicates the temperature at which the water is located when evaporating.
When absorbing thermal energy, the water cools the thermometer at a moist bulb temperature.
Why is it important?
Human beings are refreshing sweating: the water expelled through the skin eliminates excess body heat and, when evaporating, dissipates it.
The process works well in dry areas, but it can be much less effective in very warm and humid regions.
If the external temperature is close to the body, it is very difficult to cool up losing moisture by sweat if the moisture is high.
This is because, where the air is already too loaded with moisture to absorb much more, the evaporation of sweat slows down, so we can no longer cool so well.
In extreme cases, we could not sweat at all, which could cause death.
So what temperature is dangerous?
Image source, EPA-EFE/Shutterstock
A 2020 study published in the journal Science Advances revealed that “a moist bulb temperature of 35 ° C marks our upper physiological limit, and much lower values have serious consequences for health and productivity.”
Indeed, the combination of heat and humidity implies that, above a moist bulb of 35 ° C, the human body ceases to emit heat to the environment, with potentially mortal consequences, such as, for example, the interruption of the operation of the organs.
If people do not have air conditioning access, they could die in a matter of hours.
Even people in the form and healthy, who rest in the shade, without clothes and with unlimited access to drinking water, would have difficulty surviving.
As already mentioned, wet bulb temperatures are lower than typical thermometers and rarely reached 35 ° C for prolonged periods or in extensive areas.
But that might not always be the case.
What about global warming?
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The warmer the air, the more moisture can retain. Therefore, as global temperatures increase, we are likely to observe greater moisture, which would cause an increase in moist bulb temperatures.
In certain parts of the world, such as South Asia and the Persian Gulf, extreme combinations of heat and humidity have already doubled in the last 40 years, according to the study of Science Advances of 2020.
This research predicts that these dangerous levels will be much more generalized and will last much more if measures are not taken to limit global warming.
But even without reaching the threshold of 35 ° C, wet bulb temperatures can indicate where heat waves represent the greatest threat to life and who run greater risk.
“In India, for example, those who work in construction, in delivery, must go out to work. Unlike those who do not depend on the weather, they have no other way of making a living,” says Anjal Prakash, director of specialized research in climate change and adaptation of the Indian Business School.
Wet bulb measurements help us understand what areas are approaching a potentially deadly threshold and, from there, governments can take specific measures to adapt.
“For example, if the predictions show that in some areas it is likely that wet bulb temperatures reach 35 ° C in ten years, governments could adapt by establishing early alert systems, modifying school schedules and adopting specific cooling measures,” Prakash explains.
How bad things are now? Will they get worse?
Image source, Getty Images
Scientists are increasingly concerned about the frequency of global heat waves.
In 2022, most of South Asia experienced an intense heat wave. India and Pakistan recorded record temperatures, reaching maxims of 50 ° C in New Delhi.
“I read Pakistani stories that said that, when leaving, they felt as if they were surrounded by fire. Thus they describe the high temperatures,” Prakash told the BBC.
The heat wave of 2023 hit much of Europe, especially to Mediterranean countries, such as Spain, Italy, Greece, Turkey and Cyprus.
Temperatures reached 40-45 ° C during the day in some regions.
Global record temperatures contributed to aggravate many extreme meteorological phenomena in large areas of the world in 2023, from intense heat waves and forest fires in Canada and the United States, to prolonged droughts and subsequent floods in areas of Eastern Africa.
The 2024 global average temperatures exceeded approximately 1.55 ° C those of the preindustrial period, and exceeded the record established the previous year by just over 0.1 ° C.
The last ten years (2015-2024) have been the warmest registered, being 2024 the warmest year to date, according to the World Meteorological Organization (OMM), the UN atmospheric scientific branch.
“The abrasing temperatures of 2024 demand a pioneer climate action in 2025,” said UN Secretary General António Guterres.
“There is still time to avoid the worst climatic catastrophe. But leaders must act now,” he added.
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