What is a thermal sensation and why not fry when it exceeds 80 ° C | Science and health

However, one important point is that temperature is not the same thing as thermal sensation.

"Temperature is the amount of heat provided by the sun's rays or by the environment," says meteorologist José Carlos Figueiredo, of the Unesp Meteorological Research Institute (IPMet), of State University of Paulista (Unesp) and President of the Brazilian Research Society. Meteorology. "The thermal sensation, in turn, takes into account the temperature and the relative humidity of the air."

It is also necessary to put in the equation the "functioning" of the human being. In humans, sweat is a mechanism of heat loss that allows the skin to evaporate, reducing body temperature and feeling of warmth.

In very humid environments or climates, the water in the form of vapor, hovering in the air, reduces the rate of evaporation of the sweat of the skin and thus forces a person to feel more than heat to one place than others in a dry environment of the same temperature.

Hence the confusion between the two concepts. Temperature is the concrete, actual and absolute value of heat – or cold – measured by thermometers. In a different way, the thermal sensation is something subjective that, as its expression suggests, is the heat or cold that people feel.

This may therefore vary from one individual to another or even according to the clothes each wears or the place of his birth and the adapted climate.

It should also be noted that even if the temperature reaches 100 ° C – as some calculation formulas show – the water does not boil, because objects and inanimate objects do not feel anything, as we know. .

The concept and term thermal sensation began to become popular after World War II, when German troops were defeated during an invasion attempt in Russia, during its harsh winter, known as "General Winter", the same that had already helped to defeat Napoleon Bonaparte in 1812.

After the end of the world war in 1945, the US military created a cold index relative to the wind speed. This index became popular and became known with the temperatures. In Brazil and other hot countries, the thermal sensation is related to the relative humidity of the air and not the wind, although the wind can also decrease it.

The problem is that there are many different formulas to calculate it. Several are available on the Internet. Since the beginning, about 70 years ago, more than 160 others have been created, each with its own criteria. "All are made in different places," explains Figueiredo. "Since 1978, different formulas have emerged, mainly over the last ten years, because of the interest of the press for the climate".

According to the meteorologist Fabio Luiz Teixeira Gonçalves, professor in the Department of Atmospheric Sciences of the Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo (IAG-USP) , the calculation of the thermal sensation takes into account many variables such as the relative humidity of the air, solar radiation, lack or the presence of wind and clothing. "These are semi-empirical formulas," he says. "They are adjusted with questionnaires to the inhabitants of each region, but they are subjective and vary from person to person."

The two most famous and widely used formulas in the world are the Heat Index, created in the United States, and Humidex, Canada, both available on the Internet. Semipar did not specify the formula used, but only the temperature and the relative humidity of the air. "At 14:00, the heat at Antonina was 44.3 ° C and 65% of the unit," says Samuel Braun, one of the agency's meteorologists. "According to our calculations, the thermal sensation reached 78 ºC."

It did not reach the 81º C rating published by some news portals. Which, it is said, does not make much difference. The truth is that Semipar did not use the Heat Index or Humidex.

In the first case, the result recorded for temperature and humidity in the city of Paraná would be a thermal sensation of 88.5 ° C and, in the second, of 72 ° C.

is certain that the human being is able to resist this. At least, that's what guarantees Gonçalves, from the USP.

Can we tolerate high temperatures?

" We are extremely tolerant at high temperatures and not just the thermal sensation, "says the meteorologist." We are among the best in the mammal group. We sweat very well and we do not have hair. Nobody burns in the saunas or in the humid ones, which can reach 50 ° C with a relative humidity of 70-80% or in times of drought. 100 ° C and humidity less than 10%. "

Much less pleasant than Antonina.With these figures, by heat index, the thermal sensation in the first case would be 133.7 to 155.7 ºC and 129.7 ºC in the second. 19659006] Professor of Medical Practice Jamiro da Silva Wanderley of the Unicamp Faculty of Medical Sciences also emphasizes the great human tolerance for weather hazards: "We have a fantastic ability to adapt to low and high temperatures. A number of coping mechanisms are triggered as needed. "

For example, when the heat is too intense, people begin to sweat to maintain their body temperature in acceptable conditions.

" We began to urinate less and less and more concentrated (dark urine, yellow gold), in order to preserve the water, "says Wanderley.

That does not mean, however, that it does not matter. There will be no problem. "If we continue with high temperatures and do not hydrate properly, we will have dry mouth, dehydrated, and we may have headaches, prostration, mental confusion, loss of consciousness and even meals, "he warns, and there may be kidney problems.

According to Onivaldo Cervantes, a professor at the University of São Paulo (Unifesp), it would seem that the body human can withstand up to 127 ° C (without sensation of heat) for up to 20 minutes.

"But the fact is that above 28 ° C, without wind, the heat becomes already unpleasant for the body," he warns. "In addition, the body temperature should not exceed 40 ° C, although in some cases it can reach 42 ° C., which is very dangerous.In this feverish state, blood proteins begin to denature (they lose their structure and cease to be active), resulting in circulatory difficulties and a consequent decrease in tissue oxygenation. "

In light of all this, Figueiredo argues that there should be no formula for calculating the thermal sensation.

"This is unnecessary because the formulas adopted do not take into account metabolic factors, pregnancy, obesity, skin color, height, weight and rest. or not people, "he criticizes.