What is a thermal sensation and why not fry when it exceeds 80 ºC?

The information published by the Paraná meteorological system (Simepar) that the thermal sensation in the city of Antonina, 87 km from Curitiba, reached a high temperature of 81 ° C on December 18, surprised many people. Not for less. It's more or less the temperature of a cafe or gauchos chemarrão. However, there is only a reduction of about 20 ° C in the boiling temperature of the water.

However, one important point is that temperature is not the same thing as thermal sensation. the amount of heat provided by the sun's rays or the environment, "explains meteorologist José Carlos Figueiredo, from the Unesp Meteorological Research Institute (IPMet), São Paulo State University (Unesp) and president of the Brazilian Society of 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 "Work" of the Human Being In humans, sweat is a mechanism of heat loss that lets the skin evaporate, reducing body temperature and feeling of warmth. 19659002] In very humid environments or climates, water in the form of vapor, floating in the air, reduces the rate of evaporation of sweat from the skin and thus forces a person to feel more heat to one place than others in a dry environment of the m same temperature

hence the confusion between the two concepts. Temperature is the expression of the concrete, real 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 clothing each wears or the place of birth and the adapted climate.

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

Origin of the Thermal Sensation

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

After the end of the World War, in 1945, the US Army creates an index of cold badessment related to 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 latter can also reduce 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 appeared, mainly in 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, in addition to the temperature, such as relative humidity, solar radiation, the absence or the presence of wind and clothing. "These are semi-empirical formulas," he says. "It is subjective and varies from one person to the other."

Two of the world's best-known and most widely used formulas are the United States-based Heat Index 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, 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 withstand high temperatures?

"We are extremely tolerant of 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 have no hair, and no one burns in wet saunas or can reach 50 ° C with a relative humidity of 70-80% or in periods 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 155.7ºC and 129.7ºC in the second.

Jamiro da Silva Wanderley, a professor at the Unicamp School of Medicine, also pointed out the great human tolerance to weather hazards. "We have a fantastic adaptability, both for high temperatures and low temperatures."

When the heat is very intense, for example, people start to sweat to keep your body temperature in acceptable.

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