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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 of 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 l & 39; equation the "work" of the human being In the man, sweat is a heat loss mechanism that evaporates from the skin and thus reduces the body temperature and the sensation of temperature
In very humid environments or climates, the water in the form of vapor, floating in the air, reduces the rate of evaporation of sweat on the skin and therefore makes you feel more heat in one place than another in a dry environment and the same time
Hence the confusion that reigns between the two concepts. Temperature is the concrete, actual and absolute value of heat – or cold – measured by thermometers. Otherwise, the thermal sensation is something subjective that, as the expression suggests, is the heat or cold felt by people.
So it can vary from one individual to another or even according to the clothing that each one is
It should also be noted that even if it reaches 100 ° C – as shown by some formulas calculation – the water does not boil, because objects and inanimate objects feel nothing, as The concept and expression of the thermal sensation began to become popular after the Second World War, when German troops have been defeated to try to invade Russia during its harsh winter.
known as "General Winter", the same who had already helped defeat Napoleon Bonaparte in 1812.
After the end of the world war, in 1945, the US military created a clue to 39, cold badessment. 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 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 ° C"
. It has not reached the 81 ° C mark posted by some news portals. Which, it is said, does not make much difference.
In the first case, the result of the temperature and humidity recorded in the city of Paraná would be a thermal sensation of 88.5 ° C and, in the second, of 72 ° C.
The truth is that the human being is able to bear that.
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 a humidity of less than 10%. "
Much less suitable than at 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 underlined the great human tolerance for climate hazards: "We have a fantastic ability to adapt to both high temperatures and low temperatures." [19659002] When the heat is very intense, for example, people start to sweat to maintain "
" We will urinate less and less (dark urine, yellow gold) to preserve water, "says Wanderley.
This does not mean, however, that there will be no problem. "If we continue with high temperatures and do not hydrate properly, we will have dry mouths, dehydration and perhaps headaches, prostration, confusion and unconsciousness and even eating," he warns. According to the physician Onivaldo Cervantes, professor at the Federal University of São Paulo (Unifesp), it has been reported that the human body could withstand up to 127 ° C (sensation of non-thermal heat) for up to 20 minutes
] "But above 28ºC, 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), which leads to circulatory difficulty and a consequent decrease in tissue oxygenation.
In light of all this, Figueiredo argues that it should not there are formulas to calculate the thermal sensation
do not take into account metabolic factors, pregnancy, obesity, skin color, height, weight and rest or not of people. "
" How are the information on humidity and temperature collected in the shadows, they leave home, they have no idea what is going on? they feel. For me, only information without scientific criteria is displayed p by the press. "
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