A study published in Nature has shown that the so-called feels-like temperature — an indicator that takes into account humidity and wind — is rising faster than the usual air temperature. This leads to an increase in the number of health-threatening heat periods and tropical nights, reports UNN citing Euronews.
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The world is facing a sharp increase in dangerous heat stress as the continued use of fossil fuels increasingly heats the planet.
According to the EU's Copernicus Climate Change Service (C3S), temperatures in Europe have risen by about 2.5 °C compared to pre-industrial levels, despite efforts to curb global warming. As a result, Europe remains the fastest-warming continent on Earth.
However, scientists are increasingly analyzing not only air temperature but also the so-called "feels-like temperature" to better understand how heat affects the human body.
The feels-like temperature reflects how hot or cold the weather is perceived by the human body. Unlike the usual air temperature given in forecasts, this indicator takes into account wind speed, air humidity, and the specifics of heat exchange between the human body and the environment.
A new study published in the scientific journal Nature warns that extreme feels-like temperatures, days with heat stress, and tropical nights — when the temperature does not drop below 20°C during the day — have become a "sharply more frequent" phenomenon.
Even regions that were never previously affected are now experiencing heat stress.
What is heat stress
Heat stress is the accumulation of heat in the body, which can be generated internally during muscle work or come from the external environment. It occurs when the amount of heat the body absorbs from the environment exceeds the body's ability to release it.
"Heat stress is usually the result of a combination of factors such as high ambient temperature, humidity, physical activity, and insufficient fluid intake," C3S notes.
"The ability of the human body to maintain body temperature within certain limits is influenced by a whole range of factors," the study states.
The heat produced by the human body can be balanced by the heat exchanged with the environment thanks to our thermoregulatory system (which is why we sweat when we are hot). Behavioral factors also play a role, such as maintaining hydration, wearing loose clothing, and avoiding physical exertion during the hottest hours of the day.
When the body fails to maintain this balance, a range of symptoms can occur: elevated body temperature, rapid heartbeat, rapid breathing, profuse sweating, nausea, and dizziness.
In severe cases, heat-related illnesses such as heat exhaustion or heat stroke can be fatal.
Where in Europe heat stress is felt the strongest
The researchers examined heat stress at three levels: strong (index temperatures not below 32°C), very strong (index temperatures not below 38°C), and extreme (index temperatures not below 46°C).
They found that in southern Spain, Italy, Greece, and Turkey, the number of days with strong heat stress in some areas has increased by 40 per year compared to 50 years ago. Most of southern Europe already experiences almost an additional month of strong heat stress compared to the 1970s.
According to the study's lead author, Rebecca Emerton, it is particularly notable that heat stress is intensifying not only in traditionally hot regions but is also spreading to areas where such phenomena were previously rare or completely unobserved.
A similar trend is observed outside Europe. In some areas of Namibia and Angola, as well as in certain regions of Tanzania, Kenya, Uganda, Mexico, and Central America, the number of days with strong heat stress could increase by about 50 per year compared to the 1970s.
Night heat
The study also showed that the feels-like temperature during the warmest nights of the year is rising faster than during the hottest days.
The temperature during the ten warmest nights of each year increased on average by 0.32°C per decade, while for the ten hottest days this figure was 0.27°C.
High nighttime temperatures can significantly affect human health, as the body relies on nighttime coolness to regulate body temperature and recover from daytime heat. This can lead to increased strain on the cardiovascular system and sleep disturbances.
"Nighttime heat is often underestimated, but it can be particularly dangerous because people are usually at home and may not have access to cool, air-conditioned spaces," Ruth Engel, a data specialist in environmental health and extreme heat at the World Resources Institute (WRI), told Euronews Earth.
"In Europe, where air conditioning (AC) use remains relatively rare and temperatures are rising faster than in any other region, tropical nights are becoming a serious public health issue," she emphasized.
Studies show that high nighttime temperatures are associated with increased mortality, especially among the elderly and patients with chronic diseases.