Extreme heat affects 1 billion more people than in the 1970s, study finds
A man holds a child in Brasília during sunset on Wednesday (20); Brazil is experiencing a heat wave. Adriano Machado/Reuters Extreme heat is no longer a problem for just a few places and just a few days. A global survey released this Monday (22) in the scientific journal “Nature Climate Change” calculates that around 1 billion more people now face at least one day of extreme heat per year compared to the 1970s — and shows that the portion of the world’s population exposed to this condition jumped from 16% to 22%. 📱Download the g1 app to see news in real time and for free The study reveals an intensification that researchers call “multidimensional”: the heat presses during the day, at night and, increasingly, on both ends at the same time. And there is a detail that draws attention: the hottest nights of the year are warming up faster than the hottest days. Now on g1 The research was conducted by Rebecca Emerton and colleagues from the European Center for Medium-Range Weather Forecasts (ECMWF), in the United Kingdom and Germany. The team analyzed a global database of heat stress from 1950 to 2024 and compared the most recent decade (2015–2024) with the 1970s, from which point the indicators began to rise clearly and continuously. 🌡️ UNDERSTAND: Thermal stress is the net load of heat that falls on the body. It depends not only on temperature, but also on humidity, wind and solar radiation. To measure it, scientists used the UTCI, an acronym in English for Universal Thermal Climate Index, a type of “thermal sensation” that combines these factors and simulates how the human body reacts to the environment. The index has heat categories ranging from moderate, from 26 °C, to strong, very strong and extreme, when there is a serious risk to health and immediate action is necessary. One of the study’s main findings appears after sunset. On the global average, the ten hottest nights each year have warmed by 0.32°C per decade since the 1970s, above the rate observed in the ten hottest days, of 0.27°C per decade. According to Emerton, this occurs because the atmosphere, heated by the greater concentration of greenhouse gases, retains more heat at night, when the surface should cool down. Increased humidity and changes in cloud cover can also make this cooling difficult. The problem is that the body depends on the night to recover. “Nocturnal heat is important for human health because people depend on cooler nights to get relief and recover from the heat of the day,” the researcher told g1. Without this break, the body remains under heat stress for longer. READ ALSO: Giant geological structure in the Sahara desert looks like an ‘eye’ seen from space; see IMAGE ‘What I learned from living alone for a year with a cat on a remote island’ Boy uses hose to cool off during extreme heat wave in Peshawar, Pakistan Fayaz Aziz/Reuters What the study points out for Brazil 🌎 South America is among the regions where the heat has advanced the most. In much of the continent, including Brazil, the maximum thermal sensation on the hottest days has increased by 2 °C to 4 °C since the 1970s. At night, in the same periods, the minimum temperature has increased by 1 °C to 3 °C. The number of dangerous days has also increased. In the north of South America, there are up to 80 more days per year with “very strong” heat compared to the 1970s. In subtropical areas, such as the South and Southeast of Brazil, the study identified up to 50 more days per year with strong to extreme heat. READ ALSO: Why Amsterdam banned any advertising of meat on the streets BEFORE and AFTER: NASA image shows glacier in Antarctica that retreated 25 km in record time When only extreme heat is observed, the occurrence in South America was 2.5 times greater than in the 1970s, the same factor recorded in Europe, the highest among the continents. Still, the researchers warn that the data may underestimate the reality in cities, where urban heat islands raise temperatures even further. The study also analyzed compound events: sequences in which a day of intense heat is followed by a tropical night, with no recovery time for the body. These episodes became more frequent, longer and intense on all continents. In Europe, one-day events have increased by 73% since the 1970s; sequences lasting 15 to 30 days became 3.4 times more common; and episodes lasting up to 120 days almost doubled. In North Africa, sequences of 271 to 365 days became 2.8 times more frequent. A woman cools herself with a fan as she walks through the streets of Ronda, Spain, one day before the start of the heat wave predicted by the country’s meteorological agency. REUTERS/Jon Nazca One billion more The jump in exposure combines two ingredients: the warming climate and the growing population. For exposure to at least one day of extreme heat per year, population growth had a greater weight: it accounted for around 4.5% of the increase, while climate change explained 1.4%. In other words, in this specific section, more people started to live in affected places, in addition to these places also becoming hotter. But this data, according to Emerton, is the exception, not the rule. For longer exposures — such as 30 or 90 days of extreme heat — and for the categories of strong and very strong heat, the advance driven by climate change is equal to or greater than that caused by population growth. In other words: the more severe and lasting the heat, the more the climate’s “fingerprint” appears. The human scale becomes clear in another section: in the 1970s, 55% of the world’s population lived in places with at least 90 days of intense heat per year. Today, it is 70%. And a Unicef report cited in the study recalls that around 559 million children are already exposed to a high frequency of heat waves — an especially vulnerable population, as they regulate their own temperature worse. New species of “zombie fungus” is discovered in Brazil
