Adaptation has limits; human physiology has a ceiling.
Em 2023, o calor matou quase 48 mil pessoas na Europa — entre elas, 1.432 em Portugal —, revelando que o aquecimento climático já não é uma ameaça futura, mas uma causa de morte presente e mensurável. Um estudo do Instituto de Saúde Global de Barcelona, publicado na Nature Medicine, mostra que as mulheres e os mais velhos pagam o preço mais alto, e que, sem duas décadas de adaptação desde a vaga de calor de 2003, o número de mortes seria 80% superior. A humanidade aprendeu a resistir melhor ao calor, mas o planeta aquece mais depressa do que a sociedade consegue acompanhar.
- Quase 48 mil europeus morreram de causas relacionadas com o calor em 2023 — o ano mais quente de que há registo —, com Portugal a registar 1.432 vítimas e a ocupar o sexto lugar na mortalidade per capita.
- A desigualdade é brutal: as mulheres morreram a uma taxa 55% superior à dos homens, e os maiores de 80 anos apresentaram uma mortalidade 768% mais elevada do que os que têm entre 65 e 79 anos.
- Duas vagas de calor concentradas em julho e agosto foram responsáveis por mais de 57% das mortes estimadas, sublinhando como episódios curtos mas intensos podem ser devastadores.
- Duas décadas de sistemas de alerta precoce e melhorias nos cuidados de saúde evitaram que o cenário fosse catastrófico, mas os investigadores alertam que a fisiologia humana tem limites que nenhuma adaptação consegue ultrapassar.
- Com metade dos dias de 2023 já a exceder o limiar de 1,5°C do Acordo de Paris, os cientistas preveem que a Europa ultrapasse esse limite antes de 2027, deixando uma janela de ação cada vez mais estreita.
Em 2023, o calor matou 47.690 pessoas na Europa. Em Portugal, o número chegou a 1.432 mortes — o suficiente para colocar o país em sexto lugar no continente em mortalidade ajustada à população, com 136 óbitos por milhão de habitantes. Os dados provêm de um estudo publicado na Nature Medicine por investigadores do Instituto de Saúde Global de Barcelona, que analisaram registos de mortalidade e dados de temperatura em 35 países europeus.
O peso da crise caiu sobretudo no sul. A Grécia liderou o ranking com 393 mortes por milhão, seguida da Bulgária, Itália, Espanha e Chipre. Mas por detrás dos números globais esconde-se uma desigualdade profunda: as mulheres morreram a uma taxa 55% superior à dos homens, e os maiores de 80 anos registaram uma mortalidade 768% mais elevada do que os que têm entre 65 e 79 anos. Duas vagas de calor intenso, em meados de julho e no final de agosto, foram responsáveis por mais de 57% das mortes estimadas no ano.
O estudo traz, porém, uma mensagem inesperada: sem duas décadas de adaptação desde a catastrófica vaga de calor de 2003, o número de mortes seria 80% superior. Sistemas de alerta precoce, melhorias nos cuidados de saúde e planos de prevenção fizeram com que os europeus se tornassem progressivamente menos vulneráveis ao calor. A temperatura mínima a partir da qual o risco de mortalidade aumenta subiu de 15°C no início do século para 17,7°C entre 2015 e 2019 — um sinal de adaptação real.
Ainda assim, os investigadores reconhecem que os seus números podem estar subestimados: corrigindo as limitações dos dados, o total de mortes relacionadas com o calor em 2023 poderá chegar às 58.000. E o horizonte é preocupante. Em 2023, quase metade dos dias ultrapassou o limiar de 1,5°C estabelecido pelo Acordo de Paris. O investigador Joan Ballester Claramunt alertou que a Europa deverá ultrapassar esse limite antes de 2027, e que a fisiologia humana tem um teto além do qual nenhum sistema de alerta ou melhoria hospitalar consegue proteger contra o calor letal. A adaptação comprou tempo — mas o ritmo do aquecimento pode em breve superar a capacidade da sociedade para responder.
Across Europe in 2023, heat killed 47,690 people. In Portugal alone, the toll reached 1,432 deaths—a figure that places the country sixth among European nations when adjusted for population size, with 136 deaths per million inhabitants. These numbers come from a study published this week in Nature Medicine by researchers at the Barcelona Institute of Global Health, who analyzed mortality records and temperature data from 35 European countries spanning 823 regions.
The burden fell heaviest on southern Europe. Greece topped the grim rankings with 393 deaths per million inhabitants, followed by Bulgaria at 229, Italy at 209, Spain at 175, and Cyprus at 167. Portugal's 136 per million placed it firmly in this cluster of vulnerability. What the raw numbers obscure, however, is a pattern of profound inequality: women died at rates 55 percent higher than men, and people over 80 experienced mortality rates 768 percent higher than those aged 65 to 79. Among Portuguese victims, women accounted for 143 deaths per million compared to 103 for men—a disparity that held across the continent.
Two episodes of intense heat in mid-July and late August were responsible for more than 57 percent of the year's estimated heat deaths, accounting for over 27,000 lives. The summer of 2023 differed from 2022, when persistent extreme temperatures gripped central Europe from mid-July through mid-August. Last year's heat came in sharper, more concentrated waves, yet the damage was still substantial. The researchers note that 2023 was the warmest year on record globally, and Europe continues warming at twice the rate of the planet as a whole.
Yet the study carries a counterintuitive message: without two decades of adaptation measures, the death toll would have been far worse. Early warning systems, improvements in healthcare, and public health initiatives implemented since the catastrophic 2003 heat wave would have prevented deaths from being 80 percent higher. The minimum temperature at which mortality risk peaks has gradually shifted upward across the continent—from 15 degrees Celsius in 2000-2004 to 17.7 degrees in 2015-2019—suggesting that Europeans have become less vulnerable to heat than they were at the century's start. This adaptation reflects broader societal progress: better economic conditions, individual behavioral changes, and coordinated heat prevention plans.
Elisa Gallo, the study's lead author, emphasized that these adaptations have "drastically reduced" heat vulnerability and the mortality burden of recent summers, particularly among the elderly. Yet the researchers acknowledge their figures may underestimate the true toll. Inconsistent daily mortality records forced them to rely on weekly Eurostat data, which tends to obscure heat deaths. When corrected for this bias, the probable number of heat-related deaths in 2023 across the 35 countries studied could reach 58,000.
The findings arrive as climate projections grow more alarming. In 2023, nearly half of all days exceeded the 1.5-degree Celsius threshold established by the Paris Agreement. Joan Ballester Claramunt, principal investigator of the European Research Council's EARLY-ADAPT program, warned that Europe is likely to breach the 1.5-degree limit before 2027, leaving only a narrow window for action. He stressed that human physiology and social structures have inherent limits to adaptation—there is a ceiling beyond which no amount of warning systems or healthcare improvements can protect against lethal heat.
The researchers call for urgent implementation of strategies to further reduce mortality in coming summers, combined with comprehensive monitoring of climate impacts on vulnerable populations. These adaptation measures, they argue, must be paired with mitigation efforts from governments and the public to prevent crossing critical thresholds. The study makes clear that while Europe has learned to live with heat better than before, the accelerating pace of warming may soon outstrip society's capacity to adapt.
Citações Notáveis
The minimum temperature at which mortality risk peaks has gradually shifted upward across the continent, indicating that Europeans have become less vulnerable to heat than they were at the century's start.— Elisa Gallo, lead researcher, Barcelona Institute of Global Health
We must account for the limits inherent to human physiology and social structure, which are likely to establish a ceiling for the potential of adaptation in the future.— Joan Ballester Claramunt, principal investigator, European Research Council's EARLY-ADAPT program
A Conversa do Hearth Outra perspectiva sobre a história
Why does Portugal rank so high in heat deaths when countries like Spain and Italy are warmer?
It's not just about temperature—it's about how prepared a society is. Portugal's ranking reflects both exposure and vulnerability. The elderly and women are disproportionately affected, and healthcare systems, housing quality, and access to cooling vary. A hotter country with better adaptation infrastructure can fare better than a cooler one caught off guard.
The study says adaptation measures prevented deaths from being 80 percent higher. That sounds like a success story. Why the alarm?
Because that success has a ceiling. Early warning systems and better healthcare bought us time, but they can't protect people indefinitely as temperatures keep rising. The researchers are saying we've adapted well—so far. But if the 1.5-degree threshold breaks in 2027 as projected, we're entering territory where adaptation alone won't be enough.
Why are women and the elderly so much more vulnerable?
Women live longer, so there are simply more elderly women. But there's more to it. Elderly people have less physiological capacity to regulate body temperature. Women, particularly older women living alone, may have less access to air conditioning, less mobility to reach cooling centers, and less social support networks checking on them during heat waves.
If 2023 was cooler than 2022, why didn't deaths drop more?
Because 2023 was still the hottest year on record globally. The heat came in concentrated bursts rather than sustained waves, but those bursts were still deadly. And the baseline keeps rising—what felt like an extreme event a decade ago is becoming normal.
What happens if adaptation measures can't keep pace?
That's the question the researchers are asking. At some point, you can't cool a city fast enough or warn people quickly enough if the heat itself becomes incompatible with human survival. We're not there yet, but the window to prevent it is closing.