Global warming will push billions of people out of the “climate niche” in which humanity has thrived for millennia, exposing them to temperature unprecedented ea extreme weather conditions. A new study, published in Nature and conducted by researchers at the Global Systems Institute of the University of Exeter, Great Britain, and the University of Nanjing, China makes us reflect on the enormous human cost of the climate crisis.
The costs of climate change are often estimated at termini monetary, but this undoubtedly also raises ethical questions. The study aimed to precisely quantify the number of people who would remain outside the “human climate niche”, defined as the “historically conserved distribution of relative human population density relative to annual mean temperature”.
In “worst-case scenarios” of 3.6°C or even 4.4°C global warming, half of the world’s population could be exposed – posing what the researchers call an “existential risk”
This graphic shows how heat-exposed areas grow as the world warms pic.twitter.com/y6ukFTpTo2
— University of Exeter News (@UniofExeterNews) May 22, 2023
Climate change has already put around 9% of people (over 600 million) outside this niche. By the end of the century (2080-2100), with global warming of approx 2,7 °C a third (22-39%) of people could stay out of this niche. Reducing global warming from 2.7 to 1.5°C would result in an approximately 5-fold decrease in the population exposed to unprecedented heat (i.e. marked by an average annual temperature of 29°C).
It emerged that most people lived in places with average annual temperatures ranging between 13°C and 25°C. Conditions outside these average temperatures are too hot, too cold or too dry and are associated with higher death rates, lower food production and lower economic growth. The scientists then used climate and population models to examine likely future changes in the number of people outside the climate niche, which they defined as above an average annual temperature of 29°C.
The research therefore focused on what a overheating of the kind for people who would find themselves living outside the “climate niche” in which the human species has thrived in the last 300,000 years or so. Despite the commitment ofParis Agreement to keep global warming well below two degrees above pre-industrial levels, current policies in the absence of stringent measures could cause a warming of 2.7°C by the end of the century.
The analysis is there first of its kind and it is able to treat all citizens equally, unlike previous economic assessments of the harms of the climate crisis, which have always been biased towards the very wealthy. Economic estimates almost always value the rich more than the poor, because they have more assets to lose, and they tend to value who is alive now versus who will live in the future. In this study, according to the authors, all people come au pairs.
In countries with large populations and already warm climates, most people will be pushed outside the human climate niche, with India e Nigeria who will have to face the worst changes. India already suffers from extreme heatwaves, and a recent study found that more than a third of heat-related deaths in the summers 1991-2018 occurred as direct consequence of man-made global warming.