In the next five decades, more than three billion people—one third of the world's population—could live in regions with climate conditions considered unlivable, according to a new study.
Researchers at Washington State University, Nanjing University in China, and Wageningen University in the Netherlands examined the history of the conditions in which humans have comfortably lived, starting in the mid-Holocene era about 6,000 years ago and up to the present day.
Over that period of time, the study shows, the vast majority of the world's population has lived in areas with a mean annual temperature between 50º and 60º Fahrenheit.
Scientists are pushing world governments to take action to keep the warming of the Earth below 1.5º Celsius above pre-industrial levels by the end of this century, by drastically reducing fossil fuel emissions. But many fear limiting global warming to this degree won't be possible.
With every 1º Celsius (1.8º Fahrenheit) that the planet's temperature rises, the new study says, one billion people will be forced to either migrate or adapt to new climate conditions which will affect crops and livestock and may make their outdoor environments impossible to work in.
"I think it is fair to say that average temperatures over 29º [84º Fahrenheit] are unlivable," Professor Marten Scheffer of Wageningen University told The Guardian. "You'd have to move or adapt. But there are limits to adaptation. If you have enough money and energy, you can use air conditioning and fly in food and then you might be okay. But that is not the case for most people."
About 25 million people today live in the hottest areas of the world, mainly in the Sahara region of Africa where mean annual temperatures top 84º Fahrenheit.
At the rate the planet is expected to warm, a larger share of Africa and parts of India, South America, Southeast Asia, and Australia could become too hot for people to live comfortably—driving many to migrate elsewhere in order to grow crops and obtain sufficient food and water. These areas are now home to about 3.5 billion people.
"It's a bit unfortunate that most population growth happens to be in the place that will be hardest to live in," Scheffer told The Washington Post.
As the coronavirus pandemic has caused carbon emissions to drop due to reduced traffic and shut-down economies around the globe, Adam Browning of Vote Solar tweeted, "we should look to recover from this crisis in ways that prevent the next."
New study: in 50 years, ~3.5 billion people will be living in areas that will be too hot to live in, absent successful action on climate change.
That's why we should look to recover from this crisis in ways that prevent the next.https://t.co/nf2fThJMay
— Adam Browning (@adambrowning) May 5, 2020
According to The Guardian, more than one billion people are expected to live in untenably hot climates by 2070 "even in the most optimistic outlook" presented by the study, which was published Monday in the Proceedings of the National Academy of Science.
"We were frankly blown away by our own initial results. As our findings were so striking, we took an extra year to carefully check all assumptions and computations," Xu Chi, a researcher at Nanjing University who co-authored the study, told the Sydney Morning Herald. "Clearly we will need a global approach to safeguard our children against the potentially enormous social tensions the projected change could invoke."
The study demonstrated how the world could look very different than it does now by 2070, even in parts of the world which aren't expected to face the extreme temperatures the researchers described, with billions of people forced to migrate elsewhere.
"It is likely climatic changes will in effect move large cities and whole countries into temperature niches that present inhabitants would find unimaginable," Neil Adger of the University of Exeter, who reviewed the study, told the Post. "So will cities move? Unlikely. But will they become less attractive destinations for people to move to? Definitely. And ultimately some present cities will stop growing and ossify."