One billion people will pay the human cost of the climate crisis that will hit harder, wider, very soon than believed earlier. The mass will be either displaced or forced to endure intolerable heat for every additional 1C rise in the global temperature, research reveals.
The areas that are at present home to a one-third population of the world will be as hot as the hottest parts of the Sahara within 50 years in a worst-case scenario of accelerating emissions, the paper warns. Even if the most optimistic outlook is taken, still 1.2 billion people will be outside the comfortable “climate niche” in which humans have flourished for around the last 6,000 years.
The authors of the study were “floored” and “blown away” by the findings as they had not expected our species to be so vulnerable.
“The numbers are flabbergasting. I literally did a double-take when I first saw them,” Tim Lenton, of Exeter University, said. “I’ve previously studied climate tipping points, which are usually considered apocalyptic. But this hit home harder. This puts the threat in very human terms.”
More changes expected in the next 50 years than in the past 6,000 years
Instead of taking climate change as a problem related to physics or economics, the paper, published in the Proceedings of the National Academy of Sciences, examines how it affects the human habitat.
The regions where the vast majority of humanity has always lived with average annual temperatures hovering around 6C (43F) to 28C (82F) is ideal for human health and food production. However, as a result of human-made global heating, this human-friendly spot is shifting and shrinking, dropping more people into what the authors describe as “near unliveable” extremes.
As we have concentrated on land, which is warming faster than the oceans, humanity, in particular, is found sensitive and also because most future population growth will be in already hot regions of Africa and Asia. These demographic factors will cause the average human to experience a temperature increase of 7.5C when global temperatures reach 3C, and that is forecast towards this century’s end.
About 30% of the world’s population would live in the extreme heat of average 29C (84F) temperature at that level. Other than the most scorched parts of the Sahara, these conditions are infrequent. However, with global heating of 3C, they are projected to cover 1.2 billion people in India, 485 million in Nigeria, and more than 100 million in each of Pakistan, Indonesia, and Sudan.
The migration pressures would increase additionally and pose challenges to food production systems.
“I think it is fair to say that average temperatures over 29C are unliveable. 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 OK. But that is not the case for most people,” said one of the lead authors of the study, Prof Marten Scheffer of Wageningen University.
The study started as a thought-experiment, said Scheffer, an ecologist by training. As he had previously studied the climate distribution of rainforests and savanna, he wondered what the result would be if the same methodology applied to humans.
“We know that most creatures’ habitats are limited by temperature. For example, penguins are only found in cold water and corals only in warm water. But we did not expect humans to be so sensitive. We think of ourselves as very adaptable because we use clothes, heating and air conditioning. But the vast majority of people live – and have always lived – inside a climate niche that is now moving as never before.”
We were blown away by the magnitude,” he said. “There will be more change in the next 50 years than in the past 6,000 years.”
According to the authors, their findings should encourage policymakers to accelerate emission cuts and work together to cope with migration because avoiding each degree of warming will save a billion people from falling out of humanity’s climate niche.
“Clearly we will need a global approach to safeguard our children against the potentially enormous social tensions the projected change could invoke,” another of the authors, Xu Chi of Nanjing University, said.