The human cost of the climate crisis will hit harder, broader and sooner than previously thought, according to a study showing that a billion people will be displaced or forced to endure unbearable heat for every additional 1 ° C rise in global temperature.
In the worst case of accelerating emissions, areas that currently host a third of the world's population will be as hot as the hottest parts of the Sahara within 50 years, the document warns. Even in the most optimistic perspective, 1.2 billion people will be left outside the comfortable "climate niche" in which humans have thrived for at least 6,000 years.
The study authors said they were "amazed" and "shocked" by the findings because they did not expect our species to be so vulnerable.
“The numbers are staggering. I literally looked at them twice when I first saw them"Said Tim Lenton of the University of Exeter. "I have previously studied the tipping points of the weather, which are normally considered apocalyptic. But this hit harder. This puts the threat in very human terms.“
Rather than viewing climate change as a problem of physics or economics, the article, published in the Proceedings of the National Academy of Sciences, examines how it affects human habitat.
The vast majority of humanity has always lived in regions where average annual temperatures are around 6 ° C to 28C, which is ideal for human health and food production. But this point is shifting and shrinking as a result of man-made global warming, which is causing more people to slide into what the authors describe as "almost uninhabitable" extremes.
Humanity is particularly sensitive because we are focused on the land - which is warming faster than the oceans - and because most of future population growth will occur in already hot regions of Africa and Asia. As a result of these demographic factors, the average human will experience a 7.5 ° C increase in temperature when global temperatures reach 3 ° C, which is expected by the end of this century.
At that level, about 30% of the world's population would live in extreme heat, defined as an average temperature of 29 ° C. These conditions are extremely rare outside of the hottest parts of the Sahara, but with global warming of 3 ° C they are projected to involve 1.2 billion people in India, 485 million in Nigeria and more than 100 million in each of the countries of Pakistan, Indonesia and Sudan.
This would greatly increase migratory pressures and pose challenges to food production systems.
“I think it's fair to say that average temperatures over 29 ° C are uninhabitable. You would have to move or adapt. But there are limits to adaptation. If you have enough money and energy, you can use the air conditioning and import the food and then you could be fine. But that's not the case for most people.Said one of the study's lead authors, Professor Marten Scheffer of Wageningen University.
An ecologist by profession, Scheffer said the study began as a thought experiment. He had previously studied the climatic distribution of rainforests and savannah and wondered what the result would be if he applied the same methodology to humans. "We know that the habitats of most creatures are limited by temperature. For example, penguins are only found in cold water and corals only in warm water. But we didn't expect humans to be that sensitive. We consider ourselves very adaptable because we use clothing, heating and air conditioning. But in fact, the vast majority of people live, and have always lived, within a climate niche that is now moving like never before.“.
“The magnitude surprised us a lot", He said. "There will be more changes in the next 50 years than in the last 6,000 years“.
The authors said their findings should spur policy-makers to accelerate emission reductions and work together to tackle migration, because every preventable degree of warming will save a billion people from falling into it. climate niche of humanity.
“Clearly we will need a comprehensive approach to protect our children from the potentially enormous social stresses that the projected change could invoke.Said another of the authors, Xu Chi of Nanjing University.
- The average temperature of the planet (averaging the temperature of the water and the earth) has already risen 1 ° C globally (it is an average, there are areas such as the Arctic, Alaska, Canada, Antarctica that warming is greater).
- According to the effective policy commitments adopted by the countries under the Paris Agreement, we are going to a 3 ° C warming by the end of the century. As much as the "promise" of the Agreement was not to exceed 2 ° C and then it was found that exceeding 1.5 ° C was the ideal in terms of risk.
By Jonathan Watts
Source: The Guardian