Many millions of people in the tropics could be exposed to dangerous heat for half the year by 2100, even if humanity manages to meet climate goals, researchers warned Thursday.
In the most likely scenario, the world would miss those targets, which could subject people in the tropics to damaging temperatures on most days of every typical year by the end of the century, the study found.
If emissions are left unchecked, large numbers of people in these regions could face periods of potentially “nightmare” extreme heat.
“There is a possibility that if we don’t act together, billions of people will be very, very overexposed to these extremely dangerous temperatures in a way that we have fundamentally not seen,” said lead author Lucas Vargas Zeppetello. from Harvard University.
Hotter and more frequent severe heat waves due to climate change are already being felt around the world, threatening human health, wildlife and crop yields.
Most climate projections predict temperature increases under different policy scenarios, but do not say which of those paths is most likely.
In this study, published in the journal Communications Earth and Environment, researchers estimated potential exposure to dangerous heat and humidity.
They used statistical projections to predict the levels of carbon dioxide emissions from human activity and the resulting levels of global warming.
They found that many people in tropical regions could face dangerous mid-year heat levels by the end of the century, even if the world limits temperature rises to the Paris climate agreement target of less than two degrees Celsius (35.6 degrees Fahrenheit). Fahrenheit) above the pre-industrial era. levels
Outside the tropics, they said deadly heat waves are likely to become annual events.
The researchers used a heat index that puts “dangerous” levels at 39.4°C, while temperatures above 51°C are considered “extremely dangerous” and totally unsafe for humans.
The extreme measure was originally developed for people who worked in scorching indoor environments, such as a ship’s boiler room, and has rarely been observed outdoors, Zeppetello said.
But by the end of the century, the researcher said it was “virtually guaranteed” that people in some parts of the tropics would experience this level of heat every year unless emissions were severely cut, with swathes of sub-Saharan Africa and India particularly in risk.
“It’s pretty scary,” he told AFP, adding that even walking outside would be dangerous in those conditions.
– ‘Nightmare’ conditions –
The Earth has warmed by almost 1.2°C so far and current predictions based on countries’ carbon reduction pledges would see the world far exceed the Paris Agreement’s 2°C target by 2100, not talk about its more ambitious aspiration of 1.5°C.
In their research, Zeppetello and colleagues looked at global climate model predictions, human population projections, and looked at the relationship between economic growth and carbon emissions.
They estimated that there is only a 0.1 percent chance of limiting average global warming to 1.5°C by 2100, and project that the world is likely to reach 1.8°C by 2050.
In 2100, the researchers found that the most likely global average temperature rise would be 3°C, which Zeppetello said would spell “nightmare” conditions for many people.
In a worst-case scenario, where emissions continue unchecked, he said extreme temperatures could last for up to two months each year in parts of the tropics.
But he said it depends on how quickly humanity can reduce emissions.
“We don’t have to go to that world. There’s nothing right now that says it’s a certainty, but people need to be aware of how dangerous it would be if it happened,” she said.
The researchers said that in all scenarios there could be a large increase in heat-related illnesses, particularly among the elderly, the vulnerable and those who work outdoors.
“I think this is a very important point that is getting very little attention,” said Kristin Aunan, a research professor at the Center for International Climate Research specializing in emissions and human health, who was not involved in the study.
“Reduced workability in outdoor environments could have large economic impacts on top of the human suffering from having to work in extreme temperatures,” he told AFP, adding that crop and livestock production can also be affected by extreme temperatures. .