Dangerous heat waves are predicted every day in the tropics

Even if the goals of the Paris Agreement are met, many people in the tropics are at risk of “dangerous” heat waves more than half the year by the end of the century, a study warned on Thursday.

And if this goal of keeping temperature rises below 2°C compared to the pre-industrial era is largely exceeded, they could face prolonged “nightmare” heat waves, according to work by American researchers published in Communications Earth. and environmental journal.

As a result of global warming, heat waves are already increasing, most recently in Western Europe or currently in China, with consequences such as droughts, poor harvests or fires, and threats to health and biodiversity.

Based on statistical estimates of warming induced by different scenarios of greenhouse gas emissions linked to human activities, the researchers estimated exposure to dangerous levels of heat and humidity.

The result: In the tropics, even if the Paris target is met, “many days in a normal year” the heat will reach dangerous levels for humans.

Otherwise, temperatures can reach very dangerous levels for long periods of time. All tropical regions are concerned, the Indian subcontinent and sub-Saharan Africa being most exposed.

Outside the tropics, devastating heat waves are likely to become an annual phenomenon, the study said.

“If we don’t pull ourselves together, billions of people could be exposed to the most dangerous temperatures ever seen,” said lead author Lucas Vargas Zeppetello of Harvard University.

The study is based on a scale that defines “dangerous” for humans from 39.4°C and “extremely dangerous” at 51°C.

The highest thresholds were initially defined in relation to specific working environments (for example boilers) and have so far not been observed in outdoor environments.

But by 2100, it is “virtually certain” that some tropical regions will face it, unless emissions drop dramatically, Mr. Zeppetto stated. “It’s very scary,” he told AFP.

However, global warming has already reached around 1.2°C, and current global emission reduction commitments paint a trajectory of more than 2°C by 2100.

The study predicts a warming of 1.8°C in 2050 and a further +3°C in 2100, resulting in these “nightmare” temperature periods, Mr. Zeppetello warned.

In a worst-case scenario, the most affected areas could experience extreme temperatures for two months of the year.

“We are not obligated to go towards this world”, however the researcher emphasized. “Today, nothing says it’s certain, but people need to be aware of the risk of it happening.”

All of the scenarios developed also highlight an increase in heat-related health problems, particularly among the elderly, vulnerable or those who work outdoors.

“It’s a very important point that we’re not paying enough attention to,” said Kristin Aunan, professor at the Center for International Climate Research in Norway. “Reducing the ability to work outside could have significant economic impacts in addition to induced human suffering,” a researcher who was not involved in the study told AFP.