A study warned Thursday that many people in the tropics are at risk of “dangerous” heat waves for more than half the year by the end of the century, even if the goals of the Paris Agreement are met.
And if this goal of containing warming below 2 degrees Celsius compared to pre-industrial times is largely exceeded, they could face long “nightmare” periods of heat waves, according to work by US researchers published in Communications Earth. and Environment Magazine.
Under the influence of global warming, heat waves are already increasing, most recently in Western Europe or currently in China, with the consequences of drought, poor harvests or fires, endangering health and biodiversity.
The researchers assessed potential exposure to dangerous levels of heat and humidity, based on statistical projections of warming from different scenarios of greenhouse gas emissions associated with human activity.
The result: in the tropics, temperatures can reach dangerous levels for humans “most days of a typical year,” even if the Paris target is met.
Otherwise, temperatures can reach very dangerous levels for extended periods of time. All tropics are involved, the most exposed being the Indian subcontinent and sub-Saharan Africa.
Outside the tropics, devastating heat waves are likely to become an annual phenomenon, according to the study.
“If we don’t pull ourselves together, billions of people could be exposed to extremely dangerous temperatures in ways we haven’t seen before,” said lead researcher Lucas Vargas Zeptillo of Harvard University.
The study is based on a scale defined as “hazardous” for human temperatures of 39.4 degrees Celsius, and “extremely dangerous” at 51 degrees Celsius.
The highest thresholds were initially set for certain working environments (eg boilers) and have not yet been observed in the outer atmosphere.
But by 2100, it’s “almost certain” that some tropical regions will encounter them, unless emissions drop sharply, Mr. Zeptillo notes. “This is very scary,” he told AFP.
However, warming has already reached close to 1.2°C and current commitments to reduce global emissions chart a path well above 2°C in the year 2100.
The study envisions a 1.8°C warmer in 2050 and a more likely +3°C scenario for 2100, leading to periods of “nightmare” temperatures, warns Zeptillo.
In a worst-case scenario, extreme temperatures can last two months a year in the worst-affected areas.
“We don’t have to go into this world,” the researcher nonetheless asserts. “Today, nothing says this is for sure, but people should be aware of the risk of this happening.”
All of the scenarios developed also highlight the increase in heat-related health issues, especially among the elderly, frail or working outdoors.
“This is a very important point, to which we are not paying enough attention,” said Kristin Onan, a professor at the International Climate Research Center in Norway. “Reducing the ability to work outdoors could have significant economic impacts, in addition to induced human suffering,” the researcher, who was not involved in the study, told AFP.
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