Global warming has greatly exacerbated the severe heat wave that has been smothering much of Pakistan and India this spring and has increased the likelihood that it will occur, climate scientists said on Monday.
According to scientists, the chances of such a heat wave occurring have multiplied by at least 30 times since the 19th century, before widespread emissions of gases that warm the planet began. The heat wave is on average one degree centigrade hotter than a similar event that had occurred in those pre-industrial times, the researchers said.
“Climate change really changes everything when it comes to heat waves,” said Friederike Otto, a climatologist at Imperial College London. “It’s a factor of greater importance.” Otto is the author of a report on the World Weather Attribution heat wave, a collaborative effort by scientists to examine extreme weather events to see whether or not they have been influenced by climate change.
The relentless heat, with temperatures rising above 38 degrees centigrade for days on end, especially in northwestern India and southeastern Pakistan, has already claimed at least 90 deaths, caused flooding from melting glaciers in the Himalayas, contributed to electricity and stunted India’s wheat crop, helping to fuel an emerging global food crisis.
The study concluded that a heat wave like this has an approximately 1 in 100 chance of occurring in any given year. Before climate warming started, the odds would have been 1 in 3,000 or less. And the probability will increase to as much as 1 in 5, the scientists said, if the world reaches 2 degrees Fahrenheit, which it is on track to do, unless countries reduce their emissions by a lot. The world is already about 1.1 degrees Celsius warmer since the late 19th century.
Heat at this time of year is normal in South Asia, but the current heat wave started early, near the beginning of March, and is continuing in some areas where there is little prospect of relief until monsoon rains arrive in the next few years. months.
Scientists analyzed daily maximum temperatures from March and April and used computer simulations of the world as it is today and of a fictional world where neither emissions nor warming has occurred. The study was not peer-reviewed, but these model-matching techniques were peer-reviewed in the past and are now widely used and accepted.
Due to the absence of a long observational record and other uncertainties, the researchers said, the conclusions are conservative, and the odds of such an event are likely more than 30 times greater than they were before the planet’s warming began.
The analysis also examined the effects of prolonged heat. Arpita Mondal, a climatologist at the Bombay Institute of Technology in Mumbai and one of the study’s authors, said it was difficult to gather data on the heat wave’s effects on wheat, which is sensitive to extreme heat, but that there were anecdotal reports. about losses.
“But something that was amazing was that India banned wheat exports to the rest of the world,” she said. “That alone is evidence that our agricultural productivity has been affected.”
Added to the effects of the Russian invasion of Ukraine on Ukrainian wheat exports, India’s export ban is leading international agencies to fear a potential global famine.
Another study author, Roop Singh, climate risk adviser at the Red Cross Red Crescent Climate Center, said this heat wave, like others, shows that the effects tend to be felt disproportionately by the poor.
According to Singh, there are reports of widespread power cuts, in part because the need for more cooling puts a strain on the system and in part because of a coal shortage in India. “This has a special impact on the poorest people, who may have access to a fan or air conditioner, but may not be able to run it because they cannot afford the cost of a generator,” she explained.
The study’s findings are in line with many other analyzes of similar events over the past two decades, including an extraordinary heat wave last summer in the Pacific Northwest and western Canada. Known as attribution analysis, this field of research has contributed to a growing understanding among scientists and the public that the harmful effects of global warming are not a distant future problem, but are already occurring.
Because emissions have raised the world’s base temperature, the link between heat waves and climate change is especially clear. Otto said that in studies of other extreme events such as floods or droughts, climate change is often just one factor taken into account among many.
In a recent paper, she and other scientists argued that the influence of global warming on heat waves is already so evident that “it is rapidly becoming an obsolete question.” They wrote that the next frontier of attribution science will be providing information to help people decide how to adapt to extreme heat.
Translation by Clara Allain
