Climate change likely juiced rainfall by up to 50% late last month in two southern Pakistan provinces, but global warming wasn’t the biggest cause of the country’s catastrophic flooding that has killed more than 1,500 people, a new scientific analysis finds.
Pakistan’s overall vulnerability, including people living in harm’s way, is the chief factor in the disaster that at one point submerged one-third of the country under water, but human-caused “climate change also plays a really important role here,” said study senior author Friederike Otto, a climate scientist at Imperial College of London.
There are many ingredients to the still ongoing humanitarian crisis—some meteorological, some economic, some societal, some historic and construction oriented. Add to that weather records that don’t go back far enough in time.
With such complications and limitations, the team of international scientists looking at the disaster couldn’t quantify how much climate change had increased the likelihood and frequency of the flooding, said authors of the study. The study was published on Thursday, but has not been peer-reviewed.
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What happened “would have been a disastrously high rainfall event without climate change, but it’s worse because of climate change,” Otto said. “And especially in this highly vulnerable region, small changes matter a lot.”
But other human factors that put people in harm’s way and weren’t adequate to control the water were even bigger influences.
“This disaster was the result of vulnerability that was constructed over many, many years,” said study team member Ayesha Siddiqi of the University of Cambridge.
August rainfall in the Sindh and Balochistan provinces—together nearly the size of Spain—was eight and nearly seven times normal amounts, while the country as a whole had three-and-a-half times its normal rainfall, according to the report by World Weather Attribution, a collection of mostly volunteer scientists from around the world who do real-time studies of extreme weather to look for the fingerprints of climate change.
They examined the provinces for five days. The team saw an almost 50% increase in intensity due to climate changes. The team also examined the whole Indus region for two months, and found a 30 percent increase in rainfall.
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The scientists not only examined records of past rains, which only go back to 1961, but they used computer simulations to compare what happened last month to what would have happened in a world without heat-trapping gases from the burning of coal, oil and natural gas—and that difference is what they could attribute to climate change. According to the U.S. National Academy of Sciences, this technique is scientifically sound.
Fahad Saeed (a Climate Analytics and Center for Climate Change Sustainable Development scientist in Islamabad) was co-author of this study. He said that many factors contributed to the monsoon season being wetter than usual.
Saeed explained that there were other contributing factors to climate change. A nasty heat wave in the region earlier in the summer—which was made 30 times more likely because of climate change—increased the differential between land and water temperatures. This differential is what determines the amount of moisture that goes to the ocean and the monsoon, which means it causes more water to drop.
Saeed explained that climate change has had a small impact on the jet stream and storm tracks, as well as where low pressure is located. This may have resulted, Saeed claimed, in greater rainfall for southern regions than what they normally get.
“Pakistan has not contributed much in terms of causing global climate change, but sure is having to deal with a massive amount of climate change consequences,” said University of Michigan environment dean Jonathan Overpeck, who wasn’t part of the study.
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Overpeck said, along with three others outside scientists on climate science, that the study was logical and accurately nuanced in order to account for all risks.
The nuances help “avoid overinterpretation,’’ said Stanford University climate scientist Chris Field. “But we also want to avoid missing the main message—human-caused climate change is increasing the risks of extreme events around the world, including the devastating 2022 Pakistan flooding.”
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