Climate change likely cut rainfall by up to 50% late last month in Pakistan’s two southern provinces, but global warming was not the main cause of the country’s devastating floods that killed more than 1,500 people , a new scientific analysis finds.
The overall vulnerability of Pakistan, including people living in harm’s way, is the main factor in the disaster that at one point submerged one-third of the country, but man-made “climate change also plays a very important role here, ” said the study. senior author Friederike Otto, climate scientist at Imperial College of London.
The ongoing humanitarian crisis has many components — some meteorological, some economic, some societal, some historical and construction oriented. Add to that weather records that don’t go back far enough in time.
With such difficulties and constraints, the international team of scientists looking at the disaster could not quantify how much the likelihood and frequency of floods has increased due to climate change, the study’s authors said. It was released on Thursday but is yet to be peer-reviewed.
It would have been a catastrophic high rainfall scenario without climate change, but climate change has made it worse,” Otto said. “And especially in this very fragile region, small changes matter a lot.”
But other human factors had even greater impacts that put people in harm’s way and were insufficient to control the water.
“This disaster was the result of a vulnerability built up over many years,” said study team member Ayesha Siddiqi from the University of Cambridge.
August rainfall in the provinces of Sindh and Balochistan — together almost the size of Spain — was eight and nearly seven times normal, and 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 conduct real-time studies of extreme weather to search for the fingerprints of climate change.
The team looked at just the two provinces over five days and saw an increase of up to 50% in the intensity of rain likely due to climate change. They also looked at the entire Indus region over two months and saw an up to 30% increase in rainfall there.
The scientists not only examined past rainfall records, which only go back to 1961, but used computer simulations to compare what happened last month with what would happen in a world without capture heat-gas from burning coal, oil and natural gas. gas — and it is that difference that they could attribute to climate change. This is a scientifically valid technique, according to the US National Academy of Sciences.
Study co-author Fahad Saeed, a climate scientist at Climate Analytics and the Center for Climate Change and Sustainable Development in Islamabad, Pakistan, said multiple factors made this monsoon season much wetter than usual, including La Nina , the natural cooling of part of the Pacific Ocean that changes the weather around the world.
But there were other signs of climate change, Saeed said. A nasty heat wave in the region earlier this summer — made 30 times more likely by climate change — widened the differential between land and water temperatures. That differential determines how much moisture goes from the ocean to the monsoon and means more of it falls.
And the climate change appeared to have caused a slight shift in the jet stream, storm tracks and the location of low pressure, bringing more rain to the southern provinces than they normally receive, Saeed said.
“Pakistan has not contributed much to global climate change, but it certainly has to deal with a huge amount of climate change consequences,” said University of Michigan Environment Dean Jonathan Overpeck, who was not part of the study.
Overpeck and three other outdoor climate scientists said the study makes sense and is properly nuanced to bring in all the risk factors.
The nuances help “avoid over-interpretation,” said Stanford University climate scientist Chris Field. “But we also want to not lose sight of the main message — human-caused climate change is increasing the risks of extreme events around the world, including Pakistan’s devastating floods in 2022.”
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