Warming, other factors exacerbated floods in Pakistan, study finds

Warming, other factors exacerbated floods in Pakistan, study finds

Climate change was likely to have caused up to 50% rainfall in Pakistan’s two southern provinces late last month, according to a new scientific analysis, but global warming was not the biggest cause of the country’s catastrophic flooding, which killed more than 1,500 people.

Pakistan’s overall vulnerability, including people at risk, is the main factor in the disaster that at one point flooded a third of the country, but man-made “climate change also plays a very important role here”. the study said. senior author Friederike Otto, climate scientist at Imperial College of London.

There are many ingredients to the ongoing humanitarian crisis – some meteorological, some economic, some social, some historical and constructional. 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 was unable to quantify how much climate change had increased the probability and frequency of the floods, the study authors said. It was released Thursday, but has not yet been peer-reviewed.

What happened “would have been a disastrous amount of rain without climate change, but it’s worse because of climate change,” Otto said. “And especially in this very vulnerable region, small changes are very important.”

But other human factors that put people at risk and were not enough to control the water were even bigger influences.

“This disaster was the result of vulnerability built up over many, many years,” said study team member Ayesha Siddiqi of the University of Cambridge.

August rainfall in the provinces of Sindh and Balochistan — together nearly the size of Spain — was eight to nearly seven times the normal amount, while the country as a whole had three and a half times the normal rainfall, according to the report by World Weather Attribution, a collection from mostly volunteer scientists from around the world doing 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 rainfall intensity likely due to climate change. They also looked at the entire Indus region for two months and saw up to 30% more rainfall there.

Not only did the scientists examine records of past rains, dating only to 1961, but they used computer simulations to compare what happened last month with what would have happened in a world without heat-trapping gases from coal combustion. , oil and natural gas – and that difference is what they could attribute to climate change. According to the US National Academy of Sciences, this is a scientifically valid technique.

Study co-author Fahad Saeed, a climate scientist with Climate Analytics and the Center for Climate Change and Sustainable Development in Islamabad, Pakistan, said numerous factors made this monsoon season much wetter than usual, including a La Nina, the natural cooling of part of the Pacific Ocean changing the weather worldwide.

But other factors were characteristic of climate change, Saeed said. A nasty heat wave in the region earlier in the summer — made 30 times more likely by climate change — increased the difference between land and water temperatures. That difference determines how much moisture goes from the ocean to the monsoon and means more of it goes down.

And climate change seemed to slightly alter the jet stream, storm tracks and where low pressure prevails, bringing more rain to the southern provinces than they usually get, Saeed said.

“Pakistan hasn’t contributed much to causing global climate change, but it certainly faces a huge amount of impacts from climate change,” said Jonathan Overpeck, University of Michigan environmental dean, who was not part of the study.

Overpeck and three other outside climate scientists said the research makes sense and is appropriately nuanced to include all risk factors.

The nuances help “avoid over-interpretation,” says Stanford University climate scientist Chris Field. “But we also want to avoid overlooking the most important message: human-induced climate change increases the risks of extreme events around the world, including the devastating floods in Pakistan in 2022.”

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