Pakistan floods worsened by multiple factors, not just climate change: study

Climate change likely increased rainfall by up to 50% late last month in two southern provinces of Pakistan, but global warming was not the main cause of catastrophic floods that killed more than 1,500 people , according to a new scientific analysis.

Pakistan’s overall vulnerability, including people at risk, is the main driver of the disaster which at one point submerged a third of the country under water, but “man-made climate change is also playing a very important role here”, according to a study. lead author Friederike Otto, climatologist at Imperial College London.

There are many ingredients to the ongoing humanitarian crisis – some weather, some economic, some societal, some historical and some construction related.

Photo: AP

With such complications and limitations in weather records not going back far enough in time, the team of international scientists studying the disaster could not quantify how much climate change had increased the likelihood and frequency of floods. , the study authors said.

The research was published Thursday, but has not been peer reviewed.

What happened “would have been a severe rainfall event without climate change, but it’s worse because of climate change,” Otto said. “Especially in this very vulnerable region, small changes matter a lot.”

However, other human factors that put people at risk and were not enough to control water were even more important influences.

“This disaster is the result of a vulnerability that has built up over many, many years,” said study team member Ayesha Siddiqi, from the University of Cambridge.

Rainfall last month in Sindh and Baluchistan provinces – together almost the size of Spain – was around seven to eight times normal, while the country as a whole more than tripled its normal rainfall, according to the World Weather Attribution report, a collection of mostly volunteer scientists from around the world who conduct real-time studies of extreme weather events to search for evidence of climate change.

The team only looked at the two provinces for five days and found an increase of up to 50% in rainfall intensity, likely due to climate change. They also looked at the entire Indus region over two months and found an increase in rainfall there of up to 30%.

Scientists not only looked at records of past rains, which only date back to 1961, but they used computer simulations to compare what happened last month to what would have happened in a world without trapping gas. heat from burning coal, oil and natural resources. gases – and this difference is what they might attribute to climate change.

This is a scientifically valid technique, according to the US National Academy of Sciences.

Many factors have made this monsoon season much wetter than normal, including a La Nina weather pattern that naturally cools part of the Pacific Ocean that alters weather around the world, the co-author of the report said. study Fahad Saeed, climatologist at Climate Analytics and the Center for Climate. Change and sustainable development in Islamabad, Pakistan.

However, other factors have the signature of climate change, Saeed added.

An intense heat wave in the region in early summer – which was made 30 times more likely due to climate change – increased the differential between land and water temperatures. This differential determines how much moisture goes from the ocean to the monsoon, and means there is more.

Climate change appeared to slightly alter the jet stream, storm tracks and where the low pressure is, bringing more rainfall to the southern provinces than they usually receive, Saeed said.

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

Overpeck and three other outside climatologists said the study made sense and was properly nuanced to consider all risk factors.

The nuances help “avoid over-interpretation,” said Stanford University climatologist Chris Field.

“We also want to avoid missing the main message – human-induced climate change is increasing the risk of extreme events around the world, including the devastating floods in Pakistan in 2022,” he said.

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Teresa H. Sadler