Warming worsened Pakistan floods: study

·3-min read

Climate change may have increased rainfall by up to 50 per cent in two southern Pakistan provinces, but global warming was not the biggest cause of catastrophic flooding that has killed more than 1500 people, a new study says.

Pakistan's overall vulnerability, including people living in harm's way, is the chief factor in the disaster that at one point submerged a third of the country.

But human-caused "climate change also plays a really important role here", according to the study's senior author Friederike Otto, a climate scientist at Imperial College of London.

There are many ingredients to the ongoing humanitarian crisis - some meteorological, some economic, some societal, some historic and construction oriented.

With such complications and limitations, the team of international scientists looking at the disaster could not quantify how much climate change had increased the likelihood and frequency of the flooding.

The study was released on Thursday but has not yet been peer reviewed.

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 were not adequate to control the water were even bigger influences.

"This disaster was the result of vulnerability that was constructed over many, many years," study team member Ayesha Siddiqi, of the University of Cambridge, said.

August rainfall in the Sindh and Balochistan provinces - together nearly the size of Spain - was eight and nearly seven times normal amounts respectively, while the country as a whole had three-and-a-half times its normal rainfall, according to the report by World Weather Attribution (WWA).

The WWA is 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.

The team looked at the two provinces over five days and saw an increase of up to 50 per cent in the intensity of rainfall that was probably due to climate change.

They also looked at the entire Indus region over two months and saw up to a 30 per cent increase in rainfall there.

The scientists not only examined records of past rains, which only go back to 1961, but 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.

That difference is what they could attribute to climate change.

Study co-author Fahad Saeed, a scientist at Climate Analytics and the Centre for Climate Change and Sustainable Development in Islamabad, Pakistan, said numerous factors made this monsoon season much wetter than normal.

Those factors included a La Nina weather event, the natural cooling of part of the Pacific that alters weather worldwide.

But other factors had the signature of climate change, Saeed said.

A heat wave in the region earlier in the northern summer - which was made 30 times more likely because of climate change - increased 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 drops.

"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," University of Michigan environment dean Jonathan Overpeck, who was not part of the study, said.