Flood not due to just global warming
Climate change likely juiced rainfall by up to 50 per cent 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 1500 people, a scientific analysis finds.
Pakistan’s overall vulnerability, including people living in harm’s way, was the chief factor in the disaster that at one point left a third of the country under water, but humancaused climate change also played a major role, said study senior author Friederike Otto, a climate scientist at Imperial College of London.
There are many ingredients to the still ongoing humanitarian crisis — meteorological, economic, societal, historic and construction oriented.
The study was released yesterday without peer review.
What happened “would have been a disastrously high rainfall event without climate change, but it’s worse because of climate change,” Otto said.
But other human factors that put people in harm’s way and weren’t adequate to control the water had been even greater 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 was eight and nearly seven times normal amounts, according to the report by World Weather Attribution.
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 likely due to climate change.
They also looked at the entire region over two months and saw up to a 30 per cent increase in rainfall there.
The scientists used computer simulations to compare what happened last month to what would have happened in a world without heattrapping gases from the burning of coal, oil and natural gas — and that difference is what they attribute to climate change.
This is a scientifically valid technique, according to the US National Academy of Sciences.
Study co-author and climate scientist Fahad Saeed said many factors made the monsoon season much wetter than normal, including a La Nina, the natural cooling of part of the Pacific that alters weather worldwide.
But other factors had the signature of climate change, Saeed said.
A nasty heat wave in the region in the 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.
And climate change seemed to slightly change the jet stream, storm tracks and where low pressure sits, bringing more rainfall for southern provinces than they usually got, Saeed said.
“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.