“Fingerprints” of climate change are clear in Pakistan’s devastating floods
Climate change very likely intensified the South Asian monsoon that flooded Pakistan in recent weeks, killing more than 1,000 people and destroying nearly 2 million homes.
This is according to a new analysis done by World Weather Attribution. This network of scientists uses climate models, weather observations and other tools to determine if global warming has increased the severity or likelihood of recent extreme weather events.
In this case, however, just how big a role climate change played isn’t clear. It is relatively easy to conduct an attribution study. This examines the impact of heat waves. These are where higher average temperatures push up the base temperature from which such sweltering events take flight. The group has precisely calculated how much climate change altered the odds of the blistering Pacific Northwest heat wave last year (such conditions would be “at least 150 times rarer without human-induced climate change”), the recent UK heat wave (climate change made it “at least 10 times more likely”), and the one in Pakistan and India earlier this year (“30 times more likely”).
But, using climate models to determine the role of global warming in amplifying the monsoon season proved more difficult, researchers stated in a press release. World Weather Attribution attributed the uncertainty to a combination of large variability in heavy rain patterns over long periods, natural processes that the models may not fully capture, as well as the weather quirks of this territory. The Indus River basin lies at the western edge the region’s monsoon zone. There are large differences in rainfall trends between dry west and wet eastern.
On the other hand, weather records clearly show that the region’s heaviest periods of rainfall have become more intense in recent decades, by about 75% in the two hardest-hit provinces. Some models found that climate change may have increased rainfall by as much as 50% during the five wettest days of the two-month monsoon season in those areas.
” “While it is difficult to give a precise figure to climate change’s contribution, the fingerprints are evident that global warming is a factor,” Friederike Otto (a senior lecturer in climate sciences at Imperial College London) said in a statement. She is also one of the founders of World Weather Attribution.
In a scientific paper released on Thursday, the team of researchers noted that a combination of meteorological forces drove the extreme rainfall. These included a La Nina event that cools the upper ocean and carries more than usual rainfall across large areas of the world. This was combined with unusually hot springs and summer weather across Pakistan. The melting of thousands of glaciers that supply the Indus River was also accelerated by the simmering temperatures, though it is not known how much.
Climate scientists warn that global rainfall patterns will become more unpredictable as the planet heats. This could lead to more wet and dry periods. Warmer air, among other factors, holds more moisture, sucks water out of soils, plants, and alters atmospheric pressure system. The UN’s climate panel projects that the South Asian monsoons will become more variable from year to year in the coming decades but increase in intensity overall across the 21st century. Pakistan’s most severe days of rain will likely increase as temperatures rise, according to World Weather Attribution. This highlights the need for Pakistan to strengthen its river banks, homes and other infrastructure to protect citizens. It also calls for rich nations, which have contributed a large amount of climate pollution, to do all they can to help.
I’m a journalist who specializes in investigative reporting and writing. I have written for the New York Times and other publications.