The “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.
In this case, however, just how big a role climate change played isn’t clear.
It’s easy to conduct an attribution study. This examines the impact of warming in heat waves. These are where higher average temperatures push up the baseline from which such sweltering phenomena take off.
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”).
However, using climate models to determine global warming’s role for amplifying the full monsoon seasons proved more difficult, the 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 west.
PAULA BRONSTEIN/ GETTY IMAGES
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 quantify the impact of climate change, the fingerprints are evident,” Friederike Otto, a senior lecturer in climate sciences at Imperial College London and one the leaders of World Weather Attribution said in a statement.
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 accompanied by 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 have warned for years that global rainfall patterns are likely to become more unpredictable as the planet heats. This will lead to more frequent very wet periods and more 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.
