In this case, however, the role of climate change remains unclear.
It is relatively straightforward to perform an attribution study that evaluates the effects of warming during heatwaves, where hotter average temperatures push up the baseline where such sweltering events occur. The team calculated exactly how climate change alters outbreak rates Pacific Northwest Heatwave last year (such conditions would be “at least 150 times rarer without human-caused climate change”), recently Heatwaves in the UK (climate change makes it “at least 10 times more likely”) and Pakistan and India earlier this year (“likely more than 30 times”).
But using climate models to determine the role of global warming in amplifying the entire monsoon season proved more complicated, the researchers noted in a press statement. World Weather Attribution has created uncertainty for some combination of large variability in long-term heavy rainfall patterns, natural processes at work that models may not capture. complete and the weather phenomena of the territory. The Indus River Basin lies on the western edge of the monsoon region of the region, where there is a large difference in rainfall trends between the dry west and the wet east.
On the other hand, weather records clearly show that the region’s heaviest rainfall periods have become more intense in recent decades, with about 75% in the two worst-affected provinces. Some models found that climate change could increase rainfall by up to 50% during the five wettest days of the two-month monsoon season in those regions.
Friederike Otto, senior lecturer in climate science at Imperial College, London and one of the leaders of World Weather Attribution, said in a statement.
In one scientific article published Thursday, the team of researchers noted that a combination of meteorological forces caused the extreme rainfall. These include a La Niña event, which cooled the waters above the ocean and brought more-than-normal rainfall across large areas of the world, along with unusually hot spring and summer weather across the country. Pakistan. That boiling temperature also accelerates the melting of thousands of glaciers that feed the Indus River, although it is unknown how much contributed to the flooding.
Climate scientists have long warned that global rainfall will become more erratic as the planet warms, making both very wet and very dry periods more common. Among other factors, warmer air holds more moisture, draws water away from soil and plants, and alters the atmospheric pressure system. UN Climate Department project that the South Asian monsoon will vary more from year to year in the coming decades but increase in overall intensity in the 21st century.
The heaviest rainy days in Pakistan could get even more extreme as temperatures soar, World Weather Attribution found. That underscores the country’s need to fortify its riverbanks, homes and other infrastructure to protect its citizens — and for the wealthy nations that have created a proportion of climate pollution. too disproportionate to do everything to help.