However, in this case, it is not clear how big a role climate change has played.
It is relatively easy to perform an attribution study evaluating the effect of warming in heat waves, as hotter average temperatures drive the baseline from which such extreme heat events set off. The group has precisely calculated how much climate change has altered the odds of bubbles. Pacific Northwest heat wave last year (such conditions would be “at least 150 times rarer without human-caused climate change”), the latter Heat wave in the United Kingdom (Climate change made it “at least 10 times more likely”), and one in Pakistan and India earlier this year (“30 times more likely”).
The researchers noted in a press release that using climate models to determine the role of global warming in amplifying the entire monsoon season has been more challenging. The proportion of global weather inferred uncertainty to a combination of the wide variability in heavy precipitation patterns over long periods, natural processes at work that models may not fully capture, and the region’s atmospheric quirks. The Indus Basin lies at the western edge of the region’s monsoon zone, where there are large differences in precipitation directions between the dry west and the wet east.
On the other hand, weather records clearly show that periods of heavy rainfall in the region have become more intense in recent decades, by about 75% in the two hardest-hit counties. Some models have found that climate change may have increased rainfall by up to 50% during the five wettest days of the two-month monsoon season in those regions.
“So, while it is difficult to pinpoint an exact figure for the contribution of climate change, the fingerprints of global warming are clear,” Frederic Otto, Senior Lecturer in Climate Science at Imperial College London and one of the leaders at global weather attribution, said in a statement.
In a scientific paper released Thursday, the team of researchers noted that a combination of meteorological forces led to the torrential rains. They included the La Niña event, which cools the upper ocean waters and causes more than normal rainfall in large parts of the world, along with hot spring and unusual summer weather across Pakistan. These high temperatures also accelerated the melting of the thousands of glaciers that feed the Indus, although it is not known how much this contributed to the flooding.
Climate scientists have long warned that global precipitation patterns will become more variable as the planet warms, making very wet and very dry periods more common. Among other factors, warmer air retains more moisture, absorbs water from soil and plants, and changes atmospheric pressure regimes. UN Climate Commission projects The South Asian monsoon will become more variable from year to year in the coming decades but will generally increase in intensity during the twenty-first century.
The World Weather Referral Report found that Pakistan’s heaviest rainy days are likely to become more severe as temperatures rise. This underscores the state’s need to strengthen river banks, homes and other infrastructure to protect citizens – and for rich nations that have produced a vastly disproportionate share of climate pollution to do whatever they can to help.