Flood-slammed Karachi could face worsening urban inundations in coming years, in part as the South Asian monsoon shifts, climate scientists have warned. The winds that drive Pakistan’s annual monsoon, which arrives from the Bay of Bengal and the Arabian Sea, appear to be altering as a result of climate change, which could push more rainfall to Karachi – and less to key agricultural regions, they said. “It’s new phenomenon and we need to understand it. It hasn t rained like this in Karachi for more than half a century,” said Shaukat Ali, a meteorologist and senior scientific officer at the Global Change Impact Studies Centre (GCISC). He said winds driving the monsoon from the Bay of Bengal appear to be shifting it northwards, away from its traditional core zone in the agricultural breadbasket of Punjab. Winds from the Arabian Sea have traditionally been weak but now seem to be strengthening, Ali said. This year monsoon winds were “extremely erratic”, he said, with hotter temperatures in the Arabian Sea leading to monsoon depressions that dumped unexpectedly heavy rainfall on an unprepared Karachi, Pakistan s financial hub. “The sea and winds behaved very differently this monsoon,” he noted. Record-breaking heavy rain in Karachi in August killed over 100 people and disrupted the lives of many of the city s more than 15 million residents as water flooded main roads and homes. The city received its largest-ever-recorded rainfall total in a single day on August 24, when 230 mm (9 inches) of rain fall in just 12 hours, according to the Pakistan Meteorology Department. Over the month, Karachi received 484 mm (19 inches) of rain, the highest total in at least 90 years, it noted. But as climate change warms oceans, it is also accelerating evaporation of water, which then falls as rain – one significant additional driver of Karachi s floods, he said. Both scientists have been part of a research effort through GCISC to better predict extreme weather in South Asia and help countries adapt to it.
