West Bengal News: Warming Oceans Blamed For Kolkata’s Record-Breaking Rainfall

Kolkata witnessed its heaviest rainfall in nearly four decades as a relentless downpour lashed the city, flooding large parts and leaving around ten people dead. The India Meteorological Department (IMD) reported 251.4 mm of rain between Monday night and Tuesday morning, making it the highest single-day rainfall since 1986 and the sixth-highest in 137 years of records.

The rain peaked between 3 am and 4 am on September 23 with 98 mm falling in just one hour. Though intense, it narrowly missed the 100 mm threshold required to be termed a cloudburst. IMD officials said a low-pressure system that formed on September 22 over Odisha and the northwest Bay of Bengal moved toward Gangetic West Bengal, pulling in moisture and triggering the deluge.

Meteorologists called the event “rare and unusual” and pointed to climate change as a major driver. “Continuous warming of the Bay of Bengal has led to more evaporation, which fuels these systems. The low-pressure zone over Odisha kept drawing moisture, leading to prolonged and intense rainfall over Kolkata,” said Mahesh Palawat, Vice President of Meteorology and Climate Change at Skymet Weather.

Climate scientist Dr. Raghu Murtugudde, Emeritus Professor at the University of Maryland, added that global ocean warming is altering weather patterns across India. “Multiple typhoons in the Pacific are demanding high levels of moisture. They pull in moisture from the North Indian Ocean, which in turn influences the Bay of Bengal. The system that hit Kolkata was a result of this interaction. Such disruptions will delay the withdrawal of the monsoon and cause more erratic rainfall in cities like Kolkata and Mumbai,” he said.

Studies show oceans absorb over 90 percent of global warming. A recent Nature report revealed that oceans have warmed by more than 1.5°C since the industrial era, with the Indian Ocean heating faster than most others. This rapid rise has triggered more marine heatwaves, which disrupt monsoon patterns by reducing rainfall in central India while enhancing it in southern regions.

Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology, warned that sea surface temperatures in the Indian Ocean are projected to remain above 28°C throughout the year by the end of this century. “These conditions are highly conducive for extreme rainfall and cyclone formation. The number of severe cyclones and heavy rainfall events has already gone up since the 1950s and will increase further as ocean temperatures climb,” he said.

The Indian Ocean’s warming has been identified as the single largest contributor to global sea surface temperature rise. Researchers predict that marine heatwaves here could jump from about 20 days a year to nearly 250 days annually, pushing the ocean into a near-permanent heatwave state. This would not only intensify storms but also devastate marine ecosystems through coral bleaching and seagrass loss.

Kolkata’s historic downpour, experts warn, may not be a one-off disaster but a preview of what lies ahead as warming seas continue to reshape the monsoon and amplify extreme weather across the region.