Separated by a distance of 4,659 km, Kolkata in the eastern state of West Bengal in India and the Malaysian capital of Kuala Lumpur both bore the brunt of natural disasters on Monday night.
A sudden storm uprooted trees and ripped roofs in the Malaysian capital on Monday night. Barely hours later, Kolkata was hit by one of its worst downpours in decades, when around a month’s combined rainfall poured over the city in just around four hours and left large parts of the city submerged with several dead and life upended.
The city was still reeling from the after-effects on Wednesday with large swathes still inundated and power outages common.
The La Nina, a climate phenomenon associated with unusually cold temperatures in the Pacific Ocean, has brought Kolkata and Kuala Lumpur together this September, explained Nairwita Bandyopadhyay, HoD of Geography at Haringhata College.
“2025 is an excessive wet year,” Nairwita, who is also the founder-director of Meghduutt, an organisation working on early climate warnings and sustainable development, told The Telegraph Online. “This is not a normal cycle. Normal temperature is absent in the Pacific.
“Because of climate change, the cycles of both El Nino [characterised by hot sea surface temperatures in central and eastern tropical Pacific Ocean] and La Nina have changed. Earlier if El Nino used to happen twice in a decade, La Nina would happen once; now both happen almost every alternate year,” she said.
She classified Monday night’s rain as a cloudburst – which means very high rainfall in very little time, typically over 100 mm of rain within an hour.
Between 12 midnight and 5am on Tuesday in Kolkata, Garia received 330mm of rain. Ballygunge and Kalighat got over 250mm each, The Telegraph reported on Wednesday. The last time it rained as much was on September 26, 1986. The Alipore count then was 259.5mm.
Both Kolkata and Kuala Lumpur were hit by sudden weather phenomena, which Nairwita attributed to climate change.
“Earlier we used to see that for a cloud formation to reach depression and deep depression from a low pressure trough would take between four to five days. That has completely changed to where almost overnight a low pressure trough intensifies into a deep depression and a cyclonic circulation,” she said.
“This intensification has become rapid now. This is a direct fallout of climate change.”
Between the stormy rains accompanied by deafening lightning in Kuala Lumpur and Kolkata on Monday night, the world’s most powerful tropical cyclone this year, super typhoon Ragasa, was approaching Taiwan. By Wednesday it had ravaged Taiwan and Hong Kong, leaving a trajectory of death and destruction, and made landfall in China as well.
The Met office in Kolkata has tipped September 27 (Panchami) to be the wettest day, with heavy rainfall and squalls up to 50 kmph hitting the city and adjoining districts.
“There is a possibility of heavy rainfall days till October 10. One low pressure area is already forming over the Bay of Bengal. Another is likely to intensify around October 2,” Nairwita said.
Vishwas Chitale of the Delhi-based policy think-tank Council on Energy, Environment and Water (CEEW) said the rainfall in Kolkata through Monday night was 50 per cent higher than normal.
“Between September 22-23, Kolkata received close to 250 mm of rainfall. This is almost a 50 per cent increase compared to the normal rainfall for the same period in the city,” Chitale said. “CEEW research highlights there has been an increase of up to three to five heavy rainfall days per year in the last 10 years in the southern districts of West Bengal.”
The monsoon season typically lasts in India between June and September, followed by post-monsoon rainfall. In Malaysia, the northeast monsoon carries heavy rains till March. Add La Nina to the mix and what we get is increased rainfall and stronger storms.
The eastern side of Malaysia, specifically the South China Sea is a part of the Pacific Ocean, while the Strait of Malacca on the western side of the southeast Asian country connects it to the Indian Ocean.
Nairwita Bandyopadhyay suspects remnants of the super typhoon Ragasa will escape westwards and once entering the Bay of Bengal will create the possibility of another high intensity rainfall episode.
“With these changing rainfall patterns, we must prepare our cities to adapt to these extreme rainfall events by establishing effective urban flooding action plans and strategies like weather observation and forecasting at ward level,” said Chitale.
Heatwaves, rain, cold waves
La Nina is also expected to usher in one of the harshest winters in decades in the Delhi-NCR region, which could engulf the northern states of Uttar Pradesh and Bihar, touching Bengal later this year. Between December 2025 and February 2026 there is a high possibility of temperatures dipping several degrees below normal accompanied by frequent cold waves.
A recent global study has compared data from the years between 1991 and 2020 to the projections for the years 2021 to 2050 to look at how heatwaves or cold waves can overlap with heavy rain or dry extremes.
The study, featured in the United Nations Office for Disaster Risk Reduction and also published in the journal Nature, re-established climate change as the primary driver of rising exposure to such extreme weather events globally.
“The August 2022 heatwave in Europe and the 2015 heatwave in India and Pakistan resulted in thousands of deaths, while hundreds perished during the 2006 cold wave in Moscow,” the study said.
The steepest rise in compound hot-wet and hot-dry extremes are likely to be faced in the world’s largest greenhouse gas emitters, such as China, the US, India, the EU, Russia and Brazil.
“… India and China are expected to experience a substantial increase in exposure to hot-wet extremes,” the paper said.
“Urban areas characterised by high population density are particularly vulnerable. Urbanisation is expected to accelerate throughout the 21st century, with the urban population projected to grow from 55 per cent of the global total today to 68 per cent by 2050. The majority of this population will be residing in the developing countries, significantly amplifying the challenge of managing associated impacts.”