Cyclones Leave Trail Of Destruction In South Asia As Indian Ocean Heats Up

by GoNews Desk 11 months ago Views 1339

Cyclones Leave Trail Of Destruction In South Asia
A satellite image showing temperature anomalies in north Indian Ocean on May 19, a day before Cyclone Amphan made landfall in eastern India. There was a variation of more than 2C on May 19 in the Bay of Bengal [image by: Physical Oceanography Distributed Active Archive Centre/NASA]

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Nisarga, the first cyclone to have threatened Mumbai in more than 70 years, has left India’s financial capital largely unharmed after it made landfall in the nearby beach town of Alibaug on June 3. Gujarat and Maharashtra along India’s western coast have traditionally been more sheltered from cyclones than the country’s eastern coast. But this time unusually warm surface temperatures in the Indian Ocean resulted in a weather depression that rapidly intensified into a severe storm in the Arabian Sea, scientists said.

South Asia has been hit by two cyclones in as many weeks, with Cyclone Amphan ravaging parts of eastern India and Bangladesh on May 20. Such extreme weather events in close proximity have once again highlighted the impact climate change has in the region. Coming at a time when countries in South Asia are grappling with the Covid-19 crisis, this has only multiplied the plight of millions.

Such extreme weather events in the northern Indian Ocean are no longer exceptional. Severe cyclones are expected to increase in number and intensity on both the east and west coasts of the Indian subcontinent because of a rapidly warming Indian Ocean, climate scientists said.

“In the case of both the recent cyclones, Amphan and Nisarga, the anomalously warm ocean temperatures are giving them a major boost,” said Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology. Temperatures in the Bay of Bengal were between 30-33C when Cyclone Amphan formed in mid-May and surface temperatures over the Arabian Sea were 30-32C before the weather depression that evolved into Cyclone Nisarga. “Such high temperatures aid rapid intensification of cyclonic systems,” Koll said.

Climate connection

Climate change amplifies the cyclonic storms that typically form in the northern Indian Ocean. Increasing sea surface temperatures can make cyclones more powerful. Warmer oceans mean there is higher rainfall during storms. Rising sea levels due to global warming make for higher storm surges, which reach larger inland areas. Higher temperatures also lead to cyclones forming much faster, as was the case with Nisarga and Amphan.

“This year both Arabian Sea and Bay of Bengal were about 1 degree warmer than normal (in early May) and hence the conditions were conducive to increasing the strength of the cyclones,” said Jayaraman Srinivasan, scientist at Divecha Centre for Climate Change, Indian Institute of Science. “A warmer ocean does not automatically mean there will be more cyclones, but if the cyclones are born, they will become stronger on account of a warmer sea.”

These recent cyclones are due to ocean heat waves and warming up of oceans, according to Anjal Prakash, research director at Bharti Institute of Public Policy of Indian School of Business and one of the authors of the Ocean and Cryosphere in a Changing Climate, a special report of the Intergovernmental Panel on Climate Change (IPCC). “The impact of the warming of the ocean means that there would be an increase in the incidences of tropical cyclone winds and rainfall, and increases in extreme waves, combined with relative sea level rise, extreme sea level events and coastal hazards,” Prakash said.

Although this is a global phenomenon, it is especially true for the Indian Ocean, which is the warmest of all five oceans, partly because the African-Asian landmass obstructs the entry of cold water from the Arctic. The north Indian Ocean, which comprises the Arabian Sea and the Bay of Bengal, generates 7% of the world’s cyclones, according to a May 2018 research paper by Sushil Gupta of Risk Management Solutions India, a think tank.

“However, their impact is comparatively high and devastating, especially when they strike the east Indian and Bangladesh coasts bordering north Bay of Bengal due to high population density clustered around low-lying areas along these coastlines,” Gupta said in his study. About one third of the global population lives around the Indian Ocean, many in low-lying coastal areas, small islands, developing states and least developed countries that are particularly vulnerable to climate impacts.

Till recently, the Arabian Sea was spared severe cyclones but that no longer seems to be the case. It had five cyclones in 2019. “IPCC reports indicate an increase in Arabian Sea cyclones during the pre- and post-monsoon seasons as a response to the rapid ocean warming trends,” Koll said.

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