Satellite image of super cyclone Amphan over the Bay of Bengal.

Climate Change Tracker: Cyclone Amphan is supercharged by climate change

2 min read . Updated: 20 May 2020, 08:31 PM ISTBibek Bhattacharya

Abnormally high surface temperatures in the Bay of Bengal turned Amphan into a super cyclone in 48 hours

As cyclone Amphan made landfall in the Sunderbans on 20 May (between Digha in West Bengal and Hatiya island in Bangladesh), it had sustained wind speeds of over 160 kmph, with wind gusts of up to 190 kmph. That made it an extremely severe cyclonic storm, according to the terminology of the India Meteorological Department (IMD), the equivalent of a Category 2 Atlantic hurricane. However, over 18-19 May, while Amphan was in the Bay of Bengal, it had reached sustained wind speeds of over 231 kmph, making it a super cyclone, the first since the 1999 super cyclone.

So, for a while, Amphan was as strong as a Category 4 hurricane. In fact, according to the US Joint Typhoon Warning Centre on 19 May, Amphan had recorded sustained wind speeds of up to 270 kmph, making it a Category 5 and the strongest cyclone ever recorded in the Bay of Bengal, even eclipsing the one in 1999.

But the point here isn’t how strong the cyclones are, but the reasons that lead to the creation of such strong cyclones. Last year’s cyclone Fani was also a Category 4, and hit earlier in May. Although India’s cyclone season is September-October, we are seeing more and stronger pre-monsoon cyclones. As the world’s oceans become hotter, absorbing the heat generated by human-caused climate change, they make storms bigger and more violent.

According to Roxy Mathew Koll, a scientist at the Indian Institute of Tropical Meteorology in Pune, the Bay of Bengal recorded surface temperatures of 32-34 degrees Celsius just prior to the formation of cyclone Amphan. “We have never seen such high values until now. Tropical cyclones draw their energy from the ocean surface and these temperatures can supercharge a cyclone, leading to its rapid intensification. Cyclone Amphan intensified from a category-1 cyclone to category-5 cyclone in a short span of 18 hours," he wrote in a Facebook post on 19 May. Isn’t it strange how it all comes back to climate change?

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