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An ‘El Nino’ in Indian Ocean by 2050?

TV Jayan New Delhi | Updated on May 08, 2020 Published on May 08, 2020

If current warming trends continue, an Indian Ocean El Niño could emerge as early as 2050.   -  REUTERS

But Indian scientists studying monsoon pick holes in the US study

Global warming may revive an ancient climate patten similar to El Niño in the Indian Ocean by the middle of this century, resulting in more severe floods, storms and droughts on landmasses abutting the ocean, including some parts of India, according to a study by researchers in the US.

The scientists, led by Pedro DiNezio, a climate scientist at the University of Texas Institute for Geophysics, using computer simulations showed that global warming could disturb the Indian Ocean’s surface temperatures, causing them to rise and fall year to year much more steeply than they do today. The seesaw pattern is strikingly similar to El Niño, a climate phenomenon that occurs in the Pacific Ocean and affects the weather globally, they argued in a paper published in the journal Science Advances on Wednesday.

Contrary view

However, multiple Indian scientists studying the Indian monsoon and other global weather phenomena said that while the findings are interesting, they may not represent reality.

“Our research shows that raising or lowering the average global temperature just a few degrees triggers the Indian Ocean to operate exactly the same as the other tropical oceans, with less uniform surface temperatures across the equator, more variable climate, and with its own El Niño,” said DiNezio in a statement.

According to them, if current warming trends continue, an Indian Ocean El Niño could emerge as early as 2050. The findings build on a work published last year, in which the authors, including some involved in this study, found evidence of a past Indian Ocean El Nino hidden in the shells of microscopic marine organisms that lived 21,000 years ago. That study was led by Kaustubh Thirumalai, a geoscientist with the University of Arizona, who is a co-author of the current study. The way glacial conditions affected wind and ocean currents in the Indian Ocean in the past is similar to the way global warming affects them in the simulations, Thirumalai said.

Change in wind direction

The Indian Ocean today experiences very slight year-to-year climate swings because winds blow gently from west to east. According to the simulations, global warming could reverse the direction of these winds, destabilising the ocean and tipping the climate into swings of warming and cooling akin to the El Niño and La Niña climate phenomena in the Pacific Ocean. This could bring more frequent droughts to East Africa and south India, apart from increased rainfall over Indonesia.

“The study claims that the Indian Ocean variability was higher during the Ice Age and would also be higher under strong global warming. They fail to explain how the dynamics can be the same in both cases. Especially if models can produce such an outcome erroneously,” said Raghu Murtugudde, a professor at the University of Maryland.

‘Academic exercise’

For Suryachandra Rao, who heads the team that studies Indian Ocean Dipole at the Pune-based Indian Institute of Tropical Meteorology, it was purely an academic activity using a single model.

“Systematic biases in some of the present day models also show similar pattern, therefore to get a realistic figure we have to do lot of model experiments and understand how well these models are simulating the present day climate. Without carrying out these experiments it will be too early to conclude on the results presented in this paper,” said Rao.

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Published on May 08, 2020
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