Monsoon pattern may see rapid shift
The pattern of monsoon rainfall in India may see a major shift by the end of this century with southern India likely to register the most increase in extreme rainfall , researchers from the Indian Institute of Technology (IIT), Kharagpur, in West Bengal, have found.
The researchers also expect rainfall to increase in the Arabian Sea and south-Asian countries, including Myanmar, Thailand and Malaysia.
“In the worst-case scenario of climate change, rainfall could increase by 2.7 mm per day in north India with the Himalayan foothills expected to receive the heaviest rain. In south India, rainfall could increase by 18.5 mm per day with the Western Ghats expected to be affected the most,” said Rajib Maity, a professor of civil engineering at IIT Kharagpur, who led the study.
The scenario could play out towards the end of the century, between 2071 and 2100. The researchers analysed data of Indian Summer Monsoon precipitation for close to five decades (1971 – 2017), considering the period between 1930 and 1970 as the base.
In meteorological terms, fifty years, the time it will take for the change to manifest itself, isn’t much. And the change itself, could have a significant bearing on cropping patterns in a country where much of the agriculture is still rain-fed.
“South Asia, as we know, despite advances in irrigation systems, is highly dependent on the monsoons. Results of this study will be useful to the designers of water infrastructure and agricultural communities, especially in the southern parts of India and Himalayan foothills, to prompt a possible change in design criteria and agricultural practices including cropping pattern,” Virendra Tewari, director of IIT Kharagpur said, in a statement issued by the institute.
The results have been published in the Scientific Reports journal brought out by Nature publishing group.
“Our analysis shows a change in the direction of the southwest monsoon winds blowing towards the east over the Indian Ocean. This directional change will intensify the already observed precipitation contrast in future between South and North India, and cause more extreme precipitation events in countries such as Myanmar, Thailand and Malaysia” Maity added.
The researchers said that the Indian Ocean Dipole – popularly referred to as the ‘Indian Nino’ because of its similarity to its Pacific equivalent – is intensifying which could lead to increase in rainfall activity throughout India.
The Indian Ocean Dipole refers to the difference in sea-surface temperatures in opposite parts of the Indian Ocean which, in turn, affects rainfall patterns.
“The possibility of such a shift can’t be ruled out but such projections need more research and analysis as the association between the Indian Ocean Dipole and monsoon is still not well defined,” said R Krishnan, executive director, Centre for Climate Change Studies at the Indian Institute of Tropical Meteorology (IITM).
To be sure, over the years, a significant correlation has been established between the Indian Ocean Dipole and the monsoon.
IITM, in various studies, has documented the change in monsoon rainfall pattern and increase in extreme rainfall events since 1871. It has found that the period between 1981 and 2016 witnessed higher frequency of extreme rain during monsoon months. Studies by then IITM professor, M Rajeevan, now secretary ministry of earth sciences, have shown that monsoon rain has increased in western parts of India, namely Rajasthan and Gujarat and has declined in Central and north-western India.