The summer monsoon in South Asia, including Bangladesh, is weakening significantly due to increasing temperatures in the Indian Ocean and relatively subdued warming over land in the central Indian sub-continent, according to a new study published in Nature Communications, reports UNB.
Six authors, led by Roxy Mathew Koll of the Centre for Climate Change Research at the Indian Institute of Tropical Meteorology (IITM) in Pune, analysed data between 1901-2012 to establish this long-term trend.
They found that there was a 10-20 per cent decrease in the mean rainfall in the Indian subcontinent. The monsoon was decreasing over central South Asia - from south of Pakistan through India to Bangladesh, according to indiaclimatedialogue.net.
Rainfall over the central-east and northern regions of India, along the Ganga-Brahmaputra-Meghna basins and the Himalayan foothills, had declined.
The decline is crucial because in these regions agriculture is still largely rain-fed. The South Asian monsoon brings sustenance to around two billion people.
"The main thing is that unlike other oceans, that are open to the north and south, the Indian monsoon region is landlocked," Koll told indiaclimatedialogue.net.
The intense heating during late spring and summer around the equator, with the earth rotating to the right, leads to south-westerly winds under normal conditions.
Due to the higher ocean temperatures in the Indian Ocean, the normal movement of cooler air from the sea to hotter land, with clouds bearing rain, is weakening. This lower contrast between sea and land temperatures is responsible for the declining monsoon over South Asia.
As the authors state, "The variability of the monsoon makes the region one of the most susceptible areas around the world to the impacts of climate-related natural disasters such as droughts and floods."
Andrew Turner of the University of Reading in Britain said: "The study shows that rapid warming of the equatorial Indian Ocean is a cause for declining rainfall in parts of India over the last century.
As they show with their own model experiment, imposing surface warming over the equator will lead to ascending motions there and suppress ascending air over India, leading to declining rainfall over the Indian region. Such a result is not surprising."
Raghu Murtugudde of University of Maryland, a co-author, said: "The monsoon pattern is quite different because of the unique land-ocean configuration with the continent coming so close to the equator with a warm ocean to supply the moisture. But this also means that there is a competition for rain between the land and ocean."
Monsoon from Pak’s south to BD thru India on decline: Study
FE Team | Published: June 17, 2015 00:00:00 | Updated: November 30, 2026 06:01:00
Share if you like