Wadia Institute of Himalayan Geology has come up with a study on impact of climate change on the Indian summer monsoon in last 10,000 years covering the related aspects of migrations, agrarian practices and societal collapses in India. A K Gupta, director WIHG conducted this study through the methods of carbon dating and studying Istotopic variations and bore drilling sediments of samples from Tso-moriri Lake of Ladakh, caves in Meghalya in North East and Arabian Sea and Bay of Bengal.

"Some 200 samples of sand dug out from the Tso-moriri lake at 5 meter depth which were carbon dated with Atomic Mass Spectro Meter of 14 unstable isotope of carbon showed that there was good monsoon during 10,00 to 7000 years ago which allowed domestication of plants and livestock. This was a drastic transformation in civilization, as hunter gatherers became pastorals and, the establishment of permanent settlements came into being," Gupta said.

In complete contrast to that these settlements got disturbed and human migration in the Indian subcontinent started with the beginning of an arid phase between 4200 to 2900 years ago resulting into annihilation and displacement of Sindhu valley civilisation which was at the peak of its era. Dry phases badly impacted their agriculture practices. "The monsoon pattern is determined by astronomical cycle controlled by earth geology and high solar insulation," Gupta said.

His data also suggest that highly revered Sarasvati river existed unto 1500 years ago, which has now been reduced in the form of small nalah or stream and as buried channel scattered through the states of Haryana, Rajasthan, Gujarat.

"A strong summer monsoon has been registered from BC 400 to AD 500 followed by medieval warm period and floods during 950-1350 AD. Then came Little Ice Age 1450-1850 AD which was a weak and dry monsoon phase. British attacked tropical area of the world including India where monsoon was weak to escape from cold climate of ice-age," he said.

He further said that although climatic deterioration played a significant role in displacement of the human settlement in India, the rise and fall of ancient and medieval Indian kingdoms were also closely linked to socio-political turmoil unrest. There is no discontinuity in climatic history of India and climate has largely been conducive during the last 10,000 years.

Source: May 19, 2017, The Times of India