Climate change snuffed out this civilisation, finds out a team that includes two city scientists

With the deficient monsoon giving India the blues, this scientific discovery has obviously got the entire country and the world sitting up and taking notice. An international research study says it was climate change that snuffed out the Indus valley civilisation. Chennai has a special reason to be proud of with this finding, as two scientists from the city were part of the research team.

At Chennai’s Institute of Mathematical Sciences, when Ronojoy Adhikari and Kavita Gangal were analysing the growth and decline of the Indus valley sites (also called Harappan sites) over time, they found that something curious happened around 1900 BCE.

Sudden disappearance

“There were lots of sites around 2500 BCE. But around 1900 BCE, the Harappan cities along the Ghaggar-Hakra river (often identified with the Saraswati) suddenly disappeared, with much smaller towns and villages appearing upstream, followed by a gradual decline of Harappan sites,” Ronojoy elaborates. Meanwhile, far away, at the Woods Hole Oceanographic Institution in Falmouth, the U.S., Liviu Giosan, a geologist, came across this study. He found that the Chennai scientist duo’s data fit in well with his own findings on the change in monsoon patterns during those times, and the teams began to work together.

In this analysis, sediment data, topography data, fluvial data and archaeological data were combined and the study made it to the cover of (America’s) prestigious Proceedings of the National Academy of Sciences (PNAS). “Thinking about a situation from several different angles gives a much more detailed and reliable picture,” states Kavita. By superimposing the collective data of Giosan and others, the team came to the conclusion that the decline in monsoon and consequent lack of water had led to the collapse of the Harappan civilisation. “The monsoon-fed Ghaggar-Hakra was their lifeline. With the monsoon shifting continually eastward, they began to get less and less water, and consequently little water was available for urban centres downstream. This would have forced the Harappans to move upstream to make use of the little water available, putting pressures on urbanism, finally leading to its decline,” explains Ronojoy.

In the past, several attempts had been made to fathom the reason for the mysterious decline of this highly evolved ancient civilisation with its great orderly cities, sophisticated construction, sanitation systems, arts and crafts, and writing. Well, if it was climate change that finished it off, maybe, we should take climate change more seriously. Or, history could repeat itself.

The rapid reduction in the Harappan sites between 2000 BCE and 1900 BCE can be seen graphically at