doi:10.1038/nindia.2017.93 Published online 27 July 2017
Indian monsoons have strengthened over past 15 years with more rain to come over northern and central India reversing a 50-year dry spell, says a new study by scientists at the Massachusetts Institute of Technology1.
The team tracked India's average daily monsoon rainfall from 1950 till now from the thousands of rain gauges in India, as well as measurements of rainfall and temperature from satellites monitoring land and sea surfaces.
They noted that since the 1950s, the Indian monsoons were bringing less rain to north central India but this trend started to reverse from 2002. A shift in India's land and sea temperatures may partially explain this increase in monsoon rainfall, they say. Starting 2002, nearly the entire Indian subcontinent has experienced very strong warming (reaching up to and 1 degree Celsius per year) while the Indian Ocean — which used to be warm — slowed its warming all of a sudden.
What exactly caused this reversal is not known yet, but the authors say "this sharp gradient in temperatures — high over land, and low over surrounding waters — is a perfect recipe for whipping up stronger monsoons." The authors say their study dismisses concerns that India, which is heavily polluted by manmade aerosols and also heavily deforested, is going to dry up.
On the contrary, "India has already begun to reverse its dry spell." But J Srinivasan, distinguished scientist at Divecha Centre for Climate Change in Bengaluru says the revival in the last 10 years could a part of the decadal variability of the Indian monsoon. "We need to wait for another 10 to 20 years before we can be certain that it is related to global climate change or is a part of the natural decadal variability."
1. Jin, Qinjian & Wang, Chien. A revival of Indian summer monsoon rainfall since 2002. Nat. Clim. Change (2017) doi: 10.1038/nclimate3348