An MIT study published today in Nature Climate Change finds that the Indian summer monsoons, which bring rainfall to the country each year between June and September, have strengthened in the last 15 years over north central India.
This heightened monsoon activity has reversed a 50-year drying period during which the monsoon season brought relatively little rain to northern and central India. Since 2002.
the researchers have found, this drying trend has given way to a much wetter pattern, with stronger monsoons supplying much-needed rain, along with powerful, damaging floods, to the populous north central region of India.
A shift in India’s land and sea temperatures may partially explain this increase in monsoon rainfall. The researchers note that starting in 2002, nearly the entire Indian subcontinent has experienced very strong warming, reaching between 0.1 and 1 degree Celsius per year. Meanwhile, a rise in temperatures over the Indian Ocean has slowed significantly.
Chien Wang, a senior research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences, the Center for Global Change Science, and the Joint Program for the Science and Policy of Global Change, says this sharp gradient in temperatures — high over land, and low over surrounding waters — is a perfect recipe for whipping up stronger monsoons.
“Climatologically, India went through a sudden, drastic warming, while the Indian Ocean, which used to be warm, all of a sudden slowed its warming,” Wang says. “This may have been from a combination of natural variability and anthropogenic influences, and we’re still trying to get to the bottom of the physical processes that caused this reversal.”
Wang’s co-author is Qinjian Jin, a postdoc in the Joint Program for the Science and Policy of Global Change.