The monsoon season in India has in the last 15 years recovered from a 50-year dry spell, during which the northern and central parts of the country received relatively lesser rain, a study led by researchers from the Massachusetts Institute of Technology (MIT) has claimed.
The findings showed that since 2002, the drying trend has given way to a much wetter pattern, with stronger monsoon supplying much-needed rain — along with powerful, damaging floods — to the populous north central region.
A shift in India’s land and sea temperatures may partially explain this increase in monsoon rainfall, the researchers said.
“Climatologically, India went through a sudden, drastic warming, while the Indian Ocean which used to be warm, all of a sudden slowed its warming,” said Chien Wang, a senior research scientist at MIT.
“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 added.
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.
This sharp gradient in temperatures — high over land, and low over surrounding waters — is a perfect recipe for whipping up stronger monsoon, Wang said.
For the new study, detailed in the journal Nature Climate Change, the team tracked India’s average daily monsoon rainfall from 1950 to the present day.
The team used six global precipitation datasets, each of which aggregate measurements from the thousands of rain gauges in India, as well as measurements of rainfall and temperature from satellites monitoring land and sea surfaces.
Between 1950 and 2002, the researchers found that north central India experienced a decrease in daily rainfall average, of 0.18 millimetres per decade, during the monsoon season.
However, they discovered that since 2002, the precipitation in the region has revived, increasing daily rainfall average by 1.34 millimetres per decade.
Although during the 2015, a brief drying period in the monsoon season that caused widespread droughts throughout the subcontinent was observed due to a severe El Nino season, “but even counting that dry year, the long-term [wetting] trend is still pretty steady”, Wang said.