India's summer monsoons, vital for watering the country's farmlands, could see frequent failures in the next two centuries with global warming, researchers say.

The effects of such frequent and severe failures would be devastating to India's economy, they said.

Writing in the journal Environmental Research Letters, researchers at the Potsdam Institute for Climate Impact Research and Potsdam University in Germany said increasing temperatures and a change in strength of a Pacific Ocean circulation pattern known as the Pacific Walker circulation in spring could cause more frequent and severe changes in monsoon rainfall.

The Walker circulation usually brings areas of high pressure to the western Indian Ocean but in El Nino years this pattern gets shifted eastward, bringing high pressure over India and suppressing the monsoon, they said.

Computer simulations show that with future global warming the Walker circulation is likely to bring more high pressure over India even without an increase in El Nino events.

These failures of the monsoon system suggested by the simulation, defined as a 40 percent to 70 percent reduction in rainfall below normal levels, were unprecedented in the researchers' observational record, taken from the India Meteorological Department dating back to the 1870s.

"Our study points to the possibility of even more severe changes to monsoon rainfall caused by climatic shifts that may take place later this century and beyond," lead author Jacob Schewe said.