Pre-monsoon showers, or rainfall in the months of March, April and May, that have usually been a good pointer to the timing of the summer monsoon, have been steadily on the increase over northern India in the last two decades, said K. Krishnakumar, a leading meteorologist at the Indian Institute of Tropical Meteorology (IITM).
While pre-monsoon showers do not directly affect India’s agricultural productivity, as they account for little over 3% of the country’s annual rainfall, meteorologists say these showers do give a good sense of the timing of the summer monsoon, which accounts for over 80% of India’s annual rainfall, and is crucial to the country’s agricultural health.
However, Krishnakumar doesn’t say whether global warming was responsible for the gradual development of the pre-monsoon showers, in line with climatologists across leading research institutions in India. “If it was global warming, temperatures should have been increasing, right?” he asks.
On an average, this May has been the coolest in 20 years for the Capital, with temperatures touching 41 degree Celsius, only four times, as opposed to the usual 10-15 times, if averaged over the last 15 years.
Krishnakumar did note that global warming-induced climate change involved a lot of climate factors, which are being researched in institutes across the world.
Governments across the world are figuring out ways to mitigate the possible impact of climate change. India, whose coastlines stand to be adversely affected if global warming raises temperatures between 1-2 degrees by 2050, has recently constituted a committee to assess the impact of climate change over India.
A new programme called “Climate Dynamics and Extended Range Prediction of Monsoon,” is likely to take shape at the IITM, say people familiar with the idea. High on the programme’s agenda is estimating the monsoon climate under different climate change scenarios.
Pre-monsoon showers follow a phenomenon called Western Disturbances, an air-trough movement , which originates over parts of Europe and Central Asia and passes over North India, bringing rainfall along with it.
“If these disturbances build up, they could be a barrier to the incoming monsoon from Kerala,” said Ravi Nanjundiah, a senior climatologist at the Indian Institute of Science, Bangalore.
S. Raghuraman, a trade analyst with Agriwatch, an independent research and consultancy firm, said that as most of Punjab, Haryana and Uttar Pradesh depended on irrigation, pre-monsoon showers didn’t make or break production. “But some of the kharif crop in the Northeast, such as paddy, are somewhat dependent on the pre-monsoon showers,” he added.
Madhavan Rajeevan, Director, National Climate Centre, Pune which is responsible for India’s official monsoon forecasts, said: “This year the disturbances have been unusually high, but last year, and the years before that, it was rather weak.” He said it would be premature to attribute patterns and trends to the western disturbances.
Scientists say that even though there might be variations in rainfall, the net average rainfall has pretty much remained the same. “The only noteworthy point is a decadal increase and decrease in rainfall, over the last 100 years,” said S. K. Dash, a professor in the atmospheric sciences department at IIT, Delhi.