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Indian Science Congress: Shift in monsoon patterns worries experts

india Updated: Jan 07, 2015 16:21 IST
Snehal Rebello
Uttarakhand floods

Tourists flocking to Uttarakhand and Himachal Pradesh in May and June may need to change travel plans and head to the north-east instead.

An analysis by the Delhi-based National Physical Laboratory (NPL) has found that early monsoon in hilly regions like Uttarakhand has increased at the expense of the normal monsoon months, while that in the north-east regions has decreased.

The data was presented at a session on climate change, a first at the 102nd Indian Science Congress on Tuesday, which had scientists talk about various factors influencing Indian monsoons and the need for robust planning to avoid natural disasters.

The research assumes significance in the backdrop of the June 2013 cloudburst in Uttarakhand that caused devastating floods and landslides resulting in loss of life and damage to property.

Temperature data between 1900 and 2010 for Uttarakhand showed that the temperature in the month of March, which is still considered winter for the hilly region, controlled rainfall for the four monsoon months in the region. Narrowing down the mean air temperature data further from 1990 to 2010 during March to May however tells a different story.

"The grip of March temperature on the rainfall is loosening," said Rajesh Agnihotri, scientist, radio and atmospheric sciences, NPL. "Post 1990, early monsoon intensity (May-June) is increasing over northwestern Himalayas, while a decreasing rainfall trend has been observed in the monsoon months of June, July, August and September (JJAS)."

"It appears that the major contributors towards decreasing JJAS rainfall are the months of June and August," added Agnihotri.

In addition to Jharkhand, Chattisgarh and Kerala, drought-prone Marathwada which has seen poor monsoons and farmer suicides over the last two years will receive even less rainfall. "Marathwada needs more attention. The government needs to do something extraordinary," said Agnihotri. "Policy makers should not make policies based on electoral strength."

Referring to the Uttarakhand disaster, geologist Dhruv Sen Singh, Centre for Advanced Study in Geology, Lucknow said, "Anthropogenic (manmade) factors are accelerating the change in climate. Himalayan glaciers are fast retreating and rivers are shrinking. The vacant land is being used for unplanned settlements and therefore there is a high risk of Uttarakhand-type of rain-led devastation."

"Artificial dams are constructed during summer when the river discharge is minimum; an example of bad planning. There is a need to calculate maximum water discharge that the river is capable of accommodating," Singh said.

* Polar region, especially the Arctic, does have an influence on the Indian monsoon system, said S Rajan, director, National Centre for Antarctic and Ocean Research, Goa.

* This is not a recent phenomenon. Studies have shown the link between cold episodes in North Atlantic and weakened Asian monsoon during the last glacial period as well as the Holocene. Holocene is a geological epoch which started when the glaciers began to retreat 11, 500 year ago and continues till today.

* Indian scientists have been actively working in the Antarctic region for 33 years, and 10 years in Arctic region.