Changing global weather pattern causing concern

Written by ASHOK B SHARMA | Chidambaram, Jan 7 | Updated: Oct 15 2007, 19:34pm hrs
Experts are trying to find out the reasons behind the recent changes in the monsoon rainfall pattern in the country and ways to save farmers from the fast-changing global climate and vagaries of weather at the 94th Indian Science Congress, which concluded here on Sunday.

The topic assumed importance when Prime Minister Manmohan Singh, in his inaugural address on Wednesday, asked scientists to engage in exploring the links between greenhouse gas emissions and climate change. He also wanted them to examine its impact on monsoon rains and emphasised on the need to upgrade weather forecasting systems, which can help farmers.

The president of the Indian Science Congress Harsh Gupta quoting a recent detailed study done by BM Goswami and his colleagues at Punes Institute of Tropical Meteorology said, The study shows a significant rise in the frequency and the magnitude of extreme rain events and decreasing trend in the frequency of moderate events over central India. It also points that the seasonal mean rainfall does not show a significant trend as contribution from extreme event is compensated by a decrease in moderate events.

Monsoon system, although quite stable, shows intricate pattern of space-time variability, leading to floods and droughts. The causes of this variability is partly due to heating in the Bay of Bengal and also due to El Nino phenomena (warming of Pacific waters). Thus, according to the study both local and global dimensions of the problem are involved. In 2005 and 2006, the country had witnessed a unique shift in the monsoon rainfall pattern, heavy rains in drought-prone areas and low rainfall in flood-prone areas. Particularly, the west coast of the country received heavy rains, leading to floods at places

According to Manish Tiwari of the Goa-based National Centre for Antartic & Ocean Research (NCAOR), a recent high-resolution study has shown that the increase in rainfall over the west coast coincided with the first step of de-glaciation in central Asia and Tibetan plateau which enhanced the land-sea air pressure difference during summer.

Climatic Facts

In 2005 and 2006, the country had witnessed a unique shift in the monsoon rainfall atternheavy rains in drought-prone areas and low rainfall in flood-prone areas

The monsoon system does show an intricate pattern of space-time variability, leading to floods and droughts

Futuristic projections show that annual rainfall will increase by 3.4% in the Nilgiris and by 47% over Umiam, while winter rains will decrease in Tehri Garwal

Another study done by Dr Mihir K Dash of NCAOR alongwith Dr PC Pandey of Kharagpur-based Indian Institute of Technology and Dr SM Bhandari of Ahemdabad-based Space Application Centre revealed: Tele-connection between melting of Antartica Sea ice and the frequency of El Nino and Southern Occillation phenomena (ENSO). ENSO is responsible for droughts in different parts of the globe. Recently, India experienced the worst drought in the century in 2000 due to emergence of El Nino. According to Dr VN Sharda of Dehradun-based Central Soil and Water Conservation Research and Training Institute, annual rainfall are projected to increase at places and decrease in different parts of the country.

The study was done for the period 2071-2100. Futuristic projections show that annual rainfall would increase by 3.4% in Nilgiris in Tamil Nadu and by 47% over Umiam in Meghalaya, while winter rains would decrease over Tehri Garwal. Monsoon rains would decrease over Nilgiris and Poglur in Tamil Nadu and post-monsoon rains would decrease over Almas, Antisar in Gujarat.