KOLKATA, 5 JULY: Disappointing monsoon and delay in its onset indicate shift in monsoon activity on the Indian region as a whole due to climate change, say climate experts.
According to the Indian Meteorological Department (IMD), seasonal rainfall during this year’s monsoon (till 27 June) has been 23 per cent below the long period average (LPA). The cumulative seasonal rainfall was below normal in all the regions except east and northeast India, where it was above normal by 4 per cent from LPA.
Gangetic West Bengal suffered a rainfall deficit of as much as 46 per cent.
West Bengal apart, states of Jammu and Kashmir, Uttarakhand, Madhya Pradesh, Bihar Jharkhand, Chattisgarh, Andhra Pradesh, Maharastra, Karnataka and Tamil Nadu also bore the brunt of an erratic monsoon and so far have rainfall deficit of 22 to 59 per cent.
The state action plan for climate change, which has been compiled by several scientists and climatologists, states that a general late onset coupled with late withdrawal suggests a shift in the monsoon activity in the country.
The onset of Monsoons in the country starts from Andaman and Nicobar Islands and enters other states as the monsoon progresses north. The maximum delay in onset of monsoon over Andaman and Nicobar Islands, has been observed to be 11 days in the period 1941-1970 and the delay has been maximum by seven days between 1971-2000.
The mean withdrawal dates are found to be later than the existing normal, in both the 30 years slot of 1941-1970 and 1971-2000, by about one to one and a half week.
A recent report of the IMD (Status of Climate in India, 2010, IMD) indicates that there are distinctive changes in observed pattern of rainfall between 1901 and 2003 between the northern (Darjeeling, Jalpaiguri Cooch Behar, Uttar Dinajpur and Dakshin Dinajpur, and Malda) and southern regions of West Bengal (the rest of the districts from Malda south-ward).
The report interpreted that the state is facing inadequate and erratic rainfall in successive years mainly in south Bengal Districts. More than 80 per cent of annual precipitation occurs during monsoon and that too erratically, causing drought like situations in summer and flood during monsoons. The onset of monsoon is also delayed. There is an overall warming with minimum temperatures increasing faster than the maximum temperatures, as happened during the summers this year.
An analysis of total annual rain fall between 1990 and 2008, for the six agro-climatic zones in West Bengal, carried out using the rainfall statistics published in the district handbooks, indicate that there is an overall decrease in the total rain in 2008 with respect to 1990 in the Terai zone, New Alluvial zone, Old Alluvial zone, Red and Laterite zone, and the Saline Coastal zone except for the hill zone.