Observing that there are significant changes and a definite shift in temperature and rainfall patterns, both temporally and spatially across India in view of climate changes in the recent past compared to 1951-1980, scientists from the Indian Meteorological Department (IMD) have said it is time to reconsider the classification of country's agro-climatic zones.
The then Planning Commission of India (now known as Niti Aayog) has divided the country into fifteen broad agro-climatic zones on the basis of physiography, soils, geological formation, climate, cropping patterns, and development of irrigation and mineral resources for extensive agricultural planning and developing future strategies.
Using various long-term gridded data from 1985 and instrumental datasets starting from 1951 to 1980, IMD scientists examined the trends and spatial/temporal variability of temperature, rainfall, rainy days, and heavy rainfall in different agroclimatic zones of the country, to help better understanding of the further initiatives on reclassification of agroclimatic zones, if required.
The team comprising scientists N Chattopadhyay, A K Sahai, P Guhathakurta, S Dutta, R Balasubramanian, K Malathi, Swati Chandras, A K Srivastava from India Meteorological Department, Shivajinagar, Pune and S D Attri from IMD Delhi office, noted the regions were witnessing significant changes and shift in the patterns of temperature and rainfall. For instance, increasing temperature is affecting Indian agriculture by reducing the productivity of rabi crops like wheat and mustard.
At the national level, an increase of 0.4°C has been observed in surface air temperature during the past century.
Analysis of minimum temperature trends in the country indicates no significant changes in various regions, except significant warming trends observed over most of the states during the monsoon season in various temporal scales, said the study.
Following analysis, the scientists also noted that there were great regional and temporal variation in the distribution of rainfall. For instance, over 80% of the annual rainfall is confined to the four rainy months from June to September. In winter, the northern part of the country and during pre-monsoon season, West Bengal and adjoining states and also NE India receive rainfall due to thunderstorm activities.
This is the first of its kind comprehensive, and relatively long-term assessment of climate change for agroclimatic zones in the country.