Change in climate in India during last few decades

Abstract

Classification of Indian geography based on climate was done long back. The climate datasets used in such studies were very old from now. Climate change literature about India showed enough evidence of rising mean temperatures during post 1970 period. The rising temperatures would affect potential evapo-transpiration and consequently aridity is expected to increase at least at the macro level though there may be spatial variation at a smaller geographical scale. It is considered important to reassess state-wise extent of area under arid, semi-arid, dry sub-humid climates using more recent climatic data. The present study used 0.5° x 0.5° grid level rainfall data and average potential evapo-transpiration for 144 stations located across India for the time period 1971-2005 to compute moisture index needed for delineation of different climatic zones. The study examined state-wise changes occurred in the area under arid, semi-arid zones over time. Arid region was found to increase in Rajasthan, Gujarat and Karnataka. Semi-arid zone has expanded in Madhya Pradesh, Uttar Pradesh, Andhra Pradesh, Maharashtra and Tamil Nadu. Some of the moist sub-humid pockets in Orissa, Chhattisgarh and Jharkhand turned dry sub-humid. The revisited moisture availability calls for a relook at choice of crops in the states. An attempt was made to estimate state-wise net sown area experiencing moisture stress when climate and irrigation components are considered together. About 40 % of net sown area (56 m ha) of India is under dry climate and constrained irrigation. It is mainly concentrated in Maharashtra, Rajasthan, Karnataka, Gujarat and Andhra Pradesh. Appropriate developmental programmes are to be planned in the regions getting drier.