Impacts of Climate Change on the Indian Summer Monsoon

Book excerpt: Variability of the Indian summer monsoon has increased significantly since the 1950s. For several regions across India, this means an increase in long dry periods with low or no rainfall, intermittent with short, intense spells of rainfall. These changes are particularly significant for the western, central and eastern states of India where more than 55% of the cultivated area is largely rainfed and where the adaptive capacity is the lowest. The large-scale secular changes in monsoon rainfall are attributed to the increase in global emissions of greenhouse gases and air pollutants. At the same time, local changes through urbanization, land use changes and deforestation have brought in a non-uniform response in these rainfall trends. Changes in the onset, duration and intensity of the rainfall call for a reassessment of the crop calendar and climate resilient measures for the food-water-energy sectors of the country. Global warming has also altered the relationship between sea surface temperatures and other predictors of monsoon rainfall, introducing increasing challenges and uncertainties in the monsoon forecasts. Climate projections indicate a further increase in the monsoon variability and a shortening of the rainy season in the future, though there is considerable disagreement between model simulations.