Climate Change and Consequential Rainfall Trends: An Indian Perspective

This article presents an overview of different studies pertaining to the trends observed in rainfall over India and its constituent regions. The spatial scale of trend estimation considered in the reviewed studies is an important aspect that dictates the overall trends over a given scale and helps in ascertaining the influence of anthropogenic activities upon the resultant trends. In this article, Indian trend analysis studies conducted on a national, meteorologic sub-divisional, river basin and agro-climatic zonal level as well as for different time periods and time scales have been reviewed. One of the more recent national-scale studies were able to detect overall negative trends in the annual rainfall over India with a more prominent decline observed during the latter half of the 20th century and first decade of 21st century. Also, 17 out of 30 meteorological sub-divisions for which trend analysis was carried out exhibited increasing tendencies though, all were insignificant. Most of the river basins of India have shown an increasing trend in annual rainfall with Indus (lower) and Tapi basins observing maximum rise. Decreasing trends were however, recorded over most of the basins especially after 1970. The conclusions drawn from the review of suitable studies highlight the variation in trends across different studies due to a different set of variables and factors involved in individual studies. The practical significance of trend analysis has also been discussed along with a need of a more subjective assessment of the mathematical outputs obtained from commonly used trend analysis methods.