Kumar, V., Jain, S.K. and Singh, Y. 2010. Analysis of long-term rainfall trends in India. Hydrological Sciences Journal 55: 484-496.
The authors write that "the study of precipitation trends is critically important for a country like India, whose food security and economy are dependent on the timely availability of water." And since they say that "according to the Intergovernmental Panel on Climate Change (IPCC, 2007), future climate change is likely to ... increase the risk of hunger and water scarcity," such that "freshwater availability in many river basins in India is likely to decrease due to climate change (Gosain et al., 2006)," they felt it extremely important to investigate what might have occurred in this regard over the Little Ice Age-to-Current Warm Period transition, noting that "Pant and Kumar (1997) analyzed the seasonal and annual air temperatures from 1881-1997 and have shown that there has been an increasing trend of mean annual temperature at the rate of 0.57°C per 100 years," and that "Singh et al. (2008) found a warming trend in seven of the nine river basins in northwest and central India."
What was done
Working with rainfall data obtained from a network of 306 stations from 30 meteorological sub-divisions covering the whole of India (excluding islands) that were supplied them by the India Meteorological Department -- which they say "carries out quality checks to ensure that error-free data are used in analysis and design" -- Kumar et al. analyzed numerous rainfall parameters in their search for trends that may have been caused by, or at least associated with, the concomitant warming that occurred over the 135-year period of 1871-2005.
What was learned
In the words of the three researchers, "half of the sub-divisions showed an increasing trend in annual rainfall, but for only three was this trend statistically significant." Similarly, they state that "only one sub-division indicated a significant decreasing trend out of the 15 sub-divisions showing decreasing trend in annual rainfall." In terms of monthly rainfall during the monsoon months of June to September, they found that "during June and July, the number of sub-divisions showing increasing rainfall is almost equal to those showing decreasing rainfall," and in August they say that "the number of sub-divisions showing an increasing trend exceeds those showing a decreasing trend, whereas in September, the situation is the opposite." In addition, they report that "the majority of sub-divisions showed very little change in monthly rainfall in most of the months," while "for the whole of India, no significant trend was detected for annual, seasonal, or monthly rainfall."
What it means
In every way that the data could be analyzed, Kumar et al. could find no hint of the decrease in rainfall that the IPCC had suggested would occur over India as that country -- and the world -- warmed at a rate and to a level that that organization continues to claim was unprecedented over the past millennium or more.
Gosain, A.K., Rao, S. and Basuray, D. 2006. Climate change impact assessment on hydrology of Indian river basins. Current Science 90: 346-353.
IPPC (Intergovernmental Panel on Climate Change). 2007. Summary for policymakers. In Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L. (Eds.) Climate Change 2007: The Physical Science Basis. Cambridge University Press, Cambridge, United Kingdom.
Singh, P., Kumar, V., Thomas, T. and Arora, M. 2008. Basin-wide assessment of temperature trends in the northwest and central India. Hydrological Sciences Journal 53: 421-433.Reviewed 1 June 2011