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A Twentieth-Century Rainfall History of India
Reference
Joshi, M.K. and Pandey, A.C. 2011. Trend and spectral analysis of rainfall over India during1901-2000. Journal of Geophysical Research 116: 10.1029/2010JD014966.

Background
In light of global warming projections made by models used by the Intergovernmental Panel on Climate Change (IPCC), the authors write that several scientists have suggested that "ocean temperature patterns in the tropics and subtropics will change in ways that will lead to noteworthy changes in rainfall patterns."

What was done
Based on precipitation data they obtained from 1384 rain-gauge stations maintained by the India Meteorological Department, Joshi and Pandy looked for both long-term trends and short-term cycles in the 100-year (1901-2000) gridded rainfall data for all of India, as well as its southwest (11.5°N-21.5°N, 73.5°E-76.5°E), southeast (8.5°N-16.5°N, 77.5°E-80.5°E), central (20.5°N-26.5°N, 79.5°E-85.5°E) and northwest (23.5°N-31.5°N, 71.5°E-76.5°E) sub-regions, while they calculated concomitant changes in global and regional sea surface temperature (SST) from the HadISST v.1.1 data set created by the Hadley Centre for Climate Prediction and Research, as reported by Rayner et al. (2003).

What was learned
The two researchers state that for all of India, as well as for each of its four sub-regions, there was substantial inter-decadal variability of annual rainfall that could be "attributed to the inter-decadal variability of eastern equatorial Pacific SST (Niņo 3) or Indian Ocean Dipole Mode," but they say that "no significant trend is discernable during the last ten decades, when the linear least squares fitting method and Mann-Kendall statistic to identify the trend and the normalized test statistic and statistical probability to quantify the significance of the trend are applied on the annual rainfall data for all India and its sub-regions."

What it means
Contrary to the implications of global climate models employed by the IPCC, the global warming of the past century -- which many of the contributors to its reports describe as being unprecedented over the past millennium or more -- has not led to any significant concomitant change in the mean annual rainfall of all of India or that of any of its four sub-regions.

Reference
Rayner, N.A., Parker, D.E., Horton, E.B., Folland, C.K., Alexander, L.V., Rowell, D.P., Kent, E.C. and Kaplan, A. 2003. Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. Journal of Geophysical Research 108: 10.1029/2002JD002670.

Reviewed 20 April 2011