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Indian Monsoon Rainfall: Effects of Global Warming
Kripalani, R.H., Kulkarni, A., Sabade, S.S. and Khandekar, M.L.  2003.  Indian monsoon variability in a global warming scenario.  Natural Hazards 29: 189-206.

What was done
The authors note that monsoon rainfall is an important socio-economic feature of India, and that climate models suggest that global averaged temperatures are projected to rise under all scenarios of future energy use (IPCC, 2001), leading to "increased variability and strength of the Asian monsoon."  Hence, they examined Indian monsoon rainfall using observational data maintained by the Indian Institute of Tropical Meteorology that were collected from 306 stations distributed across the country over the 131-year period 1871-2001.

What was learned
Kripalani et al. discovered decadal variations running through the record that reveal "distinct alternate epochs of above and below normal rainfall," which epochs "tend to last for about three decades."  In addition, they report "there is no clear evidence to suggest that the strength and variability of the Indian Monsoon Rainfall (IMR) nor the epochal changes are affected by the global warming."  They also report that "studies by several authors in India have shown that there is no statistically significant trend in IMR for the country as a whole."  Last of all, they report that "Singh (2001) investigated the long term trends in the frequency of cyclonic disturbances over the Bay of Bengal and the Arabian Sea using 100-year (1890-1999) data and found significant decreasing trends [our italics]."

What it means
In the words of the authors, "there seem[s] to be no support for the intensification of the monsoon nor any support for the increased hydrological cycle as hypothesized by [the] greenhouse warming scenario in model simulations."  In addition, they say "the analysis of observed data for the 131-year period (1871-2001) suggests no clear role of global warming in the variability of monsoon rainfall over India."  Hence, the climate models appear to strike out with respect to both of their Asian monsoon-related projections.

Singh, O.P.  2001.  Long term trends in the frequency of monsoonal cyclonic disturbances over the north Indian ocean.  Mausam 52: 655-658.
Reviewed 13 August 2003