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CMIP5 Simulations of the Indian Summer Monsoon
Shashikanth, K., Salvi, K., Ghosh, S. and Rajendran, K. 2014. Do CMIP5 simulations of Indian summer monsoon rainfall differ from those of CMIP3? Atmospheric Science Letters 15: 79-85.

The authors write that "Indian summer monsoon rainfall (ISMR) provides more than 80% of the total annual rainfall in the country [of India] and directly relates to water resources, agriculture, ecosystem, health and food security," citing Webster et al. (1998) and Turner and Annamalai (2012). And, therefore, they say it is important to compare the performances of the newer CMIP5 models with those of the older CMIP3 models, in order to see what progress has been made in this ever-evolving field of research.

What was done
According to Shashikanth et al., a comparative study of ISMR projections was performed with (1) the original ISMR results derived from the two sets of general circulation models (CMIP3 and CMIP5), and (2) the statistically downscaled outputs of five GCMs from each of the two CMIP populations.

What was learned
The four Indian researchers discovered that the multi-model average of the more recent CMIP5 simulations does not exhibit any visible improvements in bias over the older CMIP3 simulations. And they add that the original CMIP5 simulations "have more multi-model uncertainty than those of CMIP3."

What it means
As stated in their concluding remarks, Shashikanth et al. indicate that their results highlight the facts that "even with the improvements in understanding of climate physics of CMIP5 (Taylor et al., 2012), the simulations of ISMR with coarse resolution climate models have become worse, with similar bias, but with higher uncertainties."

Taylor, K.E., Stouffer, R.J. and Meehl, G.A. 2012. An overview of CMIP5 and the experiment design. Bulletin of the American Meteorological Society 93: 485-498.

Turner, A.G. and Annamalai, H. 2012. Climate change and the South Asian summer monsoon, model projections. Nature Climate Change: 10.1038/nclimate1716.

Webster, P.J., Magana, V.O., Palmer, T.N., Shukla, J., Tomas, R.A., Yanai, M. and Yasunari, T. 1998. Monsoons: processes, predictability and the prospects for prediction. Journal of Geophysical Research 103: 14,451-14,510.

Reviewed 23 July 2014