In the concluding sentence of his paper's abstract, the U.S. researcher -- a Distinguished Senior Scientist in the Climate Analysis Section at the National Center for Atmospheric Research -- states that model-simulated precipitation "occurs prematurely and too often, and with insufficient intensity, resulting in recycling that is too large and a lifetime of moisture in the atmosphere that is too short, which affects runoff and soil moisture," while in the text of the paper he writes that "all models contain large errors in precipitation simulations, both in terms of mean fields and their annual cycle (such as the spurious migration of the Intertropical Convergence Zone into the other hemisphere), as well as their characteristics: the intensity, frequency, and duration of precipitation, plus the amount (e.g. IPCC, 2007; Bosilovich et al., 2008; Liepert and Previdi, 2009)." And he states that "it appears that many, perhaps all, global climate and numerical weather prediction models and even many high-resolution regional models have a premature onset of convection and overly frequent precipitation with insufficient intensity," citing the work of Yang and Slingo (2001) and Dai and Trenberth (2004).

Continuing, Trenberth states that "confidence in model results for changes in extremes is tempered by the large scatter among the extremes in modeling today's climate, especially in the tropics and subtropics (Kharin et al., 2007), which relates to poor depiction of transient tropical disturbances, including easterly waves, Madden-Julian Oscillations, tropical storms, and hurricanes (Lin et al., 2006)." These phenomena, in his words, "are very resolution dependent, but also depend on parameterizations of sub-grid-scale convection, the shortcomings of which are revealed in diurnal cycle simulations," wherein "models produce precipitation that is too frequent and with insufficient intensity (Yang and Slingo, 2001; Trenberth et al., 2003; Dai and Trenberth, 2004; Dai, 2006)."

In light of these several observations, Trenberth concludes that "major challenges remain to improve model simulations of the hydrological cycle." And until such is accomplished and it is proven that the models can at least correctly simulate something as basic as precipitation, it would seem unwise in the extreme to make major global-economy-impacting political decisions on so flimsy a basis as what today's climate models are currently predicting, not only with respect to the meteorological phenomena that are discussed by Trenberth, but with respect to the many other extreme weather and climatic events that the world's climate alarmists use to terrorize the public on a never-ending basis via their over-the-top rhetoric about impending catastrophic consequences if anthropogenic CO2 emissions are not drastically reduced.

Sherwood, Keith and Craig Idso

References
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Dai, A. 2006. Precipitation characteristics in eighteen coupled climate models. Journal of Climate 19: 4605-4630.

Dai, A. and Trenberth, K.E. 2004. The diurnal cycle and its depiction in the Community Climate System Model. Journal of Climate 17: 930-951.

IPCC. 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the IPCC. Solomon, S., Qin, D., Manning, M., Chen, Z. Marquis, M., Averyt, K., Tignor, M. and Miller H.L. (Eds.). Cambridge University Press, Cambridge, United Kingdom.

Kharin, V.V., Zwiers, F.W., Zhang, X. and Hegerl, G.C. 2007. Changes in temperature and precipitation extremes in the IPCC ensemble of global coupled model simulations. Journal of Climate 20: 1419-1444.

Liepert, B.G. and Previdi, M. 2009. Do models and observations disagree on the rainfall response to global warming? Journal of Climate 22: 3156-3166.

Lin, J.L., Kiladis, G.N., Mapes, B.E., Weickmann, K.M., Sperber, K.R., Lin, W., Wheeler, M.C., Schubert, S.D., Del Genio, A., Donner, L.J., Emori, S., Gueremy, J.-F., Hourdin, F., Rasch, P.J., Roeckner, E. and Scinocca, J.F. 2006. Tropical intraseasonal variability in 14 IPCC AR4 climate models. I. Convective signals. Journal of Climate 19: 2665-2690.

Trenberth, K.E. 2011. Changes in precipitation with climate change. Climate Research 47: 123-138.

Trenberth, K.E., Dai, A., Rasmussen, R.M. and Parsons, D.B. 2003. The changing character of precipitation. Bulletin of the American Meteorological Society 84: 1205-1217.

Yang, G.Y. and Slingo, J. 2001. The diurnal cycle in the Tropics. Monthly Weather Review 129: 784-801.