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Changes in Global Precipitation Over Land in a Warming World
Reference
Sun, F., Roderick, M.L. and Farquhar, G.D. 2012. Changes in the variability of global land precipitation. Geophysical Research Letters 39: 10.1029/2012GL053369.

Background
The authors write that "with global warming, climate models project increased precipitation variability in most regions at daily (O'Gorman and Schneider, 2009), monthly (Benestad, 2006) and inter-annual (Rind et al., 1989; Held and Soden, 2006; Boer, 2009; Wetherald, 2010) timescales," while additionally noting that "expectations are for precipitation extremes in storm events to increase with the saturation vapor pressure in the atmosphere," citing Trenberth et al. (2003).

What was done
In a study designed to assess the virtues (or not) of climate model precipitation projections, Sun et al. analyzed "observations of monthly precipitation (1940-2009) over the global land surface using a new theoretical framework that can distinguish changes in global precipitation variance between space and time."

What was learned
The three Australian researchers report discovering that "on average, dry regions/months became wetter and wet regions/months became drier over the 1940-2009 period," and they say that "this conclusion holds in all available databases and also holds for 1940-1999." In addition, they further remark that the patterns observed "show no relationship to local or global changes in temperature," and that "if anything, these results constitute a slight decline in meteorological drought over the last 70 years."

What it means
Once again, some of the most basic predictions of the world's climate alarmists are found to be invalid for the entire world.

References
Benestad, R.E. 2006. Can we expect more extreme precipitation on the monthly time scale? Journal of Climate 19: 630-637.

Boer, G.J. 2009. Changes in interannual variability and decadal potential predictability under global warming. Journal of Climate 22: 3098-3109.

Held, I.M. and Soden, B.J. 2006. Robust responses of the hydrological cycle to global warming. Journal of Climate 19: 5686-5699.

O'Gorman, P.A. and Schneider, T. 2009. The physical basis for increases in precipitation extremes in simulations of 21st-century climate change. Proceedings of the National Academy of Sciences USA 106: 14,773-14,777.

Rind, D., Goldberg, R. and Ruedy, R. 1989. Change in climate variability in the 21st century. Climatic Change 13: 5-37.

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.

Wetherald, R.T. 2010. Changes of time mean state and variability of hydrology in response to a doubling and quadrupling of CO2. Climatic Change 102: 651-670.

Reviewed 15 May 2013