Milliman, J.D., Farnsworth, K.L., Jones, P.D., Xu, K.H. and Smith, L.C. 2008. Climatic and anthropogenic factors affecting river discharge to the global ocean, 1951-2000. Global and Planetary Change 62: 187-194.
The authors write that global warming "could accelerate the hydrologic cycle (e.g., Trenberth, 1999; New et al., 2001; Huntington, 2006) .. leading to increased river discharge."
What was done
To explore what may have happened in this regard over the last half of the 20th century, Milliman et al. computed temporal discharge trends for 137 rivers that provide what they call a "reasonable global representation," as their combined drainage basins represent about 55% of the land area draining into the global ocean.
What was learned
In the words of the five researchers, "between 1951 and 2000 cumulative discharge for the 137 rivers remained statistically unchanged." In addition, they report that "global on-land precipitation between 1951 and 2000 remained statistically unchanged."
What it means
In a simple and straightforward conclusion, Milliman et al. write that "neither discharge nor precipitation changed significantly over the last half of the 20th century, offering little support to a global intensification of the hydrological cycle," such as is generally claimed by climate alarmists to be a consequence of CO2-induced global warming.
Huntington, T.G. 2006. Evidence for intensification of the global water cycle: review and synthesis. Journal of Hydrology 319: 83-95.
New, M., Todd, M., Hulme, M. and Jones, P. 2001. Precipitation measurements and trends in the twentieth century. International Journal of Climatology 21: 1899-1922.
Trenberth, K.E. 1999. Conceptual framework for changes of extremes of the hydrological cycle with climate change. Climatic Change 42: 327-339.Reviewed 25 June 2008