We will present results from ongoing research that involves assessing the extent that the global hydrological cycle (GHC) is projected to accelerate under future climate change conditions. We analyze 20th and 21st century general circulation models (GCMs) simulations contributed to the IPCC's 4th Assessment Report (AR4). This analysis includes evaluating changes projected in precipitation, evaporation and precipitable water on interannual, subseasonal, synoptic and diurnal time scales. We examine both global changes as well as basin/regional changes. For a measure of validation, we draw on a number of satellite estimates where available and appropriate (e.g., SSM/I, GPCP) and we evaluate the level of agreement in these projections to provide a measure of uncertainty.