1. Trends in Tropical Water Vapor (1980-2004): Satellite and GCM Comparison Satellite Observed ---- Model Simulated __ Held and Soden 2006: Robust Responses of the hydrological cycle to global warming, J Climate, 19, 3354-3360. Total column water vapor over tropical oceans has increased over the past 20 years Models accurately reproduce the observed variability and moistening of the tropical atmosphere.

2. Impact of Convectively Detrained Cloud Ice On Upper Tropospheric Water Vapor Satellite Observations (AIRS/MLS) GCM Simulations (IPCC AR4) John and Soden, 2006: Does convectively-detrained cloud ice enhance water vapor feedback?, Geophys. Res Lett., 33, L20701. Spatial distribution of upper tropospheric water vapor is strongly correlated with amount of cloud ice Models capture observed correlation between cirrus ice and upper tropospheric water vapor. Water vapor feedback is insensitive to strength of relationship between cloud ice and water vapor

3. A Comparison of AIRS Water Vapor Retrievals with GCM Simulations John and Soden, 2007: Temperature and humidity biases in IPCC AR4 models, in preparation. Zonal Annual Mean Bias in Relative Humidity Compared to AIRS Retrievals ECMWF/NCEP Reanalyses IPCC AR4 GCMs Both IPCC AR4 GCMs and NCEP/ECMWF reanalyses produce a more humid troposphere than indicated by AIRS retrievals.

4. Weakening of the Walker Circulation due to Anthropogenically-Forced Changes in the Hydrological Cycle Vecchi et al. 2006: Weakening of the tropical Pacific atmospheric circulation... Nature, 441, 73-76. Change in Sea Level Pressure (1861-1992) ObservedModel Simulated Climate models predict a weakening of the Walker circulation in response to hydrological cycle changes in a warmer climate. Observations from 20 th Century reveal changes in SLP consistent with model projected weakening of Walker Cell.