On the Robustness of the Water Vapor Feedback: GCM Vertical Resolution and Formulation

Abstract

Expectations of the size of climate change are generally based on models in which relative humidity (RH) changes little under climate change. A wide variety of general circulation models (GCMs) show such a response, but it has been suggested that this may be an artifact of their having inadequate vertical resolution, and that in reality the climate is much less sensitive to external forcing. This paper compares GCM simulations with a wide range of vertical resolutions, as well as completely different schemes for convection or advection. All these cases show similar water vapor feedbacks, suggesting that the consensus of GCMs on this feedback may well be correct.