Water vapor and lapse rate feedbacks in the climate system

Water vapor is the most important greenhouse gas in Earth's atmosphere, absorbing more solar terrestrial radiation than any other atmospheric constituent. Because vapor concentrations increase exponentially with temperature, the interaction of water vapor with the vertical thermal structure of the atmosphere introduces a critical positive climate feedback to planetary warming induced by anthropogenic greenhouse gases. This article describes the relevant physical processes, empirical evidence for the feedbacks, representation of these processes in global models of the Earth system, and gaps requiring further research.