WATER VAPOR AND THE DYNAMICS OF CLIMATE CHANGES
Article first published online: 2 JUL 2010
Copyright 2010 by the American Geophysical Union.
Reviews of Geophysics
Volume 48, Issue 3, September 2010
How to Cite
2010), Water vapor and the dynamics of climate changes, Rev. Geophys., 48, RG3001, doi:10.1029/2009RG000302., , and (
- Issue published online: 2 JUL 2010
- Article first published online: 2 JUL 2010
- Manuscript Accepted: 3 DEC 2009
- Manuscript Received: 29 JUN 2009
- climate change;
- water vapor;
- general circulation
 Water vapor is not only Earth's dominant greenhouse gas. Through the release of latent heat when it condenses, it also plays an active role in dynamic processes that shape the global circulation of the atmosphere and thus climate. Here we present an overview of how latent heat release affects atmosphere dynamics in a broad range of climates, ranging from extremely cold to extremely warm. Contrary to widely held beliefs, atmospheric circulation statistics can change nonmonotonically with global-mean surface temperature, in part because of dynamic effects of water vapor. For example, the strengths of the tropical Hadley circulation and of zonally asymmetric tropical circulations, as well as the kinetic energy of extratropical baroclinic eddies, can be lower than they presently are both in much warmer climates and in much colder climates. We discuss how latent heat release is implicated in such circulation changes, particularly through its effect on the atmospheric static stability, and we illustrate the circulation changes through simulations with an idealized general circulation model. This allows us to explore a continuum of climates, to constrain macroscopic laws governing this climatic continuum, and to place past and possible future climate changes in a broader context.