So it's clear that carbon dioxide is a strong greenhouse gas. But what about water vapor? Water vapor is also a strong greenhouse gas, but it stays relatively constant and falls out of the atmosphere quickly (as compared to carbon dioxide which stays in the atmosphere for hundreds of years). More importantly, water vapor is a positive feedback in the climate and is very sensitive to carbon dioxide warming. That is, when carbon dioxide increases and the globe warms, the amount of water vapor in the atmosphere increases as well, due to increased evaporation, and this causes the atmosphere to get even warmer. This is a well known process, and current climate models take this into account.
Friday, January 7, 2011
Carbon Dioxide Forcing
A spectrum of the greenhouse radiation showing the effects of carbon dioxide versus other greenhouse gases (Evans et al., 2006):