6.9.2. Greenhouse Feedbacks

GCMs have estimated the CO2 doubling temperature change in the absence of feedback processes to be approximately 1.2C. The existence of feedback loops within the climate system results in a climate sensitivity of 1.5C to 4.5C, and makes an otherwise linear association between radiative forcing and global temperature distinctly non-linear. Three of the most important direct climatic feedbacks to greenhouse forcing include the water vapour feedback, the cloud feedback and the ice-albedo feedback. (See also section 2.7).