I would guess that the slow feedbacks, at least the ones that are faster than tectonic plate movements, seem likely to be bad news rather than good news, so the classic sensitivity definition is an understatement. And there's Hansen's concern that the ice sheet feedbacks may not be so slow.
The climate sensitivity classically defined is the response of global mean temperature to a forcing once all the 'fast feedbacks' have occurred (atmospheric temperatures, clouds, water vapour, winds, snow, sea ice etc.), but before any of the 'slow' feedbacks have kicked in (ice sheets, vegetation, carbon cycle etc.).
Wednesday, August 15, 2007
Random new climate change fact re climate sensitivity
Didn't know this factoid before, from RealClimate: