Stone: Our group at MIT is currently working on including other important forcings, such as solar irradiance and land-use changes, in simple climate models.
Mahlman: The low inferred paleo-estimation of climate sensitivity (presumably Seq) needs further explaining. The original Milankovich orbital climate forcing that preceded the last ice age was originally -1 Wm−2. Roughly 10,000 years later, the inferred effective total forcing was roughly -4 to 6 Wm−2. The total positive feedbacks that led to this remarkably large climate cooling came mainly from ice albedo, water vapor, and CO2 feedbacks. However, these inferred large positive feedbacks do not necessarily imply higher-than-expected positive feedbacks in the human-caused climate warming problem that we currently face.