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 S_eq) 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.