Anteros, I’m sorry I missed your question to me about Hansen’s thoughts on long term sensitivity.
The distinction he draws between slow and fast feedbacks is fine and serves as a widely recognizable characterization of what he is describing.
The value of about 3 for the standard “Charney” equilibirum sensitivity is also unexceptional; it’s just background to the discussion, referring to the current best available rough estimate.
The longer term sensitivity he means needs feedbacks that are slower than the response of the ocean to come up to an approximate thermal equilibrium. They are a proposed gradual response to the new higher temperature reached after the Earth comes into energy balance again.
The value he proposes, of 6 degrees, on the other hand, is not generally accepted. Nor is it easily rejected or falsified, given the time scales. The testing of those ideas needs to be more indirect (which is okay in principle) but will need much better modeling. For my own part, I don’t think a single number makes a lot of sense; since the magnitude of the kinds of response being considered is unlikely to be even approximately linear, I think. But going into my reasons would be another topic; and I’m not really an expert anyway.