Nevertheless, an estimate of total climate sensitivity that considers all feedbacks is crucial for checking these model results. (usask.ca)
In order to avoid controversy, let me define a new quantity, what I call the ab initio Total Climate Sensitivity (aiTSC). (judithcurry.com)
Analysis of the Pliocene (c.f. the Nature geoscience article by Lunt et al) would tend to support total climate sensitivities at or even beyond the high end of the IPCC range (I make that about 4.5 C for a doubling, extrapolating from Lunt's Pliocene warming). (dotearth.blogs.nytimes.com)