The key is to redo their work, use a series of models with a wide range of climate sensitivity parameters... you know what to do. (judithcurry.com)
By assuming a constant climate sensitivity parameter, forcing can be translated directly into a temperature response. (nap.edu)
A Cess climate sensitivity parameter λ can then be computed as λ = ΔTs / ΔG, where Ts denotes global mean SST, G is TOA net radiative flux, and Δ indicates the difference between warming and present - day simulations» (climateaudit.org)