The manuscript uses a simple energy budget equation (as employed e.g. by Gregory et al 2004, 2008, Otto et al 2013) to test the consistency between three recent «assessments» of radiative forcing and climate sensitivity (not
really equilibrium climate sensitivity in the case of observational studies).
Not exact matches
The other major problem here is that you can't
really compare a trend against against
equilibrium sensitivity; you're better to compare with the transient
climate response.
Once you go way back in time, it's questionable whether the concept of
sensitivity really applies (it needs an
equilibrium climate to exist, for starters).
As you've said, «Once you go way back in time, it's questionable whether the concept of
sensitivity really applies (it needs an
equilibrium climate to exist, for starters).»