As we said in the paper there is a huge gulf between the original simple energy balance model from Budyko and the one we use. (dotearth.blogs.nytimes.com)
What I hear Gavin saying is that the complex models aren't really the basis for the 3 - 4 degrees but much simpler energy balance models and empirical evidence from paleoclimate. (realclimate.org)
But we also speak of «forcing» and «feedback» when emulating GCMs with simple energy balance models. (gfdl.noaa.gov)