The dT(CO2)x above is based on x*ln(CO2/280)/ln(2) using the BEST CO2 interpolation to 1958 and the Mauna Loa CO2 data from 1958 to present. GISS (Goddard Institute of Space Studies) Global land and ocean data and the Hadley Climate Research Unit version 4 Global surface temperature data set.
In this time scale, the no feedback "sensitivity" seems to be in the ballpark. We don't know what is in, or was in, the deep ocean pipeline though.
Is this the right way to look at the problem? Dunno, but it never hurts to consider other frames of reference.
UPDATE: Since some who will remain nameless require more...