Annan's comments are consistent with the body of mainstream climate science research, and most of his colleagues believe that climate sensitivity is most likely close to 3°C surface warming in response to doubled CO2; unlikely to be more than 4.5°C or less than 2°C. One good example of this was Hansen et al. (2008), which concluded that equilibrium climate sensitivity is
"3 ± 1°C for the 4 W/m2 forcing of doubled CO2."
And the probable range of equilibrium climate sensitivity cited by Annan is fully consistent with the body of scientific literature (Figure 2).
Really all Annan is disputing is the 'long tail' of possible climate sensitivity values above 4.5°C, which Annan believes are more improbable than the IPCC report has stated. Nevertheless, the 'long tail' represents very low probability scenarios even in the IPCC report.