What are the values for DF2x/DT2x for the Hadley Centre GCM (HadCM3)?
DF2x and DT2x are the forcing and temperature change for a CO2 doubling respectively. For the IPCC process I tuned the MAGICC model to a number of GCMs and the tuning parameters are given in the TAR ch 9 Appendix 9.1 page 577. Thus for HadCM3 DF2x = 3.74 Wm-2 and DT2x = 3.0. These results are published in: Raper, S.C.B., Gregory, J.M., and Stouffer, R.J., 2002: The Role of Climate Sensitivity and Ocean Heat Uptake on AOGCM Transient Temperature Response. J. of Climate 124-130. But as pointed out in the above reference, you should be aware that the climate sensitivity of HadCM3 may be non-constant. However, for the UNFCCC experiments I [S. Raper] think that the DT2x value of 3.0°C would be appropriate.
