FAQ
| 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. |
| How were the values of the HadCM3 climate model parameters on the web site calculated? |
| They were calculated using routines provided by Visual Numerics as part of their product PV-WAVE. The routines in question were LINLSQ and CONVOL1d. An alternative fit to the HadCM3 temperature data, using a different method, was performed by Jesper Gunderman who found a value for Tfinal that was 3% less than the value on the web page. |
| What should I use as constant life times for CH4, N2O, PFCs, HFCs and SF6? |
| Take lifetimes from the IPCC TAR WG I, Table 4.1(a) and (b), page 244. These are the same as in Chapter 6, table 6.7, page 388. For CH4 and N2O take the value that considers chemical feedback: 12 years (CH4) and 114 years (N2O) These are the lifetimes used for the calculation of the GWPs in the TAR. |