Figure 9.9

Figure 9.9. Estimated contribution from greenhouse gas (red), other anthropogenic (green) and natural (blue) components to observed global mean surface temperature changes, based on ‘optimal’ detection analyses (Appendix 9.A). (a) 5 to 95% uncertainty limits on scaling factors (dimensionless) based on an analysis over the 20th century, (b) the estimated contribution of forced changes to temperature changes over the 20th century, expressed as the difference between 1990 to 1999 mean temperature and 1900 to 1909 mean temperature (°C) and (c) estimated contribution to temperature trends over 1950 to 1999 (°C per 50 years). The horizontal black lines in (b) and (c) show the observed temperature changes from the Hadley Centre/Climatic Research Unit gridded surface temperature data set (HadCRUT2v; Parker et al., 2004). The results of full space-time optimal detection analyses (Nozawa et al., 2005; Stott et al., 2006c) using a total least squares algorithm (Allen and Stott, 2003) from ensembles of simulations containing each set of forcings separately are shown for four models, MIROC3.2(medres), PCM, UKMO-HadCM3 and GFDL-R30. Also shown, labelled ‘EIV’, is an optimal detection analysis using the combined spatio-temporal patterns of response from three models (PCM, UKMO-HadCM3 and GFDL-R30) for each of the three forcings separately, thus incorporating inter-model uncertainty (Huntingford et al., 2006).