And the CMIP experiments are conducted just for fun, not for the IPCC? And in the absence of such experiments, the IPCC should not be providing “very likely” confidence assessments regarding 20th century attribution.
I don’t expect much more from the AR5, although I thought overall the design of the CMIP5 simulations was better than the CMIP3 simulations.
In terms of 20th century attribution, natural internal variability gets one sentence in Ch9 AR4: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-4-1-2.html
“Variations in the Atlantic Multi-decadal Oscillation could account for some of the evolution of global and hemispheric mean temperatures during the instrumental period (Schlesinger and Ramankutty, 1994; Andronova and Schlesinger, 2000; Delworth and Mann, 2000); Knight et al. (2005) estimate that variations in the Atlantic Multi-decadal Oscillation could account for up to 0.2°C peak-to-trough variability in NH mean decadal temperatures.”