While an updating of the simplified expressions to account for the stratospheric adjustment becomes necessary for radiative forcing estimates, it is noted that GCM simulations of CO2-induced climate effects already account for this physical effect implicitly (see also Chapter 9). In some climate studies, the sum of the non-CO2 well-mixed greenhouse gases forcing is represented by that due to an equivalent amount of CO2. Because the CO2 forcing in the SAR was higher than the new estimate, the use of the equivalent CO2 concept would underestimate the impact of the non-CO2 well-mixed gases, if the IPCC values of radiative forcing were used in the scaling operation.