For example the ozone production term for road traffic is the ozone production rate
multiplied by the fraction of road traffic NOx to total NOx. A comparison between the tagging method and the perturbation method is given in Section 2.2. The adjusted radiative forcing calculation (Dahlmann et al., 2011) was performed with the E39 climate model, separately for each tagged ozone field taking into account the seasonal cycle. For Fig. 1a, simulations were performed with the box model Caaba/MECCA (Sander et al., 2011).