Difference between 3D CEMP and 1D MARCS models as a function of metallicity. Top: Relative temperature difference (in percent). Middle: Logarithmic density differences (in dex). Bottom: CH/H number density fraction, where n* = n_CH/n_H is the CH number density relative to the hydrogen number density. Dashed blue lines correspond to T_eff = 5750 K, log(g) = 4.5 models, solid red curves to T_eff = 5250 K, log(g) = 3.0. The differences in each figure are computed at the representative formation height of the strong lines in the G band. See Sect. 3.2 for more information.