Top panel: temperature profiles of the average ⟨3D⟩ model (T_eff = 5020 K, log g = 2.5, and [M/H]  = −3.0) calculated with scattering treated as true absorption (red solid line) and with scattering opacity neglected at small τ_Ross (red dashed line). Black lines mark the 5th and 95th percentiles of the temperature distribution in the 3D model with scattering treated as true absorption (solid lines) and scattering opacity neglected in optically thin regions (dashed lines). Horizontal bars indicate the approximate location where lines of several trace elements form at λ = 400 nm and χ = 0 and 4 eV and of the CO molecule at λ = 400 nm and χ = 0 and 3 eV (bars mark the regions where the equivalent width, W, of a given spectral line grows from 5% to 95% of its final value). Bottom panel: difference in the temperature profiles corresponding to the average ⟨3D⟩ models calculated with the two different treatments of scattering.