Transit spectrum generated by Pytmosph3R from the outputs of a GCM simulation of GJ 1214 b (Charnay et al. 2015). The black curve represents the effective radius obtained when accounting only for the part of the atmosphere explicitly modelled by the GCM (down to ~ 0.5 Pa). The blue curve shows the result when the model is extended by an isothermal atmosphere down to 10⁻⁴ Pa. Further lowering the pressure of the model top does not alter the spectrum.