Potential temperature of the deep adiabat of the four planets as a function of the internal water mixing ratio. Models taking into account the mean molecular weight effect are shown with a red dashed curve. Black stars highlight the actual models shown in Fig. 4. The dashed gray horizontal line gives the reference for a dry adiabat, and blue dots show the temperature expected for a usual two-layer moist adiabat. The scale on the right hand side of each plot yields the conversion in real temperature at the pressure level roughly corresponding to the quenching of CO inside each planet (~400 bar for Jupiter and Saturn and ~2000 bar for Uranus and Neptune).