In order to understand the early history of telluric interiors and atmospheres during the ocean magma stage, a coupled interior-atmosphere-escape model is being developed. This paper describes the atmospheric part and its first preliminary results. A unidimensional, radiative-convective, H2O-CO2 atmosphere is modeled following a vertical temperature profile similar to Kasting [1988] and Abe and Matsui [1988]. Opacities in the thermal IR are then computed using a k-correlated code (KSPECTRUM), tabulated continuum opacities for H2O-H2O and CO2-CO2 absorption and water or sulphuric acid clouds in the moist convective zone (whenever present). First results show the existence of two regimes depending on the relative value of the surface temperature TS compared to a threshold temperature Tc, function of the total gaseous inventory. For TS < Tc, efficient blanketing results in a cool upper atmosphere, a cloud cover and a long lifetime for the underneath magma ocean with a net thermal IR flux between 160 and 200 W/m2. For TS > Tc, the blanketing is not efficient enough to prevent large radiative heat loss to space through a hot, cloudless atmosphere. Our current calculations may underestimate the thermal flux in case of hot surfaces with little gaseous content in the atmosphere.