Planetary and exoplanetary Astronomy Lunch Seminar (PALS) for 2022-10-31

Series: Planetary and exoplanetary Astronomy Lunch Seminar (PALS)
Date: Monday 31-October-2022
Time: 11:15-12:15
Location: Zoom
Speaker: Guillame Chaverot
Title: First exploration of the entire runaway greenhouse transition with a 3D global climate model

Abstract: The new generation of telescopes will detect an increasing number of small, rocky, temperate exoplanets (e.g., PLATO, NIRPS, ExTrA) and characterize the best targets of them (e.g., JWST, RISTRETTO, HIRES, METIS). The runaway greenhouse is an important process for terrestrial planets, studied in particular to determine the inner limit of the habitable zone (HZ). This unstable state also distinguish two possible families of terrestrial atmospheres: atmospheres with habitable temperatures, and atmospheres with extreme temperatures and pressures - thus highly uninhabitable. Therefore, the understanding of the runaway greenhouse is pivotal to assess the possible evolution of terrestrial planets.

Using a 1D radiative-convective model, we have shown that a radiatively inactive gas like nitrogen (N2) strongly modifies the thermal emission of the atmosphere and the onset of the runaway greenhouse. We have also highlighted the importance of some physical processes too often relegated as second order (e.g. collisional broadening of water absorption lines). In the lineage of this effort, we use here a 3D global climate model, the Generic-PCM, to study the onset of the greenhouse effect for the same type of atmosphere. Our goal is to link these simulations at moderate temperature to the results obtained at high temperature (beyond the runaway greenhouse) for similar planets. This is necessary to draw a more detailed picture of this transition, taking into account all global climate processes. We also compare the results of 3D and 1D simulations, based on the findings of our previous study, to better understand the contribution of intrinsically three-dimensional processes such as clouds and large-scale atmospheric dynamics.

For further information contact PALS coordinator Tad Komacek at


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