Study of the runaway greenhouse effect with a 3D global climate model

<p>The runaway greenhouse effect [1-4] is a very interesting process for terrestrial planets, studied in particular to determine the inner limit of the Habitable Zone (HZ). This limit is usually defined via the calculation of the asymptotic limit of thermal emission of the planet (OLR = Outgoing Longwave Radiation), also called Simpson-Nakajima limit. We have recently shown, using a 1D radiative-convective model, that a radiatively inactive gas such as nitrogen (N<sub>2</sub>) strongly modifies the OLR of the atmosphere [5] and can extend the inner edge of the HZ towards the host star [6]. We have also highlighted the importance of some physical processes sometimes considered as second order processes (e.g., collisional broadening of water lines).</p><p>In continuation of this work, we use a 3D global climate model, LMD-Generic, to study the onset of the runaway greenhouse for similar atmospheres. Some studies have shown that evaporation can lead to a moist stable state [7, 8], while others suggest an inevitable runaway greenhouse effect [9].</p><p>Here, we re-explore these possible moist stable states to better understand the key physical processes that potentially lead an Earth-like planet to a surface warming of several thousand degrees. We compare the results from 3D and 1D simulations, based on the conclusions of our previous study [5], in order to better understand the contribution of each process with a focus on clouds and dynamics, which are inherently three-dimensional processes.</p><p> </p><p><strong>References</strong></p><p>[1] Komabayasi, M. 1967, Journal of the Meteorological Society of Japan. Ser. II</p><p>[2] Ingersoll, A. 1969, Journal of the Atmospheric Sciences</p><p>[3] Nakajima, S., Hayashi, Y.-Y., & Abe, Y. 1992, Journal of the Atmospheric Sciences</p><p>[4] Goldblatt, C. & Watson, A. J. 2012, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences</p><p>[5] Chaverot G., Bolmont, E., Turbet, M., Leconte, J. 2021, Astronomy & Astrophysics</p><p>[6] Goldblatt, C., Robinson, T. D., Zahnle, K. J., & Crisp, D. 2013, Nature Geoscience</p><p>[7] Wolf, E. T., Toon, O. B. 2015, Journal of Geophysical Research</p><p>[8] Pop, M., Schmidt, H., Marotzke, J. 2016, Nature Communications</p><p>[9] Leconte, J., Forget, F., Charnay, B. et al., 2013, Nature</p>