First exploration of the entire runaway greenhouse transition with a 3D global climate model

<p align="justify"><span lang="en-US">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). </span><span lang="en-US">This is also important to understand a possible evolution of </span><span lang="en-US">terrestrial planets </span><span lang="en-US">from </span><span lang="en-US">temperate </span><span lang="en-US">Earth-like planets </span><span lang="en-US">to</span> <span lang="en-US">magma-ocean</span><span lang="en-US"> planets. </span><span lang="en-US">This runway greenhouse transition is </span><span lang="en-US">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 (N2) 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 </span> <span lang="en-US">(e.g., collisional broadening </span><span lang="en-US">of water lines)</span><span lang="en-US">.</span></p> <p align="justify"><span lang="en-US">In continuation of this work, we use a 3D</span><span lang="en-US"> global climate model, LMD-Generic, to study the runaway greenhouse for similar atmospheres. </span><span lang="en-US">First, we explore the runaway evaporation </span><span lang="en-US">in a temperature range that goes</span><span lang="en-US"> beyond every previous work </span><span lang="en-US">which </span><span lang="en-US">only </span><span lang="en-US">studied up to the tipping point </span><span lang="en-US">[7,8]. </span><span lang="en-US">We aim to </span><span lang="en-US">understand the contribution of the inherently three-dimensional processes (e.g. </span><span lang="en-US">clouds and </span><span lang="en-US">dynamics) </span><span lang="en-US">to</span><span lang="en-US"> the evolution of the atmosphere</span><span lang="en-US">. </span><span lang="en-US">We find strong differenc</span><span lang="en-US">e</span><span lang="en-US">s with 1D simulations but also with the usual climat</span><span lang="en-US">e</span><span lang="en-US"> pattern of temperate stable states. Second, w</span><span lang="en-US">e also explore the evolution of the atmosphere when the entire water ocean is evaporated, and the convergence on a post-runaway state. This allow us to have a complete overview of the runway transition by linking our results to previous studies of hot </span><span lang="en-US">Earth-like</span><span lang="en-US"> planet</span><span lang="en-US">s</span><span lang="en-US"> [</span><span lang="en-US">9</span><span lang="en-US">].</span></p> <p lang="en-US" align="justify"> </p> <p lang="en-US"> </p> <p lang="en-US"><strong>References</strong></p> <p lang="en-US">[1] Komabayasi, M. 1967, Journal of the Meteorological Society of Japan. Ser. II</p> <p lang="en-US">[2] Ingersoll, A. 1969, Journal of the Atmospheric Sciences</p> <p lang="en-US">[3] Nakajima, S., Hayashi, Y.-Y., & Abe, Y. 1992, Journal of the Atmospheric Sciences</p> <p lang="en-US">[4] Goldblatt, C. & Watson, A. J. 2012, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences</p> <p lang="en-US">[5] Chaverot G., Bolmont, E., Turbet, M., Leconte, J. 2021, Astronomy & Astrophysics</p> <p lang="en-US">[6] Goldblatt, C., Robinson, T. D., Zahnle, K. J., & Crisp, D. 2013, Nature Geoscience</p> <p><span lang="en-US">[</span><span lang="en-US">7</span><span lang="en-US">] Pop, M., Schmidt, H., Marotzke, J. 2016, Nature Communications</span></p> <p><span lang="en-US">[</span><span lang="en-US">8</span><span lang="en-US">] Leconte, J., Forget, F., Charnay, B. et al., 2013, Nature</span></p> <p><span lang="en-US">[</span><span lang="en-US">9</span><span lang="en-US">] Turbet, M., Bolmont, E., Chaverot, G., et al. 2021, Nature</span></p>