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

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 is also important to understand a possible evolution of terrestrial planets from temperate Earth-like planets to magma-ocean planets. This runway greenhouse transition 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 (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 (e.g., collisional broadening of water lines).

In continuation of this work, we use a 3D global climate model, LMD-Generic, to study the runaway greenhouse for similar atmospheres. First, we explore the runaway evaporation in a temperature range that goes beyond every previous work which only studied up to the tipping point [7,8]. We aim to understand the contribution of the inherently three-dimensional processes (e.g. clouds and dynamics) to the evolution of the atmosphere. We find strong differences with 1D simulations but also with the usual climate pattern of temperate stable states. Second, we 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 Earth-like planets [9].

 

 

References

[1] Komabayasi, M. 1967, Journal of the Meteorological Society of Japan. Ser. II

[2] Ingersoll, A. 1969, Journal of the Atmospheric Sciences

[3] Nakajima, S., Hayashi, Y.-Y., & Abe, Y. 1992, Journal of the Atmospheric Sciences

[4] Goldblatt, C. & Watson, A. J. 2012, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

[5] Chaverot G., Bolmont, E., Turbet, M., Leconte, J. 2021, Astronomy & Astrophysics

[6] Goldblatt, C., Robinson, T. D., Zahnle, K. J., & Crisp, D. 2013, Nature Geoscience

[7] Pop, M., Schmidt, H., Marotzke, J. 2016, Nature Communications

[8] Leconte, J., Forget, F., Charnay, B. et al., 2013, Nature

[9] Turbet, M., Bolmont, E., Chaverot, G., et al. 2021, Nature