04 Mar 2024
 | 04 Mar 2024

The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model

Andrea Mosso, Thomas Hocking, and Thorsten Mauritsen

Abstract. Clouds affect the sensitivity of the climate system by changing their distribution, height and optical properties under climate change. Additionally, clouds have a masking effect on CO2 forcing and can affect other feedback mechanisms such as the surface albedo feedback. To shed light on the overall effect of clouds, we compute how much the equilibrium climate sensitivity to a doubling of CO2 (ECS) changes when clouds are made transparent to radiation in an Earth system model (MPI-ESM1.2). Practically, to stabilise the model climate at near pre-industrial temperatures the solar constant was reduced by 8.8 percent. Our experiments suggest that clouds play a stabilising role in the model, with a clear-sky ECS of 4.34 K, which is higher than the corresponding full-sky ECS of 2.80 K. Detailed partial radiative perturbation diagnostics show that clouds strengthen the lapse rate and water vapour feedbacks and dampen the albedo feedback.

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Andrea Mosso, Thomas Hocking, and Thorsten Mauritsen

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-618', Anonymous Referee #1, 18 Apr 2024
  • RC2: 'Comment on egusphere-2024-618', Anonymous Referee #2, 19 Apr 2024
  • AC1: 'Reply to all Reviewers', Andrea Mosso, 17 Jul 2024
Andrea Mosso, Thomas Hocking, and Thorsten Mauritsen
Andrea Mosso, Thomas Hocking, and Thorsten Mauritsen


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Short summary
Clouds play a crucial role in the energy balance of the earth, as they can either warm up or cool down the area they cover depending on their height and depth. It is expected that they will alter their behaviour under climate change, which will affect the warming generated by greenhouse gases. This paper proposes a new method to estimate their overall effect by simulating a climate where clouds are transparent. Results show that, with the model used, clouds have a stabilising effect on climate.