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

<p>Clouds affect the sensitivity of the climate system by changing their distribution, height, and optical properties under climate change. Although the precise magnitude remains uncertain, the direct cloud response to an external forcing is known to be destabilising. Additionally, clouds have...

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Main Authors: A. Mosso, T. Hocking, T. Mauritsen
Format: Article
Language:English
Published: Copernicus Publications 2024-11-01
Series:Atmospheric Chemistry and Physics
Online Access:https://acp.copernicus.org/articles/24/12793/2024/acp-24-12793-2024.pdf
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author A. Mosso
T. Hocking
T. Mauritsen
author_facet A. Mosso
T. Hocking
T. Mauritsen
author_sort A. Mosso
collection DOAJ
description <p>Clouds affect the sensitivity of the climate system by changing their distribution, height, and optical properties under climate change. Although the precise magnitude remains uncertain, the direct cloud response to an external forcing is known to be destabilising. Additionally, clouds have a masking effect on CO<span class="inline-formula"><sub>2</sub></span> forcing and can influence other feedback mechanisms such as the surface albedo feedback. To understand the overall impact of clouds, we compute how much the equilibrium climate sensitivity (ECS) to a doubling of CO<span class="inline-formula"><sub>2</sub></span> changes when clouds are made transparent to radiation in an Earth system model (MPI-ESM1.2, the Max Planck Institute for Meteorology Earth System Model version 1.2). In practice, to stabilise the model climate at near-preindustrial temperatures, the solar constant was reduced by 8.8 %. Our experiments reveal that clouds exert a stabilising influence on the model, with a clear-sky ECS of 4.29 K, which is higher than the corresponding full-sky ECS of 2.84 K, contrasting with their direct destabilising effect. Detailed partial radiative perturbation diagnostics show that beyond directly amplifying warming by themselves, clouds also strengthen the negative lapse rate and positive water vapour feedbacks, while strongly damping the positive albedo feedback. These findings highlight the complex role of clouds in modulating climate sensitivity.</p>
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spelling doaj-art-81b1949a17f4459cad13cdb00e2b2c232024-11-19T15:15:26ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242024-11-0124127931280610.5194/acp-24-12793-2024The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate modelA. Mosso0T. Hocking1T. Mauritsen2Department of Meteorology, Stockholm University, Stockholm, SwedenDepartment of Meteorology, Stockholm University, Stockholm, SwedenDepartment of Meteorology, Stockholm University, Stockholm, Sweden<p>Clouds affect the sensitivity of the climate system by changing their distribution, height, and optical properties under climate change. Although the precise magnitude remains uncertain, the direct cloud response to an external forcing is known to be destabilising. Additionally, clouds have a masking effect on CO<span class="inline-formula"><sub>2</sub></span> forcing and can influence other feedback mechanisms such as the surface albedo feedback. To understand the overall impact of clouds, we compute how much the equilibrium climate sensitivity (ECS) to a doubling of CO<span class="inline-formula"><sub>2</sub></span> changes when clouds are made transparent to radiation in an Earth system model (MPI-ESM1.2, the Max Planck Institute for Meteorology Earth System Model version 1.2). In practice, to stabilise the model climate at near-preindustrial temperatures, the solar constant was reduced by 8.8 %. Our experiments reveal that clouds exert a stabilising influence on the model, with a clear-sky ECS of 4.29 K, which is higher than the corresponding full-sky ECS of 2.84 K, contrasting with their direct destabilising effect. Detailed partial radiative perturbation diagnostics show that beyond directly amplifying warming by themselves, clouds also strengthen the negative lapse rate and positive water vapour feedbacks, while strongly damping the positive albedo feedback. These findings highlight the complex role of clouds in modulating climate sensitivity.</p>https://acp.copernicus.org/articles/24/12793/2024/acp-24-12793-2024.pdf
spellingShingle A. Mosso
T. Hocking
T. Mauritsen
The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model
Atmospheric Chemistry and Physics
title The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model
title_full The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model
title_fullStr The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model
title_full_unstemmed The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model
title_short The presence of clouds lowers climate sensitivity in the MPI-ESM1.2 climate model
title_sort presence of clouds lowers climate sensitivity in the mpi esm1 2 climate model
url https://acp.copernicus.org/articles/24/12793/2024/acp-24-12793-2024.pdf
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