Comment on egusphere-2026-3275
Abstract
Abstract. Changes in aerosols since the preindustrial era have altered the top-of-the-atmosphere radiation balance by scattering and absorbing solar radiation (ARI) and indirectly interacting with clouds (ACI), known as aerosol effective radiative forcing (ERFaer). ERFaer persistently remains one of the most uncertain components in climate projections, due to imperfect representations of aerosol and cloud processes in climate models. Here, we construct a perturbed parameter ensemble (PPE) with the aerosol–climate model ICON2.6.4–A–HAM2.3 (hereafter ICON–HAM) to quantify key sources of ERFaer uncertainty. We perturb 42 aerosol and cloud parameters over 383 PPE members. Parametric uncertainties in aerosol and cloud processes yield an ERFaer of −1.04Wm−2, with a 90 % credible range of −1.42 to −0.65 Wm−2 for the period 2024–2025. The parameters related to emissions (anthropogenic sulfur dioxide, natural dimethyl sulfide, and emitted particle size) dominate ACI uncertainty and hence ERFaer uncertainty (80 %), while absorption-related parameters (anthropogenic black carbon emissions and aerosol refractive indices) drive ARI uncertainty (60 %). Cloud parameters account for 13 % of ERFaer uncertainty, mainly via convection and entrainment processes. The sensitivity analysis of model diagnostics to parameters reveals that many present-day aerosol and cloud observables share dominant causes of uncertainty with ACI and ARI forcing, highlighting the potential for constraining ERFaer using existing space- and ground-based measurements. Notably, model biases against SPEXone and MODIS observations coincide spatially with parametric uncertainties, suggesting that much of these biases may be mitigated through appropriate constraint with observations, while the remainder requires structural model developments in combination with improved observations.
Authors 21
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Space Research Organisation Netherlands
Affiliation as printed
SRON Space Research Organisation Netherlands, Leiden, The Netherlands
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ETH Zurich · Institute for Atmospheric and Climate Science
Affiliation as printed
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
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Space Research Organisation Netherlands
Affiliation as printed
SRON Space Research Organisation Netherlands, Leiden, The Netherlands
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Scripps Institution of Oceanography · University of California San Diego
Affiliation as printed
Scripps Institution of Oceanography and Halıcıo˘glu Data Science Institute, University of California San Diego, La Jolla, CA, USA
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Affiliation as printed
Atmospheric Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK
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Affiliation as printed
Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany
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Affiliation as printed
Department of Mathematics and Statistics, Faculty of Environment, Science and Economy, University of Exeter, EX4 4QF, Exeter, United Kingdom
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Space Research Organisation Netherlands
Affiliation as printed
SRON Space Research Organisation Netherlands, Leiden, The Netherlands
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Leibniz Institute for Tropospheric Research
Affiliation as printed
Modeling of Atmospheric Processes Department, Leibniz Institute for Tropospheric Research, Leipzig, Germany
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École Polytechnique Fédérale de Lausanne · Foundation for Research and Technology Hellas
Affiliation as printed
Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Stadiou St, Platani GR26504 Patras, Greece
School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Federale de Lausanne, Lausanne 1015, Switzerland
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École Polytechnique Fédérale de Lausanne · Foundation for Research and Technology Hellas
Affiliation as printed
Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Stadiou St, Platani GR26504 Patras, Greece
School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Federale de Lausanne, Lausanne 1015, Switzerland
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Aarhus University · École Polytechnique Fédérale de Lausanne
Affiliation as printed
Aarhus University, Department of Environmental Science, 4000, Roskilde, Denmark
School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Federale de Lausanne, Lausanne 1015, Switzerland
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Affiliation as printed
Aarhus University, Department of Environmental Science, 4000, Roskilde, Denmark
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Affiliation as printed
Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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Space Research Organisation Netherlands
Affiliation as printed
SRON Space Research Organisation Netherlands, Leiden, The Netherlands
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ETH Zurich · Institute for Atmospheric and Climate Science
Affiliation as printed
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
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ETH Zurich · Institute for Atmospheric and Climate Science
Affiliation as printed
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
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Leibniz Institute for Tropospheric Research
Affiliation as printed
Modeling of Atmospheric Processes Department, Leibniz Institute for Tropospheric Research, Leipzig, Germany
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Affiliation as printed
Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany
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Space Research Organisation Netherlands
Affiliation as printed
SRON Space Research Organisation Netherlands, Leiden, The Netherlands
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Space Research Organisation Netherlands
Affiliation as printed
SRON Space Research Organisation Netherlands, Leiden, The Netherlands
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