High sensitivity of cloud formation to aerosol changes

The susceptibility of cloud droplet number to cloud condensation nuclei number is one of the major factors controlling the highly uncertain change in the amount of solar radiation reflected by clouds when aerosol emissions are perturbed (the radiative forcing due to aerosol-cloud interactions). We investigate this susceptibility in low-level stratiform clouds using long-term (3-10-yr) in situ observations of aerosols and clouds at three high-latitude locations. The in situ observations show higher susceptibility for low-level stratiform clouds than values reported for satellite data. We estimate -1.16 W m<sup>-2</sup> for the aerosol indirect radiative forcing on the basis of our observations, which is at the higher end of satellite-derived forcing estimates and the uncertainty range of the most recent Intergovernmental Panel on Climate Change report. We evaluate four Earth system models against the observations and find large inter-model variability in the susceptibility. Our results demonstrate that, even if the susceptibility in some of the models is relatively close to observations, the underlying physics in the models is unrealistic when compared with observations. We show that the inter-model variability is driven by differences in sub-grid-scale updraught velocities and aerosol size distributions, raising a need to improve these aspects in models.

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Publication Details

Journal
Nature Geoscience
Published
2025-04-01
DOI
https://doi.org/10.1038/s41561-025-01662-y
Citations
15
Primary Topic
Atmospheric aerosols and clouds
Type
article
Field-Weighted Citation Impact
16.58

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High sensitivity of cloud formation to aerosol changes

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Nature Geoscience
Atmospheric aerosols and clouds
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High sensitivity of cloud formation to aerosol changes

Santtu Mikkonen, Harri Kokkola, Annele Virtanen, Radovan Krejčí, Ari Leskinen, Sara M. Blichner, Ilona Riipinen, Øyvind Seland, Antti Hyvärinen, Antti Lipponen, Johannes Quaas, Jorma Joutsensaari, Annica M. L. Ekman, Emanuele Tovazzi, Daniel G. Partridge, Eemeli Holopainen, Sami Romakkaniemi, Paul Zieger
article en
15 citations

Abstract

The susceptibility of cloud droplet number to cloud condensation nuclei number is one of the major factors controlling the highly uncertain change in the amount of solar radiation reflected by clouds when aerosol emissions are perturbed (the radiative forcing due to aerosol-cloud interactions). We investigate this susceptibility in low-level stratiform clouds using long-term (3-10-yr) in situ observations of aerosols and clouds at three high-latitude locations. The in situ observations show higher susceptibility for low-level stratiform clouds than values reported for satellite data. We estimate -1.16 W m<sup>-2</sup> for the aerosol indirect radiative forcing on the basis of our observations, which is at the higher end of satellite-derived forcing estimates and the uncertainty range of the most recent Intergovernmental Panel on Climate Change report. We evaluate four Earth system models against the observations and find large inter-model variability in the susceptibility. Our results demonstrate that, even if the susceptibility in some of the models is relatively close to observations, the underlying physics in the models is unrealistic when compared with observations. We show that the inter-model variability is driven by differences in sub-grid-scale updraught velocities and aerosol size distributions, raising a need to improve these aspects in models.

Nature GeoscienceVol. 18(4)
Finnish Meteorological Institute (FI), Norwegian Meteorological Institute (NO), Stockholm University (SE), University of Eastern Finland (FI), University of Exeter (GB), Bolin Centre for Climate Research (SE), Foundation for Research and Technology Hellas (GR), Leipzig University (DE)
Itä-Suomen Yliopisto, Göran Gustafssons Stiftelser, Sight Research UK, European Commission, Met Office, National Science Council, Kuopion Yliopistollinen Sairaala, Vetenskapsrådet, Natural Environment Research Council
Openalex Percentile: Top 1%
Atmospheric aerosols and clouds
16.58
DOIOpen Access PDFOpenAlex
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