@article{Mülmenstädt:2024:10.5194/acp-24-7331-2024,
author = {Mülmenstädt, J and Gryspeerdt, E and Dipu, S and Quaas, J and Ackerman, AS and Fridlind, AM and Tornow, F and Bauer, SE and Gettelman, A and Ming, Y and Zheng, Y and Ma, P-L and Wang, H and Zhang, K and Christensen, MW and Varble, AC and Leung, LR and Liu, X and Neubauer, D and Partridge, DG and Stier, P and Takemura, T},
doi = {10.5194/acp-24-7331-2024},
journal = {Atmospheric Chemistry and Physics},
pages = {7331--7345},
title = {General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path},
url = {http://dx.doi.org/10.5194/acp-24-7331-2024},
volume = {24},
year = {2024}
}

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TY  - JOUR
AB  - <jats:p>Abstract. General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the climate by aerosol–cloud interactions (ERFaci). The discrepancy is thought to stem in part from GCMs' inability to represent the turbulence–microphysics interactions in cloud-top entrainment, a mechanism that leads to a reduction in liquid water in response to an anthropogenic increase in aerosols. In the real atmosphere, enhanced cloud-top entrainment is thought to be the dominant adjustment mechanism for liquid water path, weakening the overall ERFaci. We show that the latest generation of GCMs includes models that produce a negative correlation between the present-day cloud droplet number and liquid water path, a key piece of observational evidence supporting liquid water path reduction by anthropogenic aerosols and one that earlier-generation GCMs could not reproduce. However, even in GCMs with this negative correlation, the increase in anthropogenic aerosols from preindustrial to present-day values still leads to an increase in the simulated liquid water path due to the parameterized precipitation suppression mechanism. This adds to the evidence that correlations in the present-day climate are not necessarily causal. We investigate sources of confounding to explain the noncausal correlation between liquid water path and droplet number. These results are a reminder that assessments of climate parameters based on multiple lines of evidence must carefully consider the complementary strengths of different lines when the lines disagree.                    </jats:p>
AU  - Mülmenstädt,J
AU  - Gryspeerdt,E
AU  - Dipu,S
AU  - Quaas,J
AU  - Ackerman,AS
AU  - Fridlind,AM
AU  - Tornow,F
AU  - Bauer,SE
AU  - Gettelman,A
AU  - Ming,Y
AU  - Zheng,Y
AU  - Ma,P-L
AU  - Wang,H
AU  - Zhang,K
AU  - Christensen,MW
AU  - Varble,AC
AU  - Leung,LR
AU  - Liu,X
AU  - Neubauer,D
AU  - Partridge,DG
AU  - Stier,P
AU  - Takemura,T
DO  - 10.5194/acp-24-7331-2024
EP  - 7345
PY  - 2024///
SP  - 7331
TI  - General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path
T2  - Atmospheric Chemistry and Physics
UR  - http://dx.doi.org/10.5194/acp-24-7331-2024
VL  - 24
ER  - 

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