Present-day correlations insufficient to constrain cloud albedo change by anthropogenic aerosols in E3SM v2
Abstract. Cloud albedo susceptibility to droplet number perturbation remains a source of uncertainty in understanding aerosol– cloud interactions, and thus climate states both past and present. Through E3SM v2 experiments, we probe the effects of competing parameterized processes on cloud albedo susceptibility of low-lying marine stratocumulus in the Northeast Paciﬁc. In present-day conditions, we ﬁnd that increasing precipitation suppression by aerosols increases cloud albedo susceptibility, whereas increasing cloud sedimentation decreases it. By constructing a hypothetical model conﬁguration exhibiting negative susceptibility under all conditions, we conclude that cloud albedo change due to aerosol perturbation cannot be constrained by present-day co-variabilities in E3SM v2. As such, our null result herein challenges the assumption that present-day climate observations are sufﬁcient to constrain past states, at least in the context of cloud albedo changes to aerosol perturbation.
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