Aerosol trends dominate over global warming-induced cloud feedback in driving recent changes in marine low clouds

[Geoengineering News]

https://www.researchsquare.com/article/rs-5901920/v1

Authors

Yang Cao, Hao Wang, Yannian Zhu, Minghuai Wang, Daniel Rosenfeld, Chen Zhou, Zhonghua Zheng, Hugh Coe, David Topping, Jihu Liu, Kang-En Huang, Yuan Liang, Haipeng Zhang, Heming Bai, Man Yue

https://doi.org/10.21203/rs.3.rs-5901920/v1

12 February 2025

Abstract

Over the past two decades, anthropogenic emission reductions and global warming have impacted marine low clouds through aerosol-cloud interactions (ACI) and cloud feedback, yet their quantitative contributions remain unclear. This study employs a deep learning model (CNNMet−Nd) and Community Earth System Model version 2 (CESM2) to disentangle these effects. CNNMet−Nd reveals that aerosol-driven changes in cloud droplet number concentration dominate near-global marine low cloud shortwave radiative effect changes (ΔCRE), contributing 0.42 ± 0.08 Wm⁻² per 20 years, compared to 0.05 ± 0.37 Wm⁻² from cloud feedback. CESM2 effectively reproduces the predominant influence of aerosol reductions on ΔCRE by CNNMet−Nd, lending us confidence for a stronger estimate of global effective radiative forcing due to ACI (ERFaci) of -1.29 Wm⁻² since the preindustrial era. These findings highlight the critical role of ACI in shaping marine low cloud trends and its broader climate implications, especially under ongoing emission reduction efforts.

Source: ResearchSquare