Muted extratropical low cloud seasonal cycle is closely linked to underestimated climate sensitivity in models

Journal Article · 10 September 2023 · Nature Communications

DOI: https://doi.org/10.1038/s41467-023-41360-0 · OSTI ID:1999447

Jiang, Xianan ; Su, Hui; Jiang, Jonathan H. ; Neelin, J. David; Wu, Longtao; Tsushima, Yoko ; Elsaesser, Gregory

Abstract A large spread in model estimates of the equilibrium climate sensitivity (ECS), defined as the global mean near-surface air-temperature increase following a doubling of atmospheric CO ₂ concentration, leaves us greatly disadvantaged in guiding policy-making for climate change adaptation and mitigation. In this study, we show that the projected ECS in the latest generation of climate models is highly related to seasonal variations of extratropical low-cloud fraction (LCF) in historical simulations. Marked reduction of extratropical LCF from winter to summer is found in models with ECS > 4.75 K, in accordance with the significant reduction of extratropical LCF under a warming climate in these models. In contrast, a pronounced seasonal cycle of extratropical LCF, as supported by satellite observations, is largely absent in models with ECS < 3.3 K. The distinct seasonality in extratropical LCF in climate models is ascribed to their different prevailing cloud regimes governing the extratropical LCF variability.

• Research Organization: Univ. of California, Los Angeles, CA (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE; USDOE Office of Science (SC)
• Grant/Contract Number: SC0021312
• OSTI ID: 1999447
• Journal Information: Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 14; ISSN 2041-1723
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English