Implications of a pervasive climate model bias for low-cloud feedback
Author(s)
Ceppi, P
Myers, TA
Nowack, P
Wall, CJ
Zelinka, MD
Type
Journal Article
Abstract
How low clouds respond to warming constitutes a key uncertainty for climate projections. Here
we observationally constrain low‐cloud feedback through a controlling factor analysis based on ridge
regression. We find a moderately positive global low‐cloud feedback (0.45 W m− 2 K− 1, 90% range 0.18–0.72 W
m− 2 K− 1), about twice the mean value (0.22 W m− 2 K− 1) of 16 models from the Coupled Model
Intercomparison Project. We link this discrepancy to a pervasive model mean‐state bias: models underestimate
the low‐cloud response to warming because (a) they systematically underestimate present‐day tropical marine
low‐cloud amount, and (b) the low‐cloud sensitivity to warming is proportional to this present‐day low‐cloud
amount. Our results hence highlight the importance of reducing model biases in both the mean state of clouds
and their sensitivity to environmental factors for accurate climate change projections
we observationally constrain low‐cloud feedback through a controlling factor analysis based on ridge
regression. We find a moderately positive global low‐cloud feedback (0.45 W m− 2 K− 1, 90% range 0.18–0.72 W
m− 2 K− 1), about twice the mean value (0.22 W m− 2 K− 1) of 16 models from the Coupled Model
Intercomparison Project. We link this discrepancy to a pervasive model mean‐state bias: models underestimate
the low‐cloud response to warming because (a) they systematically underestimate present‐day tropical marine
low‐cloud amount, and (b) the low‐cloud sensitivity to warming is proportional to this present‐day low‐cloud
amount. Our results hence highlight the importance of reducing model biases in both the mean state of clouds
and their sensitivity to environmental factors for accurate climate change projections
Date Issued
2024-10-28
Date Acceptance
2024-09-30
Citation
Geophysical Research Letters, 2024, 51 (20)
ISSN
0094-8276
Publisher
Wiley
Journal / Book Title
Geophysical Research Letters
Volume
51
Issue
20
Copyright Statement
© 2024. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
10.1029/2024GL110525
Subjects
climate
climate change
climate feedback
climate modeling
clouds
COVER
Geology
Geosciences, Multidisciplinary
ISCCP
MODIS
Physical Sciences
Science & Technology
Publication Status
Published
Article Number
e2024GL110525
Date Publish Online
2024-10-19