State-Dependence of the Climate Sensitivity in Earth System Models of Intermediate Complexity

Pfister, Patrik; Stocker, Thomas (2017). State-Dependence of the Climate Sensitivity in Earth System Models of Intermediate Complexity. Geophysical Research Letters, 44(20), 10,643-10,653. American Geophysical Union 10.1002/2017GL075457

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Growing evidence from general circulation models (GCMs) indicates that the equilibrium climate sensitivity (ECS) depends on the magnitude of forcing, which is commonly referred to as state-dependence. We present a comprehensive assessment of ECS state-dependence in Earth system models of intermediate complexity (EMICs) by analyzing millennial simulations with sustained 2×CO₂ and 4×CO₂ forcings. We compare different extrapolation methods and show that ECS is smaller in the higher-forcing scenario in 12 out of 15 EMICs, in contrast to the opposite behavior reported from GCMs. In one such EMIC, the Bern3D-LPX model, this state-dependence is mainly due to the weakening sea ice-albedo feedback in the Southern Ocean, which depends on model configuration. Due to ocean-mixing adjustments, state-dependence is only detected hundreds of years after the abrupt forcing, highlighting the need for long model integrations. Adjustments to feedback parametrizations of EMICs may be necessary if GCM intercomparisons confirm an opposite state-dependence.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)

UniBE Contributor:

Pfister, Patrik and Stocker, Thomas

Subjects:

500 Science > 530 Physics

ISSN:

0094-8276

Publisher:

American Geophysical Union

Language:

English

Submitter:

Monika Wälti-Stampfli

Date Deposited:

18 Apr 2018 16:47

Last Modified:

25 Oct 2019 05:13

Publisher DOI:

10.1002/2017GL075457

BORIS DOI:

10.7892/boris.112659

URI:

https://boris.unibe.ch/id/eprint/112659

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