A Test of Emergent Constraints on Cloud Feedback and Climate Sensitivity Using a Calibrated Single-Model Ensemble

Wagman, Benjamin M.; Jackson, Charles S.

doi:10.1175/JCLI-D-17-0682.1

Title: A Test of Emergent Constraints on Cloud Feedback and Climate Sensitivity Using a Calibrated Single-Model Ensemble

Abstract

A calibrated single-model ensemble (SME) derived from the NCAR Community Atmosphere Model, version 3.1, is used to test two hypothesized emergent constraints on cloud feedback and equilibrium climate sensitivity (ECS). The Fasullo and Trenberth relative humidity (RH) metric and the Sherwood et al. lower-tropospheric mixing (LTMI) metric are computed for the current climate of the SME, and the relationships between the metrics, ECS, and cloud and other climate feedbacks are examined. The tropical convergence zone relative humidity (RH_M) and the parameterized lower-tropospheric mixing (LTMIS) are positively correlated to ECS, and each is associated with a different spatial pattern of tropical shortwave cloud feedback in the SME. Yet, neither of those metrics is linked to the type of cloud response hypothesized by its authors. The resolved lower-tropospheric mixing (LTMI_D) is positively correlated to ECS for a subset of the SME having LTMID over a threshold value. LTMI and the RH for the dry, descending branch of the Hadley cell (RH_D) narrow and shift upward the posterior estimates of ECS in the SME, but the SME bias in RH_D and concerns over poorly understood physical mechanisms indicate the narrowing could be spurious for both constraints. While calibrated SME results may not generalizemore »« less

Authors:

Wagman, Benjamin M. ^[1]; Jackson, Charles S. ^[1]

Institute for Geophysics, The University of Texas at Austin, Austin, Texas

Publication Date:: Sat Sep 01 00:00:00 EDT 2018

Research Org.:: Univ. of Texas, Austin, TX (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Biological and Environmental Research (BER); Extreme Science and Engineering Discovery Environment (XSEDE) program

OSTI Identifier:: 1463227

Alternate Identifier(s):: OSTI ID: 1541848

Grant/Contract Number:: SC0006985; ATM100049

Resource Type:: Published Article

Journal Name:: Journal of Climate

Additional Journal Information:: Journal Name: Journal of Climate Journal Volume: 31 Journal Issue: 18; Journal ID: ISSN 0894-8755

Publisher:: American Meteorological Society

Country of Publication:: United States

Language:: English

Subject:: 54 ENVIRONMENTAL SCIENCES; Atmosphere; Climate sensitivity; Bayesian methods; Climate prediction; Ensembles; Probability forecasts/models/distribution

Citation Formats


                    Wagman, Benjamin M., and Jackson, Charles S. A Test of Emergent Constraints on Cloud Feedback and Climate Sensitivity Using a Calibrated Single-Model Ensemble.  United States: N. p., 2018. 
Web.  doi:10.1175/JCLI-D-17-0682.1.

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                    Wagman, Benjamin M., & Jackson, Charles S. A Test of Emergent Constraints on Cloud Feedback and Climate Sensitivity Using a Calibrated Single-Model Ensemble.  United States.  https://doi.org/10.1175/JCLI-D-17-0682.1

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                    Wagman, Benjamin M., and Jackson, Charles S. Sat .  
"A Test of Emergent Constraints on Cloud Feedback and Climate Sensitivity Using a Calibrated Single-Model Ensemble".  United States.  https://doi.org/10.1175/JCLI-D-17-0682.1.

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@article{osti_1463227,

  title        = {A Test of Emergent Constraints on Cloud Feedback and Climate Sensitivity Using a Calibrated Single-Model Ensemble},

  author       = {Wagman, Benjamin M. and Jackson, Charles S.},

  abstractNote = {A calibrated single-model ensemble (SME) derived from the NCAR Community Atmosphere Model, version 3.1, is used to test two hypothesized emergent constraints on cloud feedback and equilibrium climate sensitivity (ECS). The Fasullo and Trenberth relative humidity (RH) metric and the Sherwood et al. lower-tropospheric mixing (LTMI) metric are computed for the current climate of the SME, and the relationships between the metrics, ECS, and cloud and other climate feedbacks are examined. The tropical convergence zone relative humidity (RHM) and the parameterized lower-tropospheric mixing (LTMIS) are positively correlated to ECS, and each is associated with a different spatial pattern of tropical shortwave cloud feedback in the SME. Yet, neither of those metrics is linked to the type of cloud response hypothesized by its authors. The resolved lower-tropospheric mixing (LTMID) is positively correlated to ECS for a subset of the SME having LTMID over a threshold value. LTMI and the RH for the dry, descending branch of the Hadley cell (RHD) narrow and shift upward the posterior estimates of ECS in the SME, but the SME bias in RHD and concerns over poorly understood physical mechanisms indicate the narrowing could be spurious for both constraints. While calibrated SME results may not generalize to multimodel ensembles, they can enhance the process understanding of emergent constraints and serve as out-of-sample tests of robustness.},

  doi          = {10.1175/JCLI-D-17-0682.1},

  journal      = {Journal of Climate},

  number       = 18,

  volume       = 31,

  place        = {United States},

  year         = {Sat Sep 01 00:00:00 EDT 2018},

  month        = {Sat Sep 01 00:00:00 EDT 2018}

}

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Works referencing / citing this record:

Reducing Uncertainties in Climate Projections with Emergent Constraints: Concepts, Examples and Prospects
journal, December 2019

Brient, Florent
Advances in Atmospheric Sciences, Vol. 37, Issue 1
DOI: 10.1007/s00376-019-9140-8

Reducing Uncertainties in Climate Projections with Emergent Constraints: Concepts, Examples and Prospects
journal, December 2019

Brient, Florent
Advances in Atmospheric Sciences, Vol. 37, Issue 1
DOI: 10.1007/s00376-019-9140-8

Progressing emergent constraints on future climate change
journal, March 2019

Hall, Alex; Cox, Peter; Huntingford, Chris
Nature Climate Change, Vol. 9, Issue 4
DOI: 10.1038/s41558-019-0436-6

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