High Climate Sensitivity in the Community Earth System Model Version 2 (CESM2)

TitleHigh Climate Sensitivity in the Community Earth System Model Version 2 (CESM2)
Publication TypeJournal Article
Year of Publication2019
JournalGeophysical Research Letters
Volume46
Number14
Pages8329-8337
Date Published09/2019
Abstract / Summary

The Community Earth System Model Version 2 (CESM2) has an equilibrium climate sensitivity (ECS) of 5.3 K. ECS is an emergent property of both climate feedbacks and aerosol forcing. The increase in ECS over the previous version (CESM1) is the result of cloud feedbacks. Interim versions of CESM2 had a land model that damped ECS. Part of the ECS change results from evolving the model configuration to reproduce the long‐term trend of global and regional surface temperature over the twentieth century in response to climate forcings. Changes made to reduce sensitivity to aerosols also impacted cloud feedbacks, which significantly influence ECS. CESM2 simulations compare very well to observations of present climate. It is critical to understand whether the high ECS, outside the best estimate range of 1.5–4.5 K, is plausible.

URLhttp://dx.doi.org/10.1029/2019gl083978
DOI10.1029/2019gl083978
Journal: Geophysical Research Letters
Year of Publication: 2019
Volume: 46
Number: 14
Pages: 8329-8337
Date Published: 09/2019

The Community Earth System Model Version 2 (CESM2) has an equilibrium climate sensitivity (ECS) of 5.3 K. ECS is an emergent property of both climate feedbacks and aerosol forcing. The increase in ECS over the previous version (CESM1) is the result of cloud feedbacks. Interim versions of CESM2 had a land model that damped ECS. Part of the ECS change results from evolving the model configuration to reproduce the long‐term trend of global and regional surface temperature over the twentieth century in response to climate forcings. Changes made to reduce sensitivity to aerosols also impacted cloud feedbacks, which significantly influence ECS. CESM2 simulations compare very well to observations of present climate. It is critical to understand whether the high ECS, outside the best estimate range of 1.5–4.5 K, is plausible.

DOI: 10.1029/2019gl083978
Citation:
Gettelman, A, C Hannay, J Bacmeister, R Neale, A Pendergrass, G Danabasoglu, J Lamarque, et al.  2019.  "High Climate Sensitivity in the Community Earth System Model Version 2 (CESM2)."  Geophysical Research Letters 46(14): 8329-8337.  https://doi.org/10.1029/2019gl083978.