%AGettelman, A. [National Center for Atmospheric Research Boulder CO USA]%AHannay, C. [National Center for Atmospheric Research Boulder CO USA]%ABacmeister, J. [National Center for Atmospheric Research Boulder CO USA]%ANeale, R. [National Center for Atmospheric Research Boulder CO USA]%APendergrass, A. [National Center for Atmospheric Research Boulder CO USA]%ADanabasoglu, G. [National Center for Atmospheric Research Boulder CO USA]%ALamarque, J. [National Center for Atmospheric Research Boulder CO USA]%AFasullo, J. [National Center for Atmospheric Research Boulder CO USA]%ABailey, D. [National Center for Atmospheric Research Boulder CO USA]%ALawrence, D. [National Center for Atmospheric Research Boulder CO USA]%AMills, M. [National Center for Atmospheric Research Boulder CO USA]%BJournal Name: Geophysical Research Letters; Journal Volume: 46; Journal Issue: 14; Related Information: CHORUS Timestamp: 2023-08-28 08:51:16 %D2019%IDOI PREFIX: 10.1029 %JJournal Name: Geophysical Research Letters; Journal Volume: 46; Journal Issue: 14; Related Information: CHORUS Timestamp: 2023-08-28 08:51:16 %K %MOSTI ID: 10362020 %PMedium: X %THigh Climate Sensitivity in the Community Earth System Model Version 2 (CESM2) %XAbstract

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.

%0Journal Article