A113-0016
Regional Analysis of Climate Feedbacks and Sensitivity

Friday, 11 December 2020
Poster
Julio T Bacmeister1, Cecile Hannay2, Brian Medeiros3, Andrew Gettelman2, Richard B Neale2 and Hege-Beate Fredriksen4, (1)University Corporation for Atmospheric Research, Boulder, CO, United States, (2)NCAR, Boulder, CO, United States, (3)National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, Boulder, CO, United States, (4)University of Tromsø, Tromsø, Norway
Abstract:
We present a regional analysis of climate response to increasing CO2 in the Community Earth System Model versions 1 and 2 (CESM1 and CESM2) using 4xCO2 and 1%CO2 increase scenarios. Our analysis decomposes global radiation feedbacks into regional contributions that are used to quantitatively estimate the impact of regional warming and radiation feedbacks on the global feedback. We find for example that the increased equilibrium climate sensitivity (ECS) of CESM2 (5.4K) compared to CESM1 (4.2K) is produced by a combination of Southern Ocean and tropical ocean processes, with each of these regions contributing an approximately equal amount to the changes in radiation feedback that lead to increased ECS in CESM2. The regional decomposition can help to identify climate mechanisms that are responsible for changing feedbacks in coupled modeling systems as they evolve. We also apply the regional analysis to investigate the connection between ECS and transient climate response in CESM. Finally, we discuss the limitations of the regional decomposition.
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