Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations

Abstract Three new equilibrium mid‐Pliocene (MP) simulations are implemented with the Community Climate System Model version 4 (CCSM4) and Community Earth System Model versions 1.2 (CESM1.2) and 2 (CESM2). All simulations are carried out with the same boundary and forcing conditions following the pr...

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Autores principales:	Ran Feng, Bette L. Otto‐Bliesner, Esther C. Brady, Nan Rosenbloom
Formato:	article
Lenguaje:	EN
Publicado:	American Geophysical Union (AGU) 2020
Materias:	PMIP4 PlioMIP2 Earth System Sensitivity mid‐Pliocene tropical circulation AMOC Physical geography GB3-5030 Oceanography GC1-1581
Acceso en línea:	https://doaj.org/article/06d529d5243b46b68d347054243df6d9
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spelling	oai:doaj.org-article:06d529d5243b46b68d347054243df6d92021-11-15T14:20:27ZIncreased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations1942-246610.1029/2019MS002033https://doaj.org/article/06d529d5243b46b68d347054243df6d92020-08-01T00:00:00Zhttps://doi.org/10.1029/2019MS002033https://doaj.org/toc/1942-2466Abstract Three new equilibrium mid‐Pliocene (MP) simulations are implemented with the Community Climate System Model version 4 (CCSM4) and Community Earth System Model versions 1.2 (CESM1.2) and 2 (CESM2). All simulations are carried out with the same boundary and forcing conditions following the protocol of Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). These simulations reveal amplified MP climate change relative to the preindustrial going from CCSM4 to CESM2, seen in global and polar averages of surface warming, sea ice reduction in both the Arctic and the Antarctic, and weakened Hadley circulation. The enhanced global mean warming arises from enhanced Earth system sensitivity (ESS) to not only CO2 change but also changes in boundary conditions primarily from vegetation and ice sheets. ESS is amplified by up to 70% in CCSM4 and up to 100% in CESM1.2 and CESM2 relative to the equilibrium climate sensitivity of respective models. Simulations disagree on several climate metrics. Different from CCSM4, both CESM1.2 and CESM2 show reduction of cloud cover, and weakened Walker circulation accompanied by an El Niño‐like mean state of the tropical Pacific in MP simulations relative to the preindustrial. This El Niño‐like mean state is consistent with paleo‐observational sea surface temperatures, suggesting an improvement upon CCSM4. The performances of MP simulations are assessed with a new compilation of observational MP sea surface temperature. The model‐data comparison suggests that CCSM4 is not sensitivity enough to the MP forcings, but CESM2 is likely too sensitive, especially in the tropics.Ran FengBette L. Otto‐BliesnerEsther C. BradyNan RosenbloomAmerican Geophysical Union (AGU)articlePMIP4PlioMIP2Earth System Sensitivitymid‐Pliocenetropical circulationAMOCPhysical geographyGB3-5030OceanographyGC1-1581ENJournal of Advances in Modeling Earth Systems, Vol 12, Iss 8, Pp n/a-n/a (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	PMIP4 PlioMIP2 Earth System Sensitivity mid‐Pliocene tropical circulation AMOC Physical geography GB3-5030 Oceanography GC1-1581
spellingShingle	PMIP4 PlioMIP2 Earth System Sensitivity mid‐Pliocene tropical circulation AMOC Physical geography GB3-5030 Oceanography GC1-1581 Ran Feng Bette L. Otto‐Bliesner Esther C. Brady Nan Rosenbloom Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations
description	Abstract Three new equilibrium mid‐Pliocene (MP) simulations are implemented with the Community Climate System Model version 4 (CCSM4) and Community Earth System Model versions 1.2 (CESM1.2) and 2 (CESM2). All simulations are carried out with the same boundary and forcing conditions following the protocol of Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). These simulations reveal amplified MP climate change relative to the preindustrial going from CCSM4 to CESM2, seen in global and polar averages of surface warming, sea ice reduction in both the Arctic and the Antarctic, and weakened Hadley circulation. The enhanced global mean warming arises from enhanced Earth system sensitivity (ESS) to not only CO2 change but also changes in boundary conditions primarily from vegetation and ice sheets. ESS is amplified by up to 70% in CCSM4 and up to 100% in CESM1.2 and CESM2 relative to the equilibrium climate sensitivity of respective models. Simulations disagree on several climate metrics. Different from CCSM4, both CESM1.2 and CESM2 show reduction of cloud cover, and weakened Walker circulation accompanied by an El Niño‐like mean state of the tropical Pacific in MP simulations relative to the preindustrial. This El Niño‐like mean state is consistent with paleo‐observational sea surface temperatures, suggesting an improvement upon CCSM4. The performances of MP simulations are assessed with a new compilation of observational MP sea surface temperature. The model‐data comparison suggests that CCSM4 is not sensitivity enough to the MP forcings, but CESM2 is likely too sensitive, especially in the tropics.
format	article
author	Ran Feng Bette L. Otto‐Bliesner Esther C. Brady Nan Rosenbloom
author_facet	Ran Feng Bette L. Otto‐Bliesner Esther C. Brady Nan Rosenbloom
author_sort	Ran Feng
title	Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations
title_short	Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations
title_full	Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations
title_fullStr	Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations
title_full_unstemmed	Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations
title_sort	increased climate response and earth system sensitivity from ccsm4 to cesm2 in mid‐pliocene simulations
publisher	American Geophysical Union (AGU)
publishDate	2020
url	https://doaj.org/article/06d529d5243b46b68d347054243df6d9
work_keys_str_mv	AT ranfeng increasedclimateresponseandearthsystemsensitivityfromccsm4tocesm2inmidpliocenesimulations AT bettelottobliesner increasedclimateresponseandearthsystemsensitivityfromccsm4tocesm2inmidpliocenesimulations AT esthercbrady increasedclimateresponseandearthsystemsensitivityfromccsm4tocesm2inmidpliocenesimulations AT nanrosenbloom increasedclimateresponseandearthsystemsensitivityfromccsm4tocesm2inmidpliocenesimulations
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Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid‐Pliocene Simulations

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