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

Feng, Ran; Otto‐Bliesner, Bette L.; Brady, Esther C.; Rosenbloom, Nan

doi:10.1029/2019ms002033

Cited by 46 publications

(48 citation statements)

References 89 publications

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“…Previous modeling studies suggest that incorporating shrub/savanna vegetation over the Sahara as well as soil feedbacks in CCSM/CESM are important for the northward extension of the African monsoon during the Holocene (Levis et al, 2004; Thompson et al, 2019). Replacement of tundra with boreal forests over the NH high‐latitude continents, as indicated by pollen and macrofossil data (Figure 14), amplifies high‐latitude warming in CCSM/CESM simulations (Feng et al, 2020; Swann et al, 2010). In addition, a new optional feature in the CESM land model is the demographically structured dynamic vegetation model (Functionally Assembled Terrestrial Ecosystem Simulator), which will allow prediction of biome boundaries directly from plant physiological traits (Fisher et al, 2019; Lawrence et al, 2019).…”

Section: Summary and Discussionmentioning

confidence: 93%

A Comparison of the CMIP6midHoloceneandlig127kSimulations in CESM2

Otto‐Bliesner

Brady

Tomas

et al. 2020

Paleoceanog and Paleoclimatol

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Results are presented and compared for the Community Earth System Model version 2 (CESM2) simulations of the middle Holocene (MH, 6 ka) and Last Interglacial (LIG, 127 ka). These simulations are designated as Tier 1 experiments (midHolocene and lig127k) for the Coupled Model Intercomparison Project phase 6 (CMIP6) and the Paleoclimate Modeling Intercomparison Project phase 4 (PMIP4). They use the low-top, standard 1°version of CESM2 contributing to CMIP6 DECK, historical, and future projection simulations, and to other modeling intercomparison projects. The midHolocene and lig127k provide the opportunity to examine the responses in CESM2 to the orbitally induced changes in the seasonal and latitudinal distribution of insolation. The insolation anomalies result in summer warming over the Northern Hemisphere continents, reduced Arctic summer minimum sea ice, and increased areal extent of the North African monsoon. The Arctic remains warm throughout the year. These changes are greater in the lig127k than midHolocene simulation. Other notable changes are reduction of the Niño3.4 variability and Drake Passage transport and a small increase in the Atlantic Meridional Overturning Circulation from the piControl to midHolocene to lig127k simulation. Comparisons to paleo-data and to simulations from previous model versions are discussed. Possible reasons for mismatches with the paleo-observations are proposed, including missing processes in CESM2, simplifications in the CMIP6 protocols for these experiments, and dating and calibration uncertainties in the data reconstructions. Plain Language Summary The modeling of past climates, using physically based tools and comparing to paleo-observations, is increasingly seen as a strong test of the models that are used for the projection of future climate changes. We report on simulations by one of the latest large-scale climate models, the Community Earth System Model version 2 (CESM2), for the two most recent warm epochs: the current interglacial-the Holocene, which began 11,650 years agoand the previous interglacial-the Last Interglacial, which extended from 129,000 to 116,000 years ago. The simulations find summer warming over the Northern Hemisphere continents, reduced Arctic summer sea ice, and increased areal extent of the North African monsoon. Cryospheric and oceanic feedbacks drive year-round Arctic warmth. The CESM2 middle Holocene and Last Interglacial simulations are an important resource for the community participating in the Coupled Model Intercomparison Project phase 6 (CMIP6).

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Section: Summary and Discussionmentioning

confidence: 93%

A Comparison of the CMIP6midHoloceneandlig127kSimulations in CESM2

Otto‐Bliesner

Brady

Tomas

et al. 2020

Paleoceanog and Paleoclimatol

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“…Pollen assemblages from marine sediments have been used in Panitz et al (2016) to reconstruct fluctuations of cool temperate and boreal conditions in northern Norway between 3.6 and 3.14 Ma. Plant macrofossils preserved in sediments across the Canadian Arctic Archipelago (Fletcher et al, 2017) have shown warmer and wetter conditions up to the mid-Pliocene in that region.…”

Section: Introductionmentioning

confidence: 99%

Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)

Chan

Abe‐Ouchi

2020

Clim. Past

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Abstract. The second phase of the Pliocene Model Intercomparison Project (PlioMIP2) has attracted many climate modelling groups in its continuing efforts to better understand the climate of the mid-Piacenzian warm period (mPWP) when atmospheric CO2 was last closest to present-day levels. Like the first phase, PlioMIP1, it is an internationally coordinated initiative that allows for a systematic comparison of various models in a similar manner to the Paleoclimate Modelling Intercomparison Project (PMIP). Model intercomparison and model–data comparison now focus specifically on the interglacial at marine isotope stage KM5c (3.205 Ma), and experimental design is not only based on new boundary conditions but includes various sensitivity experiments. In this study, we present results from long-term model integrations using the MIROC4m (Model for Interdisciplinary Research on Climate) atmosphere–ocean coupled general circulation model, developed at the institutes CCSR, NIES and FRCGC in Japan. The core experiment, with CO2 levels set to 400 ppm, shows a warming of 3.1 ∘C compared to the pre-industrial period, with two-thirds of the warming being attributed to the increase in CO2. Although this level of warming is less than that in the equivalent PlioMIP1 experiment, there is slightly better agreement with proxy sea surface temperature (SST) data at PRISM3 (PRISM – Pliocene Research Interpretation and Synoptic Mapping) locations, especially in the northern North Atlantic where there were large model–data discrepancies in PlioMIP1. Similar spatial changes in precipitation and sea ice are seen and the Arctic remains ice-free in the summer in the core experiments of both phases. Comparisons with both the proxy SST data and proxy surface air temperature data from paleobotanical sites indicate a weaker polar amplification in model results. Unlike PlioMIP1, the Atlantic Meridional Overturning Circulation (AMOC) is now stronger than that of the pre-industrial period, even though increasing CO2 tends to weaken it. This stronger AMOC is a consequence of a closed Bering Strait in the PlioMIP2 paleogeography. Also, when present-day boundary conditions are replaced by those of the Pliocene, the dependency of the AMOC strength on CO2 is significantly weakened. Sensitivity tests show that lower values of CO2 give a global SST which is overall more consistent with the PRISM3 SST field presented in PlioMIP1, while SSTs at many of the PRISM4 sites are still too high to be reconciled with any of the model results. On the other hand, tropical Pacific SST in the core experiment agrees well with more recent proxy data, which suggested that PRISM3 SST there was overestimated. Future availability of climate reconstructions from proxy data will continue to help evaluate model results. The inclusion of dynamical vegetation and the effects of all possible extreme orbital configurations outside KM5c should be considered in future experiments using MIROC4m for the mPWP.

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“…Each model's climate sensitivity also influences the simulated mid-Pliocene warming in PlioMIP2. For example, relative to CCSM4 and CESM1.2, CESM2 has the largest equilibrium climate sensitivity (Feng et al, 2020;Haywood et al, 2020) and simulates the strongest North https://doi.org/10.5194/cp-2020-120 Preprint. Discussion started: 22 September 2020 c Author(s) 2020.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…In this study, we analyze simulations with the fifteen models that have participated and provided the simulated AMOC results to PlioMIP2 (Table 1). They are CCSM4 (Feng et al, 2020), CCSM4-UoT (Chandan and Peltier, 2017;, CCSM4-Utrecht (Baatsen et al 2020, in prep), CESM1.2 (Feng et al, 2020), CESM2 (Feng et al, 2020), COSMOS , EC-Earth3-LR (Döscher et al, 2020, in prep), GISS-E2-1-G, HadCM3 (Hunter et al, 2019), IPSLCM5A2 (Tan et al, 2020), IPSLCM5A , IPSLCM6A-LR (Lurton et al, 2020), MIROC4m (Chan and Abe-Ouchi, 2020), NorESM1-F (Li et al, 2020), and NorESM-L (Li et al, 2020). All fifteen models have performed simulations according to the PlioMIP2 experimental protocol .…”

Section: Introduction Of Models Used In Pliomip2mentioning

confidence: 99%

“…The atmospheric CO2 level is in line with the very latest high-resolution proxy reconstruction based on Boron isotopes for ~3.2 Ma (Chalk et al 2018). More details on the individual models and experimental design are introduced in a recent synthesis study (Haywood et al, 2020) and several individual modeling studies (Chandan and Peltier, 2017;Hunter et al, 2019;Chan and Abe-Ouchi, 2020;Döscher et al, 2020;Feng et al, 2020;Li et al, 2020;Lurton et al, 2020;Tan et al, 2020). In addition to these fifteen models, MRI-CGCM (Kamae et al, 2016) and…”

Section: Introduction Of Models Used In Pliomip2mentioning

confidence: 99%

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Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

Zhang¹,

Li²,

Guo³

et al. 2020

Preprint

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Abstract. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), coupled climate models have been used to simulate an interglacial climate during the mid-Piacenzian warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), poleward ocean heat transport and sea surface warming in the Atlantic simulated with these models. In PlioMIP2, all models simulate an intensified mid-Pliocene AMOC. However, there is no consistent response in the simulated Atlantic ocean heat transport, or the depth of the Atlantic overturning cell. The models show a large spread in the simulated AMOC maximum, the Atlantic ocean heat transport, as well as the surface warming in the North Atlantic. Although a few models simulate a surface warming of ~ 8–12 ° in the North Atlantic, similar to the reconstruction from Pliocene Research, Interpretation and Synoptic Mapping (PRISM), most models underestimate this warming. The large model-spread and model-data discrepancies in the PlioMIP2 ensemble does not support the hypothesis that an intensification of the AMOC, together with an increase in northward ocean heat transport, is the dominant forcing for the mid-Pliocene warm climate.

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

Cited by 46 publications

References 89 publications

A Comparison of the CMIP6midHoloceneandlig127kSimulations in CESM2

A Comparison of the CMIP6midHoloceneandlig127kSimulations in CESM2

Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)

Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

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