The Community Earth System Model Version 2 (CESM2)

Danabasoglu, Gökhan; Lamarque, Jean‐François; Bacmeister, Julio T.; Bailey, David A.; DuVivier, Alice K.; Edwards, J. C. W.; Emmons, L. K.; Fasullo, John T.; García, Rolando R.; Gettelman, Andrew; Hannay, Cécile; Holland, Marika M.; Large, William G.; Lauritzen, P. H.; Lawrence, David M.; Lenaerts, Jan T. M.; Lindsay, Keith; Lipscomb, William; Mills, Michael J.; Neale, Rich; Oleson, Keith W.; Otto-Bliesner, Bette; Phillips, Adam S.; Sacks, William J.; Tilmes, Simone; Kampenhout, Leo van; Vertenstein, Mariana; Bertini, Alice; Dennis, John M.; Deser, Clara; Fischer, C.; Fox‐Kemper, Baylor; Kay, J. E.; Kinnison, Douglas E.; Kushner, Paul J.; Larson, Vincent E.; Long, Matthew C.; Mickelson, Sheri; Moore, J. Keith; Nienhouse, Eric; Polvani, Lorenzo M.; Rasch, Philip J.; Strand, Warren G.

doi:10.1029/2019ms001916

Cited by 1,405 publications

(1,080 citation statements)

References 155 publications

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“…During DJF, LENS exhibited too much divergence over the western Indian ocean (Figure 10c), which is a common feature among CMIP6 models ( Figure A1k) and was associated with too much precipitation in that region. In CESM2, the excess divergence is reduced and shifted further west and accompanies a reduction in the excess precipitation bias (Danabasoglu et al, 2019). Overall, the errors in the 200-hPa velocity potential field have been reduced in DJF, making CESM2 one of the top ranking models in this metric (Figure 10g).…”

Section: Journal Of Geophysical Research: Atmospheresmentioning

confidence: 95%

“…These simulations are run under historical forcings (Hoesly et al, 2018;van Marle et al, 2017) until 2014. The coupled simulations are each initialized from different years from a preindustrial (i.e., perpetual year 1850 forcing) control that has been spun-up for over 1,000 years (Danabasoglu et al, 2019), while the prescribed SST simulations begin in 1950. For each ensemble we will only consider the period from 1979 to 2014 for comparison with modern reanalyses over the satellite era.…”

Section: Cesm2mentioning

confidence: 99%

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An Evaluation of the Large‐Scale Atmospheric Circulation and Its Variability in CESM2 and Other CMIP Models

et al. 2020

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The Community Earth System Model 2 (CESM2) is the latest Earth System Model developed by the National Center for Atmospheric Research in collaboration with the university community and is significantly advanced in most components compared to its predecessor (CESM1). Here, CESM2's representation of the large‐scale atmospheric circulation and its variability is assessed. Further context is providedthrough comparison to the CESM1 large ensemble and other models from the Coupled Model Intercomparison Project (CMIP5 and CMIP6). This includes an assessment of the representation of jet streams and storm tracks, stationary waves, the global divergent circulation, the annular modes, the North Atlantic Oscillation, and blocking. Compared to CESM1, CESM2 is substantially improved in the representation of the storm tracks, Northern Hemisphere (NH) stationary waves, NH winter blocking and the global divergent circulation. It ranks within the top 10% of CMIP class models in many of these features. Some features of the Southern Hemisphere (SH) circulation have degraded, such as the SH jet strength, stationary waves, and blocking, although the SH jet stream is placed at approximately the correct location. This analysis also highlights systematic deficiencies in these features across the new CMIP6 archive, such as the continued tendency for the SH jet stream to be placed too far equatorward, the North Atlantic westerlies to be too strong over Europe, the storm tracks as measured by low‐level meridional wind variance to be too weak and a lack of blocking in the North Atlantic sector.

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Section: Journal Of Geophysical Research: Atmospheresmentioning

confidence: 95%

Section: Cesm2mentioning

confidence: 99%

An Evaluation of the Large‐Scale Atmospheric Circulation and Its Variability in CESM2 and Other CMIP Models

et al. 2020

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“…Most CMIP6 models also projected a significant weakening of the AMOC (Weijer et al 2020). Here we focus on the role of the AMOC in the transient response of the climate system to changes in greenhouse gas forcing, a topic that has not been fully addressed, using two CMIP6 models: the Community Earth System Model version 2 (CESM2; Danabasoglu et al 2019) and the Energy Exascale Earth System Model version 1 (E3SM1; Golaz et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Role of AMOC in Transient Climate Response to Greenhouse Gas Forcing in Two Coupled Models

Roekel

Weijer

et al. 2020

Journal of Climate

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As the greenhouse gas concentrations increase, a warmer climate is expected. However, numerous internal climate processes can modulate the primary radiative warming response of the climate system to rising greenhouse gas forcing. Here the particular internal climate process that we focus on is the Atlantic meridional overturning circulation (AMOC), an important global-scale feature of ocean circulation that serves to transport heat and other scalars, and we address the question of how the mean strength of AMOC can modulate the transient climate response. While the Community Earth System Model version 2 (CESM2) and the Energy Exascale Earth System Model version 1 (E3SM1) have very similar equilibrium/effective climate sensitivity, our analysis suggests that a weaker AMOC contributes in part to the higher transient climate response to a rising greenhouse gas forcing seen in E3SM1 by permitting a faster warming of the upper ocean and a concomitant slower warming of the subsurface ocean. Likewise the stronger AMOC in CESM2 by permitting a slower warming of the upper ocean leads in part to a smaller transient climate response. Thus, while the mean strength of AMOC does not affect the equilibrium/effective climate sensitivity, it is likely to play an important role in determining the transient climate response on the centennial time scale.

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“…The model experiments described here were performed with the WACCM6. Details on CESM2 and WACCM6 model configurations, including an overview of the performance and new features, are described by Danabasoglu et al (2019) and Gettelman et al (2019), respectively. The WACCM6 atmospheric model uses a horizontal resolution of 1.25 o in longitude and 0.95 o in latitude, and 70 vertical layers, reaching up to 140 km height above sea level (6x10 −6 hPa).…”

Section: Model Descriptionmentioning

confidence: 99%

“…The earlier version of the model shows a slowing of the AMOC for the RCP8.5 scenario similar to the WACCM6 CMIP6 SSP5-85 simulation, which is however much smaller. Danabasoglu et al (2019) found that the maximum AMOC strength in 8 https://doi.org/10.5194/esd-2019-76 Preprint. Discussion started: 3 December 2019 c Author(s) 2019.…”

Section: Atlantic Meridional Overturning Circulation Changesmentioning

confidence: 99%

Reaching 1.5 °C and 2.0 °C global surface temperature targets using stratospheric aerosol geoengineering

Tilmes¹,

MacMartin²,

Lenaerts³

et al. 2019

Preprint

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Abstract. We propose new testbed model experiments for the Geoengineering Model Intercomparison Project (GeoMIP) that are designed to limit global warming to 1.5 °C or 2.0 °C above 1850–1900 conditions using stratospheric aerosol geoengineering (SAG). The new modeling experiments use the overshoot scenario defined in CMIP6 (SSP5-34-OS) as a baseline scenario and are designed to reduce side effects of SAG in reaching three temperature targets: global mean surface temperature, and inter-hemispheric and pole-to-equator surface temperature gradients. We further compare results to another SAG simulation using a high emission scenario (SSP5-85) as a baseline scenario in order to investigate the dependency of impacts using different injection amounts to offset different amounts of warming by SAG. The new testbed simulations are performed with the CESM2(WACCM6). We use a feedback algorithm that identifies the needed amount of sulfur dioxide injections in the stratosphere at four predefined latitudes, 30° N, 15° N, 15° S, and 30° S, to reach the three temperature targets. Here we analyze climate variables and quantities that matter for societal and ecosystem impacts. We find that changes from present day conditions (2015–2025) in some variables depend strongly on the defined temperature target (1.5 °C vs 2.0 °C). These include surface air temperature and related impacts, the Atlantic Meridional Overturning Circulation (AMOC), which impacts ocean net primary productivity, and changes in ice sheet surface mass balance, which impacts sea-level rise. Others, including global precipitation changes and the recovery of the Antarctic ozone hole, depend strongly on the amount of SAG application. Furthermore, land net primary productivity as well as ocean acidification depend mostly on the global atmospheric CO2 concentration and therefore the baseline scenario. Multi-model comparisons of the experiments proposed here would help identify consequences of scenarios that include strong mitigation, carbon dioxide removal with some SAG application, on societal impacts and ecosystems.

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The Community Earth System Model Version 2 (CESM2)

Cited by 1,405 publications

References 155 publications

An Evaluation of the Large‐Scale Atmospheric Circulation and Its Variability in CESM2 and Other CMIP Models

An Evaluation of the Large‐Scale Atmospheric Circulation and Its Variability in CESM2 and Other CMIP Models

Role of AMOC in Transient Climate Response to Greenhouse Gas Forcing in Two Coupled Models

Reaching 1.5 °C and 2.0 °C global surface temperature targets using stratospheric aerosol geoengineering

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