18 Oct 2023
 | 18 Oct 2023
Status: this preprint is open for discussion.

An Overview of the E3SM version 2 Large Ensemble and Comparison to other E3SM and CESM Large Ensembles

John Fasullo, Jean-Christophe Golaz, Julie Caron, Nan Rosenbloom, Gerald Meehl, Warren Strand, Sasha Glanville, Samantha Stevenson, Maria Molina, Christine Shields, Chengzhu Zhang, James Benedict, and Tony Bartoletti

Abstract. This work assesses a recently produced 21-member climate model large ensemble (LE) based on the U.S. Department of Energy’s Energy Exascale Earth System Model (E3SM) version 2 (E3SM2). The ensemble spans the historical era (1850 to 2014) and 21st Century (2015 to 2100), using the SSP370 pathway, allowing for an evaluation of the model’s forced response (FR). A companion 500-year preindustrial control simulation is used to initialize the ensemble and estimate drift. Characteristics of the LE are documented and compared against other recently produced ensembles using the E3SM version 1 (E3SM1) and Community Earth System Model (CESM) versions 1 and 2. 

Simulation drift is found to be smaller, and model agreement with observations is higher, in versions 2 of E3SM and CESM versus their version 1 counterparts. Shortcomings in E3SM2 include a lack of warming from the mid to late 20th Century likely due to excessive cooling influence of anthropogenic sulfate aerosols, an issue also evident in E3SM1. Associated impacts on the water cycle and energy budgets are also identified. Considerable model dependence in the FR associated with both aerosol and greenhouse gas responses is documented and E3SM2’s sensitivity to variable prescribed biomass burning emissions is demonstrated.

Various E3SM2 and CESM2 model benchmarks are found to be on par with the highest performing recent generation of climate models, establishing the E3SM2 LE as an important resource for estimating climate variability and responses, though with various caveats as discussed herein. As an illustration of the usefulness of LEs in estimating the potential influence of internal variability, the observed CERES-era trend in net top-of-atmosphere flux is compared to simulated trends and found to be much larger than the FR in all LEs, with only a few members exhibiting trends as large as observed, thus motivating further study.

John Fasullo et al.

Status: open (until 07 Dec 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2310', Anonymous Referee #1, 20 Nov 2023 reply
  • RC2: 'Comment on egusphere-2023-2310', Anonymous Referee #2, 20 Nov 2023 reply

John Fasullo et al.


Total article views: 192 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
139 46 7 192 17 3 4
  • HTML: 139
  • PDF: 46
  • XML: 7
  • Total: 192
  • Supplement: 17
  • BibTeX: 3
  • EndNote: 4
Views and downloads (calculated since 18 Oct 2023)
Cumulative views and downloads (calculated since 18 Oct 2023)

Viewed (geographical distribution)

Total article views: 187 (including HTML, PDF, and XML) Thereof 187 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 28 Nov 2023
Short summary
Climate model large ensembles provide a unique and invaluable means for estimating the climate response to external forcing agents, thereby allowing for the isolation of internal variability. Here, an overview of the Energy Exascale Earth System Model (E3SM) version 2 large ensemble is given along with comparisons to large ensembles from E3SM version 1 and versions 1 and two of the Community Earth System Model. The manuscript provides broad and important context for users of these ensembles.