DOI: 10.5065/pnfp-t325
title: iPOGS: CESM HR simulations under the RCP 2.6 and RCP 4.5 (2006-2100) scenario

description: Current predictions and projections of future sea-level changes are based on Coupled Model Intercomparison Project (CMIP) class climate model simulations. Although this class of models is capable of simulating global sea-level rise and its basic spatial patterns, they are unable to robustly and accurately predict or project future regional and local sea-level changes because of their limitations in representing complex coastline and bathymetry features and regional ocean circulations with their coarse (approximately 100 km) horizontal resolutions. More specifically, sea-level changes within the Gulf of Mexico are closely linked to changes in the Loop Current and its eddies, which cannot be resolved by these CMIP-class models.To address this fundamental issue, we have completed two projections with the Community Earth System Model (CESM) at a Tropical Cyclone-permitting and ocean-mesoscale-eddy-rich horizontal resolution (hereafter simply referred to as CESM-HR). The CESM-HR configuration is based on an earlier CESM version, CESM1.3, with many additional modifications and improvements. CESM-HR uses a 0.25 degree grid in the atmosphere and land components and a 0.1 degree grid in the ocean and sea-ice components. The primary reason for using an older model version, instead of the latest CESM2, is that CESM2 does not support a high-resolution version per the decision by the CESM Scientific Steering Committee. The component models within CESM1.3 are the Community Atmosphere Model version 5 (CAM5; Neale et al., 2012), the Parallel Ocean Program version 2 (POP2; Danabasoglu et al., 2012; Smith et al., 2010), the Community Ice Code version 4 (CICE4; Hunke and Lipscomb, 2008), and the Community Land Model version 4 (CLM4; Lawrence et al., 2011).Following the protocol for the CMIP phase 5 (CMIP5) experiments, the representative concentration pathway 2.6 (RCP 2.6) and representative concentration pathway 4.5 (RCP 4.5) were used to force the model from 2006 to 2100. RCP 2.6 represents a pathway where greenhouse gas emissions are strongly reduced. This scenario is a so-called "peak" scenario, which means it shows a level of radiative forcing by greenhouse gas emissions peaking by mid-century then returning to 2.6 W/m^2 by 2100. RCP 4.5 represents a stabilization scenario, which means the radiative forcing level stabilizes at 4.5 W/m^2 before 2100 by employing of a range of technologies and strategies for reducing greenhouse gas emissions. This CESM-HR ensemble was completed as part of our National Academy of Sciences (NAS) funded project entitled "Improving Prediction and Projection of Gulf of Mexico Sea-Level Changes Using Eddy-Resolving Earth System Models (iPOGS)". This effort is complementary to the 10-member ensemble of CESM-HR historical and future (with RCP 8.5 forcing) climate simulations produced by our National Science Foundation (NSF) funded project entitled "Understanding the role of mesoscale atmosphere-ocean interactions in seasonal-to-decadal climate prediction (MESACLIP)". The RCP 2.6 and 4.5 simulation starts at the end of the member #3 of the 10-member ensemble of historical simulation from MESACLIP, enabling the exploration of future projections associated with varying levels of mitigation and future greenhouse gas emissions. For example, Figure 1 [https://rda.ucar.edu/OS/web/datasets/d651043/docs/global_steric_ts.png] shows the global-mean dynamical sea level (DSL) from simulations under different forcings. The stronger warming associated with the RCP 8.5 forcing results in an additional 10 cm rise in global-mean DSL by 2100 compared to that of the RCP 6.0 ensemble.Citation: The two papers linked below are the most appropriate references for the CESM-HR ensemble. To cite the dataset, use Chang et al. (2025). We ask that you also cite the dataset itself using the reference Castruccio et al. (2025) [https://rda.ucar.edu/datasets/d651043/citation/] in any documents or publications using these data. Chang et al. (2020) describes the initial CESM-HR simulations, including the 500-year pre- industrial control simulation and the first 250-year historical and future climate simulation from 1850 to 2100. We would also appreciate receiving a copy of the relevant publications. This will help us to justify keeping the data freely available online in the future. Thank you!