Abstract

This paper documents the experimental setup and general features of the coupled historical and future climate simulations with the first version of the U.S. Department of Energy (DOE) Energy Exascale Earth System Model (E3SMv1.0). The future projected climate characteristics of E3SMv1.0 at the highest emission scenario (SSP5-8.5) designed in the Scenario Model Intercomparison Project (ScenarioMIP) and the SSP5-8.5 greenhouse gas (GHG) only forcing experiment are analyzed with a focus on regional responses of atmosphere, ocean, sea-ice, and land. Due to its high climate sensitivity, E3SMv1.0 is one of the CMIP6 models with the largest surface warming by the end of the 21st century under the high-emission SSP5-8.5 scenario. The global mean precipitation change is highly correlated to the global temperature change, while the spatial pattern of the change in runoff responds to the precipitation changes. The oceanic mixed layer generally shoals throughout the global ocean. The sea ice, especially in the Northern Hemisphere, rapidly decreases with large seasonal variability. The annual mean AMOC is overly weak with a slower change relative to other CMIP6 models. We detect a significant polar amplification in E3SMv1.0 from the atmosphere, ocean, and sea ice. Comparing the SSP5-8.5 all-forcing experiment with the GHG-only experiment, we find that the unmasking of the aerosol effects due to the decline of the aerosol loading in the future projection period causes accelerated warming in SSP5-8.5 all-forcing experiment. While the oceanic climate response is mainly controlled by the GHG forcing, the land runoff response is impacted primarily by forcings other than GHG over certain regions. However, the importance of the GHG forcing on the land runoff changes grows in the future climate projection period compared to the historical period.

Highlights

  • Compared to previous CMIP climate models, the latest CMIP phase 6 (CMIP6) models simulate a higher ensemble equi20 librium climate sensitivity (ECS) with a larger spread (Meehl et al, 2020; Zelinka et al, 2020)

  • Due to the strong land-atmosphere coupling, we speculate that the magnitude of the precipitation bias in the current climate simulation links to the projected climate change amplification in the drying signal, which needs further multi-model investigation to confirm in the future study

  • We describe the experimental setup and general features of the coupled historical and future projection simulations that E3SMv1.0 contributes to ScenarioMIP of CMIP6

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Summary

Introduction

Compared to previous CMIP climate models, the latest CMIP phase 6 (CMIP6) models simulate a higher ensemble equi librium climate sensitivity (ECS) with a larger spread (Meehl et al, 2020; Zelinka et al, 2020). Model Intercomparison Project (ScenarioMIP) aims to generate multi-model climate projections for alternate scenarios of future emissions and land-use changes produced with integrated assessment models. An ensemble analysis of the ScenarioMIP participating global coupled Earth system models has shown that the global mean surface air temperature and surface 25 precipitation response of each individual model is highly correlated to its climate sensitivity, especially for the high-emission scenario (Tebaldi et al, 2021). It is expected that E3SMv1.0 will be among the warmest models in terms of the global mean surface temperature in future climate projections due to its high ECS and TCR. Through our participation in the ScenarioMIP project, we conducted future climate projection experiments in a high-emission scenario with E3SMv1.0. We describe regional responses of key climate components, namely atmosphere, ocean, sea-ice and land runoff 45 in the high-emission scenario simulated by E3SMv1.0. The run scripts used to set up simulations beyond the default configuration in the model compset and submit jobs for these experiments are archived to reproduce these simulations (see Code availability)

The CMIP6 historical experiment
GHG-only Experiment
Atmosphere Climatology
Ocean and Sea-ice
Land climatology
Atmospheric Responses
Ocean and Sea-ice Responses
Land Responses
Summary and conclusions
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