Evaluation of CNRM Earth System Model, CNRM‐ESM2‐1: Role of Earth System Processes in Present‐Day and Future Climate

By R. Séférian, P. Nabat, M. Michou, D. Saint‐Martin, A. Voldoire, J. Colin, Bertrand Decharme, C. Delire, S. Berthet, M. Chevallier and 22 more. Journal of Advances in Modeling Earth Systems, 2019

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This study introduces CNRM‐ESM2‐1, the Earth system (ES) model of second generation developed by CNRM‐CERFACS for the sixth phase of the Coupled Model Intercomparison Project (CMIP6). CNRM‐ESM2‐1 offers a higher model complexity than the Atmosphere‐Ocean General Circulation Model CNRM‐CM6‐1 by adding interactive ES components such as carbon cycle, aerosols, and atmospheric chemistry. As both models share the same code, physical parameterizations, and grid resolution, they offer a fully traceable framework to investigate how far the represented ES processes impact the model performance over present‐day, response to external forcing and future climate projections. Using a large variety of CMIP6 experiments, we show that represented ES processes impact more prominently the model response to external forcing than the model performance over present‐day. Both models display comparable performance at replicating modern observations although the mean climate of CNRM‐ESM2‐1 is slightly warmer than that of CNRM‐CM6‐1. This difference arises from land cover‐aerosol interactions where the use of different soil vegetation distributions between both models impacts the rate of dust emissions. This interaction results in a smaller aerosol burden in CNRM‐ESM2‐1 than in CNRM‐CM6‐1, leading to a different surface radiative budget and climate. Greater differences are found when comparing the model response to external forcing and future climate projections. Represented ES processes damp future warming by up to 10% in CNRM‐ESM2‐1 with respect to CNRM‐CM6‐1. The representation of land vegetation and the CO2‐water‐stomatal feedback between both models explain about 60% of this difference. The remainder is driven by other ES feedbacks such as the natural aerosol feedback.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/18c902da1629afd1ae0da5bf91d6fb932ab046ab

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Citations in the corpus

Emergent constraints on equilibrium climate sensitivity in CMIP5: do they hold for CMIP6? (2020, result): “Tian (2015) found a link between mid-tropospheric humidity over the tropical Pacific and simulated moisture, precipitation, clouds, and large-scale circulation and thus ECS in CMIP3 and CMIP5 models. The study explains this link with the similarity of mid-tropospheric humidity and precipitation patt”
Resolving and Parameterising the Ocean Mesoscale in Earth System Models (2020, background): “…of SST in ESMs demonstrates errors that are broadly similar across a range of models with cooling in the North Pacific, warming in the Southern Ocean, warming in the Eastern Boundary Upwelling zones, and a patch of very cold water ( ‘ blue spot ’ ) in the North Atlantic [26, 28, 29, 91, 100].”