Abstract
This paper describes the GISS‐E2.1 contribution to the Coupled Model Intercomparison Project, Phase 6 (CMIP6). This model version differs from the predecessor model (GISS‐E2) chiefly due to parameterization improvements to the atmospheric and ocean model components, while keeping atmospheric resolution the same. Model skill when compared to modern era climatologies is significantly higher than in previous versions. Additionally, updates in forcings have a material impact on the results. In particular, there have been specific improvements in representations of modes of variability (such as the Madden‐Julian Oscillation and other modes in the Pacific) and significant improvements in the simulation of the climate of the Southern Oceans, including sea ice. The effective climate sensitivity to 2 is slightly higher than previously at 2.7–3.1°C (depending on version) and is a result of lower CO radiative forcing and stronger positive feedbacks.
Highlights
The evaluation and assessment of climate models that are being used for attribution of past change and projections of future change has, for the last two decades, been dominated by the Coupled Model Intercomparison Project (CMIP)
Plain Language Summary This paper describes the latest iteration of the National Aeronautics and Space Administration (NASA) Goddard Institute for Space Studies (GISS) climate model, which will be used for understanding historical climate change and to make projections for the future
Community experience over the last decade has demonstrated that constrained structural diversity in climate modeling is essential for elucidating important connections between processes and outcomes, and GISS models, with their distinct pedigree, have an important and continuing role to play in providing part of that diversity (Knutti et al, 2013)
Summary
The evaluation and assessment of climate models that are being used for attribution of past change and projections of future change has, for the last two decades, been dominated by the Coupled Model Intercomparison Project (CMIP). For that role to be successful, GISS needs to maintain and improve model realism (better process inclusion and higher skill) and continue participation in international and national climate model assessment projects. These projects allow model developers to benefit from the very broad scrutiny of results in these public archives from interested researchers and users across the world. This paper is a description and an initial assessment of the GISS‐E2.1 climate model, the first GISS contribution to CMIP6 This model version was developed as part of a long‐term strategy to improve model performance as much as possible without a significant jump in computational resources, building from the GISS‐E2 models used in CMIP5.
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