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GFDL’s Contribution to the Coupled Model Intercomparison Project

Coupled Model Intercomparison Project (CMIP) is an international effort to improve climate models by comparing multiple model simulations to observations and to each other. These comparisons support better understanding of past and future climate changes and climate and Earth System Model (ESM) improvements. CMIP falls under the direction of the Working Group on Coupled Modeling within the Earth System Modeling and Observations core project of the World Climate Research Program. CMIP has coordinated five past large model intercomparison projects. Most have been extensively used in the various Intergovernmental Panel on Climate Change (IPCC) assessment reports since 1990.


The Sixth Coupled Model Intercomparison Project, CMIP6, was used in support of the 6th assessment report (AR6) of the IPCC, published in 2021. It included not only the standard suite of control, historical, and future projections but also a suite of 23 endorsed Model Intercomparison Projects suiting a variety of scientific goals. See “Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization“, for a detailed explanation of the CMIP6 experiments.

For CMIP6, GFDL took a comprehensive approach to merging improvements in its CMIP5 suite (see below) to contribute two state-of the-art coupled models: CM4 focusing on physical climate with high (1/4°) ocean resolution, and a fully coupled chemistry-carbon-climate Earth System Model with representation of both the stratosphere and biosphere (ESM4.1). Model data from GFDL’s latest generation ESM4.1 and CM4 are available through the Earth System Grid Federation here.

More information about GFDL’s contributions to CMIP6 are described below:


Our CMIP6 experiments with CM4 focused on capitalizing on atmospheric advances in AM4 at 1° (Zhao et al., 2018a; 2018b), 1/4° MOM6 ocean (Adcroft et al., 2019), and full physical coupling with land and sea ice (Held et al., 2019).

Earth System Model 4 (ESM4)

Our CMIP6 experiments with Earth System Model version 4.1 (Dunne et al., 2020) included many of the integrations found in the long-term CMIP5 experimental design through its comprehensive representation of coupled carbon-chemistry climate interactions merging the capabilities of previous generation CM3, ESM2M, and ESM2G (see below) with new capabilities in atmospheric chemistry (Horowitz et al., 2020), and biogeochemistry and ecosystems in ocean (Stock et al., 2020) and land (Shevliakova et al., 2024).


The previous, Fifth Coupled Model Intercomparison Project, CMIP5, was used in support of the 5th assessment report (AR5) of the IPCC, published in 2013 and 2014. See “An Overview of CMIP5 and the experiment design“ for a detailed explanation of the CMIP5 experiments.  For CMIP5, GFDL continued to build on its past successful climate modeling efforts, particularly those associated with the IPCC 4th Assessment. As our work began for CMIP5, it was evident that it was not practical for us to incorporate all important avenues we were pursuing into a single comprehensive climate model. The strategy that evolved was to proceed developing several distinct modeling streams on the timescale of CMIP5 and AR5, and to postpone the attempt to incorporate all of these efforts into a single comprehensive model until after AR5.

More information about GFDL’s contributions to CMIP5 are described below:


Our CMIP5 experiments with CM3 included many of the integrations found in the long-term CMIP5 experimental design. The focus of this physical climate model is on the role of aerosols, aerosol-cloud interactions, and atmospheric chemistry in climate variability and climate change.

Two Earth System Models (ESM)

Our CMIP5 experiments with Earth System Models included many of the integrations found in the long-term CMIP5 experimental design. The ESMs, by design, close the carbon cycle and are used to study the impact of climate change on ecosystems, ecosystem changes on climate and human activities on ecosystems.


HiRAM integrated the “time slice” experiments which are part of both the near- and long-term CMIP5 experimental design. HiRAM is a high resolution model of the atmosphere and land surface, with the ocean surface conditions prescribed. It is used to investigate regional climate change, as well as past and future changes in hurricane activity and other extreme weather events.

Decadal prediction

The decadal prediction experiments are designed to assess the predictability of climate (natural and forced) changes on time scales up to 10 years. GFDL used the CM2.1 model to perform these experiments, which are part of the near-term CMIP5 experimental design.

Planning for the Seventh Coupled Model Intercomparison Project is underway, and GFDL is engaged both as a modeling center and co-leading the CMIP Panel (John Dunne) and Climate Forcings Task Team (Vaishali Naik).  Our model development goal since CMIP6 has been to leverage analysis of the CMIP6 ensemble to set development priorities and create a revised ESM taking advantage of recent internal development efforts.


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