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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 can help our understanding of past and future climate changes, and also lead to climate model improvements. CMIP falls under the direction of the Working Group on Coupled Modeling, an activity 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 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“, published in the Bulletin of the American Meteorological Society for a detailed explanation of the CMIP5 experiments.

The Sixth Coupled Model Intercomparison Project, CMIP6, will be used in support of the 6th assessment report (AR6) of the IPCC, to be published in 2021. It includes 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: CM4.0 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 CM4.0 are available through the Earth System Grid Federation here.

For the previous generation intercomparison, 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.

Our model development goal beyond CMIP5 and for the next several years is to take what we have learned from these diverse modeling activities and create a new comprehensive Earth System model.

As a result, we have several distinct contributions to CMIP5, as described below:

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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.