CMIP5 @ IPSL

At a September 2008 meeting involving 20 climate modeling groups from around the world, the WCRP's Working Group on Coupled Modelling (WGCM), with input from the IGBP AIMES project, agreed to promote a new set of coordinated climate model experiments. These experiments comprise the fifth phase of the Coupled Model Intercomparison Project (CMIP5). CMIP5 will notably provide a multi-model context for:

• assessing the mechanisms responsible for model differences in poorly understood feedbacks associated with the carbon cycle and with clouds,
• examining climate “predictability” and exploring the ability of models to predict climate on decadal time scales, and, more generally, and
• determining why similarly forced models produce a range of responses.

It is expected that some of the scientific questions that arose during preparation of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) was through CMIP5 be addressed for evaluation in the Fifth Assessment Report (AR5). CMIP5 promotes a standard set of model simulations in order to:

• evaluate how realistic the models are in simulating the recent past,
• provide projections of future climate change on two time scales, near term (out to about 2035) and long term (out to 2100 and beyond), and
• understand some of the factors responsible for differences in model projections, including quantifying some key feedbacks such as those involving clouds and the carbon cycle

Closely tied projects

• GeoMIP (Geoengineering Model Intercomparison Project)
• PMIP3 (Paleoclimate Modelling Intercomparison Project)
• TAMIP (Transpose-AMIP)
• EUCLIPSE (European Union Cloud Intercomparison, Process Study and Evaluation Project)
• LUCID (Land-Use and Climate, IDentification of robust impacts)

Experiment design

• A detailed description of the experiment design is provided by Taylor et al (2009), A Summary of the CMIP5 Experiment Design (last update 22 Jan 2011).
• Addendum to this document: Experiment_design_addendum.pdf.
• A more condensed summary of the experiment design can be found in Taylor et al, An Overview of CMIP5 and the experiment design.
• An overview of various aspects of CMIP5 is provided by WCRP Coupled Model Intercomparison Project Phase 5,Special Issue of the CLIVAR Exchanges Newsletter, No. 56.
• The objectives and strategy for the CMIP5 decadal predictions simulations are summarized in Meehl et al. 2009, Decadal Prediction.
• An outline of the strategy for including ESMs in CMIP is outlined in Meeh et al. 2007, A strategy for climate change stabilization experiments with AOGCMs and ESMs and Hibbard et al. 2007, A strategy for climate change stabilization experiments.
• The standard output document contains the list of requested variables: PDF or XLS.

CMIP5 data characteristics are:

• Each file contains a single output variable (along with coordinate/grid variables, attributes and other metadata) from a single model and a single simulation (i.e., from a single ensemble member of a single climate experiment). This method of structuring model output best serves the needs of most researchers who are typically interested in only a few of the many variables in the Model Intercomparison Project (MIP) databases. Data requests can be satisfied by simply sending the appropriate file(s) without first extracting the individual field(s) of interest.
• There is flexibility in specifying how many time slices (samples) are stored in a single file. A single file can contain all the time-samples for a given variable and climate experiment, or the samples can be distributed in a sequence of files.
• Much of the metadata written to the output files is defined in MIP-specific tables of information, which in this document are referred to simply as "MIP tables" in ASCII files.
• The metadata is constrained by the CF convention (NetCDF Climate and Forecast (CF) Metadata Convention) and as specified in the CMIP5 tables.
• The output files are written through the NetCDF API following the NETCDF_CLASSIC model and without compression of any kind.
• It is recommended that the CMOR software be used to write the model output, which will ensure compliance with the CMIP5 specifications. See the Output Requirements page for further information and see CMIP5 Model Output Format and Metadata Requirements for full specifications for writing CMIP5 output.

References

• CMIP5 citations
• The IPCC/CMIP5 AR5 schedule
• The CMIP5 Data Reference Syntax (DRS) and Controlled Vocabulary is the common naming system to be used in files, directories, metadata and URLs to identify datasets. See also the summary of controlled vocabulary for the CMIP5/IPCC5 project, derived from the DRS specification.
• CMIP5 Model output requirements for structure, format and metadata: CMIP5_output_metadata_requirements.pdf.
• The ocean variables list is in a document prepared by the Working Group on Ocean Model Development, Griffies et al., 2009: Sampling Physical Ocean Fields in WCRP CMIP5 Simulations.
• CMOR2 Users Guide.
• Towards new Scenarios for Analysis of Emissions, Climate Change, Impacts and Response Starategies: IPCC Expert Meeting Report (2007).
• The RPC White Paper about past 2100 scenarios from IAM group.
• The Modeling Groups and their Terms of Use.
• CMIP5 Errata.
• CMIP5 Publications page.
• The RCP (Reference Concentration Pathways) database.