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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

The data of following projects with close ties to CMIP5 are provided beside CMIP5 data:
  • 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

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.


Last Update: April 7, 2021, 4:29 p.m. by Admin User
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