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last modified May 28, 2015 06:38 PM
WCRP Coupled Model Intercomparison Project

Name: CMIP
Contact: Karl E. Taylor
Start: Jan 01, 1995
Lead: WGCM
Funded by: RGCM
Homepage: cmip-pcmdi.llnl.gov

Project Description

Under the World Climate Research Programme (WCRP) the Working Group on Cloupled Modelling (WGCM) established the Coupled Model Intercomparison Project (CMIP) as a standard experimental protocol for studying the output of coupled atmosphere-ocean general circulation models (AOGCMs). CMIP provides a community-based infrastructure in support of climate model diagnosis, validation, intercomparison, documentation and data access. This framework enables a diverse community of scientists to analyze GCMs in a systematic fashion, a process which serves to facilitate model improvement. Virtually the entire international climate modeling community has participated in this project since its inception in 1995. The Program for Climate Model Diagnosis and Intercomparison (PCMDI) archives much of the CMIP data and provides other support for CMIP. PCMDI's CMIP effort is funded by the Regional and Global Climate Modeling (RGCM) Program of the Climate and Environmental Sciences Division of the U.S. Department of Energy's Office of Science, Biological and Environmental Research (BER) program.

Coupled atmosphere-ocean general circulation models allow the simulated climate to adjust to changes in climate forcing, such as increasing atmospheric carbon dioxide. CMIP began in 1995 by collecting output from model "control runs" in which climate forcing is held constant. Later versions of CMIP have collected output from an idealized scenario of global warming, with atmospheric CO2 increasing at the rate of 1% per year until it doubles at about Year 70. CMIP output is available for study by approved diagnostic sub-projects.

Phase three of CMIP (CMIP3) included "realistic" scenarios for both past and present climate forcing. The research based on this dataset provided much of the new material underlying the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4).

CMIP5 is the fifth phase of the Coupled Model Intercomparison Project (CMIP5). CMIP5 provide a multi-model context for 1) assessing the mechanisms responsible for model differences in poorly understood feedbacks associated with the carbon cycle and with clouds, 2) examining climate “predictability” and exploring the ability of models to predict climate on decadal time scales, and, more generally, 3) determining why similarly forced models produce a range of responses.


CMIP database

Details of the CMIP database, together with access information, may be found on the CMIP Web site at PCDMI (see http://www-pcmdi.llnl.gov/projects/cmip/diagsub.php ). The first phase of CMIP, called CMIP1, collected output from coupled GCM control runs in which CO2, solar brightness and other external climatic forcing is kept constant. (Different CMIP control runs use different values of solar "constant" and CO2 concentration, ranging from 1354 to 1370 W m-2 and 290 to 345 ppm respectively; for details see http://www-pcmdi.llnl.gov/projects/cmip/index.php) A subsequent phase, CMIP2, collected output from both model control runs and matching runs in which CO2 increases at the rate of 1% per year. No other anthropogenic climate forcing factors, such as anthropogenic aerosols (which have a net cooling effect), are included. Neither the control runs nor the increasing-CO2 runs in CMIP include natural varations in climate forcing, e.g., from volcanic eruptions or changing solar brightness.

CMIP thus facilitates the study of intrinsic model differences at the price of idealizing the forcing scenario. The rate of radiative forcing increase implied by 1% per year increasing CO2 is nearly a factor of two greater than the actual anthropogenic forcing in recent decades, even if non-CO2 greenhouse gases are added in as part of an "equivalent CO2 forcing" and anthropogenic aerosols are ignored. Thus the CMIP2 increasing-CO2 scenario cannot be considered as realistic for purposes of comparing model-predicted and observed climate changes during the past century. It is also not a good estimate of future anthropogenic climate forcing, except perhaps as an extreme case in which the world accelerates its consumption of fossil fuels while reducing its production of anthropogenic aerosols. Nevertheless, this idealized scenario generates an easily discernible response in all the CMIP models and thus provides the opportunity to compare and possibly explain different responses arising from different model formulations.

See An Overview of Results from the Coupled Model Intercomparison Project (CMIP) by Curt Covey et al. for more details.


Most of these information have been collected from CMIP´s homepage .They have been last updated on May 28, 2015
Filed under: Project, International