Abstract
Abstract. By coordinating the design and distribution of global climate model simulations of the past, current, and future climate, the Coupled Model Intercomparison Project (CMIP) has become one of the foundational elements of climate science. However, the need to address an ever-expanding range of scientific questions arising from more and more research communities has made it necessary to revise the organization of CMIP. After a long and wide community consultation, a new and more federated structure has been put in place. It consists of three major elements: (1) a handful of common experiments, the DECK (Diagnostic, Evaluation and Characterization of Klima) and CMIP historical simulations (1850–near present) that will maintain continuity and help document basic characteristics of models across different phases of CMIP; (2) common standards, coordination, infrastructure, and documentation that will facilitate the distribution of model outputs and the characterization of the model ensemble; and (3) an ensemble of CMIP-Endorsed Model Intercomparison Projects (MIPs) that will be specific to a particular phase of CMIP (now CMIP6) and that will build on the DECK and CMIP historical simulations to address a large range of specific questions and fill the scientific gaps of the previous CMIP phases. The DECK and CMIP historical simulations, together with the use of CMIP data standards, will be the entry cards for models participating in CMIP. Participation in CMIP6-Endorsed MIPs by individual modelling groups will be at their own discretion and will depend on their scientific interests and priorities. With the Grand Science Challenges of the World Climate Research Programme (WCRP) as its scientific backdrop, CMIP6 will address three broad questions: – How does the Earth system respond to forcing? – What are the origins and consequences of systematic model biases? – How can we assess future climate changes given internal climate variability, predictability, and uncertainties in scenarios? This CMIP6 overview paper presents the background and rationale for the new structure of CMIP, provides a detailed description of the DECK and CMIP6 historical simulations, and includes a brief introduction to the 21 CMIP6-Endorsed MIPs.
Highlights
The Coupled Model Intercomparison Project (CMIP) organized under the auspices of the World Climate Research Programme’s (WCRP) Working Group on Coupled Modelling (WGCM) started 20 years ago as a comparison of a handful of early global coupled climate models performing experiments using atmosphere models coupled to a dynamic ocean, a simple land surface, and thermodynamic sea ice (Meehl et al, 1997)
We present a brief overview of CMIP6 that serves as an introduction to the other contributions to this special issue (Sect. 4), and we close with a summary
Under CMIP, credentials of the participating atmosphere– ocean general circulation models (AOGCMs) and Earth System Models (ESMs) are established by performing the DECK and CMIP historical simulations, so these experiments are required from all models
Summary
The Coupled Model Intercomparison Project (CMIP) organized under the auspices of the World Climate Research Programme’s (WCRP) Working Group on Coupled Modelling (WGCM) started 20 years ago as a comparison of a handful of early global coupled climate models performing experiments using atmosphere models coupled to a dynamic ocean, a simple land surface, and thermodynamic sea ice (Meehl et al, 1997). Coordination of the project has become more complex as CMIP includes more models with more processes all applied to a wider range of questions To meet this new interest and to address a wide variety of science questions from more and more scientific research communities, reflecting the expanding scope of comprehensive modelling in climate science, has put pressure on CMIP to become larger and more extensive. Cultural and organizational challenges arise from the tension between expectations that modelling centres deliver multiple model experiments to CMIP yet at the same time advance basic research in climate science. In response to these challenges, we have adopted a more federated structure for the sixth phase of CMIP (i.e. CMIP6) and subsequent phases. We present a brief overview of CMIP6 that serves as an introduction to the other contributions to this special issue (Sect. 4), and we close with a summary
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