With so many institutions developing and running climate models, there is a risk that each group approaches its modelling in a different way, reducing how comparable their results will be.

This is where the Coupled Model Intercomparison Project (“CMIP”) comes in.

As part of the Coupled Model Intercomparison Project (CMIP) many hundreds of climate researchers, working with modeling centres around the world, will share, compare and analyze the latest outcomes of global climate models. These model products will fuel climate research for the next 5 to 10 years, while its careful analysis will form the basis for future climate assessments and negotiations.

The “coupled” in the name means that all the climate models in the project are coupled atmosphere-ocean Climate Models. In the following video, The Met Office’s Dr Chris Jones explains the significance of the “intercomparison” part of the name:

CMIP started twenty years ago as a comparison of a handful of early global coupled climate models. In response to a growing need to systematically analyze coupled ocean and atmosphere model outputs from multiple climate modeling centres, it has subsequently grown into a large program to advance model development and scientific understanding of the Earth system. To meet these new goals, CMIP has developed well-defined climate model experiment protocols, formats, standards, and distribution mechanisms to ensure model output availability to a wide research community.

CMIP6 is now underway with the WCRP Grand Science Challenges (WCRP, 2016) as its scientific backdrop. A special issue in GMD describing the CMIP6 experiment design and organization has been published.

As well as having a core set of “DECK” (Diagnostic, Evaluation, and Characterisation of Klima) modelling experiments, CMIP6 will also have a set of additional experiments to answer specific scientific questions. These are divided into individual Model Intercomparison Projects, or “MIPs”. The 21 CMIP6-Endorsed MIPs will allow researchers to investigate specific aspects of the climate system, from clouds to deep ocean circulation to an interactive carbon cycle. Each MIP earned a commitment from at least 10 modeling centres to run all of the highest priority experiments and produce all the specified diagnostic outputs and information. The fact that CMIP6 elicits such a commitment from modeling centres indicates its enormous value to researchers and to society.

You can see the 21 MIPs and the overall experiment design of CMIP6 in the schematic below.

Schematic of the CMIP/CMIP6 experimental design and the 21 CMIP6-Endorsed MIPs. Reproduced with permission from Simpkins (2017).

CMIP6 confronts a number of new challenges. More centers will run more versions of more models of increasing complexity. An ongoing demand to resolve more processes requires increasingly higher model resolutions. Archiving, documenting, subsetting, supporting, distributing, and analyzing the petabytes of CMIP6 model outputs will challenge the capacity and creativity of the largest data centres and fastest data networks. Fundamentally, CMIP6 will allow continuous and flexible model innovation schedules while remaining mindful of the IPCC process, will ensure that CMIP products address priorities identified by the climate research community, and will foster open and inclusive participation.

CMIP is the responsibility of the Working Group on Coupled Modelling committee, which is part of the World Climate Research Programme (WCRP) based at the World Meteorological Organization in Geneva. In addition, the CMIP Panel oversees the design of the experiments and datasets, as well as resolving any problems.

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