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CMIP7 Data Request

The CMIP7 Data Request is being developed through the new Harmonised Thematic Variables process, managed by the Data Request Task Team.

Background

In an analysis of the CMIP6 Survey, most users found the CMIP6 Data Request to be too complex with too little documentation. However the value in a consistent Data Request was also commonly reported. The survey also found significant tensions, including:

  • Data users wanting more variables but data producers struggling with the size of request, and
  • Those wanting fewer updates to the Data Request with others wanting more regular version releases.

A new structure for the CMIP7 Data Request

The Data Request Task Team have developed an activity that works with community representatives to devise a controlled list of high priority variables that facilitate the majority of user needs. They proposed the following structure of the next Data Request to the CMIP Panel and WGCM Infrastructure Panel (WIP). The Panel and WIP both approved the structure.

Figure 1: The new Data Request structure consisting of three parts: the Core, Harmonised, and Unharmonised request

Core

The Baseline Climate Variables list. These variables will be requested as standard across all of CMIP7, forming a base of fundamental variables that are ideally produced by all models for all experiments. A paper outlining the variables and the process followed to identify the variables will be published in GMD soon.

Harmonised

A controlled list of high priority variables that facilitate the majority of user needs, while keeping the request as small as possible. This component complements the Core by providing a consistent list of variables across five thematic areas (ocean & sea-ice, land & land-ice, atmosphere, earth system, and impacts & adaptation), which can be mapped onto specific groups of experiments according to the scientific objectives and downstream needs of each case. Five thematic author teams have been set up to develop the controlled list of high priority variables through through an IPO-supported and Data Request Task Team coordinated paper writing process similar to that undertaken for the Core list, with co-authors representing major stakeholders of each theme.

Read more about the harmonised variable process below.

Unharmonised

This is the component of the CMIP7 Data Request that allows MIPs and other community activities to exploit data request services without being restricted by the deadlines and engagement requirements of the harmonisation process.

Harmonised Thematic Variables process and author teams

Papers across the identified five themes will define a collection of harmonised variables to support the high impact analysis of climate model output, and provide a consistent and robust set of parameters on which to build the CMIP7 archive. Each will be a collaboration between the CMIP Data Request Task Team and the MIPs and communities relevant to each theme.

The Data Request will include variable definitions and the mapping of variables against the justification for the request expressed in terms of the opportunities that the data will generate.  This will take the form of a controlled list of high priority variables that serve both the majority of user needs and create a harmonised set of data requests which balance scientific demand for data against modelling centre and infrastructure capacity.

The AR7 Fast Track experiments include a range of dual use experiments which will both provide input for AR7 and serve a wider role a control experiments for a wide range of investigations by community MIPs, many of them running on independent time lines. The Data Request will include data requirements covering both use cases so that those modelling centres wishing to support community MIPs can generate the data that they request efficiently.

This process for developing the Data Request is designed to enable a more transparent and effective approach to variable and request harmonisation and prioritisation. The planned timeline for this process is in Figure 2.

The CMIP7 Data Request is being developed through the new Harmonised Thematic Variables process.
Figure 2: Harmonised thematic variables process planned timeline
Watch an introduction to the CMIP7 Data Request presented by one of the TT co-leads Chloe Mackallah

Author teams

An open call was conducted for authors and reviewers for the thematic papers:

Appointed authors can be viewed here. The Author teams will be running open meetings and other engagement initiatives with modelling centres during this process.

Variable selection

Author teams have been asked to define:

  • What data is requested, including CF metadata,
  • Why it is needed and why it is a priority,
  • Who will make use of it
  • How it will be used.

Each team is using the CMIP6 request as a starting point, eliminating variables with limited use and adding new variables to cover areas of emerging interest or new model capabilities.

Alongside discussing individual variables, author teams have been asked to define:

  • Experiment groups: non-exclusive grouping of experiments (e.g. ‘AR7 Fast Track’, ‘DECK’, ‘Scenarios’ etc.)
  • Variable groups: non-exclusive grouping of variables (e.g. monthly time slices of the baseline variables).
  • Opportunities: intended use-case/justification for one or multiple variable groups. Opportunities are also linked to relevant experiment groups.

Creating opportunities

Identifying opportunities helps to provide a structure to map variables against requirements. Each opportunity description will convey why this combination of variables and experiments is important and how variables and experiments contribute to impact. 

Each opportunity will include:

  • A high-level description of the  science and/or societal use and impact
  • A time slice to specify a block of years for which data is needed. As with the priority and ensemble size, this applies to all data in this opportunity (optional).
  • Experiments (maybe dozens) and variables (maybe hundreds) that link to the opportunity.  Some experiments and variables will be linked to more than one opportunity.
Why do we need multiple opportunities rather than requesting all variables from all experiments?

A flat list works for simple MIPs, and was used in CMIP3.

In CMIP5 and CMIP6 the greater scope of science covered required some selectivity to avoid wasting resources by, for example, storing data for downscaling from experiments which nobody wants to downscale.

Why don’t we let each MIP or community activity define their own opportunities?

This would be technically possible, but:

  • Modelling centres and users want accessible information about the information that the archive aims to provide.
  • The process of consolidating information into a smaller number of opportunities helps to identify synergies and gaps in provision and makes the information more accessible.
Can I request for variables to be added to the Baseline Climate Variables?

The Baseline Climate Variables (BCVs) were selected based on a process across 2022-2024. The paper was recently submitted to GMD and is available for discussion. Due to this, variables can not be requested to be added to the BCV Variable Groups or Opportunity. If you have variables which you wish to request from all experiments, you can still do so but you should submit a variable group and attach it to an opportunity outlining the scientific justification for those variables.

Public consultation plans

There will be three phases of consultation; 

  • Phase 1: Building the data request – community members can engage directly with author teams, as well as directly comment on proposed opportunities, variable groups and experiment groups as they evolve.  In this real time consultation community members with input are advised to do so as early as possible.
  • Phase 2: Review of the first version of the controlled list of high priority variables.
  • Phase 3: Review of the refined version of the controlled list of high priority variables

The data request task team are available throughout the period to hear from and discuss the technical detail of the data request with modelling centres.

The first phase was published at the end of July 2024 (deadline 12th September). If you have questions about how you can contribute, see the section below.

How to contribute (consultation now open)

During public consultation phases, forms will be made available for the community to propose new opportunities, variable groups, and variables. There will also be forms to raise any issues or changes needed to existing opportunities, variable groups, and variables.

Find out more here about contributing to the “Gathering input for the CMIP7 AR7 Fast Track Data Request“ public consultation open now.

If you have any general inquiries or questions about the process, please contact the IPO. If you have a theme-specific question please make sure you state which theme and we can forward you on to the right person.

To keep updated with the thematic author teams progress and to make sure you hear about news and consultations first, sign up to the Data Request mailing list.

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