the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Apr 2026
CMIP7 Data Request: co-created guidance for the production of CMIP7 data [v1.2.2.3]
Abstract. This paper outlines the scope, development and publication of data requirements for a set of reference climate simulations, and describes the methodology used to gather and synthesise them into a cohesive 'Data Request' usable by data producers. The simulations supported by this Data Request comprise the initial phase of the next upgrade of research activities under the World Climate Research Programme (WCRP). Dunne et al. (2025) set out the scientific scope and objectives of the Assessment Fast Track and its role in initiating the seventh phase of the Coupled Model Intercomparison Project (CMIP7), a key part of the next WCRP activity upgrade.
Building on the successes of past CMIP phases which have supported an ever-expanding scope of work, the Data Request Task Team reached out to new communities to enhance engagement in CMIP. A transparent and community-led approach was adopted, where domain experts from the CMIP community were recruited into five teams by domain called 'Thematic Author Teams' to co-create data requirements through wide consultation. This paper describes the process of gathering data requirements in the initial phase of CMIP7, along with the structure of the CMIP7 Data Request itself.
Version 1.2.2.3 of the CMIP7 Data Request (DR7) covers the data production requirements for i) control simulations of the past climate (both distant and recent), ii) key sensitivity experiments focusing on critical aspects of climate and model behaviour, and iii) a range of future climate scenarios. It consists of a relational database that maps climate variables to reference experiments according to scientific objectives, with associated metadata to enable data production and tools to allow interoperability and content exploration.
The usage of climate models and CMIP data is broadening from its origins in scientific study of the physical environment to support the analysis of climate impacts, and planning for an ever-increasing portfolio of mitigation and adaptation measures. To support this growing scope, DR7 introduces a new organising component, Opportunities, to support transparent mapping between variables and experiments. The 46 Opportunities in DR7 represent the key community-driven use cases across CMIP data users – each describing why its combination of variables and experiments is important and how they contribute to impact, providing both scientific justification and technical requirements.
It is challenging to represent the needs of the rapidly expanding CMIP community and user base while respecting the capacity limitations of CMIP data production. DR7 addresses this through a process of wide stakeholder engagement centred around an open consultation and community co-creation, while prioritising stakeholder representation and diversity. Innovations in interactive web tools and enhanced WCRP support through the CMIP IPO and Task Teams were also critical to the process of developing data requirements in collaboration with the community.
Competing interests: JA and MM are co-chairs, and MJ an emeritus member, of the WCRP ESMO Infrastructure Panel (WIP). BD, EO, BT and DE are employees of HE Space Ltd which delivers the CMIP IPO service to the European Space Agency. At least one of the (co-)authors is a member of the editorial board of Geoscientific Model Development.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 09 Jun 2026)
- RC1: 'Comment on egusphere-2026-1641', Paola Petrelli, 14 May 2026 reply
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RC2: 'Comment on egusphere-2026-1641', Anonymous Referee #2, 20 May 2026
reply
I enjoyed reading this preprint, learning a lot through the development of CMIP and DR summarised in one place – a first timer, clearly articulating the motivation/demand of the change in approach for DR7 compared to previous phases. The process and technical details of DR7 are both clearly described with great attention to detail, well articulated in flowchart/schema. The case of revolutionising DR is well-justified, and its implication is thoroughly and profoundly discussed in connection with user needs and practicalities. I particularly like the reflection that consultations and community engagement activities should become a common practice for CMIP development.
Overall, the paper is well-structured, flows nicely, with the main ideas well-articulated. I have several suggestions for further improvements:
- I wondered why the account of integrating with CF conventions is in Section 3.3. It breaks the flow of the article especially because the first part of this Section consists of a description on the historical aspects. I would like to see a justification of this by the author team or some restructuring. An alternative that I can think of is to break into two parts – Chapter 2 on how things were done before and the feedback received, and Chapter 4 on the current practice (where the flowchart, Figure 2, may be cross-referenced).
- In Section 5.1, apart from the definitions of individual terms, one would wonder how the DR7 schema differs from that of DR6 overall, structurally? Perhaps a short paragraph to illustrate such difference would further strengthen the case of a community-driven structural reform.
- Summary statistics are results, not discussions. I suggest adding another section in the Results chapter for the statistical reporting (including Table 3), then refer back to it briefly in the discussions when it comes to an overall reflection of how things have evolved (integrating into Section 6.4).
Other suggestions mainly concern about the clarity of expression/language, as follows:
- Line 18 – I would prefer to express it as “adaptation and mitigation” since it's about "the usage of climate models", there are more users for adaptation than mitigation, especially as highlighted by the "Impacts and Adaptation" author team whilst none of the author teams is explicitly about mitigation. If the authors wanted to keep 'mitigation and adaptation' as it is, consider adding "the intercomparison and usage of climate models and CMIP data".
- Over the introduction, the definition of “CMIP Community” needs to be strengthened, as not even those within the community appreciate the breadth that it has grown into, let alone the other readers. Putting a better definition of this term in Section 1.2 (around Line 90, and signposting to the references in Table 1) will be beneficial for the article’s flow and clarity, especially as the statement “The usage of climate models and CMIP data is broadening from its origins in scientific study of the physical environment to support the analysis of climate impacts, and planning for an ever-increasing portfolio of mitigation and adaptation measures” is already mentioned in the abstract but any account of this kind is missing in the introduction. Also I wondered if it has any connection with the term “CMIP and Climate Community” officially defined in Line 338 – this could be a source of cross-referencing as well.
- Line 50 – Not immediately clear what it means by “It contains”, especially as it’s in a new paragraph. Suggest clarifying or merging into the above paragraph.
- Line 157 – Why “More than 2026”, but not an exact number? (especially as the number of experiments, 322, could be exactly given?)
- Line 266 – Unclear what it means by “a Cross-Theme Working Group” – are the DR-TT Theme liaisons part of it? Is it the same group as the “cross-thematic group” described in lines 366-369? If so, it might be useful to cross-reference. If not, then describe more specifically.
- Throughout the article there is inconsistency in abbreviating the Data Request Task Team. For example, it is abbreviated as “the Task Team” over various places from Lines 385-457, and as “DR-TT” in Line 424 and across Section 5.4. A unification of such would improve readability.
- Sections 5.3 – 5.4 could benefit from a better summarisation, particularly regarding the evolution from v1.0 to post-v1.2 which are described over two separate places (Lines 584-586, Lines 632-641).
Please find the attachment for the technical corrections/typo fixes required.
- I wondered why the account of integrating with CF conventions is in Section 3.3. It breaks the flow of the article especially because the first part of this Section consists of a description on the historical aspects. I would like to see a justification of this by the author team or some restructuring. An alternative that I can think of is to break into two parts – Chapter 2 on how things were done before and the feedback received, and Chapter 4 on the current practice (where the flowchart, Figure 2, may be cross-referenced).
Data sets
CMIP-Data-Request/CMIP7_DReq_Content: Data request content for v1.2.2.3 J. Anstey et al. https://doi.org/10.5281/zenodo.17986580
DR7 v1.2.2.3 (Airtable) C. Mackallah et al. https://bit.ly/CMIP7-DReq-v1_2_2_3
DR7 v1.2.2.3 (web viewer) C. Mackallah et al. https://cmip-data-request.github.io/cmip7-dreq-webview/index.html
Model code and software
CMIP-Data-Request/CMIP7_DReq_Software: v1.4 CMIP7 data request software J. Anstey et al. https://doi.org/10.5281/zenodo.17993659
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General comments
Overall, I was impressed with how the paper delivers a comprehensive and detailed description of the Data Request, its evolution, and the past and present CMIP context in which the Data Request operates. Considering the complexity of this endeavor I think the authors did a good job of presenting a clear and comprehensive picture.
The Data Request evolution is well documented with plenty of information included in forms of tables and diagrams that simplify the complex relationships mentioned throughout and with extensive references to relevant documentation. The authors did also a good job in providing concrete examples of the necessary steps, their associated challenges and the way these were resolved. This provides valuable information for anyone embarking on a similar project and for the maintainers and developers of future Data Requests.
This paper represents an important testimony of the amount of work and planning that goes into designing a governance and technical framework to a scientific collaboration project of this magnitude. By pointing out in a clear way the role that governance and funding have in these kinds of activities, it provides an opportunity to reflect on what should be done at governance and community level for these projects to be successful and sustainable.
Specific comments
The technical corrections are included in the attached pdf to preserve the formatting.