CMIP7 Data Request: co-created guidance for the production of CMIP7 data [v1.2.2.5]

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.