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Overview
CMIP is continuing to evolve into a more continuous approach with small targeted “fast track” experiment sets, in addition to the DECK and the growing number of Community MIPs. The CMIP fast tracks are designed as a compact set of experiments including the DECK and selected experiments from Community MIPs that will support specific needs. The first fast track will respond to the needs of IPCC AR7. CMIP infrastructure, standards and tools will continue to support ongoing science and assessment activities. This design reflects extensive feedback from the modelling centres and wider user community.
Guiding research questions
The CMIP Panel have collated four guiding research questions, which the data from CMIP7 will help to address substantially. Full descriptions of the science questions can be found in the CMIP7 Overview Paper (Dunne et al., 2025), available for comment on GMD.
Patterns of sea surface change: How will tropical ocean temperature patterns co-evolve with those at higher latitudes?
From Dunne et al., 2025:
“It is becoming increasingly clear that the SST trends observed in both the tropical Pacific and the Southern Ocean are at the very edge or outside the range of those simulated by CMIP6 models (Wills et al. 2022, Seager et al., 2022) raising concerns that models are able to capture neither the externally forced trend nor the magnitude of internal variability (or both) in these regions (Watanabe et al., 2024). […] Research through CMIP7 on the sea surface warming patterns bolstered by a combination of advances including improved process understanding from the Tropics community (e.g., Ray et al., 2018; Planton et al., 2021), longer observational time series of historical forcings, improved forcings constrained by new satellite and in situ observations, better understanding of forcing uncertainty and internal variability, novel ideas about teleconnection mechanisms, potential reductions in biases in the double ITCZ, Walker circulation and ENSO through model improvements and increased resolution in the atmosphere and ocean (e.g. Yeager et al. 2023), may all help.”
Changing weather: How will dangerous weather patterns evolve?
From Dunne et al., 2025:
“The more active hydrological cycle projected under warming is expected to increase the potential for large storms consistent with several recent examples of record-breaking storms such as the upper-tropospheric cut-off lows (known as DANA in Spanish) that produced severe floods in Valencia and other regions of Spain in November 2024, and rapid intensifying hurricanes, such as Otis in 2023 in the Eastern Tropical Pacific (Garcia-Franco et al., 2024) and Helene and Milton in the southeastern United States (Clarke et al., 2024), and their increase attributed to climate change (Bhatia et al., 2021; Clarke et al., 2024). There is a growing need to know how to adapt to rapid and unexpected changes, which require more robust and finer resolution projections, and better understanding of the causes and shifts in spatial and temporal distributions of dangerous and impactful weather patterns for this information to be actionable. […] Better statistics of rare events and extremes remain critical to meet the enormous research and societal challenges at hand. One key role of CMIP in the multiverse of modelling efforts is the running of multi-centennial coordinated simulations supporting characterization of frequency distributions of infrequent events. The CMIP7 focus on CO2-emissions-forced models will allow for novel investigation of extremes under climate stabilization.”
Water-carbon-climate nexus: How will Earth respond to human efforts to manage the carbon cycle?
From Dunne et al., 2025:
“Building on the introduction of Coupled Carbon-Climate ESMs in CMIP5 with more experiments added in CMIP6 towards process understanding, CMIP7 shifts the scientific focus to their response to CO2 emissions and removals and the coupled mechanisms necessary to achieve climate stabilization. As such, CMIP7 is expected to include more comprehensive process representation of coupled carbon-climate in ESMs including the non-linear role of biogeography, land use, fires, permafrost and microbes. New experiments forced by CO2 emissions (Sanderson et al., 2024) evaluate the robustness of the Transient Climate Response to cumulative Emissions (TCRE) under net zero and net negative global emissions. Improved ESMs in CMIP7 will be better positioned to contextualize the assumptions and uncertainties associated with carbon cycle response and removals used to deliver climate forcings from Integrated Assessment Models, and characterize climate response and feedbacks.”
Points of no return/ratcheting: What are the risks of triggering irreversible changes across possible climate trajectories?
From Dunne et al., 2025:
“Analysis of CMIP6 models has identified emerging advances of tipping processes such as fire (e.g., Allen et al., 2024) while application of Machine Learning (ML) methods has brought new insight into early detection of tipping points (e.g., Bury, et al., 2021). Ongoing improvements in historical simulations of warming and more constrained ECS will give greater confidence in results while the inclusion of more advanced ESMs forced by emissions combined with the provision of overshoot scenarios will provide the opportunity to explore the possibility of irreversible changes even with climate stabilization. […] New capabilities in CMIP7 models including coupled ice sheet models, expanded biogeochemical processes (including dynamic land use type) and higher resolution models will enable new insights on tipping points.”
The DECK
As in CMIP6, running the Diagnostic, Evaluation and Characterization of Klima (DECK) will remain the “entry card” for CMIP, including the AR7 Fast Track. Community feedback on potential changes to the DECK have been received by the Panel. At their meeting in March 2024, the WGCM endorsed the CMIP Panel recommendation to include the following experiments in the DECK, in addition to amip, abrupt4xCO2, piControl (and esm-piControl for ESMs), and 1pctCO2:
- historical
- esm-hist (for ESMs only)
- piClim-control
- piClim-anthro
- piClim-4xCO2
The CMIP Panel confirmed their decision to ensure emissions-driven experiments are well proven and tested before inclusion as an ESM-DECK, and to consider proposals for inclusion of LMIP and OMIP in the DECK, in the future.
The Community MIPs
- 33 MIPs have registered and can be found on the CMIP website.
- The CMIP Panel will not be endorsing MIPs but have provided best practice guidance.
- Requests for Panel feedback and support from the CMIP IPO can be submitted through the registration form.
- The Panel wants to encourage MIPs to not re-run CMIP6 experiments with new models, and to collaborate across MIPs to identify and reduce any potential duplication, and with consideration of their carbon footprint.
- If MIPs have information/news they would like to share with CMIP community, then email the CMIP IPO.
CMIP AR7 Fast Track
The CMIP Panel and WGCM Infrastructure Panel (WIP) continue to discuss and evolve the CMIP delivery timeline in close coordination with the CMIP Task Teams and through regular engagement with the wider community. For the DECK and the subset of CMIP experiments aimed at aligning with the IPCC, the CMIP AR7 Fast Track, there can be no clear timeline definition until the new IPCC leadership has confirmed their planned timeline. This is now expected to be in summer 2024 and the CMIP Panel are actively engaging and discussing with the new IPCC Bureau. Community MIPs do not need to align with that timeline, although they may choose to do so.
We do want to be as prepared as possible for when the IPCC timeline emerges and are therefore in the process of determining community readiness. The timeline below indicates current best guess estimates, which are being reviewed regularly in consultation with the community.
In September 2023 the Strategic Ensemble Design (SED) Task Team provided a first proposed set of AR7 Fast Track experiments after discussions with the Task Team members, stakeholders and MIPs. Two rounds of consultation followed with the modelling centres and with the wider community. After further discussion within the SED TT, CMIP Panel and with proposing MIPs a final recommendation of the AR7 Fast Track experiment selection (figure below) was made to the WGCM meeting in March 2024, and subsequently endorsed.
The AR7 Fast Track experiments
Want to learn more about the experiments and why they were selected for the AR7 Fast Track? The figure below summarises all of the experiments chosen for the AR7 Fast Track, along with which MIP proposed them. The interactive experiment viewer underneath the figure also outlines why each experiment was selected.
Fast Track experiment viewer
If you are having trouble viewing the experiment viewer, you can click here to view in a new tab.
We continue to welcome all feedback from across the community. To stay up to date with the latest developments, please bookmark this page and join our mailing lists here to hear about the latest news and events.
