Fast Track

The CMIP panel is currently seeking feedback from modelling centres on proposed Fast Track experiments. The Fast Track experiments are those that modelling centres should aim to run in sufficient time to be used for the next IPCC Assessment Report. The Fast Track is additional to the DECK experiments that act as the ‘entry card’ to CMIP and comprises high-priority experiments from a selection of Community MIPs including ScenarioMIP.

More information about the proposed Fast Track experiments is available in this document.
CMIP-Fast-Track-v1_Consultation-supporting-information.pdf (472.7 KB)

We will be completing one survey response on behalf of ACCESS. If you have any comments on the proposed experiments, or experiments that you think are missing, please reply to this topic so that comments can be consolidated for our survey response.

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Thanks Rachel, I agree it would be great to gather input from the ACCESS community on the current proposed Fast Track experiments.

The CMIP panel held some drop-in sessions for the modelling centres last week and the recordings of those as well as the slides shown can be found at:

We have also put together a series of Q&As from the drop-in sessions that will be sent out to modelling centres soon to help support their survey responses.

As I mentioned in todays’ ESM working group meeting (and as indicated in the slides and website), the timeline for further development of the Fast Track is as follows:

  • End of-December 2023: Deadline for modelling centre survey responses.
  • Late January 2024: Next version Fast Track proposal circulated for wider community review and survey response including a drop-in session.
  • In parallel, ongoing discussions between CMIP and IPCC Bureau (before IPCC Plenary in January).
  • Late February 2024: Deadline for community survey responses.
  • CMIP Panel and SED Task Team review of feedback and development of Fast Track proposal for approval at WGCM meeting in March 2024.

Julie (CMIP Panel member)

Hello Rachel, Julie,

Regarding the proposed PMIP fast track experiment. It is the same we did for CMIP6/PMIP4 with the ACCESS-ESM1.5, except that here the first 100 years are needed and for CMIP6 we provided years 500-600. We have to dig through our archive to see if we still have enough data for the first 100 years.
We could of course re-run it with the ACCESS-ESM1.5 or run it with the ACCESS-ESM3 to test the differences between the 2 models.


ACCESS survey response submitted 18/12/2003.
Indicated interest in performing most experiments except DCPP.
Indicated likely to complete both concentration and emissions driven simulations but focus would be on emissions driven for building ensemble size.
Provided the following comments in the free text feedback section:

If we thought of the proposal (excluding the DECK) as three broad categories of experiments: (1) scenarios, (2) characterizing climate response/historical, (3) emerging issues, is the balance right? It seems like most of the model years contribute to group (2). We think there should be more new experiments targeting emerging issues and likely more emphasis on building ensembles for the scenario simulations.

What was well used for the last IPCC report may not be a good indication of what is needed this time. Perhaps we need to build more flexibility into the fast track to add experiments as the IPCC process develops, provided they are relatively simple to implement. Would it be useful to set up another task team to facilitate interaction with IPCC authors to be responsive to emerging needs, or is this part of the strategic ensemble design task team role?

To some extent CMIP7 will be defined by the Fast Track so we think it needs to focus on what is new. Partly that will be new models but it also needs to be new experiments. Emissions-driven can be an important part of what’s new and doesn’t seem to be highlighted enough in the current proposal. (One of the arguments we are using for trying to get additional local for CMIP7 funding is that it is different/adds to CMIP6 rather than just repeats).

While it is acknowledged that there is no expectation that all models will run all experiments, the desire to provide a manageable/realistic set of experiments still tends to imply that most models will attempt most experiments. Another approach would be to have an intentionally broader set of experiments with a target number of models to complete each one. Modelling centres could be encouraged to focus on experiments that best suit their model’s capability and the interest of the modelling centre. Would it even be worth considering a more coordinated approach where modelling centres are asked to prioritize certain experiments to spread the compute cost but still end up with a sufficient multi-model ensemble?

Fast Track proposal v2

The CMIP Panel is seeking feedback on the AR7 Fast Track design. There are surveys for modelling centres and the wider CMIP community (MIPs, CMIP data users etc.)

More information is available here: .

Please use this topic to post any feedback specific to ACCESS participation in the Fast Track, for inclusion in our modelling centre survey response. Users of CMIP data are encouraged to fill out their own survey (due 6th March) to indicate how they would prioritise the proposed experiments.

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Arblaster_Hogg_CMIP_AMOS2024_updated.pdf (2.9 MB)
Here are the slides that Andy Hogg and I presented during the CMIP lunchtime discussion at AMOS. The timelines and plans continue to evolve but some of the information may be useful to others.

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