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CMIP7 Climate Variables

The CMIP7 Data Request Structure

After taking on feedback from CMIP6, the data request task team have devised a controlled list of high priority variables that faciliate the majority of user needs. This structure includes 3 main parts:

  1. Core- These are the baseline climate variables (BCVs). They are requested as standard across all of CMIP7, ideally produced for all models and experiments to form a base.

  2. Harmonised- These are high priority variables that faciliate the majority of user needs whilst keeping the data request as managable as possible. This consists of variables across 5 thematic areas: ocean & sea-ice, land & land-ice, atmosphere, Earth system, and impacts & adaptation.

  3. Unharmonised- This stage allows for MIPs and community activities to exploit the data request without the deadline and engagment restrictions present in the harmonised stage.

The CMIP7 Variable Name Structure

The way that CMIP7 variable names are written has changed notably since CMIP6: the key aim being to provide more immediate information about the variable.

For example, what was Amon.tas in CMIP6 is now written as tas_tavg-h2m-hxy-u in CMIP7 (known as a 'branded variable name'). The new structure can be explained as follows:

  • The variable ID (e.g. tas): this identifies the physical quantity and remains unchanged from CMIP6.

  • The temporal label (e.g. tavg): this identifies how the variable is sampled in the time domain.

  • The vertical label (e.g. h2m): this identifies how the variable is sampled in the vertical domain.

  • The horizontal label (e.g. hxy): this identifies how the variable is sampled horizontally. Note that this does not denote a particular choice of reporting grid.

  • The area label (e.g. u): this identifies the masked area type for which data is reported where u means that no masking is applied (unmasked).

Please see the CMIP7 Guidance Docs for more information.