Models Used

The information below summarises the various types of climate model used by, including some that are planned for future release.

Fully Coupled Global Models


This was the standard coupled model of the Met Office until a few years ago, and is still actively used for climate change research. A future release of this model is planned by Read more about this model on the Met Office website.

  • Atmosphere: 2.5 x 3.75 degrees lat-lon resolution, 19 vertical levels (known as N48; comparable resolution to ~T42)., 30 mins timestep for dynamics, 3 hours for radiative transfer.
  • Ocean: 1.25 x 1.25 degrees lat-lon resolution, 20 vertical levels, 1 hour timestep.

Sulphur and carbon cycles, dynamic vegetation etc. are optional.


HadCM3 with a reduced resolution ocean. This was used for the BBC Climate Change experiment and the completed Geoengineering experiment. The version uses two kinds of modified ocean topography, both with no Iceland.

  • Atmosphere: same as HadCM3.
  • Ocean: 2.5×3.75 degrees, 20 levels, 1 hour timestep.

This model is not used with any current experiments. It has been replaced by the newer HadCM3S (please see below).


This is another version of HadCM3 which runs for 40 years and is not flux-adjusted. It is used for the RAPID-CHAAOS and RAPID-RAPIT experiments.


This is another variation of the HadCM3 coupled ocean-atmosphere model. This version of the model is configured for short experiments of a few years length. Additionally, volcanic aerosol is now specified on each latitudinal row of the model individually, and the model also contains multiple calls to the radiation code each time step in order to diagnose the radiative forcing of certain atmospheric constituents.

It is being used for the RAPID-CHAAOS and Solar-Radiation Management Geoengineering experiment.


A fast, coarse resolution variant of HadCM3. This model has been used for the Millennium Experiment.

  • Atmosphere: 5.0 x 7.5, 11 levels.
  • Ocean: 2.5 x 3.75 degrees, 20 levels, 12 hour timestep, no Iceland.

Atmospheric Models Coupled to a Simple Ocean


HadCM3 but with 1 layer thermodynamic ocean (slab ocean). The Slab experiment, Sulphur cycle experiment, and mid-Holocene experiments all use this model.

  • Resolution: 2.5 x 3.75 degrees.

Atmosphere-only Models


Atmospheric component of HadCM3 with prescribed sea surface temperature. Never used by as a stand-alone model at the standard resolution of 2.5 x 3.75 degrees.


HadAM3, but at N144 resolution (0.83 x 1.25 degrees resolution, 30 levels) with 10 minutes timestep for dynamics, used for the attribution experiment.


As HadAM3, but N96 resolution, (1.25 x 1.875 degrees resolution, 19 levels) with 15 minutes timestep for dynamics and improved physics. This has been used for the storm-tracking experiment and was used for the Validation and Attribution experiment.

It is the standard driving model for all weather@home experiments. For each regional experiment, a new version of this model is made, focusing on the region in question. These are denoted by the region’s acronym at the end of the model name:

  • Europe: hadam3p_eu
  • Australia & New Zealand: hadam3p_anz
  • Pacific North West: hadam3p_pnw
  • Africa: hadam3p_afr


This is the same as HadAM3P but has a better land-surface scheme called MOSES2 and an interactive vegetation scheme called TRIFFID.

This model is used for the HYDRA experiment.


A high-resolution, regional configuration of HadAM3 with improved physics. This is the regional model used in PRECIS experiments by the Met Office and in all weather@home experiments.

It has 0.44 x 0.44 degrees resolution with a rotated pole to achieve approx. 50 km x 50 km resolution on 19 levels (used for the EU region, South Asia, planned for East Asia). Also used is a double resolution variant at 0.22 x 0.22 degrees (Western US, planned for EU and Africa).


This is a version of HadRM3P being used in the FMEC project, with an interactive vegetation scheme called TRIFFID which will specifically help look at the interaction between climate change and forests.

Hybrid models


HadRM3P, driven by a global model such as HadCM3, HadCM3L or HadAM3P. uses a HadAM3P driven HadRM3P for the weather@home experiment and earlier regional experiments.