Serendipity

First, we have to be clear what we mean by a climate model. Wikipedia offers a quick intro to types of climate model. For example:

• zero dimension models, essentially just a set of equations for the earth’s radiation balance
• 1-dimensional models – for example where you take latitude into account, as the angle of the sun’s rays matter)
• EMICS – earth-system models of intermediate complexity
• GCMs – General Circulation Models (a.k.a Global Climate Models), which model the atmosphere in four dimensions (3D+time), by dividing it into a grid of cubes, and solving the equations of fluid motion for each cube at each time step. While the core of a GCM is usually the atmosphere model, GCMs can be coupled to three dimensional ocean models, or run uncoupled, so that you can have A-GCMs (atmosphere only), and AO-GCMs (atmosphere and ocean). Ocean models are just called ocean models 🙂
• Earth System Models – Take a GCM, and couple it to models of other earth system processes: sea ice, land ice, atmospheric chemistry, the carbon cycle, human activities such as energy consumption and economics, and so on.

Current research tends to focus on Earth System Models, but for the last round of the IPCC assessment, AO-GCMs were used to generate most of the forecast runs. Here are the 23 AO-GCMs used in the IPCC AR4 assessment, with whatever info I could find about availability of each model :

• BCC-CM1 (Beijing Climate Center, China). The only mention of source code I can find is a link to an email address for the atmosphere model. I’ll fire off a message (Response: “it’s not ready for release yet”).
• BCCR-BCM 2.0 (Bjerknes Centre, Norway). I can’t find any info about the model in the BCCR website, but I did find a 2003 paper describing the development of the model.
• CCSM3 (NCAR, USA). Model source code is available for download, if you register.
• CGCM3 (Canadian Centre for Climate Modeling and Analysis, Canada). Source code not publicly available.
• CNRM-CM3 (Meteo-France). Not much information on the GCM, but the source code for the NEMO ocean model is available if you register.
• CSIRO-MK3.0 (Commonwealth Scientific and Industrial Research Organisation, Australia). Can’t find any info about the model at CSIRO’s website, apart from this report on the model development. [update: The MK3.0 isn’t publicly available, but a lower resolution version, the Mk3L is – see comments below]
• ECHAM5/MPI-OM (Max Planck Institute, Germany). The source code for the models is available if you sign the licence agreement.
• ECHO-G (University of Bonn, Germany and Korea Meteorological Administration, Korea). Here’s a technical report describing ECHO-G, but I can’t find much else.
• FGOALS-g1.0 (LASG/Institute of Atmospheric Physics, China). Not sure about availability, as most of the documentation is in Chinese.
• GFDL-CM2.x (GFDL, USA). Source code for AM2.1 (atmosphere only) is available if you register, as is the MOM ocean model.
• GISS-AOM, EH, and ER (NASA Goddard Institute for Space Studies, USA). Source code for various configurations of GISS-AOM is available. You can also browse the source code for the latest model, ModelE, either using the f90toHTML tool, or directly in its repository.
• INM-CM3.0 (Institute for Numerical Mathematics, Russia). Can’t find much about this model at all.
• IPSL-CM4 (Institut Pierre Simon Laplace, France). Here we hit the jackpot: open web access to the subversion repository and Trac database.
• MIROC3.2 (U Tokyo and JAMSTEC, Japan). I found documentation for MIROC, but not much else.
• MRI-CGCM2 (Meteorological Research Institute, Japan). No info about model availability.
• PCM (NCAR, USA). Unlike the CCSM above, the code for PCM doesn’t appear to be available.
• UKMO-HadCM3 and HadGEM1 (Met Office Hadley Centre, UK). Last, but definitely not least. The Met Office models are built from a shared code base, known as the Unified Model. Documentation is available, but the source code is only distributed to collaborators under a restricted licence.

Now, if you were paying attention, you’ll have noticed that that wasn’t 23 bullet points. Some labs contributed runs from more than one version of their model(s), so it does add up somehow.

Short summary: easiest source code to access: (1) IPSL (includes Trac access!), (2) CCSM and (3) ModelE.

Future work: take a look at the additional models that took part in the Coupled Model Inter-comparison Project (CMIP-3), and see if any of them are also available.

Update: RealClimate has started compiling a fuller list of available codes and datasets.