FAQ

This page is under construction. If you don’t find an answer to your question here please see the older, but more complete FAQ available on our electronic support forums: EdGCM Support Forum FAQ

Frequently Asked Questions:

How do I cite/reference/credit EdGCM?

To reference EdGCM, the Educational Global Climate Modeling software, use the following citation

Chandler, M.A., S.J. Richards, and M.J. Shopsin, 2005: EdGCM: Enhancing climate science education through climate modeling research projects. In Proceedings of the 85th Annual Meeting of the American Meteorological Society, 14th Symposium on Education, Jan 8-14, 2005, San Diego, CA, pp. P1.5. http://edgcm.columbia.edu

The reference describing the NASA/GISS Model II global climate model that EdGCM runs is

Hansen, J., G. Russell, D. Rind, P. Stone, A. Lacis, S. Lebedeff, R. Ruedy, and L. Travis, 1983: Efficient three-dimensional global models for climate studies: Models I and II. M. Weather Rev., 111, 609-662, doi:10.1175/1520-0493(1983)111<0609:ETDGMF>2.0.CO;2.

What operating systems are compatible with EdGCM?

EdGCM runs on MacOS X 10.3.9-10.6 and on Windows XP, Vista and Windows 7. (Mac OSX 10.6 and Windows 7 users must download and apply a separate update, available here.) Although the GCM itself can be run on Linux as well as on most other Unix variants, the EdGCM interface is not compatible with linux. The reason is that the 4th Dimension database underlying EdGCM is only available for MacOS and Windows. Should 4D, Inc. ever introduce a Linux version of 4th Dimension, we would be happy to provide EdGCM for that platform as well.

*We have received reports of problems running EdGCM under Snow Leopard.

Is the climate model code open source?

The source code for the NASA Global Climate Model used in EdGCM is in the public domain. Anyone who wishes to work directly with the GCM code can download the source for Model II from this page.

How do I uninstall EdGCM from my PC?

Delete the EdGCM folder (and any shortcuts or aliases) by dragging them into the Recycle Bin. You can also delete 4D Runtime and EVA from the Program File folder on the C drive.

How do I setup mixed-layer ocean model runs for running simulations that model sea surface temperatures (SSTs)?

There is a QFlux Tutorial that should be read to understand how to set up the ocean to model sea surface temperature (SSTs).

Can I change the climate model’s boundary conditions files?

Boundary conditions in the GISS GCM include topography, land coverage (continent distribution), ice sheets, vegetation, surface drag coefficient, and ocean energy characteristics. Oceans use either monthly specified sea surface temperatures (SSTs) and sea ice, or mixed-layer depths and ocean heat transports in the case of predicted “Qflux” runs.

Many types of experiments require the user to alter the boundary conditions. Some of the best examples of this are paleoclimate experiments in which many geographic features of the Earth are altered (e.g., larger ice sheets, shifted continents, higher sea levels, etc.). Unfortunately, altering the boundary conditions and getting the GCM to run successfully with them can be a significant technological challenge. EdGCM includes some specific sets of boundary conditions for some common experiments (e.g. Last Glacial Maximum files for Ice Age experiments), but we cannot allow users to change the boundary condition files themselves at present. We can try to accommodate certain requests; however, because of the complexity of interactions between boundary conditions, initial conditions and the GCM code, many problems that sound simple are not, and we cannot guarantee implementation.

How do I export/import runs between two copies of EdGCM?

See our Video Tutorials for step-by-step explanations.

How do I run simulations on one computer and analyze them on another?

See our Video Tutorials for step-by-step explanations.

How do I change the orbital parameters in EdGCM?

In the Forcings section of the Setup Simulations window, there are fields where you can provide different values for eccentricity, axial tilt, and omegaT. If you enter a value into any of the three spaces then all three will be used to specify the orbital parameters for the simulation.

In order to change the orbital parameters for a sensitivity test please follow these steps:

  1. Create a new run.
  2. Go to the Forcings section of Setup Simulations.
  3. Set the three orbital parameters to the modern values instead of zero. The modern values for the orbital parameters are:
      • Eccentricity: 0.0167
      • OmegaT: 282.9
      • Axial tilt: 23.44

Orbital parameters require complex calculations of the precession of the orbit, which are not provide in EdGCM. You can, however, access a Fortran program called ORBPAR.f, which calculates the three orbital parameters as a function of year. ORBPAR.f was written by Dr. Gary Russell, one of the original authors of the NASA/GISS GCM (EdGCM’s climate model):

Russell, Gary L., Determination of Earth’s Orbital Parameters: Orbpar.sub and Orbpar.for

The ORBPAR.f program uses the following definition of OMEGAT (called OMEGAVP in the program)
OMEGAT = longitude of perihelion = spatial angle from vernal equinox to perihelion with Sun as angle vertex.

References for the calculations in ORBPAR are from: