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env_conf IPCC_MODE setting of 1870_TO_present is not supported

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env_conf IPCC_MODE setting of 1870_TO_present is not supported

I am trying to reproduce the experiment b30.030a (20C3M), so I set the IPCC_mode in env_conf is 1870_TO_present. But the current version doesn't support this configuration. I am wondering how to solve this problem. Thanks for your suggestion!


PS:The version of CCSM3 which I am using was downloaded from

Well, running an IPCC run is not as easy as it sounds. You can start by modifying the configure script in your case directory. There is a check for IPCC modes, change this accordingly to your needs. You can then run configure and this will generate the scripts in your case directory.

Next problem are the forcing data (for example greenhouse gas concentration). If you have successfully build the namelist scripts you can see in Buildnml_Prestage/cam.buildnml_prestage.csh which files are needed. Alternatively you run the build script and then check $SCRATCH//atm/atm.stdin for filenames. Don't be surprised, the build will always stop with an error until you have all the files that are required for the build. If your forcing data are in files with different names you need to change Buildnml_Prestage/cam.buildnml_prestage.csh accordingly.

To obtain the IPCC forcing files you need to check with NCAR and possibly the ESG portal. I don't know whether or not these files have been made publicly available.

Hope this helps on your way.

Klaus Wyser
Rossby Centre
Swedish Meteorological and Hydrological Institute


This is a question for Xiaohua:

Do you mean that by in the options of the IPCC_MODE in the env_conf script, 1870_TO_PRESENT corresponds to the 20C3M run? How do you know this?

And this is a question for Klaus:

In the first step of your reply, do you mean edit the line of
set value = (OFF 1870_control RAMP_CO2_ONLY)
change this line into
set value = (OFF 1870_control RAMP_CO2_ONLY 1870_TO_PRESENT)

Do you know why in the configure script, the the option 1870_TO_PRESENT is not listed originally while in the env_conf script this option exists? (I think this is the reason Xiaohua was getting the "not supported" message.)

Thank you both


Hej Ching-Yee---

I can only speculate about the reason why the 1870_TO_PRESENT option (or any other IPCC scenario run option) is not supported by configure. I think the reason is that you need input files (forcing) for greenhouse gases, ozone, sulphur, carbon aerosols, etc. These files are not distributed along with CCSM3, and therefore enabling a 1870_TO_PRESENT wouldn't make any sense.


Klaus Wyser
Rossby Centre
Swedish Meteorological and Hydrological Institute


At the time of the ccsm3.0 release, various IPCC scenerios were either not yet completed, currently being analyzed, and/or in the process of being written up -- that is, they were not ready for release and hence not in the release. All of the runs and analysis are now complete so that a new release could be undertaken, but that is a fair amount of work and it hasn't been a sufficiently high priority to actually happen. Funding and staff reductions have something to do with this. It's possible that if you raise the issue within your working group that the priority level could be raised and this issue might be addressed.

Brian Kauffman, NCAR/CGD/CSEG

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