the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Nov 2024
A case for open communication of bugs in climate models, made with ICON version 2024.01
Abstract. Climate models are not just numerical representations of scientific knowledge, they are also human-written software programs. As such, they contain coding mistakes, which may look mundane, but can affect the results of interconnected and complex models in unforeseen ways. These bugs are underacknowledged in the climate science community.
We describe a sea ice bug in the coupled atmosphere-ocean-sea ice model ICON and its history. The bug was caused by a logical flag that was set incorrectly, such that the ocean did not experience friction from sea ice and thus the surface velocity did not slow down, especially in the presence of ocean eddies. While describing the bug and its effects, we also give an example of visual and concise bug communication. In addition, we conceptualize this bug as representing a novel species of resolution-dependent bugs. These are long-standing bugs that are discovered during the transition to high-resolution climate models due to features that are resolved at the kilometer scale. This case study serves to illustrate the value of open documentation of bugs in climate models and to encourage our community to adopt a similar approach.
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Status: open (until 25 Jan 2025)
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RC1: 'Comment on egusphere-2024-3493', David Bailey, 16 Dec 2024
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This manuscript makes the case that coding bugs happen in climate and earth system models and that there should be a more open process. I agree that bugs happen, but fervently disagree that we are somehow "hiding" bugs from the user community. For example, there are many code revision tools like github and even subversion before it. These are used for systematic software testing and robustness. One example is the CICE Consortium.
We have a public issues page here:
https://github.com/CICE-Consortium/CICE/issues
Then as we issue pull requests back to the code we have to go through a series of regression tests checking if the answers have changed against a previous version. If there are answer changes we must run a quality control suite to check if the results are statistically different from the previous version. You can see the process here:
https://github.com/CICE-Consortium/CICE/pull/965
So, yes bugs happen, but they are corrected as soon as found and clearly documented during the pull request process and then the changes are also added to the release notes for each new version. Most big modeling centers are using this type of process and it is completely open. So, to me this is a one off case for the authors particular model and I do not believe this would really be of interested to the greater GMD community.
Citation: https://doi.org/10.5194/egusphere-2024-3493-RC1
Data sets
Data and scripts for the publication "A case for open communication of bugs in climate models" Ulrike Proske et al. https://doi.org/10.5281/zenodo.14220611
Model code and software
ICON release 2024.01 The ICON partnership (DWD, MPI-M, DKRZ, KIT, C2SM) https://doi.org/10.35089/WDCC/IconRelease01
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