The April issue of Nature Climate Change features a figure produced by Climate Code Foundation, illustrating this article. This page is the “supplementary information” regarding that figure.
Updated to state these errata: in the print edition of Nature Climate Change, the ‘0.0’ label on the y-axis has been misprinted as ‘0.6’, and the caption credits ‘Climate Change Foundation’, not ‘Climate Code Foundation’.
The figure compares the global temperature anomaly analysis using our ccc-gistemp software against the analysis published by NASA using their GISTEMP software. To produce it you need to have run ccc-gistemp (to get a valid result directory), and you need to have Inkscape on your PATH. Then go python tool/multi.py nature201002. This will create nature.pdf.
As the figure caption says, the ccc-gistemp result in the figure was produced using “software revision 700“. The version of tool/multi.py (and related files) used to make nature.pdf was revision 727. Both computation and visualisation were run with Python 2.7 (although the Python version should not affect these results).
The input data for the figure is in this zip archive held at our source code repository. These are just copies of publicly available datasets (GHCN, USHCN, and so on), but because the available copies change (typically every month), we need to keep a copy if we’re going to reproduce the figure exactly.
The numbers for the GISTEMP curve come from the NASA GISTEMP website. The published datafiles change every month, but previous versions are not made publicly available. In order to exactly reproduce the Nature figure, we have to archive a copy of the file we used: again at the googlecode repository.
Why are we publishing this blog post? Across science, reproducibility of computer results is seen as increasingly important. We believe it is vital to public understanding of climate science in particular. Every number and every figure in every paper is the result of processing data with a computer program; releasing the programs allows interested readers to better understand the processing, and also to check the programs for errors. It should be possible for an interested reader to reproduce the figures exactly by re-running the programs.
[Updated to add link to Nature Climate Change article]