The two graphs are almost on top of each other. I’ll add 0.02K to the black line to separate them a bit:

We can now see the red series that the black series was hiding, and we can see that the differences between the 2 series are minute at most. 1 or 2 centikelvin here and there. Red is official GISTEMP, black is our ccc-gistemp code.

What exactly am I comparing? GISTEMP’s global temperature anomalies, one set from their website, one set from our ccc-gistemp code. I’m running the vischeck command:

code/vischeck.py -o 2 result/GLB.Ts+dSST.txt result/GLB.Ts.ho2.GHCN.CL.PA.txt

(the -o option is used to produce the offset graphs, bottom picture)

The first file is GLB.Ts+dSST.txt, that I download from NASA yesterday. The second file, GLB.Ts.ho2.GHCN.CL.PA.txt, is the result of me running ccc-gistemp yesterday.

But it’s not a very careful comparison. The inputs I am using are SBBX.HadR2 and v2.mean downloaded on 2009-12-04 and an hcn_doe_mean_data downloaded in June (!). Also, the version of the GISTEMP code we are coding against is quite old (about a year) and has been updated several times. For example, GISTEMP currently use USHCN version 2, ccc-gistemp does not (yet). The fact that we’re not keeping up with GISTEMP is Issue 7.

Furthermore the exact output may depend on the Fortran compilers being used, the architecture on which I’m running, and the Python versions we’re using.

The bottom line is that we’re already very close to the GISTEMP output, well with any meaningful error threshold. As we get closer we’ll need to be a lot more careful about keeping track of exactly what inputs and software tools are being used. We’ve requested from GISS a copy of the exact inputs and outputs for one of the runs, so that we have a fixed set for comparison purposes.