Rahmstorf (2009): Off the mark again (part 11). VR2009 Matlab codeFebruary 6, 2011
I have written much about Vermeer and Rahmstorf’s 2009 Proceedings of the National Academy of sciences paper “Global sea level linked to global temperature“ (referred to as “VR2009″ in my series of posts). I have reproduced their algorithm with my own code.
I thought it would be useful to provide any interested readers easy access to VR2009’s code. The PDF version of their paper had a link (which has been long broken) to The National Academy of Sciences website that was supposed to provide the VR2009 code in a zipped file format. After the original link was broken Kay McLaughlin (PNAS Editorial Staff) kindly sent me this new link. Just in case that link breaks, I have archived the zipped file here. If you unpack the zipped file you will get 24 files: some Matlab code files, some text files, and some .dat files. Or you can simply look at the list of 24 links at the bottom of this post to download any one of the 24 files individually.
I am not a Matlab programmer, nor was I willing to pay several thousand dollars to buy Matlab. However, there is a free set of software call GNU Octave, which is highly compatible with Matlab. With some minor modifications I was able to get VR2009’s “sealevel2.m” file to execute. The fly in the ointment is that VR2009’s “Sealevel2.m” calls another Matlab file called ‘ssatrend.m,” which is supposed to do single spectrum analysis to smooth the input sea level and temperature data. VR2009 did not write “ssatrend.m,” but rather reference Aslak Grinsted for this code. I could not get this version of “ssatrent.m” to work with VR2009’s “sealevel2.m.”
I had gone down a rabbit hole when I tried to reproduce Rahmstorf’s 2007 results, and I was not going to make the same mistake twice. So, I simply used LabVIEW to reproduce VR2009’s basic algorithm using my own preferred smoothing method, which I have written about extensively.
It is interesting to note that Rahmstorf’s 2007 science paper also used “ssatrend.m.” Nicolas Nierenberg at Neirenberg’s Climate Musings pointed out that…
I wrote Dr. Grinsted who wrote me back very promptly, and sent me the source code to ssatrend.m. He also commented that he had no idea how Dr. Rahmstorf had gotten a copy of it, and that he had never meant for it to be distributed. I think that he was just concerned about it being unsupported. My own view is that it is pretty strange to use some random piece of code in a published paper without making the code your own.
Maybe by 2009 Rahmstorf or Vermeer had made contact with Aslak Grinsted and made more conventional arrangements to use his code for VR2009, but I don’s know.
For your reading pleasure, here is an unzipped version of VR2009’s code and results.