Jeff Id emailed me today, to ask if I wanted to post this with the caveat “it’s very technical, but I think you’ll like it”. Indeed I do, because it represents a significant step forward in the puzzle that is the Steig et all paper published in Nature this year ( Nature, Jan 22, 2009) that claims to have reversed the previously accepted idea that Antarctica is cooling. From the “consensus” point of view, it is very important for “the Team” to make Antarctica start warming. But then there’s that pesky problem of all that above normal ice in Antarctica. Plus, there’s other problems such as buried weather stations which will tend to read warmer when covered with snow. And, the majority of the weather stations (and thus data points) are in the Antarctic peninsula, which weights the results. The Antarctic peninsula could even be classified under a different climate zone given it’s separation from the mainlaind and strong maritime influence.
A central prerequisite point to this is that Steig flatly refused to provide all of the code needed to fully replicate his work in MatLab and RegEM, and has so far refused requests for it. So without the code, replication would be difficult, and without replication, there could be no significant challenge to the validity of the Steig et al paper.
Steig’s claim that there has been “published code” is only partially true, and what has been published by him is only akin to a set of spark plugs and a manual on using a spark plug wrench when given the task of rebuilding an entire V-8 engine.
In a previous Air Vent post, Jeff C points out the percentage of code provided by Steig:
“Here is an excellent flow chart done by JeffC on the methods used in the satellite reconstruction. If you see the little rectangle which says RegEM at the bottom right of the screen, that’s the part of the code which was released, the thousands of lines I and others have written for the rest of the little blocks had to be guessed at, some of it still isn’t figured out yet.”
RegEM Satellite data flow chart. Courtesy Jeff C - click for larger image
With that, I give you Jeff and Ryan’s post below. – Anthony
Antarctic Coup de Grace
Posted by Jeff Id on May 20, 2009
I was going to hold off on this post because Dr. Weinstein’s post is getting a lot of attention right now it has been picked up on several blogs and even translated into different languages but this is too good not to post.
Ryan has done something amazing here, no joking. He’s recalibrated the satellite data used in Steig’s Antarctic paper correcting offsets and trends, determined a reasonable number of PC’s for the reconstruction and actually calculated a reasonable trend for the Antarctic with proper cooling and warming distributions – He basically fixed Steig et al. by addressing the very concern I had that AVHRR vs surface station temperature(SST) trends and AVHRR station vs SST correlation were not well related in the Steig paper.
Not only that he demonstrated with a substantial blow the ‘robustness’ of the Steig/Mann method at the same time.
If you’ve followed this discussion whatsoever you’ve got to read this post.
RegEM for this post was originally transported to R by Steve McIntyre, certain versions used are truncated PC by Steve M as well as modified code by Ryan.
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