Category Archives: Steig at al 2009

Why did Steig use a cut-off parameter of k=3?

A question that Jean S inquired about before we were so rudely interrupted. The expanation in Steig et al was: Principal component analysis of the weather station data produces results similar to those of the satellite data analysis, yielding three separable principal components. We therefore used the RegEM algorithm with a cut-off parameter k=3…. A […]

Re-visiting the AWS Recon PCs

Yesterday, we discussed the remarkable decomposition of the AVHRR reconstruction into 3 PCs, initially observed by Roman and discussed yesterday by Jeff Id. I thought that it would be interesting to see what happened with the PC3 in the AWS reconstruction (and in the process, do some comparisons of the RegEM emulation (file-compatible between Jeff […]

The Three AVHRR PCs

Roman Mureika perceptively observed about 10 days ago that the AWS reconstruction consisted of only 3 PCs. Jeff Id has extended this to observing that the AVHRR reconstruction consists of only 3 PCs. Jeff’s demonstration of this is correct, but a little awkward. I’ll show an alternate demonstration which shows a useful linear algebra property […]

Porting RegEM to R #1

I’ve transliterated relevant Tapio Schneider code into R (pttls.m) and parts of regem.m that seem relevant at present. Jeff Id has extracted a variety of intermediates from his Matlab run and I’ve fully reconciled through two steps with remaining differences appearing to be probably due to transmission rounding. My dXmis statistic at step one was […]

The Two Jeffs on Emulating Steig

The two Jeffs ( C and Id) have interesting progress reports on emulating Steig using unadorned Tapio Schneider code here. Check it out. One of the first questions that occurred to third party readers was whether RegEM somehow increased the proportional weight of Peninsula stations to continental stations as compared to prior studies. Jeff C […]

Steig’s “Corrections”

Roman M has already done one post on the impact of the Harry error. Ryan O has also done so [see comment here]. As has Steig. I show below some graphics that I’ve just done on AWS recon trends. At Steig’s website, he now states: awsreconcorrected.txt is a correction to the above file, using corrected […]

Deconstructing the Steig AWS Reconstruction

So how did Steig et al. calculate the AWS reconstruction? Since we don’t have either the satellite data or the exact path they followed using the RegEM Matlab files, we can’t say for sure how the results were obtained. However, using a little mathemagic, we can actually take the sequences apart and then calculate reconstructed […]

More Changes at BAS

More changes at 6 ocean stations at BAS listed here , together with a revised “credit” here. One of the 6 stations is Chatham Island, where I noticed a problem on June 13, 2008 when I was trying to replicate GISS methodology using Wellington NZ as an example. John Goetz pinned the erroneous source to […]


Moving right along since the problem with Harry was identified on Super Bowl Sunday, BAS reports: This is a list of corrections that have been made to the AWS data tables and a link to the table before the corrections were applied, any suspected errors should be reported to Steve Colwell (2/2/09)The AWS data for […]

Antarctica – digging out the data

It seems that we are all “wild about Harry” recently, and no good kerfluffle would be complete without some pictures of the weather stations in question. It seems “Harry” got buried under snow. Why is this important? Well, as anyone skilled in cold weather survival can tell you, snow makes an excellent insulator and an […]


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