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 observes:
As I became more familiar, it dawned on me that RegEM had no way of knowing the physical location of the temperature measurements. RegEM does not know or use the latitude and longitude of the stations when infilling, as that information is never provided to it. There is no “distance weighting” as is typically understood as RegEM has no idea how close or how far the occupied stations (the predictor) are from each other, or from the AWS sites (the predictand).
Jeff notes that the Peninsula is less than 5% of the land mass, but has over 35% of the stations (15 of 42). Jeff shows that the reported Steig trend is cut in half merely through geographic grouping, saying:
Again, I’m not trying to say this is the correct reconstruction or that this is any more valid than that done by Steig. In fact, beyond the peninsula and coast data is so sparse that I doubt any reconstruction is accurate. This is simply to demonstrate that RegEM doesn’t realize that 40% of the occupied station data came from less than 5% of the land mass when it does its infilling. Because of this, the results can be affected by changing the spatial distribution of the predictor data (i.e. occupied stations).
The irrelevance of geography is something that we’ve observed in other Mannian methods, starting right from the rain in Maine (which falls mainly in the Seine.) In MBH98, geographic errors didn’t “matter” either. The rain in Spain/Kenya error in Mann 2008 only “mattered” because the hemisphere changed. Had the error stayed in the same hemisphere, it wouldn’t have “mattered”. Gavin Schmidt and Eric Steig took umbrage at someone bothering to notice a geographic error in the Supplementary Information. At the time, I noted that I wasn’t sure whether the error was a typo or, as in the MBH and Mann 2008 cases, was embedded in the information files themselves. In either case, I didn’t expect the error to “matter” simply because I didn’t expect that Steig’s methods care whether a site was correctly located – a point that is a corollary to the results of the two Jeffs. Take a look.