In Dec 2004, Steig and Schmidt wrote
The Antarctic Peninsula, site of the now-defunct Larsen-B ice shelf, has warmed substantially. On the other hand, the few stations on the continent and in the interior appear to have cooled slightly (Doran et al, 2002; GISTEMP). At first glance this seems to contradict the idea of “global” warming, but one needs to be careful before jumping to this conclusion.
More recently, in Jan 2009, Steig wrote in explanation of Steig et al here
So what do our results show? Essentially, that the big picture of Antarctic climate change in the latter part of the 20th century has been largely overlooked. It is well known that it has been warming on the Antarctic Peninsula, probably for the last 100 years (measurements begin at the sub-Antarctic Island of Orcadas in 1901 and show a nearly monotonic warming trend). And yes, East Antarctica cooled over the 1980s and 1990s (though not, in our results, at a statistically significant rate). But West Antarctica, which no one really has paid much attention to (as far as temperature changes are concerned), has been warming rapidly for at least the last 50 years.
I was intrigued by the statement in Steig et al that “no one really has paid much attention to [West Antarctica ]”. How could this be?
The graphic shown below (Steig Figure 4e) shows temperature trends in Antarctica for 1979-2003 as calculated in Steig et all. The Antarctic Peninsula can be seen going off to the northwest. “West Antarctica” is the “hot” region adjacent to the Peninsula.
One of the main theses of Steig et al is that a more accurate accounting of Antarctica yields an overall profit: the profits in the Peninsula and West Antarctica outweigh slight losses/trading dollars in East Antartica. Antarctic temperature trends are not something that I’ve previously taken a position on nor had I familiarized myself with the data. As someone approaching the matter freshly (as I mentioned before), it seems surprising to me that Antarctica wouldn’t have warmed along the rest of the world; it also seems to me that there are modeling issues specific to Antarctica and modelers might well get inconsistent results in this continent without meaning that everything that they ever did was worthless (though it might be worthless on other grounds).
I downloaded GISTEMP binary data and calculated 1979-2003 GISTEMP trends for 1200 km smoothing (250 km smoothing is much sparser) and obtained the plot shown below. (I haven’t figured out how to show the scale on the plotting software, but it’s -.5 to 0.5 deg C/decade (I used the package maps – but will experiment with some of Roman’s code in the future). I required 280 out of 300 months for a trend (the availability fell off very sharply.)
Interestingly GISS uses exactly the same READER data set as Steig – see here where there are references to READER pages. (I’ve matched GISTEMP numbers to all the READER data for future reference.) To the extent that Steig claim that they can get the same result without satellite data, this means that it because they process the data differently than GISS – not that they are using different data.
Both maps show strong warming on the Peninsula, but GISS smoothing did not generate sufficient data in West Antarctica to show a trend one way or the other. Steig and Mann have deduced that this region with missing data in GISS is nonetheless warming strongly. Could be. If this were a mining map, one would certainly look for ore in regions adjacent to known ore and West Antarctica is adjacent to known Peninsula warming.
There are some other interesting differences: the “cold” area from 90-180E is mildly warming onshore in the Steig rendering. Would be interesting to know what accounts for the differences.
But first I’m going to look at what surface and AWS data is available in West Antarctica – to see what the data looks like before it goes into RegEM.
As a further observation on the inconsistency between GISS and Steig results for the Antarctic: Steig describes himself as an isotope geochemist. It’s nice that Steig’s taken time from his busy studies of isotope geochemistry to try to sort out GISTEMP data in the Antarctic – but isn’t this the sort of thing that GISTEMP should have done in the first place?
It would also be nice to hear from GISS on this: what do Steig’s results say about GISTEMP methodology? Steig didn’t analyse why GISS methods seem to have been incapable of discerning recent warming in West Antarctica (an unexpected sort of oversight), but shouldn’t there be some kind of effort at detailed reconciliation.