I post this with a caveat that I haven’t checked the math or the script but Watts Up With That there is a very interesting post on the deleted data. Steve McIntryre posts a script that attempts to recover some of this missing data. (I assume this is done by backing out the adjustments from the published data, but again the script needs to be verified.) The picture it paints is quite revealing.
Contrary to Gavin Schmidt’s claim that the decline is “hidden in plain sight”, the inconvenient data has simply been deleted.
The reason, as explained on Sep 22, 1999 by Michael Mann to coauthors in 938018124.txt, was to avoid giving “fodder to the skeptics”. Reasonable people might well disagree with Gavin Schmidt as to whether this is a “a good way to deal with a problem” or simply a trick.When I first heard about the leaked emails of Climategate my initial reaction was that the real revelation wasn’t the change in data but the proof of the gaming of the system and the behind the scene politics. But as more analysis is done I think many (including myself) are going to be surprised at just how much smoke and mirrors was involved.
Update: In the comments, Jeff makes some interesting points and clarifications. I wanted to highlight one thing.
I do know that for AGW to be true there needs to be 2 things:
1) a real measured rise in temperatures since about 1930 (we didn’t do much CO2 generation before then so going back to 1890 is cheating)
2) a good correlation between CO2 and global temperatures since 1930.Those conditions are necessary but not sufficient. Correlation in isolation does not indicate causality. Having worked with statistical problems for a number of years I have learned this lesson far too well.
Just because CO2 and global temperatures are correlated does not in an of itself prove that CO2 is the cause of global warming. One could easily imagine a system where some other factor is causing increased (or decreased) temperatures and that CO2 levels are “caused” by these temperature changes. (I’m not suggesting this is the case. My comments are focused on the limited usefulness of correlation as a method of proof.)
The climate of the earth is a staggeringly complex system and it can’t be described by one hockey-stick graph (or for that matter by blog posts like this one). Which represents the real tragedy of the behavior of the pro-AGW scientists. With a problem of this magnitude it is beyond the skills of ordinary laymen to rigorously determine accurate solutions. In these cases, one would normally turn to the appropriate experts. But if the experts are found to be falsifying the evidence, to whom do we turn?