[UPDATE - June 24, 2010: the following text has been slightly modified following some discussion at ClimateAudit and in particular a detailed explanation from Steven Mosher of what he did wrong. Changes are indicated by
strikethrough for deletions and bold for additions].
When people are obviously wrong it doesn't take much time or effort to dismiss their claims. When Joe Barton apologizes to BP we know he's spouting nonsense. When Gerhard Kramm gets simple integrals and averages confused it doesn't take much effort to convince anybody other than Kramm where he went wrong. When Tom Fuller blusters about quantitative meta analysis, Gish Gallops, and alternate universes you can tell he has trouble with logical coherence.
But the tricky cases are those who are much more subtle in their nonsense. Making stuff up is easy. Making stuff up that on the face of it looks somewhat plausible does take a bit more skill. Figuring out that the "plausible" stuff is just as much nonsense as the obviously wrong takes considerably more work, and some of these actors tend to make a lot of work for those of us trying to defend real science. One of the most skilled in creating plausible nonsense is Christopher Monckton. Prof. John Abrahams is the latest of us to take on Monckton's fabrications, and collectively thousands of hours have surely been spent tracking down the ways in which Monckton has misrepresented science.
Brian Angliss has recently put a lot of effort into tracking down the basis of some of the claims regarding "climategate", in particular looking at the implications of malfeasance on the part of the scientists whose emails were stolen. Many of
these the conclusions Angliss examined were claimed at the website ClimateAudit, and in particular in a book published by Steven Mosher and Tom Fuller. There followed an extensive thread of comment including from Fuller and Mosher, and a response from Steve McIntyre at ClimateAudit that clarified some of the claims prompting Angliss to revise his article to attempt to correct his own mistakes.
The first discussion point in Angliss' review of the claims and in the
ClimateAudit back and forth with Mosher and Fuller is the meaning of the "trick" to "hide the decline" phrase found in the stolen emails. This has been adversely interpreted in a couple of different ways but the actual meaning has been clearly identified as the process of creating graphs that do include tree-ring-based temperature "proxy" data only up to 1960, or 1980, a point where they start to diverge from temperatures measured by instrumental thermometers. There is nothing scientifically nefarious or "wrong" about this - the "divergence problem" has been extensively discussed in the scientific literature including in the text of the most recent IPCC report. If you have reason to believe a particular collection of tree ring data is a good measure of temperature before 1960 but for some still uncertain reason not after that point, then it's perfectly legitimate to create a graph using the data you think is reliable, particularly if these choices are all clearly explained in the surrounding text or caption.
Figure 2.21 from IPCC TAR WG1
Figure 6.10b from IPCC AR4 WG1
What's definitely not legitimate is presenting a graph that is specifically stated to be showing one thing, but actually showing another. That might happen just by accident if somebody messed up in creating the graph. But the
ClimateAudit discussion and Mosher/Fuller book appeared to claim that in one figure in the 3rd IPCC report (TAR WG1 figure 2.21, 2001) and in one figure in the 4th report (AR4 figure 6.10b, 2007) there was a real instance where "the scientists had actually substituted or replaced the tree ring proxy data with instrument data" deliberately, for the purpose of "hiding the decline". As Angliss cited, McIntyre definitely uses the word "substitution" (but Angliss was apparently wrong that McIntyre did this in the IPCC context), and Fuller highlighted a portion of the Mosher/Fuller book using the word "replaced". McIntyre later clarified that his claim was not related to these IPCC figures but rather something else. However, Steven Mosher in comment #7 on Brian's article at June 8, 2010 at 12:34 pm stated very clearly that he knew what the trick was and that this substitution/replacement was used for the IPCC figures: