Michael Mann is facing some embarrassment for a statement he made on RealClimate.org in 2004. In response to this remark:
Whatever the reason for the divergence, it would seem to suggest that the practice of grafting the thermometer record onto a proxy temperature record – as I believe was done in the case of the ‘hockey stick’ – is dubious to say the least.
No researchers in this field have ever, to our knowledge, “grafted the thermometer record onto” any reconstruction. It is somewhat disappointing to find this specious claim (which we usually find originating from industry-funded climate disinformation websites) appearing in this forum.
But he was misinformed. As reported in the New York Times, that’s exactly what Phil Jones did when he prepared the cover graph for the 1999 World Meteorological Organization report. Jones discussed doing so in his infamous “hide the decline” email.
This is embarrassing for Mann, whose intemperate response to the suggestion that anyone in his field would have done such a thing now looks foolish.
It’s even more embarrassing to Jones and his defenders, because they are now trying to argue that Jones’s presentation was appropriate, and Mann’s intemperate response implicitly concedes that it was not. In fact, in Mann’s comments on the scandal, he says that Jones was not trying to fudge the data, but he stops short of defending Jones’s presentation of the data.
But Christopher Horner has gone further and accused Mann of dishonesty. He points out that Jones got the “trick” from Mann’s 1998 article in the journal Nature. How then could Mann claim to be unaware that anyone does it?
That isn’t fair. In his intemperate response, Mann went on to make a distinction:
Often, as in the comparisons we show on this site, the instrumental record (which extends to present) is shown along with the reconstructions, and clearly distinguished from them.
In other words, Mann says, it’s okay to graft the instrumental record onto the reconstruction, as long as it is clearly marked which is which. That’s what he did in the Nature article, plotting the instrumental record with a dotted line that did not exactly stand out, but was clearly distinguishable. That’s also exactly what Jones did not do in the WMO report.