The title, of course, is a snark at RC; see the article A Mistake with Repercussions which points out some errors in a Zorita and Von Storch paper (they got their model setup wrong). [I’ve just snarked them in their comments; it will be intersting to see if it stays]
In this case the problem is rather more arcane, but worth explaining, so let me do that first.
[Update: no, let me first point out that there is a response by Rutherford et al. which appears to say that they fixed all these problems ages ago.]