JF asks for explanation of the R2 vs. RE statistical issue - what's necessary, what's sufficient, and why. This of course is Bartonism - question 7c, to be precise. The honest answer is, I don't know. And of course, neither does Barton. Take him away from his staffers and his notes and he wouldn't have a clue. So why is a US senator allowing himself to be used as a sockpuppet of a canadian mining consultant to parrot questions he doesn't understand? Politics, of course.
Mann responds that R2 isn't so useful because it measures the simple correlation, and doesn't assess the mean or standard deviation (i.e., if series A is 10 times series B, it would have a perfect r2 of 1, but wouldn't be a very good reconstruction). Mann prefers RE, whatever that may be... which sounds entirely plausible.
But basically folks, this is all a waste of time. Its like arguing with creationists about uranium-series dating, there will always be some tedious technical blind alley they will invite you to go down, while the rest of the world does more interestng things. Even the climateaudit groupies have realised this, with comments like "But isn’t it time to use your brain for something new?"
Oh dear... that tempted me into reading some of the CA comments. Try:
"I’m not a politician, but if I was, and saw replies that either ducked direct questions or gave woolly answers to them, then I’d be tempted to ask them for a little face time to discuss this."
This from someone who thought Mann was evasive. Funnily enough, Barton doesn't seem in any great hurry to hold any hearings, having got his fingers badly stomped on by Boehlert (more).