Could it be that Mann's Hockey Stick is upside-down?

It certainly seems to be by some accounts, or at least some of the data is.

Please note:
"This isn’t an opinion. McIntyre personally verified this data inversion with the researcher, Tiljander, who collected the original proxy data."

Mann's response?
“Multivariate regression methods are insensitive to the sign of predictors. Screening, when used, employed one-sided tests only when a definite sign could be a priori reasoned on physical grounds. Potential nonclimatic influences on the Tiljander and other proxies were discussed in the SI, which showed that none of our central conclusions relied on their use.”

Comments:
Back in high school I was pretty good at coming up with excuses for undone homework, and also for incorrect answers. However I wish I had Mann’s skill. How I would have loved to see the look on my Geometry teacher’s face when he told me a graph was upside down, and I answered, “Multivariate regression methods are insensitive to the sign of predictors. Screening, when used, employed one-sided tests only when a definite sign could be a priori reasoned on physical grounds. Potential nonclimatic influences on the Tiljander and other proxies were discussed in the SI, which showed that none of our central conclusions relied on their use.”

in reference to:

"As WUWT and Climate Audit readers know, Mann made some blatantly obvious mistakes in his use of proxy data in Mann et al 2008, where he claims to be able to make a present day “hockey stick” of climate without the use of Bristlecone Pines that he used in his flawed 1998 study which produced the original Hockey Stick. Mann inverted data, upside down if you will, notably the Tiljander sediment as pointed out by Steve McIntyre.
Steve writes:
Mann didn’t just use one Tiljander series upside down; he used all four of them upside down, a point illustrated in the graphic below from a Japanese language article that rather appealed to me.
This isn’t an opinion. McIntyre personally verified this data inversion with the researcher, Tiljander, who collected the original proxy data. Yet Mann still denies it, probably because using the data right side up doesn’t produce the desired results."
- IQ Test: Which of these is not upside down? « Watts Up With That? (view on Google Sidewiki)