1) Let's first note that it really doesn't matter whether the hockey stick shows that the late 20th century is warmer than any period in proxied history.
That's because climate today cannot be compared to climate then. Today's climate is subject to new, anthropogenic forcings that did not exist 1000 years ago. It's like comparing apples to oranges, and it has always been like comparing apples to oranges.
What really matters are today's forcings, and not those of a millenia ago.
2) Still, if you want to go there, we have been through years of suggestions (false, but suggestions) that PCA analysis is flawed and is statistically flawed. I have yet to have any real scientist tell me this, and everybody I've ever asked dismisses the M&M critique. In fact, nearly a dozen other independent analyses have found the same result.
The Tingley & Huybers result shows that the even a completely independent analysis shows the same result.
3) Now that skeptics have lost that front, we're supposed to believe that, no, it's the data that is flawed. The Yamal controversy, we know now, was manufactured all along, and in any case a few trees on a far northern peninsula could never have much of an effect on the conclusions.
Science is not about "auditing," and it has never been about auditing. It's about replication. IF skeptics like McIntyre want to be taken seriously, they need to go out and collect their own data, instead of writing endless letters to government officials complaining that someone won't play nice with them.
Of course, they never do that. They don't even try and apply for grants and explain why it's (purportedly) necessary. It's much easier to sit in your warm house in Toronto and send email all over the world than put your boots on and get to work.
And even if they could find no problems with the data, you can be sure that they would find plenty of other reasons to complain about it. After spending 8 years demanding that scientists give them their personal calendars, they would start dismissing any data taken on a Monday or Friday, because, you know, scientists were in a hurry to get back to their tents and make satellite calls home. Tuesday data would be rejected because the scientists ate chili that night, and we all know what that does to the intestinal tract.
On Thursdays, the phase of the moon was wrong.
There is, of course, no end to it, ever. That's important, because it's the first clue that ought to set off your bullshit detector, if you are intellectual honest.
And the reason, of course, is that none of the complaints are about science, or science would recognize them. (There has never been a contrary scientific idea in history -- ever -- that did not prevail -- and sooner rather than later -- because scientists are the ultimate skeptics and the scientific method promotes that.) It is, instead, about applying a Drudge-like approach to creating doubt by every and any means necessary.