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Brandon Schollenburger is compiling a list of Michael Mann's egregious errors. . . And frauds:

Here are some items I’m considering for my list, along with a (relatively) short summary for each (in no particular order):

Tiljander – The Tiljander proxies were said by the data collectors to have been corrupted due to human influences, and as such, their data from ~1800 AD was worthless as a temperature proxy. Additionally, there were only two series. Not only did Michael Mann use these series with a methodology that requires proxies measure temperatures in the modern times, he used some of them upside down, and he duplicated information by using four instead of two.
r2 – Michael Mann calculated statistical verification scores for his reconstruction. He published the favorable results while hiding the adverse results. He did this to such an extent he published some scores for one test (r2) while hiding others from the same test. When challenged on this, he lied by claiming he had never calculated any of the r2 scores (despite having published some).
Additionally, the IPCC report which made him famous claimed his reconstruction passed multiple verification tests, a claim it couldn’t have made if people had known about the hidden, adverse results. Had he disclosed those adverse results, he would never have received worldwide attention, become a major public figure in the global warming debate, have written a popular book or become a player in political campaigns.
Gaspe – Michael Mann used the Gaspe tree ring data twice. In one case, he artifically extended the series further back into the past so it could reach the 1400 AD mark his paper aimed for. He did not disclose this extension nor offer any justification for it. Without it, his results would have been notably weaker. Additionally, the Gaspe tree ring data for that period was based upon a single tree. Dendrochronologists say series based upon a single tree are inappropriate for use as temperature proxies.
Temperature record as proxies – Michael Mann included modern temperature data, measured by man made instruments, in both his original reconstruction and his 2008 reconstruction. In both cases, they were treated as proxy data derived from nature.
Precipitation record as proxies – Michael Mann has repeatedly used precipitation records as proxies in his temperature reconstructions even though he co-authored a paper criticizing other authors (Soon & Balinaus) for conflating temperature and precipitation proxies.
Non-robust – In his original work, Michael Mann claimed his temperature reconstruction was robust to the removal of tree ring data. It wasn’t. He now admits (in his book) he knew it wasn’t almost immediately after publishing his original work, but he never corrected it. Instead, he wrote an another paper which built upon the earlier work.
This last one cannot be stressed enough. Michael Mann knew his temperature reconstruction was dependent upon a small amount of tree ring data from one part of the United States. Knowing this, he allowed his work to be promoted as showing what temperatures were like for the entire northern hemisphere. Had he been honest, people would have known 90% of his data was irrelevant and all that really mattered was a small number of trees in one area.
The censored directory, misused PCA and other issues tie into that last one, but really, those two paragraphs are all people need to know. That alone, or perhaps in combination with the hiding adverse results, is easily enough for a person to believe Mann’s work was fraudulent.
(Of course, there are other topics to discuss as well. This is just a beginning of a list.)