Fred Pearce, a long-time environment reporter who believes in the warming theory, says:
The evidence of scientists cutting corners, playing down uncertainties in their calculations and then covering their tracks by being secretive with data and suppressing dissent suggests a systemic problem of scientific sloppiness, collusion and endemic conflicts of interest, but not of outright fraud. (p. 241)
h/t Climate Audit.
Remarkably, these two statements may not be contradictory. Some degree of hiding or suppressing evidence, greatly over-stating the credibility of headline-making statements, distortion, selective reading etc. may be accepted in academia as the means that are necessary to climb the greasy pole. You say you are bringing certainty to a field that has been full of uncertainty. Even better, you are questioning if not overturning the certainties of the past. As long as there is a kind of plausibility to your work (see McArdle: "not obviously false"), you are golden.
Even if someone cares to (and the big wigs at Penn State certainly don't), it is difficult to prove outright fraud. Mann knew for sure that a statement he made was false? That some other, contrary statement was true? Did he know that uncertainty was still the truth when it came to climate science, and all the interesting theories were hardly more than speculation? It is more likely, at least much of the time, that he honestly thought his bullshit was no worse than most, and better than some. Once their models seemed to work for some historical eras, the climate scientists kidded themselves that they would work for all. Once they had comitted themselves to this view, and received huge funding and attention for it, reputations and careers depended on continuing to defend it.
Steve McIntyre has said repeatedly that this has been a sobering lesson to him. In mining engineering, you either have the evidence or you don't. You either demonstrate it or you don't.