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I agree that there should be an explanation; I wonder if Dr. Mann will do it directly to McIntyre and McKitrick, since he apparently doesn't think much of their effort to analyze his data. Publishing the "audit" paper in Energy and Environment may cause Mann to not bother to reply, as he might figure that would lend more credence to their results than he wants to give them. Had they published in a a more established science journal, particularly one focused on climate science, he would have been obligated (=forced) to respond.

It will be interesting to see if the media pressure and the pressure from the skeptical community on him will be sufficient to get him to respond. He is definitely capable of responding; after the Soon, Baliunas (et al.) papers came out early this year, due to persistent inquiries from the press, he collaborated on a response that was in the American Geophysical Union Eos publication.

Mann makes a lot of stuff available on his personal home page; here's the Eos article (PDF). The first figure shows a bunch of climate reconstructions over the past 1000 years.

On Past Temperatures and Anomalous 20th-Century Warmth

A couple of years ago there was some attention paid to an analysis published by Esper et al. (to which Mann responded). Esper's data, which appears in the figure noted above, shows much deeper cold periods than Mann's data (Mann's data was multi-proxy temperature records; Esper's was only tree-ring data). Esper's data is spikier, and there are a couple of times when his temperature record is significantly higher (0.2-0.3 C) than Mann's. But the overall pattern is still the same. If Esper's data and analysis are truly independent of what Mann et al. have done (same goes for the Crowley and Lowery analysis), then the likelihood that McIntyre and McKitrick operated on an erroneous data set increases. But it certainly appears that most of the blame for them receiving a flawed data set falls squarely on Dr. Mann.

If he'd been smart, he would have made certain that they got the correct data, and if their analysis had not shown any errors, then nothing would have happened. Now Mann is in a mess of his own making. It will be interesting to see the way in which he responds now.