Last year, I wrote about why the assault on (and some of the defense of) the Mann Bradley and Hughes hockey stick was misplaced. With Stephen McIntyre and Ross McKitrick coming out with a new paper, the subject is worth revisiting. But Stefan Rahmstorf has done a much more capable job than I could, so I'll just leave you in his capable hands:
So let’s assume for argument’s sake that Mann, Bradley and Hughes made some terrible mistake in their statistical analysis, so we need to discard their results altogether. This wouldn’t change our picture of the last millennium (or anything else) very much: independent groups, with different analysis methods, have arrived at similar results for the last millennium. The details differ (mostly within the uncertainty bounds given by Mann et al, so the difference is not significant), but all published reconstructions share the same basic features: they show relatively warm medieval times, a cooling by a few tenths of a degree Celsius after that, and a rapid warming since the 19th Century. Even without Mann et al, we’d still be stuck with a "hockey stick" type of curve – quite boring.