I had a look through this defense of the Hockey Stick over at Realclimate. The author is Tamino. Here he writes at length defending Michael Mann's hockey stick graph against Steve McIntyre, Andrew Monfort, and others. He insults their integrity and character. I'm not surprised. Tamino called me an idiot and blocked me from commenting on his website when I asked, "Has there been any statistically significant warming in the past twenty years?"
Steve McIntyre has his own answer to Tamino's post. He concentrates upon how Tamino mis-quotes him.
But here's my answer to Tamino. The central argument against the Hockey Stick, as put forward by Steve McIntyre and Ross McKitrick, and confirmed by the Wegman Repot for the US congress, is that Michael Mann's data analysis generates the hockey stick from random proxy data. We explain how his analysis produces the hockey stick here, and I first posted about the effect here.
Nowhere in Tamino's discussion do I see any mention of the fact that random proxy data combined with CRU's global surface trend produces a hockey stick. Given that random input produces the hockey stick, it's pretty clear that the graph has no statistical significance. When I said as much in a comment at Realclimate, my comment was blocked. That's the third comment of mine that Realclimate has blocked.
UPDATE: In addition to the temperature hockey stick, there is also a CO2 hockey stick that you get by splicing modern CO2 measurements onto the end of the ice core measurements, like this. We talk about such splicing in the Ice Cores and Carbon Dioxide sections here. In Questioning the CO2 Hockey Stick, Jaworowski et al. challenge the absolute accuracy of the ice core CO2 measurements.
UPDATE: There's a new paper out in the Annals of Applied Science, A Statistical Analysis of Multiple Temperature Proxies: Are Reconstructions of Surface Temperature Over the Last 1000 Years Reliable? by McShane et al. You will find a copy of the paper here. The paper concludes that Michael Mann's method produces a hockey stick graph from random data, and that the hockey stick shape has no statistical significance.
UPDATE: In the new Realclimate discussion about the McShane paper, I again attempted to post a comment stating that Mann's method generated the hockey stick from random data. That's my third attempt to make the same statement. Comments posted after mine have now appeared. I assume my comment was blocked. So far as I can tell, nowhere in this latest discussion does any comment or the author mention the fact that Mann's method produces the hockey stick from random data. [24-AUG-10]