Realclimate has a good explanation of the latest battle in the hockey stick wars. It looks to me like McIntyre & McKitrick's claim (that the hockey stick is the product of an erroneous calculation) is not correct. That doesn't mean that the graph is correct of course, since the proxies the graph is built on may not measure temperatures very well.
In an editorial, the Wall Street Journal systematically misrepresents the whole affair:
In 1998, Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics published a paper in the journal Climate Research, arguing that there really had been a Medieval warm period. The result: Messrs. Soon and Baliunas were treated as heretics and six editors at Climate Research were made to resign.
In fact, the editors resigned because they felt that Soon and Balanius's paper was so badly flawed that it should not have been published.
In 2003, Stephen McIntyre, a Toronto minerals consultant and amateur mathematician, and Ross McKitrick, an economist at Canada's University of Guelph, jointly published a critique of the hockey stick analysis. Their conclusion: Mr. Mann's work was riddled with "collation errors, unjustifiable truncations of extrapolation of source data, obsolete data, geographical location errors, incorrect calculations of principal components, and other quality control defects." Once these were corrected, the Medieval warm period showed up again in the data.
This should have produced a healthy scientific debate. Instead, as the Journal's Antonio Regalado reported Monday, Mr. Mann tried to shut down debate by refusing to disclose the mathematical algorithm by which he arrived at his conclusions. All the same, Mr. Mann was forced to publish a retraction of some of his initial data,
If you actually, I don't know, read Mann's correction you'll find that he didn't retract his initial data, but corrected the description of it. And that mathematical algorithm that the WSJ alleges that Mann refused to disclose? It's right here.
Statistician Francis Zwiers of Environment Canada (a government agency) notes that Mr. Mann's method "preferentially produces hockey sticks when there are none in the data."
This strikes me as a big red herring. If you do a linear regression on random data, you'll produce a straight line. Does that mean that linear regression is invalid because it preferentially produces straight lines when there are none in the data? Of course not. What is important is whether the result of the regression is statistically significant---for random data it won't be. William Connolley did some experiments and reports:
What that appears to demonstrate is that M&M are right about one thing: it often does lead to a "hockey stick" shape in random data. But the problem is that the variance-explained of the PC1 done this way is tiny: the first eigenvalue is about 0.03. Whereas when you run it on real data the first eigenvalue is about 0.55 (back to 1000) or 0.38 (back to 1400). Which means the two problems are very different.
Somehow I posted this on another post. Apologies.
The WSJ hasn't bothered to print my comment, which was:
This opinion piece contains three significant errors that misconstrue the debate; it could stand a good editorial fact-checking.
The Soon and Baliunas piece was published in 2003, not from the start as claimed here. The reason for the poor response to the paper was it contained numerous methodological errors - the Editors of Clim Res resigned out of protest because the work was so shoddy yet was published. The data from multiproxy studies the authors presented clearly disagreed with their conclusions.
The original Mann et al. paper did not go back as far as the Medieval Warm Period (MWP), hence the MWP not being found. The subsequent Mann papers and all multiproxy studies by other authors have found evidence of both the MWP and Little Ice Age. Mann has written a textbook chapter explaining both (Encyc. of Global Environ. Change (ISBN 0-471-97796-9)).
The McIntyre and McKitrick paper has not withstood scrutiny. The methodology was shown by multiple parties to be flawed.
Any objective analysis that relies on Soon and Baliunas and McIntyre and McKitrick is surely flawed.
Instead, the comments allowed look more like a FReeper rant.
Tim, care to take a look at Andrew Bolt's latest effort?
Just wanted to say that I just ran across your takedown on Louis Hissink and it is like the ideal example of why someone would start reading a weblog. It's funny, it's full of relevant expert facts like the actual numeric heat flow from inside the earth compared to from the sun, and it has great, intelligent commenters. You're like Carl Zimmer's http://www.corante.com/loom/ -- the voice that shows that the mainstream has intelligent supporters too, since only the skeptics get much press. Bookmarked.
Rex, Andrew's effort seems to have little to do with this blogpost by Tim but here, if you'll settle for it, is my response to Andrew as posted to his article:
I think that's not a bad article Andrew, but you could consider a few critical points.
Firstly cuts to our emissions have always been expensive. It was expensive when we stopped polluting rivers and beaches with raw sewage, also cost us a pretty penny to clean the exhausts of motor vehicles and power stations so that we could breathe cleaner air, and it cost real money to replace the CFCs that threatened (amongst other things, due to their effect on the ozone layer) deadly melanoma to increasing numbers of Australians. Yes it'll be expensive to stop pouring CO2 into the atmosphere - so what? We'll just do it in the most economic way we can, and feel better about ourselves for having acted to address such a serious pollution problem.
Secondly, you shouldn't quote a geochemist on a question of marine biology like a coral reef! What would he know? You probably do know yourself that on the denialist side of climate change arguments you will find plenty of geologists, and others, who have no expertise in biology or ecology (or climate science). To make a specific point now, if something like a coral reef takes hundreds of years to grow but water temperature changes relatively rapidly, perhaps over only tens of years - don't you lose a precious thing like a reef system hundreds of years faster than it can be replaced by a new one growing in a once sub-tropical ocean? These rate of change problems appear to completely baffle at least the media-quoted geologists. Anyway I propose that you might leave rock matters to the geologists Andrew, and put biological questions to people who can answer them intelligently.
Your piece considered as a whole is a very good piece of polemic, written in support of your side only of a scientific argument. You quoted three people who've said stuff you wanted to hear - but you didn't quote a single scientist whose opinions did not suit your prejudices, although you know you'd have found a hundred times as many of them as the three you did. But never mind whether consensus is a key concept in science or not because you're in journalism and, in fairness to you, you were rebutting what you saw as somebody else's flawed article.
That wasn't a bad piece of work for its genre.
The genre, of course, is the genre of systematic lying for money.
Today in the Herald (27/2) Miranda Devine plays jolly hockey sticks and global warming.