I know the Hockey Stick is old news to most blog readers here, but it’s easy to forget that the people reading the mainstream news (ie: most of the West) have no idea of the scale of the audacity involved. Up until the 1998 MBH paper came out, it was widely understood that there was a Medieval Warm Period, indeed there were hundreds of papers available at the time. The Hockey Stick Graph completely rewrote everything, yet was accepted and widely promoted without anyone so much as asking for the data… until, of course, McIntyre and McKitrick tried. It will do down in the annuals of science as one of the most egregious examples of “the not-so-scientific” method. — JoNova
The public might not understand the science, but they do understand cheating
Dr. David Evans
6 October 2010
[A series of articles reviewing the western climate establishment and the media. The first and second discussed air temperatures, the third discussed ocean temperatures, the fourth discussed past temperatures, the fifth compared the alleged cause (human CO2 emissions) with the alleged effect (temperatures).]
Click to download a pdf file containing the whole series
Why the Establishment Had to Manufacture the Hockey Stick
Faced with the obvious disconnect between human CO2 emissions and temperature (Figures 21 and 22), the climate establishment either had to change its theory or change its data.
The establishment’s anti-scientific attitude that its theory triumphs over data was famously on display in the Climategate email where Kevin Trenberth, who believed (in 2008) that global warming was still occurring but was bemoaning that no one could find it using actual real-world measurements, said “The fact is that we can’t account for the lack of warming at the moment, and it is a travesty that we can’t.”
They chose not to change their theory, so they had to change their data (thereby disqualifying themselves as scientists). Because the CO2 figures come from historical consumption data that are very hard to dispute, they had to change the temperature data instead.
“We have to get rid of the Medieval Warm Period”
They needed to move the start of the global warming trend from before 1700 to a time when human emissions were becoming significant compared to today’s level—to say 1910, which is also at a minimum in the warming-cooling pattern (figures 20 and 22).
And to make the current warming unprecedented, they needed the current temperature to be greater than anything in the last thousand years. In a rare insight or slip, one of the leading establishment climate scientists sent University of Oklahoma geoscientist David Deming an email in 1995 that said “We have to get rid of the Medieval Warm Period”, according to a statement by Deming to a US Senate Committee.
Michael Mann’s hockey stick graph is the most prominent and persuasive graph in the global warming debate. Most people who believe that man is responsible for global warming believe some version of the hockey stick. It was very widely publicized, and was even adopted by the IPCC for its logo (but later dropped).
Only the Climate Establishment Believes in the Hockey Stick
The hockey stick is widely discredited in scientific circles outside climate science (this has been done to death elsewhere, so we’ll just go big-picture here):
- The statistical processing used by Mann puts a lot of weight on any hockey-stick shaped inputs and puts very low weights on temperature proxies with other shapes. Although Mann used a variety of temperature proxies as inputs, only the tree rings from bristlecone pines really counted. This way he can say “See, I used a wide variety of temperature proxies and they all contributed to the result”, while still getting the hockey-stick shape he wanted.
- Bristlecone pines are problematic because that species is notorious for having a growth spurt in the twentieth century for reasons not directly connected to temperature. (Bristlecone pines live in dry regions and are very susceptible to CO2 fertilization and the CO2 drought resistance effect. They respond strongly to higher CO2 levels in the air, humidity levels, and to sunshine—but not to temperature. 1, 2. Also, see part 4 of this series on why tree rings make poor proxies.)
- In 2006 the US Congress requested a committee of three independent statisticians, headed by eminent statistics professor Edward Wegman, to look into Mann’s hockey stick. From the findings:
“ In general, we found [Mann’s methods] to be somewhat obscure and incomplete* and the criticisms [by their main critics] to be valid and compelling.
… It is important to note the isolation of the paleoclimate community; even though they rely heavily on statistical methods they do not seem to be interacting with the statistical community.
… Moreover, the work has been sufficiently politicized that this community can hardly reassess their public positions without losing credibility.
Overall, our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis.”
The climate establishment persists with putting forward similar temperature pictures. There are other, minor hockey sticks, similar graphs produced by climate-establishment scientists. The next most prominent is by Briffa, who refused to divulge his tree ring data for nine years (real scientists share their data). When finally revealed, his data showed that his hockey stick was based just on 10 trees in the Yamal peninsula of northern Russia, and relied almost entirely on one freak tree for the blade of the hockey stick—perhaps that special tree found a source of manure and had a growth spurt?
For more on the hockey stick shenanigans, for the more forensically inclined, see the Wegman and North Reports for Newbies.
Mann still defends his hockey stick, but gets comprehensively rubbished.
Why don’t the media inform us of the problems with the hockey stick picture, to counteract the earlier wide publicity it received?
* Scientists say “incomplete” as a polite way of saying “rubbish” or something earthier.
Full PDF versions for printing and emailing are available from the summary page.
Hockey Stick Saga links
My short sharp wrap of the Hockey Stick story, with maps of all the empirical studies demonstrating the global nature of the MWP, and some of the statistical tricks that captures the effrontery: Fraudulent hockey sticks and hidden data
The hot statisticians — McShane and Wyner 2010: Zombie Hockey stick dies again
The day the Briffa data was exposed as being based on one tree: Breaking news: Cherry Picking of Historic Proportions
— Jo Nova
Image attribution: By Oscar Wergeland (1844–1910) from Wikimedia Commons