Can we now call the "hockey stick" temperature reconstruction a certain exaggeration?

Question

A new study one the past one thousand year temperature proxy data has been published in Annals of Applied Statistics. It concludes that the Mann "hockey stick" is a baseless temperature reconstruction (thus supporting what McIntyre and McKittrick have been saying all along).

Here are some quotes from the study's conclusions:

"Climate scientists have greatly underestimated the uncertainty of proxybased reconstructions and hence have been overconfident in their models."

"Natural climate variability is not well understood and is probably quite large. It is not clear that the proxies currently used to predict temperature are even predictive of it at the scale of several decades let alone over many centuries."

"Consequently, the long flat handle of the hockey stick is best understood to be a feature of regression and less a reflection of our knowledge of the truth."

http://www.e-publications.org/ims/submission/index.php/AOAS/user/submissionFile/6695?confirm=63ebfddf

Answer 1

Absolutely. There isn't much debate these days about this particular example... the problem is that this is an emotive subject mostly discussed for political reasons, so the fact that there are more stringently-inclusive datasets out there is of less importance than the political theatre brought about by the inability to discard bad and outmoded data by the non-scientists among us.

Answer 2

Gary is correct about the study itself. It should be noted that the authors also got a 'hockey stick' shape, though one tilted downwards which basically makes the LIA disappear. The paper has not been peer-reviewed and from what I've read, may contain significant errors. Regardless, they conclude "If we consider rolling decades, 1997-2006 is the warmest on record; our model gives an 80% chance that it was the warmest in the past thousand years."

http://scienceblogs.com/deltoid/2010/08/a_new_hockey_stick_mcshane_and.php



Your additional comments show a gross misunderstanding of the basics of the AGW theory.



"the AGW theory needs recent temperature rise from the Little Ice Age to be "extraordinary" to be able to make the model projections of continued temperature rise. That's the entire reason the "hockey stick" is an AGW icon."



No, no, no. Model projections have nothing to do with the current warming being "extraordinary". Model projections are based on physics. It wouldn't matter if the planet were 2°C warmer in the MWP than it is today - that wouldn't change future model projections. Actually that would mean the climate is more sensitive to small perturbations than we think, so if anything it would make future warming projections *larger*.



And the "hockey stick" is hardly an "AGW icon". The only reason it gets so much attention is because deniers are obsessed with it, and the only reason deniers are obsessed with it is because they see it as evidence that AGW is a fraud, because they think Mann et al. "fudged the data". Which by the way is completely ignorant. Mann et al. have been accused of using incorrect statistical methods and using tree ring data which 'skeptics' want to omit, but they did not "fudge the data".



But regardless, the "hockey stick" is not even remotely critical to the AGW theory. All the hockey stick tells us is that the planet is currently warmer than it's been in several centuries. It's a pretty graph and good for convincing the public that AGW is a serious issue (which is how Al Gore used it). But the physics behind the AGW theory is not dependent upon this temperature reconstruction. If you don't understand that, then you need to spend some time learning basic climate science before you're in any position to question to the conclusions of climate scientists.

Answer 3

The paper hasn't been published yet. Of course the "skeptics" are out with their proclamations, showing for the millionth time why they don't deserve to be called skeptics. Well played skeptics. Keep nailing that coffin. Don't mind that it's empty.

Answer 4

I think we can call the methodology flawed. If it was intentional, it was fraud. Intentionality has yet to be demonstrated. In the choice of data and methods.



The manner in which the primary components method was used in MBH98 and several other reconstructions built by the Hockey Team tends to create hockey stick-shaped curves out of red noise (not random noise).



Another problem with the Hockey Team reconstructions is an over-reliance on tree ring data. In the case of MBH98, Norther California Bristlecone pines were very heavily weighted. These particular tree ring chronologies seemed to indicate strong 20th century warming. The problem was that the instrumental temperature records in that area did not reflect such warming. The original authors of those chronologies (Graybill & Idso, 1993) had concluded that the cause was CO2 fertilization. Koutavas, 2008 provided an excellent example CO2 fertilization here:



http://www.co2science.org/articles/V11/N49/Koutavas2008small.gif



The Hockey Sticks tend to filter out the low frequency component of the climate "signal." Reconstructions which honor the low frequency component don't look ominous and tend to reflect the patterns seen in ice & sediment core d18O temperature reconstructions. Moberg did a far better job in honoring the low frequency components of the climate signal. Reconstructions like these indicate a far more variable climate over the last 2,000 years than the “Hockey Sticks” do. Moberg also shows that the warm up from the Little Ice Age began in 1600, 260 years before CO2 levels started to rise.



As can be seen below, geologically consistent reconstructions like Moberg and Esper are in far better agreement with “direct” paleotemperature measurements, like Alley’s ice core reconstruction for Central Greenland…



http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/Moberg_Mann_Esper_Alley.png



From Esper, et al., 2005...



"So, what would it mean, if the reconstructions indicate a larger (Esper et al., 2002; Pollack and

Smerdon, 2004; Moberg et al., 2005) or smaller (Jones et al., 1998; Mann et al., 1999) temperature amplitude? We suggest that the former situation, i.e. enhanced variability during pre-industrial times, would result in a redistribution of weight towards the role of natural factors in forcing temperature changes, thereby relatively devaluing the impact of anthropogenic emissions

and affecting future predicted scenarios. If that turns out to be the case, agreements such as the Kyoto protocol that intend to reduce emissions of anthropogenic greenhouse gases, would be less effective than thought."



Now... "Mike's Nature Trick" is 100% fraudulent, irrespective of the Penn State & UEA whitewashes. Substituting instrumental temperature data for inconvenient tree ring temperature data, while asserting the validity of the pre-instrumental tree ring temperatures is scientific fraud.

Answer 5

I did a search in the Annals of Applied Statistics and could not find this paper. Your link only says that it was submitted, but it appears this has not been approved for publication.



Edit: I finally found it, it is coming out in the next edition.



However, one of the authors has published recently a paper on baseball statistics. Perhaps he should stick to that.

Answer 6

Mike, Mike, Mike…



<>



Why couldn’t you leave well enough alone?



It’s an interesting article that identifies valid concerns in the time series properties of proxy (and historical) climate records; in particular, time dependence in temperature series –



BUT – your statement is not in the same universe as anything the authors say.



• ”We see that our model gives a backcast which is very similar to those in the literature, particularly from 1300 AD to the present.”



• ”In fact, our backcast very closely traces the Mann et al. (2008) EIV land backcast, considered by climate scientists to be among the most skilled.”



• ”Hence, our backcast matches their backcasts reasonably well…”



• "...our model gives forecasts and backcasts that are broadly comparable to those provided by climate scientists…”



• “On the other hand, perhaps our model is unable to detect the high level of and sharp run-up in recent temperatures because anthropogenic factors have, for example, caused a regime change in the relation between temperatures and proxies.”



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Edward O -



<>



And we call you "Steady Eddie" because your IQ stays in double-digits.



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benthic_man –



<<…”the fact that there are more stringently-inclusive datasets…”>>



WTF is a “stringently-inclusive dataset”?



In any case, the article is based on the assumption that the “data selection, collection, and

processing performed by climate scientists meets the standards of their discipline”, and it is the same data the authors use.



You are the worst kind of hypocrite. You did not even read the article, but you have the innate dishonesty to pretend that you did and the ignorant arrogance to falsely criticize others for doing the very thing that you are doing.



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edit –



I said that the article, “identifies valid concerns in the time series properties of proxy (and historical) climate records” – and if you understood statistics you would know that confidence intervals (bands) are a function of the sample mean and variance.



The hockey stick is irrelevant to computer projections of future climate. In fact, I doubt you can find a single dendrochronologist who has ever said that tree-rings are worth a damn in forecasting anything. The forecasting referenced in the article has nothing to do with future climate. They are talking about split-period validation procedures that calibrate over one segment of the record and verify the model fit over the remaining part of the record.



As Dana notes, and as I have repeatedly said, the “hockey stick” was never intended to be anything more than an experiment in use of multiple proxies in a single regression analysis. Even the name is a media invention. And the only reason the tree-rings were included at all was because they provide annual resolution for calibrating the equation.



And you do realize, I hope, that the term “model” in the article has nothing to do with computer models that forecast climate. The authors are simply following the standard usage of the term where “equation” = “mathematical model”. They are referring to the regression equations used in climate reconstructions and not at all to computer “models” of future climate.



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David,



<< Substituting instrumental temperature data for inconvenient tree ring temperature data, while asserting the validity of the pre-instrumental tree ring temperatures is scientific fraud.>>



Hardly, since the divergence problem was already well documented – and the split is the mid-late 1990s, not the pre-instrumental period:



“Reduced sensitivity of recent tree-growth to temperature at high northern latitudes” Nature 391, 678-682 (12 February 1998)



http://www.nature.com/nature/journal/v391/n6668/abs/391678a0.html



<< The original authors of those chronologies (Graybill & Idso, 1993) had concluded that the cause was CO2 fertilization.>>



No, the authors (Graybill & Idso) concluded that increased water-use efficiency possibly related to the precipitation of CO2 from the atmosphere at high elevations was a hypothesis that required further testing.



Maybe your problem with AGW is a function of some reading disability rather than with the concept itself.

Answer 7

When one of the top statistical journals says that the hockey is flawed, only a denier would think otherwise.



You have to love the alarmist cheery picking quotes while ignoring the conclusion and abstract, the thrust of what the article has to say. From the abstract.



"We find that the proxies do not predict temperature significantly better than random series generated independently of temperature. Furthermore, various model specifications that perform similarly at predicting temperature produce extremely different historical backcasts. Finally, the proxies seem unable to forecast the high levels of and sharp run-up in temperature in the 1990s either in-sample or from contiguous holdout blocks, thus casting doubt on their ability to predict such phenomena if in fact they occurred several hundred years ago."



Edit: You have to love Dana's statement that the hockey is not an icon. When it first came out, it was presented as proof of the human signature on climate. It featured predominately on the IPCC reports. Now that it is falling apart, they try to downplay the significance they claimed that it had. Typical alarmist crap. Then they wonder why we do not trust them.

Answer 8

It is certain that the conclusions drawn from the data were not justified based on the statistical analysis. It is obvious from Mann's statements about not caring that some of his data was upside down that he cherry picked data to produce his obviously bogus hockey stick. The real world proved the hockey stick was a pathetic piece of pseudoscience and the fact that true believers don't acknowledge that when it was debunked just on the statistical analysis shows who the true deniers are.



More evidence that Mann cherry picked data.

http://wattsupwiththat.com/2010/08/07/russian-kola-data-refutes-the-mann-hockey-stick/

Answer 9

It was clearly BS the day is was published.



The statistical analysis in it was so flawed that 99% of random data sets applied to the model produced the hockey stick.

Answer 10

I always thought that a deliberate attempt to deceive to get money was called fraud not exaggeration.

Answer 11

We can call the hockey stick the stock market- it goes up & down.

Answer 12

It is a lie like all the Global Warming theory.