NOTE: This has been running two weeks at the top of WUWT, discussion has slowed, so I’m placing it back in regular que. – Anthony
UPDATES:
Statistician William Briggs weighs in here
Eduardo Zorita weighs in here
Anonymous blogger “Deep Climate” weighs in with what he/she calls a “deeply flawed study” here
After a week of being “preoccupied” Real Climate finally breaks radio silence here. It appears to be a prelude to a dismissal with a “wave of the hand”
Supplementary Info now available: All data and code used in this paper are available at the Annals of Applied Statistics supplementary materials website:
http://www.imstat.org/aoas/supplements/default.htm
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Sticky Wicket – phrase, meaning: “A difficult situation”.
Oh, my. There is a new and important study on temperature proxy reconstructions (McShane and Wyner 2010) submitted into the Annals of Applied Statistics and is listed to be published in the next issue. According to Steve McIntyre, this is one of the “top statistical journals”. This paper is a direct and serious rebuttal to the proxy reconstructions of Mann. It seems watertight on the surface, because instead of trying to attack the proxy data quality issues, they assumed the proxy data was accurate for their purpose, then created a bayesian backcast method. Then, using the proxy data, they demonstrate it fails to reproduce the sharp 20th century uptick.
Now, there’s a new look to the familiar “hockey stick”.
Before:
After:
Not only are the results stunning, but the paper is highly readable, written in a sensible style that most laymen can absorb, even if they don’t understand some of the finer points of bayesian and loess filters, or principal components. Not only that, this paper is a confirmation of McIntyre and McKitrick’s work, with a strong nod to Wegman. I highly recommend reading this and distributing this story widely.
Here’s the submitted paper:
(PDF, 2.5 MB. Backup download available here: McShane and Wyner 2010 )
It states in its 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.
Here are some excerpts from the paper (emphasis in paragraphs mine):
This one shows that M&M hit the mark, because it is independent validation:
In other words, our model performs better when using highly autocorrelated
noise rather than proxies to ”predict” temperature. The real proxies are less predictive than our ”fake” data. While the Lasso generated reconstructions using the proxies are highly statistically significant compared to simple null models, they do not achieve statistical significance against sophisticated null models.
We are not the first to observe this effect. It was shown, in McIntyre
and McKitrick (2005a,c), that random sequences with complex local dependence
structures can predict temperatures. Their approach has been
roundly dismissed in the climate science literature:
To generate ”random” noise series, MM05c apply the full autoregressive structure of the real world proxy series. In this way, they in fact train their stochastic engine with significant (if not dominant) low frequency climate signal rather than purely non-climatic noise and its persistence. [Emphasis in original]
Ammann and Wahl (2007)
…
On the power of the proxy data to actually detect climate change:
This is disturbing: if a model cannot predict the occurrence of a sharp run-up in an out-of-sample block which is contiguous with the insample training set, then it seems highly unlikely that it has power to detect such levels or run-ups in the more distant past. It is even more discouraging when one recalls Figure 15: the model cannot capture the sharp run-up even in-sample. In sum, these results suggest that the ninety-three sequences that comprise the 1,000 year old proxy record simply lack power to detect a sharp increase in temperature. See Footnote 12
Footnote 12:
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. While this is certainly a consistent line of reasoning, it is also fraught with peril for, once one admits the possibility of regime changes in the instrumental period, it raises the question of whether such changes exist elsewhere over the past 1,000 years. Furthermore, it implies that up to half of the already short instrumental record is corrupted by anthropogenic factors, thus undermining paleoclimatology as a statistical enterprise.
…
We plot the in-sample portion of this backcast (1850-1998 AD) in Figure 15. Not surprisingly, the model tracks CRU reasonably well because it is in-sample. However, despite the fact that the backcast is both in-sample and initialized with the high true temperatures from 1999 AD and 2000 AD, it still cannot capture either the high level of or the sharp run-up in temperatures of the 1990s. It is substantially biased low. That the model cannot capture run-up even in-sample does not portend well for its ability
to capture similar levels and run-ups if they exist out-of-sample.
…
Conclusion.
Research on multi-proxy temperature reconstructions of the earth’s temperature is now entering its second decade. While the literature is large, there has been very little collaboration with universitylevel, professional statisticians (Wegman et al., 2006; Wegman, 2006). Our paper is an effort to apply some modern statistical methods to these problems. While our results agree with the climate scientists findings in some
respects, our methods of estimating model uncertainty and accuracy are in sharp disagreement.
On the one hand, we conclude unequivocally that the evidence for a ”long-handled” hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data. The fundamental problem is that there is a limited amount of proxy data which dates back to 1000 AD; what is available is weakly predictive of global annual temperature. Our backcasting methods, which track quite closely the methods applied most recently in Mann (2008) to the same data, are unable to catch the sharp run up in temperatures recorded in the 1990s, even in-sample.
As can be seen in Figure 15, our estimate of the run up in temperature in the 1990s has
a much smaller slope than the actual temperature series. Furthermore, the lower frame of Figure 18 clearly reveals that the proxy model is not at all able to track the high gradient segment. 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. Nevertheless, the temperatures of the last few decades have been relatively warm compared to many of the thousand year temperature curves sampled from the posterior distribution of our model.
Our main contribution is our efforts to seriously grapple with the uncertainty involved in paleoclimatological reconstructions. Regression of high dimensional time series is always a complex problem with many traps. In our case, the particular challenges include (i) a short sequence of training data, (ii) more predictors than observations, (iii) a very weak signal, and (iv) response and predictor variables which are both strongly autocorrelated.
The final point is particularly troublesome: since the data is not easily modeled by a simple autoregressive process it follows that the number of truly independent observations (i.e., the effective sample size) may be just too small for accurate reconstruction.
Climate scientists have greatly underestimated the uncertainty of proxy based reconstructions and hence have been overconfident in their models. We have shown that time dependence in the temperature series is sufficiently strong to permit complex sequences of random numbers to forecast out-of-sample reasonably well fairly frequently (see, for example, Figure 9). Furthermore, even proxy based models with approximately the same amount of reconstructive skill (Figures 11,12, and 13), produce strikingly dissimilar historical backcasts: some of these look like hockey sticks but most do not (Figure 14).
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. Nonetheless, paleoclimatoligical reconstructions constitute only one source of evidence in the AGW debate. Our work stands entirely on the shoulders of those environmental scientists who labored untold years to assemble the vast network of natural proxies. Although we assume the reliability of their data for our purposes here, there still remains a considerable number of outstanding questions that can only be answered with a free and open inquiry and a great deal of replication.
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Commenters on WUWT report that Tamino and Romm are deleting comments even mentioning this paper on their blog comment forum. Their refusal to even acknowledge it tells you it has squarely hit the target, and the fat lady has sung – loudly.
(h/t to WUWT reader “thechuckr”)
For those who don’t frequent RC, Here’s the quote:
“[Response: The M&W paper will likely take some time to look through (especially since it isn’t fully published and the SI does not seem to be available yet), but I’m sure people will indeed be looking. I note that one of their conclusions “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” is completely in line with the analogous IPCC AR4 statement. But this isn’t the thread for this, so let’s leave discussion for when there is a fuller appreciation for what’s been done. – gavin]”
The message to me, and I have read the whole thing now, is that using the data the AGW set have used, Mann’s graph cannot be derived with the correct statistical tools.
They make no comment as to the robustness of the data but simply point out , indirectly, that Mann and the AGW set had to improperly torture their own data to produce the FUD hockey stick.
They are saying that Mann et al have cooked the books. Like those boys over at ENRON or Bernie Maddof they have carried out an act of fraud and 20 other good ol’ boys have validated their deceit. This was proved incontrovertibly without having to delve into the suspected alterations to the data before they were used in the fraud.
I now await a similar expose on the data by people who have the same kudos . This CO2 thing is just another boondoggle, and a small whiff of causation as seen by Arhennius is not an argument for blaming carbon for any climatic changes we may be going through. It rather reminds me of a trick we would play on the credible at school , getting people to blow into a beaker of quick lime solution and point out that there was something wrong with them as the solution turned cloudy. We always had the “cure” and the beaker of fresh water handy.
Mountebanks is what they are.
Anthony: just a thought: it would be very interesting to get Wegman’s take on this. He may not have the stomach for it, but it might be worth asking.
There seems to be quite a lot of debate at CP between Curry and the RC team. Gavin does not like all the questions posed as to the usefulness of tree ring proxy data. His response is quite telling.
“Paleo-reconstructions are not anything special in science – they are simply the result of lots of people trying to see what they can discern of the past through a rather murky lens. Your ‘auditors’ have decided that any judgement call in doing that must be challenged and insinuate continuously that every issue is being fixed for some ulterior motive. This is not a useful challenge to the science, because it undermines the making of any judgement in the analysis whatsoever. The ‘auditors’ do not produce alternatives because they too would have to make decisions about how to proceed which would open them up to their own criticisms. That is what needs to change if they are going to make a contribution. For an example of how that ‘citizen science’ can really work, look at what Ron Broberg and Zeke Hausfeather are doing with the weather station data – they aren’t sitting around declaring that ‘it can’t be done’ or that the GISTEMP/CRU/NCDC methods are fixed, they are going into the data, making choices, seeing what impact they have and determining what is robust. Indeed, that is science without the need for the quotes. Would that there would be more of that.”
What he is really saying is quite astonishing. I his opinion you can not simply say that the data and the analysis are crap since this would be unscientific. You have to try and find a better way of massaging the crap data in order to produce science. This as anyone can figure out is not a logic that applies to other areas of science. Recognizing crap for what it truly is can in some ways be the most productive way forward. But if you have a predetermined way forward that may be jeopardized by this recognition it makes sense to shift around the logic.
Lucy above – if I recall rightly Gerry North showed himself as a rather partisan commentator with his responses to Climategate. However Edward Wegman IMO still retains his integrity. As you said at CA it will be interesting to see how/if GN weighs in on this one.
The paper is referred to as McShane and Wyner 2010, but the data on their graphs end at the year 2000. Has the “hottest decade on record” been omitted?
@Evan Jones says:
August 14, 2010 at 8:48 pm
I am not sure where you are getting your figures from so I cann’t really respond. Much of the heat energy from AGW is in the oceans. Exactly how energy moves from oceans to the surface air is still hard to model. But that the heat is coming is clear.
@Re: Mike Roddy’s comment. Disciplinary arrogance is not helpful. Climatologists need to be open to learning from statisticians, and statisticians need to remember that when going outside their area of training they may overlook things. My guess is this paper will help refine how proxy studies are done, but the dust is far from settled. Academic debates like this can be very healthy. Unfortunately charlatans with political agendas will try to use such debates to undermine science. [snip]
The alarmists will still say that there is an increase in temp at the start of the industrial revolution, according to the revised graph in the paper…
GeoFlynx,
You don’t understand. Nothing was ‘omitted.’ The data used was the exact same data that Mann used.
This paper corrects the bogus, self-serving ‘statistics’ that Mann has been spoon feeding the credulous believers in CAGW.
It should be noted that the Michael Beenstock and Yaniv Reingewertz paper also demonstrated the poor statistical techniques of the climate team.
http://economics.huji.ac.il/facultye/beenstock/Nature_Paper091209.pdf
This paper does not stand alone.
I am not sure what the fuss is about. If you look here
http://wattsupwiththat.com/2009/12/09/hockey-stick-observed-in-noaa-ice-core-data/
the 2nd graph here shows exactly the same: in 1200 AD it was as warm as it is today.
I am sure this must have been due to all the methane that the animals put up in the air. When the humans killed off the animals the methane went down and it became ice cold. Lucky enough we now have humans who now put CO2 up in the air.
Excellent news and confirms my suspicion and I’m sure many others as well. AGW is built on a faith based system not a scientific based system. How they (warmists) “know” what they know has always been the central question in my mind. The brilliance of this study is accepting the manipulated data that Mann, Hansen, Jones, Schmidt et al have manufactured and showing that the conclusions they have drawn are incorrect. Unbelievable hubris on the part of these climate change “scientists”. As a US taxpayer, I do not want to pay the salaries of people who masquerade as scientists while doing advocacy work. Throw the bums out!
Michael Mann disagrees with you. He says:
http://www.meteo.psu.edu/~mann/shared/articles/Schmidtetal-QSR04.pdf
Read it with wonder when first saw it. Two points: one of the authors is at the University of Pennsylvania. Direct smack at Mann. Second, Fig. 15 shows an upward future “natural” trend, based on all the data. The IPCC forecast a “natural” neutral to cooling trend. So the difference between “natural” and IPCC CO2/forced is less. Not in the range where the CO2 models would work.
A game changer for the skeptic side, but not enough to alarm the alarmists.
Please clear up some confusion on my part:
The graphs above only cover the Northern Hemisphere proxy data. The authors decided NOT to include Southern Hemisphere proxy data in their analysis. Why? How can they reach this conclusion on global annual temperatures (in their Conclusions section) without looking at global proxy data? :
“On the one hand, we conclude unequivocally that the evidence for a “long-handled” hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data. The fundamental problem is that there is a limited amount of proxy data which dates back to 1000 AD; what is available is weakly predictive of global annual temperature.“
[Kindly do not resort to religious arguments and/or references.]
duckster…you say:
You need a theory to explain what is happening now.
Actually not. For the purposes of rejecting a hypothesis all “we” need is one counter example. All that has to be shown, is that current theories are not predictive and that they have systemic flaws. CAGW can go down in flames without another theory to take its place.
I think a letter to my congressmen with a request to suspend all funding for paleoclimatology as it relates to AGW is in order – at least until a complete review of the science can be undertaken. I hope others here in the states do the same.
It seems that McShane and Wyner omitted one vital step in their reconstruction. As any fully qualified, peer reviewed climate scientist will tell you, it’s necessary to rotate this graph by 10 degrees counter-clockwise. The reasons are so obvious that I see no need to explain them here.
Once this step has been done, it can be seen that McShane and Wyner 2010 is in pretty close agreement with Mann et al. (1999).
http://dl.dropbox.com/u/4586660/mcshane-wyner-adjusted.png
Mike:
I am not sure where you are getting your figures from so I can’t really respond.
Well, for 20th century global temperature trend, I am stipulating HadCRU (though I have serious doubts concerning adjustments, since they can’t or won’t release their raw data).
The CO2 forcing numbers and the positive feedback numbers are from the IPCC. I think the raw forcing number (+1.2C per doubling of CO2) may be accurate or near accurate.
Feedback is another bag of beans, however. And when I count those beans, they do not appear to be consistent with the IPCC inventory:
The boosting of the 1.2C effect to a midstream +3.2C effect via positive feedback loops I doubt very much because it depends on factors, such as a receding of the tundra and glaciers, which have been ongoing since the LIA turned its coldest corner around 1650. And if those factors are ongoing, then so must the feedback, if any.
Therefore a 40% increase in CO2 since 1900 (the Keeling numbers plus earlier proxies) should have produced a lot more warming than +0.7C — if the IPCC positive feedback theory is correct.
If there is no positive feedback (or even net negative feedback), then a.) Global Warming is still real, and b.) It presents no emergency, whatever.
Folks who follow this line of reasoning (I daresay many, if not most of us) are pleased to refer to ourselves as “Lukewarmers”. That is to say, if we take one of those CO2 global warming multiple choice tests, we look like genuine AGW fanatics. (YES, CO2 is a greenhouse gas. YES, there has been warming. YES, man has added CO2. YES, there has been sea level rise. etc., etc., etc.) Yet our conclusions are entirely opposite of the alarmists when it comes to the bottom line — and to policy.
There are usually (not always, but usually) two sides two sides to a controversy. I encourage you to do a doubletake and reassess. Perhaps this will not change your mind. But in any event it can only put you in more deliberate possession of your position.
Has anybody else thought, the errors in what the hockey stick told about temperature is simply not realistic? A few sources of errors, the thermometers used, the accuracy of the tree ring proxies, and all the other allegedly ACCURATE past measurement techniques. I suspect if it were within +-3 degrees Celsius that would have been great.
And what would you call a 20 foot change in sea level, other than measurement error? I mean the accuracy there would be fine for a rise of 400 feet since the last ice age. Think about it, were are talking 5% from the last ice age. Does anybody really know what the sea level was when the Bering Land Bridge was above water, and to what accuracy?
But one thing we do now know, there were ancient settlements in Greenland, that place with a funny name for being such a modern snowball, under the glaciers right now. And that is not refutable.
Mann has been five-holed! (Nutmeg for soccer fans)
In my opinion Wegman, et al sufficiently sliced and diced Mann’s methodology five years ago. This paper simply adds more evidence that the statistics employed by Mann (and his pals who used the same techniques to produce similar results) are flawed and their results invalid. I can’t get too excited, however. We’re talking about the dubious science of paleoclimatology; tree rings, sediment cores, etc. In essence they’re applying statistical analysis to “guesses” rather than “real” instrumental data.
Far more interesting, I think, is what is being done to the surface temperature record by NOAA and NASA/GISS. These taxpayer funded government agencies have credibility in the eyes of many of the public…and this is truly dangerous. Personally, I think using taxpayer dollars to study tree rings is akin to funding astrology.
Mike Roddy says:
August 15, 2010 at 7:44 am
“…….
“Climate scientists have plenty of training in statistical methodology. Those who claim superior abilities, such as McIntyre and Wegman, have not been successful in producing charts in peer reviewed publications that show anything other than the many versions of the hockey stick that have appeared in scientific publications. Their attempted corrections tend to be heavy on jargon, and in some cases question dispute the randomness of tree ring selection when they have little knowledge of the raw sampling.”
Mike, stop. Apparently your argument seems to be: Scientists are better than statisticians in the science of statistics. Throughout the history of the climate debate, we’ve been told over and over again that we laymen aren’t capable of understanding the intricacies of climate science and it is best if we leave it to the experts. (Paradoxically, it has been obvious for some time the climate scientists themselves didn’t understand the intricacies of statistics.) Be it global temp anomaly, concentration of CO2, earth’s total ice content, ect., it is all mathematical work. Still, they can’t use the argument that we should “leave it to the experts” when they don’t engage in the same practice(especially in a hard science such as math/statistics). It’s not like they haven’t been told. They were told over and over again that they were employing the wrong statistical methodologies for over a decade now. It is simply a damn shame that they had to waste the ENTIRE WORLD’S TIME, ENERGY AND MONEY before this would be shown when a true scientist would have listened to the objections and tested the objections before out-of-hand dismissing the claims as the climate-scientists have, ON EVERY LEVEL OF THE DEBATE. Truly, the world has better things to do than to disprove every simplistic blathering coming from a totalitarian, Malthusian, socialist posing as a scientist.
Mike, can you imagine what this world could have accomplished in the last 30 years if all of the mental, financial, and social energies hadn’t been diverted to this issue, from both sides of the debate?
Mike, you are wrong about the idea that “much of the heat energy from AGW is in the oceans”. In order to say what part of your thesis is most wrong, please post your mechanism for how the longwave radiation greenhouse gases emit are absorbed by the oceans. More specifically, what is your heat transfer mathematical equation for your mechanism re: LW radiation net heat forcing in layers below the surface tension (because there, the weak energy turned into heat is evaporated as soon as it hits this layer).