Is anyone else as sick as I am of repeated attacks on the "hockey stick" reconstruction of past temperatures? Joe Barton and cronies are at it again. Just when one would have hoped that the National Academy of Sciences report on this topic would provide some modicum of closure, the "skeptics" have derived yet another seeming line of attack.
As for myself, I am beyond bored with the whole thing. I'm reaching the point of despair. Listen, people: This is an argument over a study that is now some eight years old. Eight years! You would think there is nothing new under the sun in climate science.
So let us recite, once again, for those who still don't get it: One study never definitively proves anything in science. Any single study can be attacked and criticized. Any individual piece of work will have its gaps, shortcomings, and associated uncertainties. As for those who show no appreciation of this fact, who obsessively beat up on a single study for political reasons: By this behavior, they simply show that they approach scientific information as lawyerly debunkers, rather than by trying to accurately grasp the big picture.
And make no mistake: Despite the new fireworks, that big picture remains unaltered. Whether the "hockey stick" is right, wrong, or irrelevant, the underlying message on global warming is that we're causing it. Period. End of story.
What I miss in this debate, is the other important point in the NAS report, that bristlecone pine series (and a few other series) should not be used, as these have a upward trend in the 19th-20th century, not related to temperature.
Without these series, no matter the method used, there is no hockeystick, but a more U-shaped curve with a high MWP and a much lower LIA.
This is very important, as a larger natural variation in the pre-industrial past implies less variation in the current trends caused by humans. As most of the reconstructions make use of the series mentioned, that implies that only series which don't use them (like bore holes) or with reduced impact (like Moberg) should be taken into account. These are the series with the highest variations in temperature between MWP-LIA-current.
To quote a few renown climate scientists, whom made several reconstructions of the past millennium, with much wider variations than found in MBH98/99:
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.
The PDO has gone into its negative phase. Solar activity has declined sharply. The ARGOS ocean data shows a cooling trend since 2003. The satellite data shows that the monthly anomaly is at pre panic levels. The solar physics community is calling for a cooling trend that lasts until 2030 or so. And it is bloody cold outside as I write this as it has been cold for several months.
While the AGW apologists may be 'sick' of the argument it is a fact that the argument was bogus and that the claim of CO2 as a main driver of temperature has no scientific support behind it. Time to pack it in boys and girls. You are starting to remind me of the crowd that was panicking about global cooling in the mid-1970s.
It's just like hearing Creationist arguments against evolution citing the second law of thermondynamics or tornadoes in junkyards--you can't kill the arguments because, like zombies, they are the Undead (and just as thoughtful).
Here's a link to the full WSJ editorial.
And after all is said and done, you offer nothing more than your vehement statement. I would ask the previous commenter, which side is the creationists? Nether side in the global warming debate offers any real science. Despite your proclamations to the contrary, the debate is still on, and it is people like you that try to stifle legitimate avenues of inquiry that are the real torture.
I can understand your feelings about the hockey stick, perhaps it is old. But the NAS report, even if taken at face value, actually weakens the argument that global warming is caused by humans. The NAS report clearly shows that the global temperature has historically fluctuated more than enough to account for the current warming trends, even before the increase of CO2 due to human influence.
All the NAS report has done is shown that the current global temperature is higher than a time period that has historically been known by climate scientists as "The Little Ice Age". I somehow do not find that very compelling
...the underlying message on global warming is that we're causing it. Period. End of story.
The latest arguments I've been hearing concern themselves with whether we've caused all the warming so far, or just some of it. And if it's not all ours, then chances are it won't be that bad.
For instance, this is from the National Review:
"Global average temperature has risen by about 1 degree Celsius or less since the late 1800s." No serious person on either side of the global-warming debate questions this. Nor do serious commentators doubt that human activity, by increasing atmospheric concentrations of carbon dioxide, contributes to global warming...
What's in contention, scientifically, is how much of the warming we've seen so far is a consequence of human activity (as opposed to natural climate variation), and how much warming human activity will cause in the future. The policy debate focuses on how dangerous the warming is, what we can do to stop it, and whether doing so is worth the economic price we would pay.
The next stage of the argument concerns how "Al Gore and his climate scientist allies" (as they like to frame it) get some things right, but are alarmist on other things. And they use Mann and his study as an object lesson on alarmism. They're saying the hockey stick that everyone's been using in presentations over the years is not so dramatic, not based on "sound science," says something about the type of science "alarmists" rely on, yadda yadda yadda.
Anyway, those are the arguments I've been hearing.
In addition to Chris' comments about abuse of science by using single studies to support an agenda (on either side), there is also the issue about selective use of statistics.
I would argue that including anything before 1800 (i.e. most of the Little Ice Age [ http://www.scienceshelf.com/LittleIceAge.htm ] and all of the Medieval Warming Period) in that graph adds data that is irrelevant to the question at hand, namely the effect of large-scale burning of fossil fuels on the climate.
What's left is still complicated enough, since coal-burning added plenty of soot, acid, and gases other than CO2 to the atmosphere. Of course, the normal climate variation has to be considered in any interpretation. That's why the hockey stick is not only dramatic but also demands skeptical aanalysis.
The editorial writer makes a specious argument, namely that the hockey-stick graph is the only data around which the consensus has formed. It was, no doubt, the catalyst for a lot of consensus, but normal scientific skepticism put the brakes on any bandwagon effect.
Of course, the skepticism that keeps a bandwagon from rolling can be used as evidence that scientists don't agree about the conclusion.
Science abusers use both arguments at the same time. We science appreciators need to point that out when we see it. Perhaps we need to explain the difference between the excitement over a new discovery and the consensus that emerges from challenging the interpretation of that discovery.
...the NAS report, even if taken at face value, actually weakens the argument that global warming is caused by humans.
I'd encourage you to look at the Realclimate post on this subject:
...the key conclusions reached ... (i.e., that hemispheric-scale warmth in recent decades is likely unprecedented over at last the past millennium) have been substantiated by many other studies, and the confidence in those conclusions appears greater, not lesser, after nearly an additional decade of research.
And there are a number of conclusive studies that link the "signature" of CO2 with warming:
The NAS report clearly shows that the global temperature has historically fluctuated more than enough to account for the current warming trends, even before the increase of CO2 due to human influence.
Historically, CO2 and warming levels have risen and fell together:
The NAS report clearly shows that the global temperature has historically fluctuated more than enough to account for the current warming trends.
It shows no such thing. Insofar as it changes the previous results, it says that it is less certain about previous trends - which leaves space for them to be either larger or smaller than previously though. It certainly doesn't say that they are as large as current trends.
Interesting. I've followed the creation-evolution debate (a lot) and the global warming debate (a little) and I constantly see the hockey stick waved about. Whereas creationists' claims are usually easily refuted, I have less luck making sense of the climate debate. This of course may be because I'm not studying climate science, but also because those actively trying to deny human-induced global warming seem to be more in touch with the actual science (rather than religious dogma). What's a good web-source for summaries of the points-counterpoints?
What's a good web-source for summaries of the points-counterpoints?
I would say that from a lay perspective a good summary of the skeptics' arguments and their counterpoints would be this blog:
Illconsidered points to other sites, such as Realclimate.org, which discusses specific topics in more technical detail.
Although it's true that creationists and climate change denialists are different, there's some degree of overlap as well. I liked Desmogblog's breakdown of the ideological spectrum after they attended the Skeptics' Society conference:
Also, the Washington Post did a good job describing the skeptic community with this story:
I don't think this is an appropriate response to the Wegman report. Wegman, Scott, and Said have confirmed the criticisms of McIntyre and McKitrick (and in particular that the hockey stick is an artifact of the decentering methodology; they get a similar pattern by using "red noise" as data), and further argued that there is a lack of independence of data sets in paleoclimatology and isolation from appropriate review of mathematical methods (i.e., by statisticians).
The critique of Wegman et al. merits some housecleaning--bringing statistics expertise into the field of paleoclimatology--not dismissal, in my opinion.
The full Wegman report (91 pp) is here:
"Whether the "hockey stick" is right, wrong, or irrelevant, the underlying message on global warming is that we're causing it. Period. End of story."
But possibly 10-30% less of it than we've thought we were causing:
But that's Scafetta and West, old news already scrutinized, nothing new there.
For one example (Google is your friend):
Is anyone else as sick as I am of repeated attacks on the "hockey stick" reconstruction of past temperatures?
The rubes still obsessing over the hockey stick don't realize the puck has been dropped, we're three quarters of the way through the first period and the score is already 8-0 in our favour.
"The critique of Wegman et al. merits some housecleaning--bringing statistics expertise into the field of paleoclimatology--not dismissal, in my opinion."
I agree. The best way to deal with problems in science is to address them -- and address them in the standard scientific way: by publishing papers in scientific journals.
The latest report is no exception to this rule. It should be submitted for publication in a journal which will mean it gets reviewed by other statisticians for possible errors.
If it passes that test, then Mann and possibly others will be forced to address the problems and resubmit their revised paper or retract their findings. That's how science works -- or at least how it is supposed to work
In related news, the entire field of electronics has been thrown into disarray after errors were discovered in Millikan's research, on which foundation all subsequent work in electronics relies for its validity.
"This may bring down the entire edifice of scientific rationality. Wouldn't that be like, magical?" typed one weblogger, just before his computer lost its phlogiston and the smoke leaked out.
The measurements' "... accuracy was not severely affected by Millikan's choice ...."
"At first blush, this outrageous violation of scientific integrity would seem to discredit Millikan's findings. Even if one assumes that standards of reporting data earlier in the century were less rigorous, Millikan clearly misrepresented the extent of his data. One may caution students, however, that we may not want to conclude that therefore there was no good, "scientific" basis for his selective use of data.....
"Physicist-philosopher Allan Franklin has addressed the problem by using Millikan's original data to recalculate the value of e. Even when one uses various constellations of the raw data, Millikan's results do not change substantially. That is, their accuracy was not severely affected by Millikan's choice of only a subset of the observations. Millikan's selectivity, at most, gave a false impression of the variation in values or the range of "error" in the data and, therefore, of the statistical precision of the computed value.
"In fact, Franklin notes, Millikan threw out data that was "favorable" as well as "unfavorable" to his expectations. Clearly, Millikan's results were over-determined. That is, he had more data than he needed to be confident about his value for the electron's charge. Here, the redundancy of data was an implicit method for safeguarding against error. Thus, what appears as fraud from one perspective becomes, from an experimental perspective, a pattern of good technique..."
As usual, it's not the crime but the subsequent cover-up that gives a scandal legs.
If Mann & company had quickly and fully acknowledged their mistakes and made their data and methods available to other scientists for review, the problem would have disappeared in no time. Certainly less than eight years. The real problem here isn't that Mann blew it but that trying to figure out /how/ he blew it took so much time and effort and slogging through mud being thrown at McIntyre and McKitrick.
Federally funded science shouldn't mean giving money to researchers who collect data, massage it in unknown ways and just say "trust us, it's right" when their conclusions are questioned.
The panel said the results don't change significantly when the improved methods are used, and they said they're worried about the rate of warming (even though they were not asked to comment on the latter point).
Does that worry you at all?
"All the NAS report has done is shown that the current global temperature is higher than a time period that has historically been known by climate scientists as "The Little Ice Age". I somehow do not find that very compelling"
This is what the NAS report acutally said - "The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2,000 years. Not all individual proxy records indicate that the recent warmth is nprecedented, although a larger fraction of geographically diverse sites experienced exceptional warmth during the late 20th century than during any other extended period from A.D. 900 onward."
We can all pick our favourite quotes such as page 110 of the NAS report
"Largescale temperature reconstructions should always be viewed as having a "murky" early period and a later period of relative clarity. The boundary between murkiness and clarity is not precise but is nominally around A.D. 1600. Second, the finite length (about 150 years) of the instrumental temperature record available for calibration of large-scale temperature estimates places limits on efforts to demonstrate the accuracy of temperature reconstructions."
Their criticisms of bristlecones, non-centred PCA and lack of disclosure are backed up by Wegman and I find it hard to see how this will not eventually be accepted as fact and another name will eventually join that of Millikan.
Interestingly, both sides in the debate over the Mann paper claim vindication from the NAS report.
At least part of the problem (as I see it) is that the NAS scientists who wrote the report did not properly define some of their critical terms.
There is one term in particular ( "plausible" ) that stands out from all others: .
Here's the sentence from the NAS report about the Mann paper where they used the term:
"Based on the analyses presented in the original papers by Mann et al.and this newer supporting evidence,the committee ï¬nds it plausible [emphasis added] that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium."
They used the term without defining it and this has led to needless ambiguity which has diluted the ultimate value of the report as a guide for public policy.
Then again, the opposing "camps" in this case are so thoroughly entrenched that it might not have made any difference whatsoever what the NAS said.
The latter point is one more argument for moving beyond the Mann papers and focusing on more recent research.
While I think that Mann et al should address any problems with their original paper, the "debate" about the Mann paper should not be the central focus of climate science.
A great deal of independent research has been done in recent years that is relevant to the subject of global warming and to fous on a single paper does not do proper justice to either the science or the public policy.
Science doesn't provide absolute certainty or uncontrovertible proof.
It never will. Science isn't based on a foundation of perfect work.
Science starts, in any area, with early studies, flawed as they invariably have been.
You want to group Mann with Millikan?
The NAS report was more an exercise in the politics of science than a scientific review of Mann et al. As pointed out by David H. the report tries to spare Mann and the current "consensus" while also pointing out the obvious deficiencies in the study and the large uncertainties in attempting to correlate paleo-climate temperature "proxies" with the problematic empirical temperature measurements of the last 150 years.
It is certainly not a vindication of Mann or the "consensus" view that the recent warming trend is an accepted fact and indicative of a dangerous and man made phenomenon.
On the Milikan issue, as part of an undergraduate lab course we were assigned the task of repeating his experiment. Man, talk about the most tedious and challenging exercise in futility! I damn near went blind and insane trying to record the motions of those tiny oil droplets.
Our final results had a calculated error that was about five times our measurement. I chalked up our less than stellar results to our relatively hastily prepared experimental set up and the gross indifference of my equally innept lab partners. But it did make me question how anyone could get the results that Milikan obtained.
I knew that bastard was cheating!
Brian Utterback: "And after all is said and done, you offer nothing more than your vehement statement." (snip)
Wait for it, wait for it....
"Nether side in the global warming debate offers any real science. Despite your proclamations to the contrary, the debate is still on, and it is people like you that try to stifle legitimate avenues of inquiry that are the real torture."
And it's a *high* pop Freudian Projection, right into center field.
Thanks Chris, I share in your frustration. We have spent a lot of time pointing out the idealogues who continue to cherry pick the NAS report to meet their own forgone conclusions.
As for one side receiving vindication from the NAS report, I would say there is no vindication b/c the report says nothing more than what the IPCC claimed so long ago.
As for "picking quotes" to meet our own ends, there are quotes and there are conclusions in the NAS report and the conclusions are very clear -- it's hotter now than it has been in the past 1,000 and multiple lines of evidence since Mann have shown this. Oh, and humans are too blame.
Chris, think of it this way - for the past 150 years, evolution has been supported by wave after wave of biological discovery, and in turn has supported biological discovery, turning biology into a science, as opposed to collecting and naming things. However, the religious right, along with various fellow travelers, have managed to wage a pretty good delaying actions (considering that *all* of the science is against them, and they have to rely on lies, BS, poor logic and junk science). And this is all with the power of concentrated wealth neutral, or favoring science.
Therefore, considering that success, it's not surprising that the global-warming deniers will use the same tactics. And they have the added edge that concentrated wealth is generally still against the science.
To claim that anthropogenic climate change theory is on equal footing with the theory of evolution demonstrates a complete lack of understanding of the current state of one or both theories.
These kinds of statements are often followed by allusions to cigarette company shills and holocaust "deniers". They fall into the category of smear tactics. Some environmental NGOs and their attendant media outlets are pushing an aggressive "don't acknowledge the deniers" approach. It may be a good political strategy. It certainly isn't a valid scientific response.
Some environmental NGOs and their attendant media outlets are pushing an aggressive "don't acknowledge the deniers" approach... It certainly isn't a valid scientific response.
Honest curiosity -- what science have the deniers published lately? M&M is the only one I've heard mentioned in discussions (Wegman's not published), but I don't generally go looking for these things.
If they're not publishing results supporting their views, I don't see how there can even be a scientific response, or why we should even seriously consider their position.
Though I agree that AGW is certainly less solid than evolution. Evolutionary theory has had a wee bit more time to mature than the theory underlying AGW.
For more background info on the science behing global warming, see The Discovery of Global Warming, by Spencer Wart. You can read it online (http://www.aip.org/history/climate/index.html) or order the book.
I recommend reading the section on the discovery of the carbon dioxide greenhouse effect first: http://www.aip.org/history/climate/co2.htm
The Discovery of Global Warming is both a book and a wonderful comprehensive website.
The author's name is Spencer Weart.
Oh, Lordy Lord Lord Lord ..
Wegman, at the hearings: "Carbon dioxide is heavier than air. I don't know where it sits with respect to the atmospheric profile."
Hearings: Rep. Stearns (Florida) has people looking at a picture in _Inconvenient_Truth_ showing a temperature change over time. The temperature data, another representative points out, is identified in the text as from the IPCC and based on Lonnie Thompson's borehole measurements.
Stearns is saying that all these similar charts come from the IPCC, and the IPCC comes from Mann's chart, so people are being confused about the origin of the picture.
He thinks that anything that looks like a recent increase has to be based on Mann's work -- or he's trying to put in the record that misinterpretation.
These points must be scripted. Nobody can be this obtuse extemporaneously.
Barton on the purpose of the hearings said that if attempts are made to control CO2 emissions "there won't be any coal fired power plants ...."
North: "by the end of this century ... if we do nothing .... it might be 3 degreed F, it might be 8 ....even 3 degrees is not as benign as you might think ...."
Barton: "representing a coal area of the country, I have a lot of constituents coming up to me ... there's more carbon dioxide caused by natural processes ..."
North: "the problem with this is the time scale, the time constant as we say is quite long, it takes a couple of hundred years ... so if you dump in carbon dioxide ... we're pouring it in faster than the system can dispose of it."
Rep. from a timber state (can't read the screen) says he's also on the committee that handles Forestry. He just got North to agree that cutting down big old trees and planting little new ones is a good way to increase absorbtion of CO2. North at least said it was way outside his area but "intuitively it's true."
Good way to avoid looking at the real studies on old growth and old soils.
North gave a definition of "plausible" -- the word that had raised questions.
He said they used that word to describe a question on which there are many studies supporting one conclusion and none that contradicted it.
Hank posted above: Wegman, at the hearings: "Carbon dioxide is heavier than air. I don't know where it sits with respect to the atmospheric profile."
I'm no expert on the atmospehere, but it would make some sense that CO2 sits at the bottom of the atmosphere, next to the ground, wouldn't it?
I mean, isn't that why young trees (needing CO2 for photosynthesis) grow so much faster than old ones? (because they are closer to the ground where all the CO2 is. H2O too.)
Isn't that also why prairie dogs come out of their holes periodically, for a breath of oxygen?
It seems that all the CO2 (being heavier than air) would settle into the holes and if the prairie dogs did not come out now and again, they would simply die of suffocation. I beleive that is also why they actually have to (not just come out), but also sit up on their hind legs, to get above the CO2 layer, which is right next to the ground.
Lance Harting: "To claim that anthropogenic climate change theory is on equal footing with the theory of evolution demonstrates a complete lack of understanding of the current state of one or both theories."
I agree; that's why I said no such thing. I pointed out that a very successful delaying action against a powerful scientific theory was a good candidate to be copied, when attacking another one.
George, look it up, please. Tell us how you learn the answer. It might help everyone to understand this discussion.
Lance Harting: Some environmental NGOs and their attendant media outlets are pushing an aggressive "don't acknowledge the deniers" approach. It may be a good political strategy. It certainly isn't a valid scientific response.
I agree with what Davis posted above. If they're not publishing anything noteworthy, why would they merit acknowledgement?
According to Glen Raphael:
"If Mann & company had quickly and fully acknowledged their mistakes and made their data and methods available to other scientists for review, the problem would have disappeared in no time."
Yes and there would be no more global warming denialism.
CO2 is well-mixed in the atmosphere. If this were not the case, then one would get very different results measuring CO2 on Mauna Loa than one would get at sea level. In fact, one doesn't.
I can't tell you the exact reason why this is the case but I think it basically has to do with the fact that gravity is not a very large player on the scale of molecules in a gas. That is, the effects of molecular collisions in the gas will overwhelm any "settling" effect that would occur due to gravity. (And, other effects such as convection will also overwhelm it.)
You might wonder why this is not true of liquids, i.e., that liquids of different densities do often separate. However, I think that has to do with the molecular interactions that bind things together so the effect size of the unit of liquid is larger. In fact, we know that even in liquids, you will not tend to get phase separation if the liquids are miscible in each other. (And, you will not tend to get separation if you dissolve solids into a liquid, e.g., sugar or salt in a water solution.) It is only when the liquids are immiscible and thus tend to form large conglomerates of their own kind that you can end up getting phase separation with the denser liquid on the bottom and the less dense liquid on top.
'Oh, Lordy Lord Lord Lord ..
'Wegman, at the hearings: "Carbon dioxide is heavier than air. I don't know where it sits with respect to the atmospheric profile."'
I just heard that on Morning Edition (I'm in Hawaii, so hear these things later) and was just staggered by that level of ignorance from someone pretending to be an expert witness. He also went on to say something about how it would reflect less infrared if it were at low altitude.
I once heard Limbaugh use exactly the same argument about CFCs not causing the ozone hole because they are too heavy. It's one of those things that sounds plausible but is so easily refuted that citing it as evidence reveals either profound ignorance or mendacity.
I don't mean to insult George--as I said, it sounds plausible so it's excusable from someone who doesn't pretend to be knowlegable.
Joel's explanation is essentially correct--CO2 is heavier, but it sinks so slowly that the winds keep it mixed well. In areas utterly lacking turbulence--caves and perhaps prarie dog holes, emitted CO2 can build up. In addition, at very high altitudes (>100 km?) collisions between gas molecules are so rare that there is a slight separation of gases based on molecular weight.
Error in labeling that's worth noting in Wegman's report as currently posted (in a chart I believe was held up for the camera by one of the Representatives in the hearing).
A poster says that if Mann et al had quickly acknowledged their mistakes and made data available the problem would have disappeared in no time. Forgive the word, this one time:bullshit.
How could it disappear unless there was nothing to it in the first place? If there was nothing to it in the first place, what was all the fuss about? If they (the Mann authors) were attacked when there was no real problem then they were the target of idiots or of those who seek to maintain the claim of uncertainty in climate (we don't really know so do nothing). Assuming the latter was the case then any little rock they could throw would do.
Indeed, that is what happened. The attack by M&M was contained in a series of peremptory written demands for a lot of information not prefaced by any showing of expertise at all. What scientist need answer such material at all? There is no such obligation.
When some information was nevertheless courteously supplied the "ratchet" was applied, that is, more insistent demands, and with increasingly tart remarks. This behavior did indeed lead to some of the recipients of these missives refusing to answer at all. The "paper" of M&M resulting from these efforts was eventually published in a sociological magazine, in no sense a refereed journal. Of 20 pages over 17 were devoted to a detailed review of petty errors, the sort of thing that is often found in academic writing which if corrected would not change the substantial findings or conclusions at all, much like fixing typos.
Yet this dismal review of "errrors" (many were not errors at all, and some were just a pretension of errors claimed to be found) tacked on to vague suspicions that somehow the upward tilt of measurements in the recent historical period could not be right was greeted with enthusiasm by the GW deniers. They had started out with scraping the bottom of the barrel on behalf of the coal and oil magnates and were always scrounging for some kind of useful argument.
Since then all that has happened is that one journal did accept and publish a short paper or note which complained that by using a period to establish a trend that was not the same as some other procedure that some other researchers might have used, the MBH work was wrong. The MM pair then turned out a revision of their paper, in the sociological magazine with this new claim. This is a point requiring expert comparison, and it has turned out that whether one or the other method is used makes no substantial difference, so all that has been produced is a statistical curiosity that sheds no new light at all.
Since then M&M have beavered away seeking to turn their embarrassingly little pile of sticks into a mountain from whose top they may hurl nasty accusations at the Mann group of authors, a group that grows larger in their accounts as this unpleasant pair, (who cannot share a climate science qualification between them) discover more and more scientists they suspect of knowing each other and even (can it be?) going to the same data sources.
Somebody should tell them that is why organizations and funds are created to gather data and render it so the whole academic community can share it at low cost.
M&M have never appeared to be scientists or persons interested in learning about science. No one could read their eary demands for information and statements without thinking that they were not likely to get much co-operation if they talked like that. They have been concerned to attack the hockey stick from the outset. Unfortunately the most likely outcome of their final and abject failure is that many a researcher will be far less open about their opinions, and information developed than was the case in the past. The M&M campaign with its supporters among the rif raff of deniers has injured the public interest.
If you have a look at the the report itself (not at the link of RC), you will notice that Wegman explicitely says for Fig 4.3 in his report (page 32) that the graph showing the difference between decentered/centered methods is about the PC1 of the N.American network, not the full MBH reconstruction.
He also comments on the relevance of bristlecone pines in the N.American PC1, with and without the methodological differences, on page 81.
Steven Howell said" In areas utterly lacking turbulence--caves and perhaps prarie dog holes, emitted CO2 can build up."
Phew. For a minute there, I thought Joel had blown a hole clean through my prairie dogs and their desire for a better (CO2-free) world.
Now I can feel confident in submitting my theory about CO2 for publication in the "Journal of Prairie dogs and climate".
To be quite frank, all this talk about gravity, molecular collisions, density, miscible(?) and turbulence is making my brain turbulent.
Why can't we just go back to the days when hockey sticks were only used for playing hockey? (and when the length of the stick handle for an average blade was less than 12 feet)
And can't we all just get along?
Where's the Rodney King of the Climate Riots when you need him, anyway?
garhane, your attack on M&M indicates a selective blindness indicative of willful deception. The less inflammatory conclusion would be that the deception is self-induced.
Perhaps your most ridiculous remark is, "The attack by M&M was contained in a series of peremptory written demands for a lot of information not prefaced by any showing of expertise at all. What scientist need answer such material at all? There is no such obligation."
Then you lament the damage done to science by these knaves that dared question your heroes by being impertinent enough to actually see the data that backed up the study.
Uh, excuse me? Speaking as a scientist I wasn't aware that one need present proper credentials to see the data supporting a scientific study. In fact openness and transparency are absolutely vital to rigorous and productive science. As a university physics instructor I teach students to present all their data, even data that may have been discarded for legitimate reasons, and to show clearly how that data was used to reach their conclusions.
This is one of my biggest problems with climate modelers. The great majority of them do not make their data sets available, let alone their source code. They also often don't reveal the "tuning" that is done to get the models to even approximate real empirical parameters.
It is clear that you see science as an "us vs. them" political struggle. Thankfully the NAS panel disagrees with you and chided Mann for his lack of openness as well as other deficiencies in his work.
I have spent a fair amount of time reviewing McIntyre and McKintrick's work. I find it to be forthright and diligent. If you have a problem with it you are free to voice any and all objections at their website climateaudit.com. Unlike Mann's Realclimate their work is quite accessible including their data sets.
I suspect you would rather make ad hominem attacks from a distance than actually spend time thoughtfully reviewing their work and addressing any reasonable criticism to them personally. You seem to view any scientific criticism of studies that support your political position as an attack by "idiots" and "rif raff deniers" on orthodoxy rather than the mechanism of healthy scientific inquiry that it actually represents.
Lance Harting: I wasn't aware that one need present proper credentials to see the data supporting a scientific study. In fact openness and transparency are absolutely vital to rigorous and productive science.
The reason why they don't release raw data to non-scientists is perfectly understandable. As the Washington Post put it in a recent story:
"They argue not as scientists but as lawyers," says Pieter Tans, who runs a lab at NOAA in Boulder, Colo., where he examines bottles of air taken from monitoring stations all over the planet. "When they argue, they pick one piece of the fabric of evidence and blow it up all out of proportion . . . Their purpose is to confuse, so that the public gets the idea that there is a raging scientific debate. There is no raging scientific debate."
If people are acting more like hostile attorneys than good-faith members of the scientific community, then why give them all the raw data they need to make a misleading case? If it's clear that the only purpose they'd have with the data is to publish it outside peer-reviewed venues, and they don't have the background to evaluate it anyway, why give it to them?
Jon, your suggestion that data only be provided to the "right people" is emblematic of the politicization of climate science. Science is not served by the formation of cliques.
The statistical methods used by Mann et al have again been criticized by Wegman, Scott and Said, three eminent statisticians that report that Mann's methodology will give "hockey stick" results even when random red noise is used as data, just as McIntyre and Mckitrick had concluded.
Even more sanguine to the discussion is this statement in the report.
"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. Additionally, we judge that the sharing of research materials, data and results was haphazardly and grudgingly done. In this case we judge that there was too much reliance on peer review, which was not necessarily independent. Moreover, the work has been sufficiently politicized that this community can hardly reassess their public positions without losing credibility. Overall, our committee believes that Dr. 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."
I'm sure the dirty laundry squad is searching for a way to smear these respected scientists. How dare they crash the party!
Lance H. wrote:
Jon, your suggestion that data only be provided to the "right people" is emblematic of the politicization of climate science. Science is not served by the formation of cliques.
"The right people" is probably an overstatement. You just don't want to help those people whose motives are not scientific, but rather political. You don't help those who are out to damage you or your reputation. Scientists, like anyone else, have a right to ask "Who wants to know?" before sharing information.
If the raw data and methods are withheld from those doing peer review of a publication, you may not be able to publish. People doing classified research or who are involved in trade secrets have that problem, too. Is anyone saying that the referees of the "hockey stick" publication were denied access to information they considered critical to passing judgment here? Or are the referees being accused of not being properly diligent?
I can't speak to whether climate scientists are retreating into cliques; but to me, the politicization was at its worst when the administration tried to silence Jim Hansen when he was trying to be open about his work and conclusions.
Unfortunately, the nearly universal use (and sometimes misuse and even outright abuse) of statistics has basically supplanted the presentation of all the data.
It is wise to question any argument that is based on statatistical results alone. This is because even an argument that uses statistics correctly can still be "wrong", ie, lead to false conclusions. As Gomer Pile used to say, "Surprise, surprise, surprise."
It should also be noted that using statistics (or math in general) incorrectly need not necessarily lead to a false conclusion about the real world. Johannes Kepler made math mistakes and nonetheless came to the right answer about the planetary orbits.
By the same token, a demonstration that statistical analysis was performed incorrectly need not reveal anything about underlying reality, In particular, this alone does not demonstrate that the conclusions reached (based on incorrect statistical analysis) are false (do not jibe with reality).
In that regard, the question about whether statistics were properly used by Mann et al is basically a side show to the main event.
The critical question is whether humans have had a significant effect on the earth's climate. For answering that, the Mann paper is just one piece of evidence (though, for whatever reason, it has long been the center of attention).
I'm all for having the best review process possible. But my point is that there are a lot of special interests with PR machines ready to spin the significance out of any of these studies to the point where they're unrecognizable. Just look at how the word "plausible" was parsed to death after this last NAS report was released. Could you imagine what folks would do to a full raw data set? The CEI, Heritage Foundation and whoever else would descend like piranas.
I don't know the details of the processes paleoclimate scientists use to review their work. Maybe there are ways they could be improved. But this is a side issue anyway, because as Chris notes above, this is just one study, and an eight year old one at that.
But my point is that there's a lot of people out there who spend lots of time doing sophistry, not science. So I don't blame scientists for not wanting to put out raw data that anyone with a think tank and a large budget can pour over at will.
Fully qualified people with real scientific business to perform are another matter, of course.
So far as I can tell McIntyre and McKitrick were motivated by what they saw as characteristics indicating a common misapplication of PCA methods in Mann's results. They are not oil industry stooges nor do they work for the Competitive Enterprise Institute or any other "think tank".
The NAS report played both sides of the fence a bit but nonetheless validated some of their criticisms of MBH98. A panel of respected statistical scientists has now backed up their work. The "hockey stick" is dead!
To then try to down play Mann's work as "just one of many" studies after passionately defending it previously strikes me as "sour grapes". It is after all the main study upon which the IPCC report based its dire conclusions. In fact the "hockey stick" is on the cover of one of the main parts of the IPCC report and has been splashed all over the Internet and media in general as proof of our imminent demise.
Also I note, so far, no one has responded to the panels criticism of the insular and politically strident nature of the main players in the climate science "consensus".
The report appears to be a call for the climate science community to return to the normal practices and procedures common to the main body of science.
Nonsense. That's a big PR talking point right now, and it's fooling people who don't check their facts.
Who do you rely on for what you believe? Who's telling you that story? Why do you believe them?
It's one study among many, supported later by many others. The myth that science relies on "original truth" and all subsequent work depends on early work is very attractive to those whose worldview depends on revealed truth.
Here's Inhofe, illustrating the same talking point -- and the same lack of understanding about how science works:
Lance Harting: To then try to down play Mann's work as "just one of many" studies after passionately defending it previously strikes me as "sour grapes".
I don't think so. This is from a Coby Beck post early this year:
The infamous "Hockey Stick" graph was featured prominently in the IPCC TAR Summary for Policymakers. It was important in that it overturned the concept of a global Medieval Warm Period warmer than the 20th century and a pronounced Little Ice Age, both long time (cautiously) accepted features of the last 1000 years of climate history.
This caused quite an uproar in the sceptic community, not least because of its visual efficacy. Two Canadians, an economist and a petroleum geologist, took it apon themselves to verify this proxy reconstruction by getting the data and examining the methodology used for themselves. They found that there were errors in the description of data used as published in Nature. Mann et al., the Hockey Stick's creators, published a correction in Nature, noting where the description of the study did not match what was actually done. The Canadians, McIntyre and McKitrick, then proceeded to publish a paper that purported to uncover serious methodological flaws and problems with data sets used.
Everything from this point on is hotly disputed and highly technical.
For myself, I will confess immediately that the technical issues are over my head, I don't know PCA from R^2 from a hole in the ground. But I think the most critical point to remember, if you are researching this in the context of determining the validity of AGW theory, is that this row is about a single study that was published 8 years ago. This is starting to be ancient history. If you feel it is tainted (as I prefer to just assume, because as I said I do not want to put the required effort into unraveling it all for myself) then simply discard it.
The fact is there are dozens of other reconstructions. These other reconstructions do tend to show some more variability than MBH98, ie the handle of the hockey stick is not as straight, but they *all* support the general conclusions that the IPCC TAR came to in 2001: the late 20th century warming is anamolous in the last one or two thousand years and the 1990's are very likely warmer than any other time in the last one or two thousand years.
I believe the Realclimate posts I've read usually say something similar to this last paragraph.
By the way, Realclimate has a new post up on "what the effect of the PC centering changes would have had on the final reconstruction..."
Because, let's face it, it was the final reconstruction that got everyone's attention. Von Storch got it absolutely right - it would make no practical difference at all.
Realclimate shows what the "hockey stick" looks like with the PC centering changes:
If the hockey stick is dead, looks like we've got a night of the living hockey sticks on our hands.
A disclaimer: I'm not a climate scientist and I can't claim to know much about "PC centering." But the more I read, the more this whole flap seems like much ado about nothing...
Ya know, they're right. It's not a 'hockey stick' at all.
The handle IS a little more curvy, in the other charts.
"... These other reconstructions do tend to show some more variability than MBH98, ie the handle of the hockey stick is not as straight ...."
We know what this is, don't we? And what it symbolizes?
It is after all the main study upon which the IPCC report based its dire conclusions.
On what do you base this gem of a statement?
In fact the "hockey stick" is on the cover of one of the main parts of the IPCC report...
I don't see it on any of these covers.
In their recent report Surface Temperature Reconstructions for the last 2000 Years, NAS scientists expressed doubt about (placed low confidence in) Mann's claim that "the 1990's are likely the warmest decade and 1998 the warmest year in at least a millenium".
But the same NAS report also stated that "surface temperature reconstructions [like those of Mann et al] for periods prior to the industrial era are only one of mulitiple lines of evidence supporting the conclusion that climatic warming is occurring in response to human activities, and they are not the primary evidence."
So, the NAS scientists who wrote that report clearly did not believe that the results of Mann were essential to the broader conclusion that AGW is real.
But there may nonetheless be some out there who do believe that the Mann results are essential to that conclusion.
To them, I would make the following request:
Please explain how the conclusion that AGW is real is contingent upon the accuracy of the specific results/conclusions of Michael Mann.
>Is anyone else as sick as I am of repeated attacks on the "hockey stick" reconstruction of past temperatures?...
>>One study never definitively proves anything in science. Any single study can be attacked and criticized. Any individual piece of work will have its gaps, shortcomings, and associated uncertainties.
So let's see if I get this argument. We mustn't criticise the MBH'98 hockey stick, but science operates by a process where it finds the errors in bits of work. Isn't this kind of asking for MBH to be taken away from the normal process of scientific scrutiny ?
Posters have made the point that the Millikan oil drop experiments (a century old ?) can effectively be repeated, even after all this time. By contrast, both north and wegman gave evidence that the method of MBH98/99 was flawed.
>Whether the "hockey stick" is right, wrong, or irrelevant, the underlying message on global warming is that we're causing it.
The NAS report went out of its way to say that MBH didn't directly impact on AGW theories, and wegeman didn't touch on AGW. So why are you so damn nervous when no-one even mentioned the subject ?
So why are you so damn nervous when no-one even mentioned the subject ?
There are some people (not us) who want to hash this subject out ad nauseum and use it as a political football, when, as Chris says, this study is a small part of a much larger and conclusive body of evidence. This is from a recent Inhofe television appearance:
INHOFE: ... The more I checked into it, the things started with the United Nations, the International Panel on Climate Control, and they used one scientist. And his name was Michael Mann, the famous hockey stick -- remember that -- where he plotted the temperatures that went all the way across on a horizontal line, then you got to the 20th century and it started going up.
Well, one thing they forgot to do is put in the medieval warming period, which was from about 900 to 1400 A.D., when it was warmer then than it is now.
BECK: Well, and here`s the thing. When you see...
INHOFE: So in all of the recent science, as I`ve mentioned on your radio show, it confirms that I was right on this thing. This thing is a hoax.
It's fine to criticise a study (although there will be a good chance that some of your criticisms will be moot after 8 years of continued research). But when you use a purported flaw in an eight-year-old study to distort an entire body of evidence, as Inhofe is doing in this TV appearance, the public is being bamboozled. So people like us end up shaking our heads and wondering when the adults will be in charge.
A panel composed of different scientists, the NAS panel, explicitely wrote in their report: 'strip-bark' samples should be avoided for temperature reconstructions.
That means that most of the current reconstructions (not only MBH98/99) simply are unreliable. And only reconstructions without such tree series (bore holes, Huang) or with a restricted influence (Moberg) should be taken into account. Both show a much lower LIA than MBH98/99 in the pre-industrial period.
This has important consequences for climate models and future projections. If there was more natural variability in the pre-industrial past (and thus in current times), then the influence of GHGs/aerosols is less than currently implemented, because models must fit the instrumental 1.5 century temperature curve...
Focusing on the the issues with tree ring (and other surface temperature) proxies misses the forest for the trees.
The recent NAS report stated clearly that the surface temperature reconstructions are not the primary evidence in support of AGW..
They did so in the section of the report under the heading "How central are large-scale surface temperature reconstructions to our understanding of global climate change?"
"Large scale surface temperature reconstructions for the last 2,000 years are not the primary evidence for the widely accepted views that global warming is occurring, that human activities are contributing, at least in part, to this warming, and that the Earth will continue to warm over the next century."
After the above quote, they go on to list
"The primary evidence for these conclusions" on this page.
They conclude the section under the above heading with the following statement:
"Surface temperature reconstructions for the last 2,000 years are consistent with other evidence of global climate change and can be considered as additional supporting evidence. In particular the numerous indications that recent warmth is unprecedented for at least the last 400 years and potentially the last several millenia, in combination with estimates of external climate forcing variations over the same period, supports the conclusion that human activities are responsible for much of the recent warming. However, the uncertainties in the reconstructions of surface temperature and external forcings for the period prior to the instrumental record render this less conclusive than the other lines of evidence cited above. It should also be noted that the scientific concensus regarding human-induced global warming would not be substantively altered, if for example the global mean surface temperature 1,000 years ago was found to be as warm as it is today."
>Please explain how the conclusion that AGW is real is contingent upon the accuracy of the specific results/conclusions of Michael Mann.
contingent is far too strong, but the strongest case I can point you in the direction of is in the summary for policymakers of the IPCC TAR.
You appear to be jousting at windmills. Neither the NRC nor the wegman report made any case that their reports invalidated AGW. Why do you repeatedly bring this up ?
I will say this: that Jon Winsor says the public is being bamboozled. Well this is true; the hockey-stick graph has been hard sold for the last 8 years, and is still being used as publicity material. We now know that the scientific basis for the MBH hockey-stick is inadequate; if that ain't bamboozling the public, I don't know what is.
The obvious point is that without removing evidence for previous natural climate variability form the discussion, as MBH98 attempted to do, there is no consensus that unusually large, dangerous increases in global temperatures are occurring or have occurred.
This returns the "consensus" to the somewhat uncontroversial and non-alarming, "The temperature has risen approximately 1 degree Celsius over the last 100 years, that a concurrent 30% rise in atmospheric CO2 may have contributed to that rise and that humans are at least partly responsible for the rise in CO2."
I know this doesn't dovetail with the plans of some to use this "issue" as a hammer to alter the political landscape but science isn't meant to be a political tool.
Well if it will stop some people from throwing fits, they should stop using the MBH98 graph and use the other graphs. But it's quite silly to call the use of a graph from a peer reviewed study "bamboozlement".
Mann called attention to the uncertainties of his own study when it was published. It would be very surprising if the IPCC hadn't taken these kinds of uncertainties into account with its predictions of a 1.4 and 5.8 C degree increase over the next hundred years (that is, if Mann's study hasn't been superseded over the last 8 years).
>Mann called attention to the uncertainties of his own study when it was published.
was that the claim that it was 99.7% certain that the '90s were the hottest decade since 1400 ? The NRC dismiss the 0.3% figure as a realistic assessment of uncertainty.
When he calculated r2 statistics for his 15th century reconstruction, found them to be adverse, then didn't tell anyone, is that telling everyone about the uncertainties ?
When he made the claim that his reconstruction was robust to the absence of tree proxies, and in fact it doesn't survive removal of the bristlecone pines, is that telling everyone about the uncertainties ?
You have confidence that subsequent reconstructions improve on MBH. Strangely enough, I have little faith that they do. The NAS report concluded that bristlecone pines should not be used; yet they (and the flawed Mann PC1) make a substantive contribution to many of the post-MBH studies.
I think Coby Brent put it in perspective in his hockey stick post. He said that in addition to Mann's study, there are
...dozens of other proxy reconstructions, some by the same team or involving members, some by completely different people, some using tree rings, some using corals, some using stalagtites, some using borehole measurements, all of which support the general conclusions. And it is that general conclusion which is important to me, not whether or not one Bristlecone pine was or was not included correctly in a single 8 year old study.
And then there's the role of temperature reconstruction in the IPCC's assessments-- they're just one part, and they don't seem all that determinative:
I also urge anyone worried about this study and what its conclusion means for the theory of Anthropogenic Global Warming to remember this: the study of the past can be very informative, but it is not explanatory of the present or predictive of the future.
There are many other studies that go into their assessments, especially after 8 years. It's all too easy to "pick one piece of the fabric of evidence and blow it up all out of proportion," as the researcher in the WaPo article put it.
"Contingent is far too strong, but the strongest case I can point you in the direction of is in the summary for policymakers of the IPCC TAR."
My question was adressed specifially to those who believe that the AGW claim is contingent upon the Mann results (not that I expected Senator Inhofe to respond or anything, but I thought perhaps someone who does not believe AGW is real might take the challenge and actually "explain the contingency").
I would comment with regard to the above response, however, that in the US, the real policymakers (those who actually make the binding policy through enforceable laws) are those in the White House and the Congress. (I would guess that Blogs are still way down on the influence list when it comes to policymaking, for whatever it's worth.)
It is highly relevant to the current policy debate on global warming that one very prominent, powerful and vocal policy maker in the US Senate, Senator Inhofe, believes that manmade global warming "is the greatest hoax ever perpetrated on the American people".
Regardless of how anyone else might characterize the relationship between the AGW claim and Mann's hockey stick, there is ample reason to suspect that Inhofe might actually find "contingent" to be an accurate characterization:
"the more I checked into it, the things started with the United Nations, the International Panel on Climate Control, and they used one scientist. And his name was Michael Mann, the famous hockey stick..." -- Senator James Inhofe,
Finally, to those who may believe that Inhofe's statements have little relevance to current US policy on this issue, I would simply have to say that they may want to do a little research about how the US government actually works.
Jon Winsor, the predictions of a 1.4 and 5.8 C increase for a CO2 doubling are based on a good fit of the 1.5 century of instrumental record we have (a necessary but not sufficient condition). And based on several assumptions, of which the (cloud) feedbacks and aerosols are quite questionable. An investigation by Stott e.a. ( http://climate.envsci.rutgers.edu/pdf/StottEtAl.pdf ) on the Hadcm3 model revealed that solar sensitivity was probably underestimated with a factor 2 (within the constraints of the model, like a fixed minimum influence of aerosols).
Without MBH98/99 and some other reconstructions, there is no hockeystick shape, but a bathtube shape, which looks more like natural cycles. And with a much larger MWP-LIA-current variancy. To say it with the words of some eminent climate scientists (Esper, Moberg, Luterbacher,...):
"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."
Or with other words, the 1.4-5.8 range could be as well 0.7-2.9 or lower...
Ferdinand Engelbeen posted: "Or with other words, the 1.4-5.8 range could be as well 0.7-2.9 or lower..."
Where does this come from?
Not from what you have provided above.
Stott et al certainly said no such thing in the paper that you referenced.
On the contrary, Stott's specifies his estimates for reductions in future anthropogenic warming estimates (due to potential adjustments to the solar forcing) -- and they are significantly less than the halving of the IPCC numbers that you implied above.
Here's the relevant pargraph from the Stott paper:
"An enhancement of the solar forcing by a factor of 3 would therefore increase the potential future solar forcing to 0.3 W m2, the upper limit of which is more than half the lower limit of anthropogenic forcing. A reduction of the greenhouse gas contribution to 81% of its modeled value (the best estimate of the scaling factor for G in combination with LBB; Table 2), while keeping the aerosol contribution approximately the same [the best estimate of the scaling factor for S being 1.01, Table 2; note that the relative proportions of greenhouse gas and sulfur emissions change during the course of the different IPCC Special Report on Emissions Scenarios (SRES) scenarios] would result in a reduction of anthropogenic global warming forecast under the IPCC SRES scenarios (Nakicenovicand Swart 2000; Houghton et al. 2001) of 0.15K by the mid-2020s (from 0.6 K relative to the 1990s) and between 0.3 K for the B1 scenario by the 2090s(from 1.8 K relative to the 1990s) and 0.7 K for the A1FI scenario by the 2090s (from 4.1 K)."
[end Stott quote]
I have added the emphasis above.
For the period through 2020, Stott's estimated reduction of .15k from .6K is a reduction of 25% in the anthropogenic warming estimate (not 50%).
For the longer period, Stott's estimated reduction of .3 from 1.8K is reduction of 17% in the anthropogenic warming estimate and a reduction of .7K from 4.1K is also a reduction of 17% -- not a 50% reduction, as you implied with your halving of the IPCC numbers.
It should finally be noted that Stott et al made the following caveat about their estimates of solar forcing:
"Reconstructions of solar irradiance are empirically based and are very uncertain, reconstructions differing due to the various assumptions used. Despite the improvement to the modeled fit of global-mean temperatures gained by enhancing solarinduced changes, there is no improvement in the simulationof North Atlantic warming during the first half
of the century."
Or with other words, the 1.4-5.8 range could be as well 0.7-2.9 or lower...
As I commented above, this seems to be the fallback position that the denialists are arguing for these days. A quote by Mark Twain comes to mind: "The researches of many commentators have already thrown much darkness on this subject, and it is probable that if they continue we shall soon know nothing at all..."
And I'll note that many of these commentators have little in the way of credentials, and often seem to be dog paddling through their arguments.
That said, I'm dog paddling myself--we're starting to get into a level of detail that's best handled by the professional scientists, so I'm hesitating to respond. But I'll say a few things.
An investigation by Stott e.a. on the Hadcm3 model revealed that solar sensitivity was probably underestimated with a factor 2.
From everything I know, the evidence for solar forcing is very unconvincing. Realclimate has a post on the subject:
And Coby Beck has a post from a lay point of view:
Plus, common sense would ask what the odds are that the sun would coincidentally warm up precisely when we raise the CO2 content in the atmosphere by 30% ? Applying Occam's razor, GHG-induced warming is the best explanation for what we're seeing.
I like what Naomi Oreskes had to say in a recent edition of the LA Times:
...Some climate-change deniers insist that the observed changes might be natural, perhaps caused by variations in solar irradiance or other forces we don't yet understand. Perhaps there are other explanations for the receding glaciers. But "perhaps" is not evidence.
The greatest scientist of all time, Isaac Newton, warned against this tendency more than three centuries ago. Writing in "Principia Mathematica" in 1687, he noted that once scientists had successfully drawn conclusions by "general induction from phenomena," then those conclusions had to be held as "accurately or very nearly true notwithstanding any contrary hypothesis that may be imagined.... "
At this point, solar forcing seems not much more than an imagined contrary hypothesis, a "perhaps".
Without MBH98/99 and some other reconstructions, there is no hockeystick shape, but a bathtube shape, which looks more like natural cycles.
Well, here's another graph:
If I had a bathtub like that, I'd have a very wet floor.
NAS made the following statement in their recent report:
"It should also be noted that the scientific concensus regarding human-induced global warming would not be substantively altered, if for example the global mean surface temperature 1,000 years ago was found to be as warm as it is today."
There are various ways of interpreting the above, but it would at least seem to encompass the possibility of a "bathtub" shape* for the temperature reconstruction over the past 1000 years.
*If I am interpreting "bathtub" correctly: high at both ends and lower in the middle.
Dark Tent, there is an important constraint with the Hadcm3 test by Stott ea.: They fixed the influence of aerosols. The influence of aerosols and climate sensitivity for GHGs goes in tandem (see RC for the aerosol/climate sensitivity graph).
That means that the tests don't cover the full range of possibilities to the low sensitivity side (for GHGs/aerosols).
A test that I have done with a simple climate model from Oxford University shows that halving the sensitivity for GHGs, combined with 1/4th of the forcing from aerosols and 1.5 times solar fits the temperature curve over the last century as good as the original. And the projections for future warming all were halved, no matter what scenario was chosen... I am going to expand the test with the data from the MBH98 and Moberg temperature reconstructions and the solar data since around 1600, to see which sets of sensitivities gives the best fit for both reconstructions.
If there was more natural variability in the past (0.1 C volcanic, 0.1 C non-volcanic according to MBH98/99 and Jones, 0.7 C non-volcanic according to Esper, Moberg and Huang, that is a factor 7 for non-volcanic variability!), then sensitivity for GHGs and aerosols must be reduced in current models, or you can't explain the LIA dip *and* the temperature trend of the past century.
Jon Windsor, I am working for a better environment since about 1968, that is longer than even Greenpeace exists. And before the environment was big business. I have no doubts that there is some "A" in (A)GW. But I had doubts about the HS from the very first moment I saw it. Because it clearly underestimated natural variability in the past millennium.
And did you see my comment on the RC page about solar influences? What about the 8,000 years high in current solar activity?
The bath tube shape, with a much larger variation than the HS is for the past 1,000 years, see Wikipedia and compare the shape and the amplitude of the MBH99 reconstruction with those of Esper, Moberg and Huang... And as an extra, ask yourself what happens with the reconstructions after 1980 vs. the instrumental record (you may find interesting answers).
I agree with Dark Tent (and the NAS) that even if the MWP was warmer than today, that doesn't disprove (neither does a cooler MWP prove) that there is an influence of GHGs today. But the variability of the past has a very important impact on climate models and what to expect of GHG influences and future warming. Thus we urgently need better proxies...
>dozens of other proxy reconstructions,...
okay, as the NAS panel said, the bristlecones should not be used. How many reconstructions are you left with if you take out those that use the bristlecones/ Mann's PC1 ?
>And it is that general conclusion which is important to me, not whether or not one Bristlecone pine was or was not included correctly in a single 8 year old study.
this shows a fundamental misunderstanding of the nature of science; MBH'98/99 has now been completely invalidated. It uses a biased statistical method, it is absolutely dependent on bristlecone pines, and you shouldn't be using these pines anyway; and that is just what the nas panel said.
How many of these other studies will stand up to scrutiny ? It is no good relying upon the studies in aggregate; all that it takes is one study which is good. So which is the good study and will it stand up to scrutiny ?
this is what science is about; not the quantity of studies, not the self-publicity, not the consensus, but the quality.
>My question was adressed specifially to those who believe that the AGW claim is contingent upon the Mann results (not that I expected Senator Inhofe to respond or anything, but I thought perhaps someone who does not believe AGW is real might take the challenge and actually "explain the contingency").
I am not going to address that point, but I will perhaps try to illuminate. The MBH hockey stick was highlighted in the IPCC TAR, and received considerable publicity. The inference that was drawn was clear; temperatures in the last millenium have barely changed, yet since 1900 we have seen this dramatic increase. In itself, it enormously strengthens the case for AGW, and what is more, it was remorselessly used in persuading governments to sign up for Kyoto.
I could understand a politician's view that the MBH paper was the new and compelling part of the argument that was used to force governments to sign up to Kyoto.
From a personal perspective, I would see MBH as being a wholly independent form of evidence which supports the predictions of models, and together, I would find the evidence from these two independent arguments to be very strong, if not compelling. Without MBH, you are left with the models; which have known defects, and are considerably less than compelling evidence.
It is no good relying upon the studies in aggregate; all that it takes is one study which is good. So which is the good study and will it stand up to scrutiny ?
So you're not convinced by multiple lines of corroborating evidence.
It would take an awful lot of convincing to get me to believe that all of those lines of evidence at peer-reviewed scientific institutions are unreliable and corrupted... It's along the lines of, what was happening at that book depository, on that grassy knoll?
Sorry. I think it's pretty straightforward. We've upped the CO2 content in the atmosphere by 30%...
I think some are just invested in complicating the narrative.
(As for the statistics issue, see the Realclimate article that I linked to above.)
>So you're not convinced by multiple lines of corroborating evidence.
I think I have made the point that it is the quality of any one piece of evidence, rather than the number of pieces of evidence, that count. The NAS panel have said that you cannot quantify the uncertainty of reconstructions prior to 1600.
>It would take an awful lot of convincing to get me to believe that all of those lines of evidence at peer-reviewed scientific institutions are unreliable and corrupted...
You disagree with the NAS panel, but it isn't clear to me why I should hold your view over the NAS panel. You haven't taken account of the fact that many of these reconstructions contain bristlecones, or Mann's PC1; yet the nas panel explicitly say that these should not be used. So these "dozens" of reconstructions become - how many ?
You tell me that this is some conspiracy theory, because I question multiple studies. However, it is not unknown for many papers in an area to be wrong. Just look at the number of epidemiology papers with small sample sizes.
I note your bit on statistics; how about Geophys. Res. Lett., 32, L03710, which is a peer-reviewed paper on this subject. Without decentred PCA, there is no hockey-stick in pc1, and the hockey-stick is relegated to pc4. You cannot have a hockey stick reconstruction where the shape comes from pc4, and accounts for only 8% of the variance; this is obviously a non-robust conclusion.
Ferdinand said: "there is an important constraint with the Hadcm3 test by Stott ea.: They fixed the influence of aerosols. The influence of aerosols and climate sensitivity for GHGs goes in tandem (see RC for the aerosol/climate sensitivity graph)."
I am not in the best position to judge whose assumptions about aerosols (or about solar forcing, or anything else, for that matter) -- of Stott, yourself, or others (eg, IPCC) -- are closest to being correct.
But that's precisely why the scientific publication process exists, so that other scientists who are in such a position can review not only the methods, but also the assumptions made by their peers.
If you are asking me to choose your "result" of halving of the IPCC estimated range for future warming based purely on what you have said here, I would simply have to say that there is no contest. I have to go with the numbers provided by IPCC (provided and reviewed by many scientists) and reviewed by other scientists within NAS.
No disrespect is intended by this. I am not even claiming you are wrong, just saying that I simply will remain dubious about your "halving" claim until your work has gone through the normal scientific process and others have had a chance to examine it in detail and critique it.
Perhaps you have already submitted your results as a paper for publication, but you have made no indication that this is the case and have not even linked here to a paper documenting in detail your assumptions, methods and results.
I think I have made the point that it is the quality of any one piece of evidence, rather than the number of pieces of evidence, that count.
I thought you made that point too. But I wasn't sure, because it doesn't even survive a reading of the first three pages of the NAS report:
It can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries. This statement is justified by the consistency of the evidence from a wide variety of geographically diverse proxies.
(From page three.)
Of course different sources of evidence, different studies, different people doing them, make a more convincing case.
Further down the page it says that Mann's conclusions have "subsequently been supported by an array of evidence that includes both large scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators..." The "array of evidence"--in other words the same signal coming from a number of different sources--was what was convincing to the NAS.
You might have noticed that a commenter above posted something from the hearings when they spoke about what the NAS report meant by "plausible":
He said they used that word to describe a question on which there are many studies supporting one conclusion and none that contradicted it.
A wide variety of corroborating evidence makes a good case. It's basic science. A particular result, in this case reconstructed temperatures, can be reproduced from a wide array of different sources and researchers. As Coby Beck put it, "some by the same team or involving members, some by completely different people, some using tree rings, some using corals, some using stalagtites, some using borehole measurements."
This is not a misunderstanding of science.
Scientists don't labor in obscure isolation waiting to produce some sort of piece of Olympian perfection that they can bring down to the world, like they're characters in an Ayn Rand novel. They share their work. And work with uncertainties can still have value. It's a question of what the chances are that work from many different sources can produce the same results, if they're not describing the same objective reality:
Now, is "data quality" important? (to use the Republican buzzword these days when results don't fit their agenda) Of course! But if these studies were the equivalent of an epidemiological study with a small sample size published in an obscure journal (to use your example), the NAS would have told us that. They told us no such thing.
> But if these studies were the equivalent of an epidemiological study with a small sample size published in an obscure journal (to use your example), the NAS would have told us that. They told us no such thing.
They did; they told us that you cannot quantify the uncertainty associated with reconstructions prior to 1600. That is telling us that you cannot rely upon them.
>But I wasn't sure, because it doesn't even survive a reading of the first three pages of the NAS report
you are frankly wrong. Where does it say that nas accepted weak evidence, because there was lots of it ? The evidence that NAS accepted back to 1600 is good because it is so well characterised and strong; which is my point.
>A wide variety of corroborating evidence makes a good case.
not unless the individual studies are strong. A million crap studies still don't prove anything.
you have also harped on about the wide variety of reconstruction studies there are. NAS explicitly state that you shouldn't use bristlecones; yet a great number of these reconstructions use bristlecones, or Mann's flawed PC1, and should be discarded on that basis. You still haven't answered how many studies you are left with when you remove studies that fail some of the basic quality control criteria identified by NAS.
This is going to be my last post on this subject because this is getting tedious, and I think I've pointed out some pretty basic flaws in the way you're approaching this. (And I doubt we have too many readers at this point.)
Because I actually have things to do other than reinvent the wheel, I'm not going to dive into the minutiae about bristlecone pines, etc. My taxes pay people like James Hansen to worry about that sort of thing, and I have enough faith in human nature and the way the scientific meritocracy works that I believe they're doing at least a reasonably good job.
Uncertainties don't equate to "crap science". This is a basic misunderstanding. Uncertainties are business as usual in just about any scientific field. Scientists are paid to find even the most minute uncertainties that policymakers would find inconsequential, because they have very different responsibilities and different points of interest.
For instance, if you look at all the proxies that go into making this graph, some of them must be off by a certain amount at different points. In other words, they can't all be right:
But hypothetically, if you had the "real" line, it wouldn't be a surprise after looking at this graph. That's because the odds of all these lines independently suggesting the same thing and all being totally off is on the scale of winning the lottery (unless of course you've got a conspiracy theory saying that someone has their thumb on the scale). This, I think, is the take away point for policymakers.
But back to the NAS report. The NAS had "a high level of confidence" that "the last few decades of the 20th century" was hotter than any during the last four centuries. It had "less confidence" in any reconstructions in the seven centuries before that. And had "very little confidence" in temperature reconstructions before 900. But does Mann's graph say anything significantly different than this? Take a look at the gray area:
Mann's conclusion was that the "20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1000 years." The committee found this plausable, because of the array of evidence supporting his claim:
But go back to the precise wording of Mann's conclusion: "the rate and magnitude of global or hemispheric surface 20th century warming is likely to have been the largest of the millennium, with the 1990s and 1998 likely to have been the warmest decade and year."
The word he uses is "likely."
I agree with Chris. This nitpicking is torture. This will be my last comment on this subject...
I don't have the illusion that any climate journal will publish a result of a few simple tests from an engineer chemistry/process automation (retired) with too many hobbies, of which climate is one...
From my former carrier, I learned that even modelling simple physical/chemical processes where everything is (theoretically) known, is a hell of a job. Let it be climate where a lot of underlying physics and feedbacks are not even known to any accuracy. Like the influence of aerosols (as forcing) and/or clouds (as feedback).
If you have a one equation with four (more or less known) variables (GHGs, aerosols, volcanic, solar) and only one result (temperature), you can have many sets of individual sensitivities (including feedbacks), which all fit the past temperature trend... Cloud feedback in current GCM's is responsible for the wide span (1:3) of the IPCC range.
Many (if not all) current GCM's use forcings/feedbacks based on a small pre-industrial variability (and thus a huge influence of GHGs/aerosols). This is de facto overruled by the exclusion of bristlecones pines. Without these, near all reconstructions must show far more variability in the past.
I hope this will be noticed by some (real) climate specialists...
I hope this will be noticed by some (real) climate specialists...
And as I said above, that wouldn't be me ; ) .
>But go back to the precise wording of Mann's conclusion:
"it appears that the years 1990, 1995 and now 1997 (this value recently calculated and not shown) each show anomalies that are greater than any other year back to 1400 at 3 standard errors, or roughly a 99.7% level of certainty."-MBH'98
The NAS rejected the statistical value completely. As you point out, the NAS found some of these conclusions to be PLAUSIBLE; I invite you to look at a dictionary to see what the word PLAUSIBLE means. It does not mean proven, or even likely.
>not going to dive into the minutiae about bristlecone pines, etc.
The NAS panel and the wegman report, and the original literature, all say that these are not a good temperature proxy. Why on earth do you suggest that there is a contrary view ?
>Uncertainties don't equate to "crap science".
well, not always. I said that there has to be a quality of science; and if you don't have it, the work has minimal value. The NAS panel has said that there is not a minimal quality of proxies before 900, and any such reconstruction has little value at the moment. For reconstructions before 1600, the NAS panel has unquantifiable levels of uncertainty.
Their statement applies to the many reconstructions, and i put it to that their verbatim statement is a severe criticism.
Oh and by the way; for the third time, you have completely ignored the issue that many of the reconstructions include bristlecone pines, and that the NAS panel have said these should not be used. If you like, that is putting your "thumb on the scale" to bias your results. You must disregard the reconstructions which have bristlecones in them.
The NAS panel said explicitly that you shouldn't use strip-bark (bristlecone) pines; why is this so difficult ?
Realclimate, following your link, says:
"...an attempt was made to remove these potential non-climatic influences. This was done by subtracting the anomalous pattern of growth that emerges over the past couple centuries in these chronologies..."
At best, their logic is that when you look at these pines, they don't simply follow temperature; so we have fixed the figures. You then have to have a speculative assumption that these pines have never ever before shown a poor relationship with temperature (like they do now). Of course, you can't test this !
this isn't science; this is speculation piled on speculation piled on speculation.
I think Realclimate has a bit more to say than what you quote. The same with the NAS.
Wegman's comments on CO2 are not entirely kooky. We know that CO2 concentrations in the canopy of tropical forests are much higher than in the overlying free atmosphere. When Lake Nyos overturned and "burped" CO2, the gas hugged the ground causing disastorous loss of life. So, Keeling chose carefully his site for CO2 measurement to ensure that such inhomogeneities would not be sampled.
I quoted the relevant bits of realclimate and this reflects MBH'99 approach to manipulating the bristlecones. I stand by my analysis that what they have done is speculation built on speculation, and that it is completely unreliable.
From your NAS page:
"While 'strip-bark' samples should be avoided for temperature reconstructions,..."
that seems clear to me. How can you possibly defend a whole series of reconstructions which are sensitive to the inclusion of these strip-bark pines ?
I'm not going to sit here and pretend I can make the case better than Mann can himself. Mann does *avoid* those and he explains. This is statistics. Repeating myself: If the data was "crap" in all the broad range of studies, then the lines in the following graph would not agree with each other, unless you have a conspiracy theory:
And no, I will not go into the minutiae of every single study represented in that graph. You may have the time and inclination to. I do not.
Mann does *avoid* those and he explains.
no offence, but I am puzzled. Let me quote to you from page 107 of the NRC report:
For periods prior to the 16th century, the Mann et al. (1999) reconstruction that uses this particular principal component analysis technique is strongly dependent on data from the Great Basin region in the western United States. Such issues of robustness need to be taken into account in estimates of statistical uncertainties.
the great basin proxies are the bristle cone pines. The mann reconstruction includes the bristlecones, and the NRC study says it is dependent upon them.
Again, I am confused about your point for the many reconstructions. The NRC report says you shouldn't include bristlecones, yet many studies do. How is it a surprise that they all show a common shape when they all contain a common element (which is contaminated) ?
Seems to me that you are cherry-picking the conclusions you like, and the ones you don't like, from the NRC review.
Per, I think I love you. I was the lone "denialist" in here for months until you and a few other brave souls came to my rescue in a cavalry style relief effort. It has been a pleasure reading your lucent and informed posts on MHB 98.
Sorry if I haven't been pulling my weight in this thread of late but it has been nice to just sit back and watch you and a few other evil "skeptics" score blow after blow.
Jon is nothing if not resilient. He is a reasonable soul but is like a bulldog when defending his point. Sometimes you have to know when you've lost a battle and go on to regroup for the next one.
I think this is why the Democrats left Mann hanging out to dry in the recent hearings on the "hockey stick".
Mann "over board" indeed.
I was the lone "denialist" in here for months...
i know the feeling; isn't it easy to tag someone with an offensive adjective ?
But I take this to be a science issue. In science, you get evidence for and against a hypothesis, and you argue it. Beating down the arguments against a hypothesis makes the hypothesis stronger, and so it is important to make those arguments.
In science, it isn't immoral to test the evidence; as so many would have you believe.
It's like you have a 2000 piece puzzle. You know what the picture is. A piece missing from the tail or the trunk doesn't change the obvious fact that IT'S AN ELEPHANT.
There may be a number of decades (out of 2 millenia) of some of the temperature reconstructions THAT USE TREES and still use bristlecone pines. And that's been improving.
SO WHAT?? It's still an elephant. And the NAS said it was an elephant.
Nitpicking these tiny statistical issues doesn't change that.
Lance writes: I was the lone "denialist" in here for months.
If Lance and Per want to be denialists, I'm not interested in what they have to say, because they have then adopted an agenda.
I hope that they, and everyone else, are willing to be skeptical of any evidence and be respectful of scientific consensus born of skepticism.
They are right to nag us about jumping onto a bandwagon, but I am willing to nag them about being too willing to latch onto a smaller bandwagon called denialism.
The problem is that the denialists are not skeptics but are bent on misconstruing science for their own ends or simply to get attention.
As I see it, Per is not a denialist but rather a nagging skeptic. We who believe that the scientific consensus is sound need his challenges to keep us honest.
Sometimes a nagging skeptic becomes irritating when he keeps arguing after we've heard what he has to say, listented to it respectfully, and decided that the consensus interpretation makes more sense than his critique.
I think that's the kind of torture Chris was referring to when he started this thread.
An I can't believe I've decided to say something to prolong the agony!
I'm outta here!
Why do you keep repeating this stuff? It's talking point PR:
"MBH'98/99 has now been completely invalidated. It uses a biased statistical method, it is absolutely dependent on bristlecone pines"
That's three separate talking points, each refuted in the House Energy testimony.
"We certainly agree that modern global warming is real. We have never disputed this point. We think it is time to put the 'hockey stick' controversy behind us and move on."
-- Dr. Wegman, printed testmony, p. 8
What's your problem with that? Why cling to the past when there are current research reports to look at, all done better than the early ones -- typical of scientific work?
If you claim to be a scientist, look at the science. The historians of science know how this works. Old and early studies are approximations, some lead to dead ends, some lead to areas productive of further and better work.
Look at the science now.
per, I have to admit that in the heat of battle I have sunk to calling global warming advocates snide names at times, "zealot" comes to mind. As a scientist I regret having done so and attempt to use more constructive language when discussing the issue.
It can be difficult to maintain this high-minded decorum when continually being assaulted by ad hominem attacks both direct and implied.
Fred, I was using the term denialist as a vehicle of self-effacing irony. I do not consider myself a "denialist" but a rational skeptic, as all scientists should. I attempt to examine the scientific evidence with great rigor no matter its correlation to my political views.
I find the evidence supporting the most extreme claims of anthropogenic global warming to be highly suspect. I find it telling that after expending such great effort to defend MBH98 that not one of you global warming advocates will even admit that its collapse gives you even the slightest pause. This shows the emotional attachment that many have to the theory of catastrophic climate change.
wegman agrees, as does everyone, on the temperature record; the globe is warming of late. That is different from him validating theories of AGW; which I don't recall he did.
He also said that the hockey stick controversy should be put behind us. It is important to cite the context. As I recall, he pointed out that both the NRC and his report had found MBH'98/99 to be fundamentally flawed. I agree- it is dead; it is an ex-nature paper; it has ceased to be! Even Mann did not challenge wegman's statistical testimony.
Nitpicking these tiny statistical issues doesn't change that.
Jon, I have to say this is desperate; these reconstructions are all about statistics, and if the statistics are busted (a tiny issue to you), they are worthless. The NAS report said that NO reconstruction prior to 1600 had quantifiable levels of uncertainty; that may sound like a minor detail to you, but in science-land, you don't get much more serious criticism.
I have to say this is desperate;
I think I'm just deperately sick of this argument. (So I should probably make good on what I said and stop commenting already...)
if the statistics are busted (a tiny issue to you), they are worthless.
But we're not talking about "the statistics", we're talking about a tiny subset of the statistics. That's my point!! That's Coby Beck's point! That's the NAS's point.
I suppose if you want to keep saying that a corner case determines the fate of all the dozens of studies across all the proxies, that's your business. But I just don't think it's reasonable.
And that's it for me. Everyone else have fun with this...
we're talking about a tiny subset of the statistics
I view the statistics as the operations that you do on the data; I can't tell if you are referring to the data as statistics, or the operations on the data.
The NAS report said that NO reconstruction prior to 1600 had quantifiable levels of uncertainty; that means they are worthless. I don't see how you can ignore this ?
Even if you are referring to the bristlecone pine data, in MBH'98/99, the reconstruction changes dramatically if you exclude the pines. The same is true for numerous of the other reconstructions. So even if the pines are a tiny contribution to the "dozens of reconstructions", they have a ludicrously disproportionate effect on the final reconstruction.
I suggest you read Steve McIntyre's testimony to the wegman committe for some good examples of this effect.
"Results for the exclusion of the bristlecone/foxtail pine series developed according to scenario 3 are shown by the green curve in Figure 2. The exclusion of these proxy records generally results in slightly higher reconstructed temperatures than those derived from inclusion of all the proxy data series, with the greatest differences (averaging ~ +0.10Â°) over the period 1425-1510. The highest values before the 20th century in this scenario occur in the early 15th century, peaking at 0.17Â° in relation to the 1902-1980 mean, which are nevertheless far below the +0.40-0.80Â° values reported for scenario 1. The verification RE scores for this scenario (Table 2) are only slightly above the zero value that indicates the threshold of skill in the independent Feb 24, 06 Wahl and Ammann Climatic Change, in press 29 verification period, and the verification mean reconstructions are correspondingly poor. These results, which cannot be attributed to calibration overfitting because the number of proxy regressors is reduced rather than augmented, suggest that bristlecone/foxtail pine records do possess meaningful climate information at the level of the dominant eigenvector patterns of the global instrumental surface temperature grid. This phenomenon is an interesting result in itself, which is not fully addressed by examination of the local/regional relationship between the proxy ring widths and surface temperatures (noted in section 1.1) and which suggests that the "all proxy" scenarios reported in Figure 2 yield a more meaningful comparison to the original MBH results than when the bristlecone/foxtail pine records are excluded. Even in the absence of this argument, the scenario 3 reconstructions in the 15th century do not exhibit large enough excursions in the positive direction (in relation to the 20th century instrumental record) to yield a double-bladed hockey stick result that diminishes the uniqueness of the late 20th century departure from long-term trends.
I am sure you are aware that the NAS panel had access to Wahl and Ammann's opus, yet still NAS came to their views !
is that because the bristlecones give a spurious match to global temperatures, whilst showing a poor match to local temperatures ? Is it because of the diabolically bad r2 statistics ? or is it beacuse figure 2 shows that omitting the bristlecones in california make a ~0.3 C difference to the average northern hemisphere temperature in 1425 ?
somebody at the top of this page whined that someone was 'at it again' in attacking the Hockey Stick by Michael Mann, et al. I am honestly quite puzzled how anyone could truly be puzzled over any criticism of a lie.
Fact. the Hockey Stick Graph implies a stable climate since around the year 1000 AD.
Fact. There was a very warm period in earth's climatological history often called the Medieval Warm Period, which is likely to be warmer than the 1990's the alleged warmest decade ever.
Fact. following the MWP was an era of extreme cold referred to as the Little Ice Age.
Fact. these climate extremes were reported in the Second Assessment Report, the one that came out just before the Third Assessment Report. The significance of this is the SAR showed the climate as i have just pointed out and somehow, in the intervening time between the SAR and the TAR, history was wiped out.
how this happened is also factual
Fact. Michael Mann, the creator of this lie referred to as the Hockey Stick Chart or Graph was also the lead author of the TAR. is it any wonder the Hockey Stick was so prominent in the TAR?
Now, to claim that the Hockey Stick is not important to the AGW(anthropognic global warming) zealots cannot be taken serioouslly given that the lead author was also the graphs creator and also, the Graph was given such prominenet display thruout the TAR
So, whomever you are, better go back to the drawing board and make another attempt to spin away the Hockey Stick problem, because you have no basis, no basis for sayibng it doesn't matter, for saying there is AGW. the pillar of AGW has a crack in it and the AGW palace will soon fall.
Thank you for your time