I would be perfectly tolerant to new idea. I am not tolerant to insults accusations and charges presented without a hint of supporting evidence. Do YOU have any?
Liberals Continue Their Assault On Anything That Casts Doubt on Climate Change
- Thread starter easyt65
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I would be perfectly tolerant to new idea. I am not tolerant to insults accusations and charges presented without a hint of supporting evidence. Do YOU have any?
Papageorgio
The Ultimate Winner
I think climate change has been going on since the beginning of time and will continue to change. A village in Iceland was rediscovered as the climate has warmed and exposed this village that disappeared when the climate was getting colder. Deserts at one time were forests, weather, climate and earth change constantly.
I also don't trust science that is paid by governments with an agenda, nor do I trust business that pays for a result.
Much dishonesty on both sides, the fact that one side wants to suppress all discussions on the debate and end the debate is really showing the lack of confidence they have in their data.
RollingThunder
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LOLOLOLOL......a delusional denier cult dumbass cites another fraudulent denier cult dumbass, who happens to be a fossil fuel industry stooge, as 'evidence'.....LOLOLOL....so typical of you anti-science denier cult retards....
Stephen McIntyre is the primary author of the blog Climate Audit, noted for its many articles skeptical of climate change. He is a prominent critic of scientific studies of temperature records of the past 1000 years that show increasing global temperatures. Stephen McIntyre has worked in mineral exploration for 30 years, much of that time as an officer or director of several public mineral exploration companies. "I've spent most of my life in business, mostly on the stock market side of mining exploration deals," he said in 2009.[1] He is a “strategic advisor” to CGX Energy, which describes its “principal business activity” as “petroleum and natural gas exploration”
McIntyre was also a headliner at the Heartland Institute's International Conference on Climate Change (2009), a gathering of climate change skeptics in New York from March 8th-10th, 2009.
McIntyre is known to sometimes use the pseudonym Nigel Persaud [3] [4]
For more complete background information, see...Stephen McIntyre
Meanwhile, in the real world of actual science....
Novel Analysis Confirms Climate "Hockey Stick" Graph
Myth vs. Fact Regarding the "Hockey Stick"
Has the “hockey stick” graph been discredited?
Most Comprehensive Paleoclimate Reconstruction Confirms Hockey Stick
What evidence is there for the hockey stick?
bripat9643
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Your post is a classic example of what is known as the ad hominem fallacy. You're attacking the person rather than the argument. Unfortunately for you delusions, it has been proved beyond almost any reasonable doubt that the methods Mann used were invalid. Here is just a small portion of that proof:
The rise and fall of the Hockey Stick
Eventually a US senate committee of inquiry was set up under the chairmanship of Edward Wegman a highly respected Professor of mathematics and statistics and in 2006 his report was published. You can download it here.
The report examined the background to Mann’s Hockey Stick paper, the paper itself, the critique of it by McIntyre and McKitrick and took evidence from all the key players. Interestingly Wegman’s committee commissioned some original research into how the small world of climatology actually worked. The study of the social networking of the paleoclimatology world showed how closed it was and how often a small group of scientists both co-wrote and peer reviewed each others papers. For work that depended so much on making statistical claims about trends it was noted that it was surprising that no statisticians ever seemed to be involved in either the research work itself or its peer review.
The key finding in the WEgman Report was that “Our committee believes that the assessments that the decade of the 1990s was the hottest decade in a millennium and that 1998 was the hottest year in a millennium cannot be supported by the MBH98/99 [the technical name of Mann’s original Hockey Stick paper]”
The other conclusions of the Wegman Report are also very interesting; It listed the following conclusions:
Conclusion 1. The politicization of academic scholarly work leads to confusing public debates. Scholarly papers published in peer reviewed journals are considered the archival record of research. There is usually no requirement to archive supplemental material such as code and data. Consequently, the supplementary material for academic work is often poorly documented and archived and is not sufficiently robust to withstand intense public debate. In the present example there was too much reliance on peer review, which seemed not to be sufficiently independent.
Conclusion 2. Sharing of research materials, data, and results is haphazard and often grudgingly done. We were especially struck by Dr. Mann’s insistence that the code he developed was his intellectual property and that he could legally hold it personally without disclosing it to peers. When code and data are not shared and methodology is not fully disclosed, peers do not have the ability to replicate the work and thus independent verification is impossible.
Conclusion 3. As statisticians, we were struck by the isolation of communities such as the paleoclimate community that rely heavily on statistical methods, yet do not seem to be interacting with the mainstream statistical community. The public policy implications of this debate are financially staggering and yet apparently no independent statistical expertise was sought or used.
Conclusion 4. While the paleoclimate reconstruction has gathered much publicity because it reinforces a policy agenda, it does not provide insight and understanding of the physical mechanisms of climate change except to the extent that tree ring, ice cores and such give physical evidence such as the prevalence of green-house gases. What is needed is deeper understanding of the physical mechanisms of climate change.
easyt65
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'I find your ignorance a threat to my children and theirs. I intend to correct you and everyone else who spouts the dangerous bullshit you do. Get used to it. And if all you've got is to call me a Nazi, be prepared to lose and to lose badly."
Funny YOU should mention Nazis, while Liberals are discussing outlawing thought opposed to their own, banning books that teach opposing science/ideas, demonizing freedom of Christianity (while defending Islam), and engaging in violence against their political 'enemies'....
THAT is the REAL threat to this nation, our freedom, and all of oyr children, even more so than your partisan ignorance
Funny YOU should mention Nazis, while Liberals are discussing outlawing thought opposed to their own, banning books that teach opposing science/ideas, demonizing freedom of Christianity (while defending Islam), and engaging in violence against their political 'enemies'....
THAT is the REAL threat to this nation, our freedom, and all of oyr children, even more so than your partisan ignorance
RollingThunder
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Wrong again, little retard! My "attack" was on your bogus, anti-science, fossil-fuel-industry-stooge source for your fraudulent attack on sound, well confirmed science.
And you ignore all of the scientific confirmation of the hockey stick graph that I posted because it destroys your precious denier cult myths and dogmas.
That's actually one of YOUR "delusions", brittlepatsy.
In the real world, Dr. mann's graph has been repeatedly confirmed by a number of other scientific studies. As was pointed out in the articles that I cited, that you were too stupid to even look at....
Novel Analysis Confirms Climate "Hockey Stick" Graph
Myth vs. Fact Regarding the "Hockey Stick"
Has the “hockey stick” graph been discredited?
Most Comprehensive Paleoclimate Reconstruction Confirms Hockey Stick
What evidence is there for the hockey stick?
LOLOLOLOL....and the denier cult retard once again imagines that an anonymous blog full of ignorant bullshit is 'scientific evidence'.
Too bad you are so severely retarded, brittlepatsy. And so ideologically insane. And so extremely gullible!
RollingThunder
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Your rightwingnut delusional insanity is utterly pathetic, easytorefute.
bripat9643
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You're so-called "confirmation" are just instances where one of Mann's cronies used the same invalid methods and the same invalid data to produce a similar result. MCIntrye has deconstructed each one of these "confirmations" on his website, climateaudit.org. Thousands of people have claim to have invented a perpetual motion machine. Does that mean perpetual motion machines are possible? No.
This argument is known as the appeal to authority or the argument from popularity. Both are logical fallacies. The only way to prove Mann's Hokey Stick is valid is to demonstrate his data and his methods are correct, but both have serious problems which have been explained in many locations but especially at climateaudit.org.
That's actually one of YOUR "delusions", brittlepatsy.
In the real world, Dr. mann's graph has been repeatedly confirmed by a number of other scientific studies. As was pointed out in the articles that I cited, that you were too stupid to even look at....[/QUOTE]
These other "studies" are no more scientific that Mann's original study. They have all been debunked and discredited.
It doesn't matter who authored the blog. Your belief that it does is just another variation of the ad hominem fallacy, or perhaps the appeal to authority.
Anyone who defends Mann's Hockey Stick has only proven that he's a scientific ignoramus and probably has a room temperature I.Q.
RollingThunder
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Oh yeah, brittlepatsy, here's the actual facts on your fraudulent 'Wegman Report' that you denier cult dingbats take as gospel....
Wegman Report
RationalWiki
The Wegman Report (14 July, 2006) (officially the Committee on Energy and Commerce Report) was a report on the "hockey stick" graph produced by a commission headed by statistician Edward Wegman. It is now remembered as the epitome of global warming denier stupidity, in terms of both its factual errors and its college freshman-level plagiarism from textbooks and Wikipedia.
Keep going!
After notorious deniers Steve McIntyre and Ross McKitrick published a paper in Geophysical Research Letters criticizing Michael Mann et al.'s reconstruction of global temperatures that led to the hockey stick graph, the scientific community reconfirmed Mann's analysis with similar data from independent studies.[1] The denier community would not stand for this absurd science stuff, so they decided to launch a second attack on the hockey stick.
In 2006, Republican US Representatives Joe Barton and Ed Whitfield commissioned Wegman to produce a study discrediting the hockey stick. Totally ignoring any of the independent lines of research backing up Mann, Wegman went back and used McIntyre and McKitrick's shoddy models (coloquially referred to as "M&M," candies included) to claim that Mann had just made up the hockey stick. By ignoring the other lines of research and using algorithms that were intended to cherry-pick data to spit out a non-hockey stick shaped graph, Wegman produced a "refutation" of Mann's work. Of course, Wegman never submitted his "research" for peer review. The report went straight to the desks of Barton and Whitfield without any vetting besides some "review" by Wegman's colleagues. The Wegman Report was then used as "definitive evidence" by Republicans in Climategate hearings that Mann and his colleagues were guilty of scientific fraud. Never mind that Wegman's work had already been debunked by this point.
In November of 2010, the story broke that a good deal of the report had been copy-pasted from Wikipedia and some old textbooks, one of which was authored by Mann's colleague Raymond Bradley.[2] George Mason University dragged its feet in investigating charges of plagiarism and misconduct. The delay led to a scathing editorial in Nature stating that "long misconduct investigations do not serve anyone, except perhaps university public relations departments that might hope everyone will have forgotten about a case by the time it wraps up."[3]
No more gas
In 2008, Wegman submitted a modified version of the report to the journal Computational Statistics and Data Analysis. In an egregious case of "pal review," the journal's editor accepted the paper six days after submission, apparently on his own say-so without sending it out for standard peer review. The modified version dropped the climate-related material, leaving only a "social network analysis." The goal of this "analysis" seemed to be to reveal the secret warmist cabal controlling climate science. In reality, all it revealed was that Mann had written other papers with his co-authors.
Wegman apparently forgot that there are things you can get away with in politics that will get you in very hot water in the scientific world, one of those being to copy-and-paste without attribution. In 2011, the journal retracted the paper and apologized for not having detected the plagiarism earlier.[4][5][6] Keeping it classy, Wegman blamed this cock-up on one of his grad students.[7]
bripat9643
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so your entire criticism of the Wegman report is that some of it was plagiarized? Was there any claim that the plagiarized portion was incorrect?
Here we have a well know example of a classic leftwing propaganda technique: Find some small piece of an argument to attack, and then harp on that piece with a megaphone. You totally ignore the big issue of whether the larger argument is correct.
Furthermore, there's the National Academy of Sciences report:
THE HOCKEY SCHTICK: There He Goes Again: Mann Claims His Hockey Stick was Affirmed by the NAS
1. The NAS indicated that the hockey stick method systematically underestimated the uncertainties in the data (p. 107).
2. In subtle wording, the NAS agreed with the M&M assertion that the hockey stick had no statistical significance, and was no more informative about the distant past than a table of random numbers. The NAS found that Mann's methods had no validation (CE) skill significantly different from zero. In the past, however, it has always been claimed that the method has a significant nonzero validation skill. Methods without a validation skill are usually considered useless. Mann’s data set does not have enough information to verify its ‘skill’ at resolving the past, and has such wide uncertainty bounds as to be no better than the simple mean of the data (p. 91). M&M said that the appearance of significance was created by ignoring all but one type of test score, thereby failing to quantify all the relevant uncertainties. The NAS agreed (p. 110), but, again, did so in subtle wording.
3. M&M argued that the hockey stick relied for its shape on the inclusion of a small set of invalid proxy data (called bristlecone, or “strip-bark” records). If they are removed, the conclusion that the 20th century is unusually warm compared to the pre-1450 interval is reversed. Hence the conclusion of unique late 20th century warmth is not robust—in other word it does not hold up under minor variations in data or methods. The NAS panel agreed, saying Mann’s results are “strongly dependent” on the strip-bark data (pp. 106-107), and they went further, warning that strip-bark data should not be used in this type of research (p. 50).
4. The NAS said " Mann et al. used a type of principal component analysis that tends to bias the shape of the reconstructions", i.e. produce hockey sticks from baseball statistics, telephone book numbers, and monte carlo random numbers.
5. The NAS said Mann downplayed the "uncertainties of the published reconstructions...Even less confidence can be placed in the original conclusions by Mann et al. (1999) that ‘the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium.’
1. The NAS indicated that the hockey stick method systematically underestimated the uncertainties in the data (p. 107).
2. In subtle wording, the NAS agreed with the M&M assertion that the hockey stick had no statistical significance, and was no more informative about the distant past than a table of random numbers. The NAS found that Mann's methods had no validation (CE) skill significantly different from zero. In the past, however, it has always been claimed that the method has a significant nonzero validation skill. Methods without a validation skill are usually considered useless. Mann’s data set does not have enough information to verify its ‘skill’ at resolving the past, and has such wide uncertainty bounds as to be no better than the simple mean of the data (p. 91). M&M said that the appearance of significance was created by ignoring all but one type of test score, thereby failing to quantify all the relevant uncertainties. The NAS agreed (p. 110), but, again, did so in subtle wording.
3. M&M argued that the hockey stick relied for its shape on the inclusion of a small set of invalid proxy data (called bristlecone, or “strip-bark” records). If they are removed, the conclusion that the 20th century is unusually warm compared to the pre-1450 interval is reversed. Hence the conclusion of unique late 20th century warmth is not robust—in other word it does not hold up under minor variations in data or methods. The NAS panel agreed, saying Mann’s results are “strongly dependent” on the strip-bark data (pp. 106-107), and they went further, warning that strip-bark data should not be used in this type of research (p. 50).
4. The NAS said " Mann et al. used a type of principal component analysis that tends to bias the shape of the reconstructions", i.e. produce hockey sticks from baseball statistics, telephone book numbers, and monte carlo random numbers.
5. The NAS said Mann downplayed the "uncertainties of the published reconstructions...Even less confidence can be placed in the original conclusions by Mann et al. (1999) that ‘the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium.’
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RollingThunder
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Nope! Too bad you're too goddamn stupid to read what is in front of you, brittlepatsy.
Totally ignoring any of the independent lines of research backing up Mann, Wegman went back and used McIntyre and McKitrick's shoddy models to claim that Mann had just made up the hockey stick. By ignoring the other lines of research and using algorithms that were intended to cherry-pick data to spit out a non-hockey stick shaped graph, Wegman produced a "refutation" of Mann's work. Of course, Wegman never submitted his "research" for peer review.
Wuwei
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All about debate? Have you seen some of the debates on this forum? Avid deniers have screwed up ideas of the laws of physics and don't believe in basic tenets like quantum mechanics, and radiation physics. It is hard to be open to ideas of those who are anti-science and can only guess what science actually is. They put scientific words in sentences that make absolutely no sense. Many of the more thoughtful folks here have kept up long patient dialogues with those who can't understand even simple scientific issues. Debating of that kind is impossible.
bripat9643
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That's an absolute distortion of what the Wegman report said. I quoted you what it said. What you posted doesn't resemble it in any way. For example, M & M never produced any "models." They simply criticized the statistical methods used in Mann's model. No one has successfully refuted these criticism. The Wegman report agreed that the statistical methods used are invalid. When tested against totally random data, they still produced a hockey stick. That alone is irrefutable proof that Mann's results are pure manure.
You're just a lying douche bag.
From "Surface Temperature Reconstructions for the Last 2,000 Years" [the NAS document referenced] by the Board on Atmospheric Sciences and Climate, Division of Earth and Life Studies, National Research Council, of the National Academies of Science
PREFACE
This committee was asked to describe and assess the state of scientific efforts to reconstruct surface temperature records for the Earth over approximately the last 2,000 years. (The full Statement of Task appears in Appendix A.) Normally, a technical issue such as surface temperature reconstructions might not generate widespread attention, but this case brings interesting lessons about how science works and how science, especially climate science, is communicated to policy makers and the public. The debate began in 1998 when a paper by Michael Mann, Raymond Bradley, and Malcolm Hughes was published in the journal Nature. The authors used a new methodology to combine data from a number of sources to estimate temperatures in the Northern Hemisphere for the last six centuries and later for the last 1,000 years. This research received wide attention, in part because it was illustrated with a simple graphic, the so-called hockey stick curve, that many interpreted as definitive evidence of anthropogenic causes of recent climate change. The research was given prominence in the 2001 report of the Intergovernmental Panel on Climate Change and then was picked up by many in the wider science community and by the popular media. Science is a process of exploration of ideas—hypotheses are proposed and research is conducted to investigate. Other scientists work on the issue, producing supporting or negating evidence, and each hypothesis either survives for another round, evolves into other ideas, or is proven false and rejected. In the case of the hockey stick, the scientific process has proceeded for the last few years with many researchers testing and debating the results. Critics of the original papers have argued that the statistical methods were flawed, that the choice of data was biased, and that the data and procedures used were not shared so others could verify the work. This report is an opportunity to examine the strengths and limitations of surface temperature reconstructions and the role that they play in improving our understanding of climate. The reconstruction produced by Dr. Mann and his colleagues was just one step in a long process of research, and it is not (as sometimes presented) a clinching argument for anthropogenic global warming, but rather one of many independent lines of research on global climate change.
Using multiple types of proxy data to infer temperature time series over large geographic regions is a relatively new area of scientific research, although it builds upon the considerable progress that has been made in deducing past temperature variations at single sites and local regions. Surface temperature reconstructions often combine data from a number of specialized disciplines, and few individuals have expertise in all aspects of the work. The procedures for dealing with these data are evolving—there is no one “right” way to proceed. It is my opinion that this field is progressing in a healthy manner. As in all scientific endeavors, research reported in the scientific literature is often “work in progress” aimed at other investigators, not always to be taken as individual calls for action in the policy community. With this as context, the committee considered the voluminous literature pertinent to its charge and received briefings and written contributions from more than two dozen people. We have organized our report knowing that we have at least two different audiences—the science community and the policy community. The principal conclusions of the committee are listed in the Summary and explained in the Overview using nontechnical language. More extensive technical justifications for the committee’s conclusions, including references, are presented in the chapters that follow. Finally, let me thank the members of the Committee on Surface Temperature Reconstructions for the Last 2,000 Years. The committee worked tirelessly to assess the status of this field of research so that the public can see exactly what is involved, what we currently know about it, and what the prospects are for improving our understanding. We have tried to make clear how this piece of the climate puzzle fits into the broader discussions about global climate change.
Gerald R. North, Chair
Committee on Surface Temperature Reconstructions for the Last 2,000 Years
...
STRENGTHS AND LIMITATIONS OF LARGE-SCALE SURFACE TEMPERATURE RECONSTRUCTIONS
The committee identified the following key strengths of large-scale surface temperature reconstructions:
• Large-scale surface temperature reconstructions are based on proxy records that are meaningful recorders of environmental variables. The connections between proxy records and environmental variables are well justified in terms of physical, chemical, and biological processes.
• Tree rings, the dominant data source in many reconstructions, are derived from regional networks with extensive replication, and they are a good indicator of environmental variables at the regional scale. Regional tree ring series are highly correlated with measures of temperature and drought. These connections have a convincing biophysical basis related to tree physiology and growing-season climate. Temperature dominates in some environments and precipitation in others, as is consistent with ecological expectations of limits to growth (Fritts 1976).
• The same general temperature trends emerge from different reconstructions. Some reconstructions focus on temperature-dependent trees and use wood density measures (Briffa et al. 2002), others focus on temperature-dependent trees and use ring widths (D’Arrigo et al. 2006), and still others incorporate extensive data from precipitation-dependent trees and ice cores and use climate field correlations to derive temperature (Rutherford et al. 2005). One reconstruction does not use tree ring networks at all for century-scale and longer changes, but instead relies on a combination of geochemical and sedimentary proxies (Moberg et al. 2005b).
• Temperature records from about A.D. 1600 to the present derived from largescale surface temperature reconstructions are consistent with other sources of temperature information for the period, including borehole temperatures and glacier length records.
• Prior to about 1600, information is sparser and the pattern of change is not necessarily synchronous, but periods of medieval warmth are seen in a number of diverse records, including historical information from Europe and Asia; cave deposits; marine and lake sediments; and ice cores from Greenland, Ellesmere Island, Tibet, and the equatorial Andes. Many challenges remain as research progresses to use large-scale surface temperature reconstructions to learn about climate history (Hughes 2002, Rutherford et al. 2005, D’Arrigo et al. 2006). There are two major structural challenges. First, the amount of high-quality proxy data available for analysis decreases markedly as one moves back in time. The great richness of tree ring network data available for 1700, for example, is largely depleted by A.D. 1000. Large-scale 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. Further research should be aimed at providing independent checks on reconstructions using borehole temperatures, glacier length records, and other proxies. The role of statistical methods is not trivial. Each individual proxy provides a record of environmental change, but the process of combining these environmental signals into a large-scale spatially averaged temperature requires statistical evaluation. Even if a single proxy is a perfect recorder of the local environment, the question remains of whether the local environments are adequately or representatively sampling the large-scale temperature field. In addition, most proxy records lack the annual chronological precision found in tree ring data; the typical dating error might be 1–5 percent of the age of the sample for annually layered records such as lake varves and 5– 10 percent for radiometrically dated records spanning the last 2,000 years. The committee identified the following limitations of large-scale surface temperature reconstructions that would benefit from further research:
• There are very few degrees of freedom in validations of the reconstructed temperature averaged over periods of decades and longer. The RE validation metric used by Mann et al. (1998, 1999) is a minimum requirement, but the committee questions whether any single statistic can provide a definitive indication of the uncertainty inherent in the reconstruction. Demonstrating performance for the higher-frequency component (e.g., by calculating the CE statistic) would increase confidence but still would not fully address the issue of evaluating the reconstruction’s ability to capture temperature variations on decadal-to-centennial timescales.
• Using proxies sensitive to hydrologic variables (including moisture-sensitive trees and isotopes in tropical ice cores and speleothems) to take advantage of observed correlations with surface temperature could lead to problems and should be done only if the proxy–temperature relationship has climatological justification.
• The observed discrepancy between some tree ring variables that are thought to be sensitive to temperature and the temperature changes observed in the late 20th century (Jacoby and D’Arrigo 1995, Briffa et al. 1998) reduces confidence that the correlation between these proxies and temperature has been consistent over time. Future work is needed to understand the cause of this “divergence,” which for now is considered unique to the 20th century and to areas north of 55°N (Cook et al. 2004).
• For tree ring chronologies, the process of removing biological trends from ringwidth data potentially obscures information on long-term changes in climate.
• Temperature reconstructions for periods before about A.D. 1600 are based on proxies from a limited number of geographic regions, and some reconstructions are not robust with respect to the removal of proxy records from individual regions (see, e.g., Wahl and Ammann in press). Because the data are so limited, different large-scale reconstructions are sometimes based on the same datasets and thus cannot be considered as completely independent.
• Reconstructions of low-frequency variations in the temperature record that make use of proxies other than tree rings (Moberg et al. 2005b) are limited by the small number of available records, by dating uncertainties, and by the sensitivity of many proxies to hydrologic variables as well as to temperature. These data gaps highlight the need for continued coordinated efforts to collect proxy data over broad geographic regions. Specifically concerning the reconstructed temperature variability over short time periods (year-to-decade scale), the committee identified the following as limitations that would benefit from further research:
• Large-scale surface temperature reconstructions demonstrate very limited statistical skill (e.g., using the CE statistic) for proxy sets before the 19th century (Rutherford et al. 2005, Wahl and Ammann in press). Published information, although limited, also suggests that these statistics are sensitive to the inclusion of small subsets of the data. Some of the more regionally focused reconstructions (D’Arrigo et al. 2006) have better demonstrated skill back to the 16th century or so, and possibly earlier. To improve the skill of reconstructions, more data need to be collected and possibly new assimilation methods developed.
• Accurately inferring the absolute values of temperature for single years and decades from proxies sensitive to variability at this timescale requires accurate reconstruction of the longer term mean.
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ibid
OVERALL FINDINGS AND CONCLUSIONS
Based on its deliberations and the materials presented in Chapters 1–11 and elsewhere, the committee draws the following overall conclusions regarding large-scale surface temperature reconstructions for the last 2,000 years:
• The instrumentally measured warming of about 0.6°C during the 20th century is also reflected in borehole temperature measurements, the retreat of glaciers, and other observational evidence, and can be simulated with climate models.
• Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium, including relatively warm conditions centered around A.D. 1000 (identified by some as the “Medieval Warm Period”) and a relatively cold period (or “Little Ice Age”) centered around 1700. The existence of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence including ice cores, tree rings, borehole temperatures, glacier length records, and historical documents. Evidence for regional warmth during medieval times can be found in a diverse but more limited set of records including ice cores, tree rings, marine sediments, and historical sources from Europe and Asia, but the exact timing and duration of warm periods may have varied from region to region, and the magnitude and geographic extent of the warmth are uncertain.
• 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.
• Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified.
• Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.
OVERALL FINDINGS AND CONCLUSIONS
Based on its deliberations and the materials presented in Chapters 1–11 and elsewhere, the committee draws the following overall conclusions regarding large-scale surface temperature reconstructions for the last 2,000 years:
• The instrumentally measured warming of about 0.6°C during the 20th century is also reflected in borehole temperature measurements, the retreat of glaciers, and other observational evidence, and can be simulated with climate models.
• Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium, including relatively warm conditions centered around A.D. 1000 (identified by some as the “Medieval Warm Period”) and a relatively cold period (or “Little Ice Age”) centered around 1700. The existence of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence including ice cores, tree rings, borehole temperatures, glacier length records, and historical documents. Evidence for regional warmth during medieval times can be found in a diverse but more limited set of records including ice cores, tree rings, marine sediments, and historical sources from Europe and Asia, but the exact timing and duration of warm periods may have varied from region to region, and the magnitude and geographic extent of the warmth are uncertain.
• 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.
• Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified.
• Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.
I'm sorry, but I've kinda reached my quota of fools and idiots to chat with around here. Buh-bye.
bripat9643
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NAS Panel Report
The early rumors on the NAS Panel was that it was “two handed” -on the one hand,…, on the other hand, … with something for everyone. I’d characterize it more as schizophrenic. It’s got two completely distinct personalities. On the one hand, they pretty much concede that every criticism of MBH is correct. They disown MBH claims to statistical skill for individual decades and especially individual years.
However, they nevertheless conclude that it is “plausible” – whatever that means – that the “Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium”. Here, the devil is in the details, as the other studies relied on for this conclusion themselves suffer from the methodological and data problems conceded by the panel. The panel recommendations on methodology are very important; when applied to MBH and the other studies (as they will be in short order), it is my view that they will have major impact and little will be left standing from the cited multiproxy studies. You can find the report and the recorded briefing here.
Update: Eduardo Zorita’s take posted up below was:
in my opinion the Panel adopted the most critical position to MBH nowadays possible. I agree with you that it is in many parts ambivalent and some parts are inconsistent with others. It would have been unrealistic to expect a report with a summary stating that MBH98 and MBH99 were wrong (and therefore the IPC TAR had serious problems) when the Fourth Report is in the making. I was indeed surprised by the extensive and deep criticism of the MBH methodology in Chapters 9 and 11 .
I thought that the tone of the question period showed that some reporters were pretty unsettled – there were questions about the "over-selling" of MBH with the panel taking pains to suggest that IPCC would be repsonsible rather than MBH (conveniently omitting that Mann was section author of the section promoting MBH and in his capacity of IPCC author, ratcheted up the statistical claims) ; there was discussion of what "plausible" meant, with a reporter wondering if this was "damning with faint praise".
Overview
In the preface, North summarizes the criticisms:
Critics of the original papers have argued that the statistical methods were flawed, that the choice of data was biased, and that the data and procedures used were not shared so others could verify the work. (ix)
He left out the criticism that concerned the Barton Committee and launched the entire matter – that adverse results were withheld or even misrepresented. In its text, the panel concedes every one of our criticisms of the statistical methods, providing some useful new guidelines. However, they do not apply these guidelines to either to MBH or to other studies.
They do not clearly discuss biased data selection, but concede that strip-bark samples, such as bristlecones, which we had strongly criticized, “should be avoided in temperature reconstructions”. However, they then proceed to rely on studies that rely on strip-bark bristlecones (and foxtails) and even the criticized MBH PC1 (which is even illustrated in an alter ego in Figure 11-2.)
They do not grasp the nettle of reporting on previous data and method availability, but do endorse the principle that sharing data and methods is a good thing in paleoclimate. Schizophrenically, their graphics and conclusions rely heavily on studies where data and/or methods are not available.
They stay well away from grasping the nettle of providing an opinion on whether adverse MBH results were withheld or misrepresented. However, they report factual findings that MBH failed cross-validation tests and was not robust to presence/absence of all dendroclimatic indicators, contrary to prior claims of Mann et al.
Flawed Statistical Methods
On p 107, the panel reports our two principal criticisms of MBH statistical methods, finding
“Some of these criticisms are more relevant than others, but taken together, they are an important aspect of a more general finding of this committee, which is that uncertainties of the published reconstructions have been underestimated. Methods for evaluation of uncertainties are discussed in Chapter 9.”
Chapter 9 then sets out some important guidelines, dealing with several critical issues that we raised in our presentation: that it is inadequate to just consider one statistic in assessing a statistical model; that confidence interval calculations should use verification period residuals rather than calibration period residuals; that autocorrelation should be considered in calculating confidence intervals.
The panel’s schizophrenia is very evident here, because, having set out these methods, they do not apply these methods to the models in front of them. D’Arrigo et al 2006 report that their model does not verify after 1985 during the period of warming of most direct interest. The panel was aware of this, the matter came up in presentations, but did not directly report or discuss this.
The panel recommends the use of a Durbin-Watson statistic for calibration, but do not report the failure of the various models under this statistic, even though they were aware of this failure. (We presented this information to them in our presentation.
Choice of Data
If you try to trace how the panel considered criticisms about biases in the choice of data by searching the word “bias”, you will find that the panel simply did not report on the matter. The closest is a mention on p. 106 to our criticism of the “selection of proxies, especially the bristlecone pine data, used in some of the original temperature reconstruction studies”, which they promise to “explore briefly in the remainder of the chapter”, a promise which is unfulfilled.
They state (p. 107) that
“several recent research efforts have explored how the selection of proxies affects surface temperature reconstructions”
but then, in the next sentence, go on to discuss a totally unrelated study and never return to the issue. They agree (p 107) that
” 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.”
(“Data from the Great Basin region” is code here for bristlecones)
They go on to state that
“…such issues of robustness need to be taken into account in estimates of statistical uncertainties.”
However, in their statistical chapter, they do not address how such robustness issues should be “taken into account” in the estimation of statistical uncertainty, although we may presume that it would increase them.
We note that the panel had previously (p. 86) agreed entirely with our criticism of Mann’s principal components method, concluding that the “baseline with respect to which anomalies are calculated can influence principal components in unanticipated ways” and stated (p. 106) that the Mann method is “not recommended”.
They linked this criticism (p 107) to the overweighting of bristlecones and noted that “the more important aspect of this criticism is the issue of robustness with respect to the choice of proxies used in the reconstruction”, a point with which we agree. Indeed, it is a point specifically made in McIntyre and McKitrick [E&E 2005], a publication not cited by the panel.
In their section on tree rings (p. 50), they had previously discussed bristlecones, citing many references that we provided them. They report that strip-bark bristlecones are “sensitive to higher atmospheric CO2 concentrations” and state that “‘strip-bark’ samples should be avoided for temperature reconstructions” – an even stronger position than calling for non-robustness to be “taken into account” in some method that they do not describe.
Here’s where their typical schizophrenia sets in.
In order to decide on the “plausibility” of late 20th century uniqueness, their key graphics (Figure O-5, S-1, 11-1, 11-2) use reconstructions from Mann and Jones 2003, Hegerl et al 2006, Esper et al 2002 and Moberg et al 2005 and a collection of proxies from Osborn and Briffa 2006.
Remarkably, Mann’s “not recommended” PC1 using the strip-bark bristlecones that “should not be used” crops up at the very top of Figure 11-2, innocuously labeled “W.USA (regional)”. For good measure, another strip-bark foxtail (interrelated to bristlecones) series occurs in Figure 11-2 labeled this time “W.USA (Boreal/Upperwright)”. Thus the most disputed series make up 2 of the 14 series in Osborn and Briffa 2006 and, not coincidentally, the two most HS-shaped series. In the graphics illustrating a supposed generic similarity, Mann and Jones 2003, of course, uses Mann’s PC1.
At this point, I do not know for sure what sites are in Hegerl et al 2006, as the article itself does not disclose this information. Last fall, when I asked the authors of the then unpublished paper to identify the sites in connection with IPCC peer review, the authors refused and IPCC threatened to expel me as a reviewer if I made a further attempt to obtain data or information from an author of unpublished studies. However, I have reasons to believe that, like Osborn and Briffa, Hegerl et al 2006 will include both Mann’s “not recommended” PC1 and a strip-bark foxtail series, probably the identical series used in Osborn and Briffa 2006. Esper et al 2002 includes two strip-bark foxtail series: the Boreal and Upper Wright sites, which are combined as one average in Osborn and Briffa 2006 (and probably Hegerl et al 2006). Moberg et al 2005 includes 3 different bristlecone sites (although, in this case, unlike the others, they are not the “active ingredient”).
Thus, 3 of the 4 illustrated reconstructions as well as the key Figure 11-2 all schizophrenically rely on proxies not meeting criteria set out elsewhere in the report.
Yamal Substitution
While the panel mentions our concern over biased choice of series, they did not discuss an egregious situation that we presented to them. In 1998, updated sampling at the Polar Urals site resulted in a series with elevated MWP values, as opposed to previous results used in earlier multiproxy studies which had low MWP values at this site. At about the same time, a site about 100 miles away (Yamal) was developed which had a very pronounced HS-shape. This site was substituted for the Polar Urals site in all but one multiproxy reconstruction.
It is used for example in Osborn and Briffa 2006 -see Figure 11-2 where it is labeled “NW Russia (Yamal)”. If the Polar Urals update (in the Esper et al 2002) version is used instead of the Yamal series, then the conclusions of the relative levels of the MWP and modern periods are altered in the Briffa 2000 reconstruction (www.climateaudit.org) and almost certainly in the D’Arrigo et al 2006 reconstruction which has a virtually identical roster.
The panel noted in passing that results were sensitive in these small subsets, but did not squarely address the issue and inconsistently stated the opposite on one occasion in the report.
Data Availability
Despite a specific request from the Boehlert committee to comment on availability of data, we predicted that the panel would merely espouse generalities here and this has proved to be the case.
They did not discuss either problems with Mann et al or other studies and merely espoused a few sentences of platitudes encouraging data sharing, platitudes previously expressed by a previous NAS Panel in 1995, in a section entitled: What Comments Can Be Made On The Value Of Exchanging Information And Data?
They stated platitudinously:
Our view is that all research benefits from full and open access to published datasets and that a clear explanation of analytical methods is mandatory. Peers should have access to the information needed to reproduce published results, so that increased confidence in the outcome of the study can be generated inside and outside the scientific community. Other committees and organizations have produced an extensive body of literature on the importance of open access to scientific data and on the related guidelines for data archiving and data access (e.g., NRC 1995). Paleoclimate research would benefit if individual researchers, professional societies, journal editors, and funding agencies continued
Obviously, we do not disagree with this. In this context, we observe that we have attempted to obtain data for both D’Arrigo et al 2006 and Hegerl et al 2006, both cited and relied on by the panel and were unsuccessful.
In the last few months, a limited amount of measurement data has been archived by the D’Arrigo group, but only a fraction.
With respect to Osborn and Briffa, Science has refused to require the authors to disclose the measurement data for Yamal, Tornetrask, Taimyr and Alberta sites on the grounds that the earlier data was from Briffa (2000). Osborn and Briffa have refused to provide the earlier measurement data. Even the identity of the sites used in the Briffa density study remain undisclosed and the authors have refused several requests to identify the sites.
The panel cites ice core data from Thompson. Prior to our initiative in 2004, no information had been archived from any of the Himalayan sites, including core drilled in 1987. A cursory archive was provided in 2004, in which no chemical information was provided and no sample details.
Since several different, inconsistent and unreconciled “grey” versions of the Dunde series were floating around, there is a pressing need to examine individual sample information. Again, we have been unsuccessful in attempts with Science magazine to get access to detailed information.
We will of course be asking the National Academy of Sciences to provide us with the data which they have relied on and which has been previously refused to us.
Withholding Adverse Results
The questions that launched the inquiry were the original Barton questions to Mann et al. about the withholding of adverse results, and, in particular, the withholding of adverse verification statistics (the r2 statistic) and the misrepresentation of robustness to the presence/absence of “all” dendroclimatic indicators, let alone bristlecones.
One of the panelists asked Mann about the verification r2 statistic: Mann said that “he did not calculate the verification r2 statistic – that would be a silly and incorrect thing to do”. The statement that the verification r2 was not calculated was untrue and the panel had evidence of this. The panel did not agree that this would be “silly and incorrect” since they endorsed the use of the closely related CE statistic for estimation of confidence intervals.
However, they did not grasp the nettle of whether the adverse verification r2 statistics had been calculated and withheld. They did report that the MBH reconstruction had extremely low r2 and CE values prior to the instrumental period, citing Wahl and Ammann (but not us, although we had originally made the point.) They also acknowledged that the MBH reconstruction was “strongly dependent” on bristlecones, a point obviously inconsistent with previous MBH claims of “robustness” to the presence/absence of all dendroclimatic indicators.
Again they do not grasp the nettle of trying to reconcile the facts to the prior claims.
Other Points
The report is long and interesting point and obviously this is a very quick comment. Here are a few other points caught my eye.
We commended Naurzbaev et al 2004 (including MBH coauthor Hughes) as an excellent example of a strategy for millennial climate reconstruction.
The panel commended the strategy of this study as follows:
An especially suitable strategy to minimize confounding effects is to sample sites along ecological gradients, such as elevation or latitude (Fritts and Swetnam 1989, Bugmann 1996). For example, (Naurzbaev et al. 2004) selected sites along latitudinal (from 55 to 72°N) and elevational (from 1120 to 2350 m above sea level) transects, and used the parameters of the Regional Curve Standardization to infer climatic influences and past temperature variability.
However, they didn’t report that Naurzbaev’s conclusions from this “especially suitable strategy” was that the MWP was 2-3 deg C warmer than the 20th century or make any attempt to reconcile this finding with the Yamal reconstruction that they display in Figure 11-2.
The "Divergence Problem" falls into the category of a “main area of uncertainty” . It arises because the majority of temperature-sensitive tree ring width "site chronologies" go down in the last half of the 20th century. Cuffey asked the $64 question to D’Arrigo: if tree rings are not picking up late 20th century warmth, how can you be certain that they might not have had a similar response to a comparable warm period in the past (e.g. in the Medieval Warm Period). The NAS panel acknowledges the “divergence problem” (p 47, 110), but doesn’t summarize it as one of the “major areas of uncertainty”.
They report:
(111) The observed discrepancy between some tree ring variables that are thought to be sensitive to temperature and the temperature changes observed in the late 20th century (Jacoby and D’Arrigo 1995, Briffa et al. 1998) reduces confidence that the correlation between these proxies and temperature has been consistent over time. Future work is needed to understand the cause of this “divergence,” which for now is considered unique to the 20th century and to areas north of 55°N (Cook et al. 2004)… also that the difference between northern and southern sites found after about 1950 is unprecedented since at least A.D. 900.
Relying on the “southern sites” for firm ground here is going to be difficult as these “southern sites” in Cook et al 2004 include the bristlecones.
Here Bunn et al 2003 (as Graybill and Idso 1993 had before him) found a different “divergence” problem – between strip-bark and full-bark sites, which is considered to be related to fertilization. If one peels beneath the surface of Cook et al 2004, one will find that strip-bark sites – which are “not to be used” as a temperature proxy – have been relied upon to supposedly reconcile the “divergence problem”.
More frustratingly, the panel failed to report the impact of the “divergence problem” on proxy reconstructions in the warm 1980s, including the validation failure of D’Arrigo et al.
Conclusion
It will take a while to assess the impact of this study. It’s long and interesting. One thing that appears certain: far from ending the controversy over millennial climate studies, it looks to me like it is merely one more step.
bripat9643
Diamond Member
- Apr 1, 2011
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It's not due to human GHG emissions. The earth has been warming since the end of the Little Ice Age.
Papageorgio
The Ultimate Winner
If it was only on this board I would not say a thing. You already have settled the debate in your mind, you aren't open to any discussion as you already labeled deniers as screwed up. You don't want debate, you want silence.
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