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Presentation to the KTH Climate Science Seminar

Stephen McIntyreToronto Ontario

Stockholm, Sweden, Sept. 11, 2006.

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IPCC 1990

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“Get Rid of the MWP”

D. Deming, Science 1995

“With the publication of the article in Science [in 1995], I gained significant credibility in the community of scientists working on climate change. They thought I was one of them, someone who would pervert science in the service of social and political causes. So one of them let his guard down. A major person working in the area of climate change and global warming sent me an astonishing email that said “We have to get rid of the Medieval Warm Period.”

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Warmest Year and Decade

March. 4, 1999. Researchers at the Universities of Massachusetts and Arizona who study global warming have released a report strongly suggesting that the 1990s were the warmest decade of the millennium, with 1998 the warmest year so far… "even the warmer intervals in the reconstruction [for medieval times] pale in comparison with mid-to-late 20th-century temperatures," said Hughes.

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IPCC TAR Spaghetti Graph

Black -MBH98-99; red - Jones, Briffa et al 1998; green -Briffa, Jones et al 2001 – orange- instrumental (Jones)

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Canadian Government 2002

 

“The 20th century was the warmest in the Northern Hemisphere for the past 1000 years and the 1990s the warmest decade on record... The science of climate change has been subjected to international scrutiny, open to all qualified experts, peer review, atmospheric modeling and process studies – Liberal Caucus, Aug. 22, 2002

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How do they know that 1998 was the warmest year of the millennium?

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April 2003 - My First Inquiry Dear Dr. Mann, I have been studying MBH98 and

99. I located datasets for the 13 series used in 99 ... and was interested in locating similar information on the 112 proxies referred to in MBH98… Yours truly, Stephen McIntyre

Dear Mr. McIntyre,  These data are available on an anonymous ftp site we have set up. I've forgotten the exact location…. best regards, Mike Mann

Steve, The proxies aren't actually all in one ftp site (at least not to my knowledge). I can get them together if you give me a few days. … Scott [Rutherford]

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Sept 2003 Inquiry Here is the pcproxy.txt file sent to me last April

by Scott Rutherford at your direction. I wanted to verify that it is the correct file

Owing to numerous demands on my time, I will not be able to respond to further inquiries.Other researchers have successfully implemented our methodology based on the information provided in our articles  [see e.g. Zorita et al [2003]

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McIntyre and McKitrick [2003]

collation errors, unjustifiable truncation or extrapolation of source data, obsolete data, geographical location errors, incorrect calculation of principal components and other quality control defects

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Corrected Version

Mann et. al. 1998

McIntyre and McKitrick [2003]

The extent of errors and defects in the MBH98 data means that the indexes computed from it are unreliable and cannot be used for comparisons between the current climate and that of past centuries, including claims like “temperatures in the latter half of the 20th century were unprecedented”

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Mann: “Wrong Data”“In short, here's what happened: M&M asked an associate of Mann to supply them with the Mann et. al. proxy data in an Excel spreadsheet, even though the raw data is available here. [ftp://holocene.evsc.virginia.edu/pub/MBH98/] An error was made in preparing this Excel file, in which the early series were successively overprinted by later and later series, and this is the data M&M used. .... “

Mann adds: .... The authors had access to the full data, which has been available on a public ftp site for nearly two years. When they noticed, as described in their paper, some signs of problems with the Excel spreadsheet version of the data, one might think that they would have bothered to check the data available on our public ftp site."

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MBH 2003 Response

Difference came from North American PC1 series.

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MM05 #1: Hockeysticks from Random Data

At the newly disclosed FTP site, there was code for one step – the tree ring PC calculations. There was an unreported step in which data was de-centered, accounting for discrepancy. The decentered method also produced hockeysticks from random data.

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MM05 #2: MBH method overweights bristlecone pines – a flawed proxy

Graybill and Idso: “The possibility that changes in climate during the past century might be responsible for the unusual increases in ring width growth of subalpine conifers [bristlecones] was investigated extensively…None of the models are capable of explaining the late 19th to 20th century growth increases.”

Hughes and Funkhouser 2003: bristlecone growth spurt is a “mystery”

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MM05 #3: MBH fails Verification r2 test

MBH98: [RE] is a quite rigorous measure of the similarity between two variables…. For comparison, correlation (r) and squared-correlation (r2) statistics are also determined.

IPCC: MBH reconstruction …had significant skill in independent cross-validation tests

MM05: verification r2 for AD1500 step was ~0 (0.02; CE: -0.24) i.e. no skill.

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The CENSORED File

We discovered that an undocumented directory at Mann’s FTP site entitled “CENSORED” contained calculations without bristlecones. Without the bristlecones, none of the PC series had a hockey stick shape.

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realclimate.org instead of replying in peer-reviewed literature, Mann

and associates launched pre-emptive response to criticisms at newly-created blog realclimate.org

Early posts focussed on attacking us Myth vs. Fact Regarding the "Hockey Stick“ Dummies Guide to the latest 'Hockey Stick' controversy On Yet Another False Claim by McIntyre and McKitrick Peer Review: A Necessary But Not Sufficient Condition

 

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Wall Street Journal, Feb. 14, 2005

Dr. Mann says his busy schedule didn't permit him to respond to "every frivolous note" from nonscientists…

Mr. McIntyre thinks there are more errors but says his audit is limited because he still doesn't know the exact computer code Dr. Mann used to generate the graph. Dr. Mann refuses to release it. "Giving them the algorithm would be giving in to the intimidation tactics that these people are engaged in," he says.

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www.climateaudit.org Candid discussion of multiproxy studies and proxy studies Counter-reporting Over 10,000 hits per day – at this level for over a year Over 800 posts Over 25,000 comments A few experts have written in from time to time – Eduardo Zorita,

Judith Curry, Gerd Bürger… Some very active stats post-docs

 

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Climate Science Reaction Houghton: “Very recently the assertions by McIntyre and

McKitrick (2005a, b) (MM), alluded to in the question (references at end of answer), have been shown by several papers to be largely false in the context of the actual data used by Mann and co-workers.”

KNMI (Holland): As far as science is concerned: since the start of 2005, the points criticised by McIntyre and McKitrick have been mostly refuted in various studies. But no doubt the last word in the hockey stick debate is yet to come

UCAR Press Release: the highly publicized criticisms of

the MBH graph are unfounded. 

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House Energy and Commerce Committee Questions

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Wegman Report 2006Wegman, Chairman of U.S. NAS Committee on Applied Statistics:

“The debate over Dr. Mann's principal components methodology has been going on for nearly three years. When we got involved, there was no evidence that a single issue was resolved or even nearing resolution. Dr. Mann's RealClimate.org website said that all of the Mr. McIntyre and Dr. McKitrick claims had been 'discredited'. UCAR had issued a news release saying that all their claims were 'unfounded'. Mr. McIntyre replied on the ClimateAudit.org website. The climate science community seemed unable to either refute McIntyre's claims or accept them. The situation was ripe for a third-party review of the types that we and Dr. North's NRC panel have done.

 

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Wegman Report 2006

“We found MBH98 and MBH99 to be somewhat obscure and incomplete and the criticisms of MM03/05a/05b to be valid and compelling … our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis.”

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National Academy of Sciences Panel “Schizophrenic”

• “Mann et al. used a type of principal component analysis that tends to bias the shape of the reconstructions … and is not recommended

• ‘strip-bark’ [i.e. bristlecone] samples should be avoided for temperature reconstructions

• McIntyre and McKitrick 2003, 2005a,b) [argue that] the choice of “significance level” for the reduction of error (RE) validation statistic is not appropriate and … that different statistics, specifically the coefficient of efficiency (CE) and the squared correlation (r2), should have been used… they are an important aspect of a more general finding of this committee, which is that uncertainties of the published reconstructions have been underestimated.

BUT

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BUT …

Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. 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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Wahl and Ammann

• Main reply from the “Hockey Team”, often cited as “independent” study

• Ammann was PhD student of Mann and Bradley;• Wahl and Ammann are coauthors in 2005 with Mann;• Argued that errors did not “matter” because if you used

enough principal components, you “got” a similar result; and that you could get a similar results using Mann’s regression method without PCs

• UCAR national press release when submitted said our claims were unfounded;

• Submission to GRL rejected, but submission to Climate Change accepted

• Very influential in climate science circles long before publication

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Verification r2 Statistics (Wahl and Ammann) nearly identical to MM05

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Wahl and Ammann and MM05 agree that “practically” PC methods and bristlecone weighting are equivalent issues. WA: reconstructions without bristlecones lack “climatological meaning”.

Reconstructions under three NOAMER PC variations. Left: with bristlecones; Right – without

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Q.e.d.…

MBH cannot assert 20th century uniqueness based on their data and method because:Reconstruction without bristlecones is

rejected based on failed RE statistics (Wahl and Ammann)

Bristlecones should be avoided in temperature reconstructions (NAS Panel)

q.e.d.

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VZ: bad method doesn’t affect pseudoproxy network; BUT didn’t study robustness. One contaminated HS series can yield hockeystick PC1

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Mann method weights the contaminated series rather than the “signal”

Left – without contamination; right – with one nonclimatic HS series

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Over-fitting plus contamination

                                       Magenta – WA; Black - Two synthetic HS series plus 68 red noise series. Statistical pattern is identical to MBH under WA variation: high RE, high calibration r2; ~0 verification r2; negative CE. Similar examples used in Reply to Huybers.

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Synthetic HS plus red noise networks under WA variation

                                       Magenta – WA; Black - Two synthetic HS series plus 68 red noise series. Statistical pattern is identical to MBH under WA variation: high RE, high calibration r2; ~0 verification r2; negative CE.

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Other Studies: NAS Panel Spaghetti Graph

Mann and Jones 2003 (red); Moberg (maroon); Esper (green) plus addition of Hegerl et al 2006 (gold, 1251 start)

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NAS did not check if other studies used bristleconesQuestion from Stephen McIntyre:

Did the Panel carry out any due diligence to determine whether these proxies [bristlecones] ere used in any of the other studies illustrated in the NRC spaghetti graph?

NorthThere was much discussion of this matter during our deliberations. We did not dissect each and every study in the report to see which trees were used. …The strip-bark forms in the bristlecones do seem to be influenced by the recent rise in CO2 and are therefore not suitable for use in the reconstructions over the last 150 years.

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North’s Texas A&M Seminer

At minute 55 or so, he describes NAS panel operating procedure by saying that they “didn’t do any research”, that they just “took a look at papers”, that they got 12 “people around the table” and “just kind of winged it”

http://www.met.tamu.edu/people/faculty/dessler/NorthH264.mp4

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Many other studies use bristlecones/ foxtails, but NAS did not assess impact

All 4 studies in NAS spaghetti graph and 6 of 7 studies in MWP portion of Wikipedia spaghetti graph, viz,

Crowley and Lowery 2000 (2) Esper et al 2002 (2) Mann and Jones 2003 Moberg et al 2005 (3) Hegerl et al 2006 (2) Osborn and Briffa 2006 (2)

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Medieval-modern levels in Crowley 2000 change without bristlecones

Left: Figure 4 of Crowley (2000) comparing that reconstruction to MBH. Instrumental data has been spliced since 1870.

Right in red – Without bristlecones, horizontal line showing closing level with at least 5 proxies. No instrumental data is spliced.

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Second: The “Divergence” Problemtree ring widths and density decline in late 20th century

Left - Briffa et al 2001 reconstruction (left) from 387 temperature-sensitive sites; right – from Briffa et al 1998: heavy solid – MXD (used in Briffa et al 2001); dashed – RW; thin solid – temperature.

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Plausible explanations - Nonlinear relationship between

temperature and ring widths; water (i.e., drought stress) has become

the limiting factor (see TTHH site chronology –right)

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Truncation of Briffa et al 2001 in IPCC TAR

IPCC truncated the Briffa et al 2001 reconstruction (green) in 1960. Thus no visible “divergence”.

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The untruncated reconstruction has low late 20th century proxy values

Would the untruncated Briffa et al 2001 recon-struction (purple dashed) have raised questions about unanimity?

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Briffa’s “Explanation”

In the absence of a substantiated explanation for the decline, we make the assumption that it is likely to be a response to some kind of recent anthropogenic forcing. On the basis of this assumption, the pre-twentieth century part of the reconstructions can be considered to be free from similar events and thus accurately represent past temperature variability. [Briffa et al. 2002]

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Third: Cherrypicking and Data Snooping

D’Arrigo:

You have to pick cherries if you want to make cherry pie

Esper:if the purpose of removing samples is to enhance a desired signal, the ability to pick and choose which samples to use is an advantage unique to dendroclimatology.

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Two Related Problems

Re-use of proxies invalidates statistical procedures

Bias in choice of series being re-used

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Briffa et al 1995: 1032 was coldest year of the millennium (Polar Urals )

11th century supposedly “cold”, but fewer than 5 cores in the early part of the 11th century. This version for Polar Urals used in MBH99; Jones et al 1998; Crowley and Lowery 2000; Jones and Mann 2004, where it has a material impact lowering 11th century values.

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The Yamal Substitution

1998 update of Polar Urals yielded high MWP values. Briffa 2000 did not report this, but instead presented series from Yamal, 70 miles away (used in all subsequent studies).

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Impact of Yamal substitution on Briffa (2000).

Red shows impact of using Polar Urals update in Briffa (2000) reconstruction (black). In MWP, 5 of 6 sites in D’Arrigo et al 2006 overlap with 5 of 7 sites in Briffa 2000 (including Yamal).

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SUMMARY

A. MBH has fatal problems with methodoloy, proxy selection and statistical verification;

B. Other studies have biased selection of proxiesC. “divergence” problem invalidates hypothesis of

a linear relationship between tree ring proxies and NH temperature .

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End of Presentationvisit www.climateaudit.org

Left: A dead trunk above current treeline from a foxtail pine that lived about 1000 years ago near Bighorn Plateau in Sequoia National Park.

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Moberg Sensitivity Study Polar Urals Update Yang Composite without Thompson ice core Normalize distributions of Arabian Sea G.

bulloides and Agassiz melt Eliminate one of the duplicate bristlecone

series used. Eliminate extrapolations by persistence Use Discrete Wavelet Transform instead of

CWT

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C. OUT-OF-SAMPLE TESTING AND DATA MINING/SNOOPING

• canonical multiproxy studies assume a linear relationship between temperature and proxies (primarily ring widths)

• “Data mining, in the form of a search through the data for high-R2 predictors, results in regressions whose apparent explanatory power occurs by chance.” Ferson 2003 about eonomics.

• “There is a simple and honest way to avoid invalid testing. To be specific, suppose in 1980 one surveys the literature on money demand and decides the models could be improved. File the proposed improvement away until 2010 and test the new model over data with a starting date of 1981.” (Greene, 2000)

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Verification statistics under red noise overfitting plus HS-contamination

                                       Statistical pattern is identical to MBH under WA variation: somewhat high RE, high calibration r2; ~0 verification r2; negative CE.

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Other O&B proxies

All have been previously used. Left – China (Yang) plus van Engeln documentary to 1251; right – the other two (Greenland dO18 and Chesapeake Mg/Ca).

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Sensitivity variation of Moberg

Top – sensitivity study (emulation). Bottom - archived

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Another MBH regression problem - overfitting

Top left – WA variation on 68 non-strip-bark series; black – WA variation AR1=0.2 red noise simulations; red- average of non-strip-bark network. Note the flipping,

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Cook’s “Explanation”: only” a problem for north sites and 20th century, but doesn’t discuss impact of foxtails on South network

Network is supposedly “coherent” prior to 20th century.This is from 14-site Esper RW network not 387-site Schweingruber network. 2 of 5 South sites are foxtails.

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Recon #7: Moberg Issues: Yamal rather than Polar Urals Update 3 bristlecone series used, including 2 from the same site

(but not Sheep Mountain-type) Yang Composite with Thompson ice core % coldwater diatoms offshore Oman is most influential proxy

for medieval-modern difference (used as precipitation proxy in Treydte et al 2006)

Highly non-normal distributions in two most influential proxies: Arabian Sea; Agassiz melt

Old data. Sometimes even older than MBH98. Many series are extrapolated for decades Replication problems Poor statistical verification

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Moberg Verification

RE r2–cal r2-ver CE DW

Archived 0.31 0.01 0.04 -0.53 0.60

Emulation -0.16 0.25 0.02 -1.56 1.43

Variation -0.07 0.28 0.02 -1.37 1.40

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Classes of Reply

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Truncation or divergence problems in:

Jones et al 1998 Crowley 2000 Briffa et al 2001 Esper et al 2002 Rutherford et al 2005 Moberg et al 2005 D’Arrigo et al 2006 Hegerl et al 2006

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“Non-parametric” HS anomaly in O&B 2006 comes entirely from “stereotypes”:

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Recon #9: Esper et al 2002 (used by NAS)

Green - archived. Red dashed – average and re-scale. Blue – without TWO foxtail sites.

• Late 20th century results cannot be replicated on present record • Average of 14 site chronologies shows divergence• Divergence exacerbated without foxtails

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Handling “Divergence”

truncation of troublesome data in spaghetti graphs

“cargo cult” theories

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Recon #1: MBH Without Bristlecones

MBH99 reconstruction (black) and estimated MBH99-type reconstruction without bristlecones (red).

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Recon #6: Osborn and Briffa 2006 – a “non-parametric” hockey stick

Difference between number of proxies with normalized values >0 and normalized values <0 (1865-1990 standardization,)

2 Bristlecone/foxtails series

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Recon #5: Impact of Polar Urals Update on Jones et al 1998

Top: Jones et al 1998; Bottom – Polar Urals Update, if used, reverses medieval-modern differential

Yamal rather than Polar Urals Update Thompson’s Himalaya dO18

A. MBH- uses flawed proxies and methods (e.g. bristlecones);

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Average of 7 tree ring sites without strip-bark, Yamal

Is there an incipient Divergence Problem?

A. Jones-type: Data “Snooping”/ Cherry picking

B. Briffa: The “Divergence” Problem Thompson’s Himalaya ice cores (if they are an

“independent” line of evidence, then they should be disaggregated from

Many other proxies used over and over. Selection in Hegerl et al 2006 almost exactly matches Osborn and Briffa 2006

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NAS Panel avoided issue

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 …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).