Transcript Presentation at Vrije Universiteit, Amsterdam Stephen McIntyre Toronto Ontario De Bilt, Holland Sept. 14, 2006.

Presentation at
Vrije Universiteit,
Amsterdam
Stephen McIntyre
Toronto Ontario
De Bilt, Holland Sept. 14, 2006.
1
IPCC 1990
2
“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.”
3
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 midto-late 20th-century temperatures,"
said Hughes.
4
IPCC TAR Spaghetti Graph
Black -MBH98-99; red - Jones, Briffa et al 1998; green Briffa, Jones et al 2001 – orange- instrumental (Jones)
5
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
6
How do they know that 1998
was the warmest year of the
millennium?
7
“Proxies”
• Tree rings
• Ice core dO18
• Tree rings
• Coral
• Tree rings
• Documentary
• Tree rings
• Sediments
• Tree rings
Also Tree rings
8
April 2003 - My First Inquiry
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9
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]
Sept 2003 Inquiry
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10
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]
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
11
McIntyre and McKitrick [2003]
Temperature Index (deg C)
0.5
0.4
Corrected Version
0.3
Mann et. al. 1998
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
1400 1450 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950
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”
12
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."
13
MBH 2003 Response
Difference came from North American PC1 series.
14
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.
15
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”
16
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 crossvalidation tests
MM05: verification r2 for AD1500 step
was ~0 (0.02; CE: -0.24) i.e. no skill.
17
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.
18
realclimate.org
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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
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19
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
Natuurwetenschp & Techniek
20
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.
21
www.climateaudit.org
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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
Climate Science Reaction
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23
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.
House Energy and Commerce
Committee Questions
24
Wegman Report 2006
Wegman, 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.
25
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.”
26
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
27
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”
28
House Energy and Commerce
Committee
Mann at left; Ralph Cicerone, President, U.S.
National Academy of Sciences; me.
29
Verification r2 Statistics (Wahl and
Ammann) nearly identical to MM05
30
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
31
Q.e.d.…
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MBH cannot assert 20th century
uniqueness based on their data and
method because:
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32
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.
VZ: bad method doesn’t affect
pseudoproxy network; BUT didn’t study
robustness. One contaminated HS series
can yield hockeystick PC1
33
Mann method weights the contaminated
series rather than the “signal”
Left – without contamination; right – with one nonclimatic HS
series
34
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.
35
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.
36
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)
37
NAS did not check if other studies used
bristlecones
Question 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?
North
There 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.
38
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
39
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)
40
Medieval-modern levels in Crowley 2000
change without bristlecones
0.4
0.2
0.0
-0.2
-0.4
1000
1200
1400
1600
1800
2000
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 41
least 5 proxies. No instrumental data is spliced.
Second: The “Divergence” Problem
tree ring widths and density decline in late 20th
century
Left - Briffa et al 2001 reconstruction (left) from 387 temperaturesensitive sites; right – from Briffa et al 1998: heavy solid – MXD
(used in Briffa et al 2001); dashed – RW; thin solid – temperature.
42
Plausible explanations 

43
Nonlinear relationship between temperature
and ring widths;
water (i.e., drought stress) has become the
limiting factor (see TTHH site chronology –right)
Truncation of Briffa et al 2001 in
IPCC TAR
IPCC truncated the Briffa et al 2001 reconstruction
(green) in 1960. Thus no visible “divergence”.
44
The untruncated reconstruction has low
late 20th century proxy values
Would the untruncated Briffa et al 2001 reconstruction (purple dashed) have raised questions
about unanimity?
45
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 pretwentieth 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]
46
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.
47
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.
48
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).
49
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).
50
Studies don’t use up-to-date
proxies
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51
Proxy reconstructions end in about 1980. Then
instrumental versions are spliced.
If the proxies are any good, then the warm
1990s should have off-the-chart values.
If they don’t, how can we be confident that they
would have picked up warm MWP decades?
Shouldn’t we validate proxies by bringing
them up-to-date?
The Heavy-Equipment Excuse
Mann: Most reconstructions only extend through
about 1980 because the vast majority of tree-ring,
coral, and ice core records currently available in
the public domain do not extend into the most
recent decades. While paleoclimatologists are
attempting to update many important proxy
records to the present, this is a costly, and
labor-intensive activity, often requiring
expensive field campaigns that involve
traveling with heavy equipment to difficult-toreach locations (such as high-elevation or remote
polar sites). For historical reasons, many of the
important records were obtained in the 1970s and
1980s and have yet to be updated.
52
Heavy equipment
53
Esper et al 2002 (used by NAS)
• Late 20th century results cannot be replicated on
present record
• Average of 14 site chronologies shows divergence
• Divergence exacerbated without foxtails
Green - archived. Red dashed – average and re-scale.
Blue
– without TWO foxtail sites.
54
Does the Hockey Stick “Matter”?
The 1990s were the warmest
decade of the millennium, with
1998 the warmest year so far
55
By now, just about everyone has
heard of these tubes…Most U.S.
experts think they are intended to
serve as rotors in centrifuges used to
enrich uranium
End of Presentation
visit 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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