EAS Seminar,
Georgia Tech
Stephen McIntyre
Toronto Ontario
Atlanta Feb 8, 2008
1
An interesting ride
Left: Front page, Wall Street Journal, Feb 2005; Middle - House Energy and
Commerce Committee, Oversight and Investigations Subcommittee: Mann,
Ralph Cicerone (NAS), me, Jay Gulledge, Ed Wegman; Right: Best Science
Blog 2007
2
Conclusions
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3
No “meaningful” conclusion about
modern-medieval climate can be
derived from the existing corpus of
1000 year studies and which is warmer
remains an open question;
The main problem is not finding the
“right” multivariate method, but getting
better proxies and better local data.
Some Disclaimers
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4
I’ve never asserted or implied that AGW policy stands
or falls on the HS.
I’ve never suggested that perfect certainty is needed to
make climate decisions. People make decisions under
uncertainty all the time.
I’ve avoided all policy discussions other than archiving.
If I had a big policy job, I would be guided by official
institutions. I’ve never suggested that any of the
issues that I’ve been involved should affect climate
policy decisions.
Conversely, the “big picture” doesn’t excuse using poor
methods or poor dislosure.
Even if the HS is irrelevant to climate policy, I’ve
become interested in the statistical and historical
issues in 1000-year climate reconstructions.
The Hockey Stick
Left: John Houghton at IPCC TAR WG1 Press
conference; right - Al Gore, Inconvenient Truth
5
The iconic hockey stick
6
“The Warmest Decade and Year”
The past decade was the world's warmest decade of the
century. And that century was the warmest of the past
millennium. Without action, the long-term consequences
will be devastating. – David Anderson, Oct. 27, 2001
The 20th century was the warmest in the Northern
Hemisphere in the past 1000 years. The 1990s was the
warmest decade on record and 1998 was the warmest year
- in Canada and internationally." - David Anderson, April 5,
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
7
“Forgotten the Location”
Dear Dr. Mann, I have been studying MBH98 and 99. I located datasets for
the 13 series used in 99 at
ftp://eclogite.geo.umass.edu/pub/mann/ONLINEPREPRINTS/Millennium/DATA/PROXIES/ (the convenience of the ftp:
location being excellent) and was interested in locating similar information
on the 112 proxies referred to in MBH98, as well as listing (the listing at
http://www.ngdc.noaa.gov/paleo/ei/data_supp.html is for 390 datasets, and
I gather/presume that many of these listed datasets have been condensed
into PCs, as mentioned in the paper itself. Thank you for your
attention. Yours truly, Stephen McIntyre, Toronto, Canada
Dear Mr. McIntyre, These data are available on an anonymous ftp site we
have set up. I've forgotten the exact location, but I've asked my
Colleague Dr. Scott Rutherford if he can provide you with that information.
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. Do you
want the raw 300+ proxies or the 112 that were used in the MBH98
reconstruction? Scott
8
MBH98
The Neofs-length solution vector g is obtained by solving the above
overdetermined optimization problem by singular value decomposition for
each proxy record i= 1,…Nproxy. This yields a matrix of coefficients
relating the different proxies to their closest linear combination of the Neofs
PCs .This set of coefficients will not provide a single consistent solution,
but rather represents an overdetermined relationship between the optimal
weights on each on the Neofs PCs and the multiproxy network.
These Neofs eigenvectors were trained against the Nproxy indicators, by
finding the least-squares optimal combination of the Neofs PCs
represented by each individual proxy indicator during the N=79 year
training interval from 1902 to 1980 (the training interval is terminated at
1980 because many of the proxy series terminate at or shortly after
1980).… This proxy-by-proxy calibration is well posed (that is, a unique
optimal solution exists) as long as N>Neofs (a limit never approached in
this study) and can be expressed as the least-squares solution to the
overdetermined matrix equation, Ug =Y[,i] , where U is the matrix of annual
PCs, and Y[,i] is the time series vector for proxy record i. The Neofs-length
solution vector g is obtained by solving the above overdetermined
optimization problem by singular value decomposition for each proxy
record i=1,…Nproxy. This yields a matrix of coefficients relating the
different proxies to their closest linear combination of the Neofs PCs .This
set of coefficients will not provide a single consistent solution, but rather
represents an overdetermined relationship between the optimal weights on
each on the Neofs PCs and the multiproxy network.
9
“Statistical Skill”
IPCC TAR: “reconstruction which had significant skill
in independent cross-validation tests. Self-consistent
estimates were also made of the uncertainties”
MBH98: β [or RE] …correlation (r) and squaredcorrelation (r2) statistics are also determined.
10
“Robustness” to presence/absence of
dendro proxies
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11
Mann et al. 2000: possible low-frequency bias due to
non-climatic influences on dendroclimatic (tree-ring)
indicators is not problematic in our temperature
reconstructions…Whether we use all data, exclude tree
rings, or base a reconstruction only on tree rings,
has no significant effect on the form of the
reconstruction for the period in question.
MBH98: the long-term trend in NH is relatively robust
to the inclusion of dendroclimatic indicators in the
network, suggesting that potential tree growth trend
biases are not influential in the multiproxy climate
reconstructions. (p. 783, emphasis added.)
MM2003, 2005a,b,c,d
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12
MBH principal components algorithm was severely biased such that it
“mined” for HS-shaped data. This precluded attributing any statistical
significance to such a reconstruction.
their reconstruction failed important statistical tests in early portions
e.g. the verification r2 statistic shown in one of their figures. These
adverse results were not reported.
we reflected on what it means when one statistic is “99.9%
significant” and another statistic is a bust.
their reconstruction was not “robust” to the presence/absence of all
dendro proxies. It was not even robust to the presence/absence of
bristlecones..
Bristlecones are located only in high arid U.S. Southwest and had
been previously identified by specialists as problematic, e.g. Biondi
(Hughes) et al. (1999) said: “[Bristlecones] are not a reliable
temperature proxy for the last 150 years”. Without bristlecones, no
HS.
Merely using a standard covariance PC algorithm, the weights of
bristlecones were reduced such that no HS was obtained.
Red Noise Simulations
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13
Data decentered against post-1902 mean.
Preferentially adds weight to hockey stickshaped series in PC1
The counterattack
Mann: This claim by MM is just another in a series
of disingenuous (off the record: plainly dishonest)
allegations by them about our work.
I hope you are not fooled by any of the "myths" about
the hockey stick that are perpetuated by contrarians,
right-wing think tanks, and fossil fuel industry
disinformation.
UCAR Press Release: “the highly publicized
criticisms of the MBH graph are unfounded. “
14
The Defense

Our criticisms were “wrong” because:
 They could get an HS without using principal components.
 If they retained more PCs (down to the PC4), they could still
“get” a HS;
 Other people got an HS using different methods.
In MM (EE 2005) we discussed these permutations and
combinations. Yes, you can “get” an HS by changing your methods,
but each of these other methods has its own problems.Wegman
was vey critical of after-the-fact methodology changes.

After Wahl and Ammann grudgingly confirmed the verification r2
failure, they argued that verification r2 statistic was no good as it
was supposedly prone to rejecting valid reconstructions. Mann to
the NAS Panel: calculating a verification r2 statistic would be a
“foolish and incorrect thing” to do.

Wahl and Ammann agreed that you can’t “get” a HS without the
bristlecones, but argued that a bristlecone-free reconstruction fails
verification RE statistic) and would never have been proposed and
thus claim that bristlecones contain valid and necessary
information.
15
Proposal to Ammann and Wahl
in my view, the climate science community has little interest at this point in
another exchange of controversial articles (and associated weblog
commentaries) and has far more interest in the respective parties working
together to provide a joint paper, which would set out: (1) all points on which
we agree; (2) all points on which we disagree and the reasons for
disagreement; (3) suggested procedures by which such disagreements can
be resolved. Because our emulations are essentially identical, I think that
there is sufficient common ground that the exercise would be practical, as well
as desirable.
Accordingly I propose the following:
(1) we and our coauthors (McKitrick and Wahl) attempt to produce a joint
paper in which the above three listed topics are discussed;
(2) We allow ourselves until February 28, 2006 to achieve an agreed text for
submission to an agreed journal (Climatic Change or BAMS, for example,
would be fine with us), failing which we revert back to the present position;
(3) as a condition of this “ceasefire”, both parties will put any submissions or
actions on hold. On your part, you would notify GRL and Climatic Change of a
hold until Feb. 28, 2005. On our part, we would refrain from submitting
response articles to GRL or Climatic Change or elsewhere and refrain from
blog commentary on the topic.
16
Wegman Report 2006
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.
While the work of Michael Mann and colleagues presents what appears to be
compelling evidence of global temperature change, the criticisms of McIntyre
and McKitrick, as well as those of other authors mentioned are indeed valid.
I am baffled by the claim that the incorrect method doesn’t matter because
the answer is correct anyway. Method Wrong + Answer Correct =
Bad Science.
17
NAS Panel – “Schizophrenic”
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Agreed with our point that the MBH PC method was
wrong;
Agreed that bristlecones were problematic and said
that “strip bark” trees should be “avoided” in
temperature reconstructions;
Agreed in general terms with our statistical criticisms:
“Reconstructions that have poor validation statistics
(i.e., low CE) will have correspondingly wide
uncertainty bounds, and so can be seen to be
unreliable in an objective way.”
On no occasion did they contradict any explicit MM
statement.
18
NAS Panel
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19
Concluded that things were “murky” as
you went further back.
Overall result was “plausible” showing
other recons.
North at the House Committee
CHAIRMAN BARTON. Dr. North, do you dispute the conclusions or the
methodology of Dr. Wegman’s report?
DR. NORTH. No, we don’t. We don’t disagree with their criticism. In fact,
pretty much the same thing is said in our report.
DR. BLOOMFIELD. Our committee reviewed the methodology used by
Dr. Mann and his coworkers and we felt that some of the choices they
made were inappropriate. We had much the same misgivings about his
work that was documented at much greater length by Dr. Wegman.
20
Zorita on the NAS Panel
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 IPCC 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.
21
North’s Texas A&M Seminer
At a Texas A&M seminar, North said 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/NorthH
264.mp4 minute 55 or so
“We did not dissect each and every study in the report
to see which trees were used. “
22
Why hasn’t this been settled?
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23
the issue isn’t important enough that it needs to
be settled;
Science may be “self-correcting” (so are
markets). Market imperfections can continue
uncorrected for some time and so can science
imperfections.
still some intellectual work that needs to isolate
the issues more surgically than has been done
to date.
Outline
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24
Reconstructions in a statistical context;
Econometric thoughts on spurious regression
Some important data sets
A. Reconstruction Methods
Jones and Mann 2004
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Composite-plus-scale (CPS)
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Climate Field Reconstruction (CFR)
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25
Proxies are normalized and averaged (perhaps with weights
“ e.g., based on area represented or modern correlations
with colocated instrumental records” [Jones and Mann
2004]
average is then simply scaled against the available
temporally overlapping instrumental record
“Multivariate calibration of the large-scale information in the
proxy data network against the available instrumental data”
“most involve the use of empirical eigenvectors of the
instrumental data, the proxy data, or both”
“Because the large-scale field is simultaneously calibrated
against the full information in the network, there is no a
priori local relationship assumed between proxy indicator
and climatic variable.”
Multivariate Calibration:
Cook (Briffa, Jones) 1994
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Considers “inverse” OLS regression of each gridcell in
a network X (MBH98 – 1082) against a network of
proxies Y (MBH98 – 415)
Applying this to the MBH98 network would lead to the
generation of 1082*415=449,030 coefficients from only
79*415=32,785 proxy measurements in the calibration
period.
Cook et al observed:
 “experience in reconstructing climate from tree rings
indicates that such models frequently produce
reconstructions that cannot be verified successfully
when compared with climate data not used in
estimating the regression coefficients. This can
happen regardless of the statistical significance of the
overall regression equation.”
26
MBH Method
1.
2.
3.
4.
5.
6.
7.
27
Standardize gridcell temperatures by area-weighting
and standard deviations;
Calculate temperature PCs;
Estimate “transfer coefficients” for proxies to PCs in
calibration period by “over-determined optimization”
Estimate reconstructed PCs in reconstruction by “overdetermined optimization”
Re-scale reconstructed PCs to observed PCs
Expand back to gridcell temperatures
Calculate NH average temperature
“Advantage”
of MBH Method
“MBH98’s method yields an estimation of the value of the
temperature PCs that is optimal for the set of climate
indicators as a whole, so that the estimations of
individual PCs cannot be traced back to a particular
subset of indicators or to an individual climate
indicator. This reconstruction method offers the
advantage that possible errors in particular indicators are
not critical, since the signal is extracted from all the
indicators simultaneously.”
28
NH Composite: Linear Algebra
All the operations are linear and on the right of the
reconstructed PCs. Simple expression for expansion
and reflating of reconstructed PCs to area-weighted
NH average:
where
- Reconstructed NH temperature index
- Reconstructed TPCs
- Gridcell eigenvalues, eigenvectors (EOFs)
- Gridcell standard deviations
- Gridcell area weights
29
These are the weights (λ) for each
reconstructed temperature PC in NH
temperature reconstruction
30
All operations in reconstructed Temperature
PCs are linear. Optimizations” are Regressions
Calibration
Reconstruction
Rescaling
in 1-D Case
1-D Case
(AD1000, AD1400)
- Matrix of temperature PCs (individual PC)
- Matrix of proxies (standardized)
- Rescaled estimated PCs; Pre-rescaled PC estimates
31
Arbitrary MBH weights; correlation to temperature PC(1)
All MBH operations are linear operations on the
right hand side of the proxy matrix Y. Because
matrix multiplication is associative, weights can be
assigned for each individual proxy.
Where, for one-PC case (AD1000, AD1400)
weighted
unweighted
S,V from temperature SVD, σ, μ are
gridcell standard deviations, cosine
latitude area weights
32
Weights can be assigned for proxies
within PC networks as well
Regional tree ring PCs are linear combinations of the
underlying tree ring network (here X)
The mixed MBH proxy network (“regular” and tree ring
PCs can be represented as follows (the dimension of
V,k is (say) 79 x2 (for 79 tree rings and 2 PCs)
33
Contributions by proxy type can be
calculated
By allocating weights to individual sites and by
classifying sites by continent and type (ice core,
bristlecone, other trees, coral, etc), the relative
contribution of each class to the MBH reconstruction
can be measured (bristlecone plus Gaspé in red). (In
deg C)
34
Weights can be shown graphically
Prominent weights are for the NOAMER PC1 (bristlecones),
Gaspé, Tornetrask and Cook’s Tasmania tree ring. There are 22
weights
in this picture in total.
35
Keynes 1940 on Tinbergen
(anticipating RegEM?)
But my mind goes back to the days when Mr Yule
sprang a mine under the contraptions of optimistic
statisticians by his discovery of spurious correlation. In
plain terms, it is evidence that if what is really the same
factor is appearing in several places under various
disguises, a free choice of regression coefficients can
lead to strange results. It becomes like those puzzles
for children where you write down your age,
multiply, add this and that, subtract something else
and eventually end up the number of the Beast in
Revelation.
36
Different weights yield different
reconstructions. Plausible ex ante
methods yield different weights and
results.
Burger and Cubasch 2006
37
MBH and Scaled-Composite Reconstructions

standardize, average and inflate so variance matches
“target variance”

With correlation weights
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MBH (AD1000, AD1400 steps)
38
CPS with Correlation Weights = OneStage Partial Least Squares
Bair et al 2004.
39
OLS and PLS
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40
OLS regression coefficients are a rotation
(and dilation) of the PLS coefficients in
coefficient-space
From the Frying Pan into the Fire
In cases where there is little correlation between proxies,
then the rotation matrix is “near-orthogonal” and PLS
increasingly approximates OLS
41
Phillips 1998 Figure 4. n: x^2 in interval –pi to pi, repeated
periodically. The regression using 1000 observations and 125
white noise regressors
Wahl and Ammann’s no PC case: a “near”-OLS
regression 79 years long against 65-90 “predictors”.
Calibration residuals are meaningless.
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.. In deg C
42
If you insert synthetic HS series plus low-order red
noise, you get recons that look like the “no-PC”
recons
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. In deg C
43
You can get the same verification
results using tech stocks instead of
the Bristlecone PC1+Gaspe. In deg C
44
Ridge Regression is not a magic bullet
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45
Stone and Brooks 1990 “Continuum Regression” : Ridge
regression coefficients can be arranged as a 1parameter “continuum” between OLS and PLS
Borga et al 2000 Taxonomy
Solutions to
46
for cases below:
Two-parameter mixing
You can do one-parameter mixing of
and identity
matrix to get to CCA (Canonical Correspondence
Analysis).
47
OLS gets “cute” with coefficients
with values all over the place. In
this network, simple is better.
48
How do you test reconstructions – the
problem of “spurious regression”?
Is there a valid statistical relationship
between “climate field” (the
temperature PC1) and bristlecones?
49
Yule 1926 - this is RE-resistant
Mortality per 1000 (points) and proportion of Church of
England marriages per 1000 marriages (line)
50
Hendry’s “Theory of Inflation” 1980
Hendry’s theory of inflation is that a certain variable (of great interest in this
country) is the “real cause” of rising prices. .. there is a “good fit”, the coefficients
are “significant”, but autocorrelation remains and the equation predicts badly.
Assuming a first order autoregressive error process, the fit is spectacular, the
parameters are “highly significant”, there is no obvious residual autocorrelation
(on an “eyeball ” test and the predictive test does not reject the model. …C is
simply cumulative rainfall in the UK. It is meaningless to talk about “confirming
theories” when spurious results are so easily obtained. Doubtless some
equations extant in econometric folklore are little less spurious than those I have
51
presented.
Granger and Newbold 1974
“It is very common to see reported in applied econometric literature
time series regression equations with an apparently high degree of fit,
as measured by the coefficient of multiple correlation R2 but with an
extremely low value for the Durbin-Watson statistic. We find it very
curious that whereas every textbook on econometric methodology
contains explicit warnings of the dangers of autocorrelated errors, this
phenomenon crops up so frequently in well-respected applied work....
… It has been well known for some time now that if one performs a
regression and finds the residual series is strongly autocorrelated,
then there are serious problems in interpreting the coefficients of the
equation. Despite this, many papers still appear with equations having
such symptoms and these equations are presented as though they
have some worth. It is possible that earlier warnings have been stated
insufficiently strongly. From our own studies we would conclude
that if a regression equation relating economic variables is found
to have strongly autocorrelated residuals, equivalent to a low
Durbin-Watson value, the only conclusion that can be reached is
that the equation is mis-specified, whatever the value of R2
observed.
52
Canonical reconstructions fail
0.0
1.0
2.0
All multiproxy reconstructions, except MBH99, fail DurbinWatson statistic (minimum 1.5). Passing a DW test is a
necessary but not sufficient test of model validity.
J98
MBH99
MJ03
CL00
BJ00
BJ01
Esp02 Mob05
0.0
0.4
0.8
Cross-Validation R2
J98
53
MBH99
MJ03
CL00
BJ00
BJ01
Esp02
Mob05
Ferson et al 2003
Data mining for predictor variables [proxies] interacts
with spurious regression bias. The two effects reinforce
each other because more highly persistent series are
more likely to be found significant in the search for
predictor variables. Our simulations suggest that many of
the regressions in the literature, based on individual
predictor variables, may be spurious…
The pattern of evidence in the instruments in the
literature is similar to what is expected under a spurious
mining process with an underlying persistent expected
return. In this case, we would expect instruments to
arise, then fail to work out of sample.
54
Greene et al 2000
From this perspective data-mining refers to
invalid statistical testing as a result of naive
over-use of a sample. In particular, the use of a
sample both for learning-inspiration and for
testing of that which was learned or mined from
the sample. Any test of a theory or model is
corrupted if the test is conducted using data
which overlaps that of any previous empirical
study used to suggest that theory or model. The
moral is clear.
55
The same proxies are used over and over
again.
Two problems: severe data mining renders statistical testing
meaningless; lack of independence between data sets makes
multiple reconstructions vulnerable to data problems.
56
IPCC Box 6.4 Figure 1
The most stylized and repetitively data mined series are
shown in IPCC AR4 Box 6.4 Figure 1. Mann’s incorrectly
calculated PC1 is even shown.
57
Greene et al 2000 #3
But testing in un-mined data sets is a difficult standard to meet
only to the extent one is impatient. 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.. Only new data represents a new
experiment. I do not consider this a pessimistic outlook. This is
because I thinks much can be learned from exploring a sample.
Patience and slow methodical progress are virtuous.
58
“Bring the Proxies Up to Date”
Michael Mann: “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-to-reach 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.”
59
The “Divergence” Problem
The graphs below show results from the only large-population
(387 sites) survey: Schweingruber sites chosen ex ante as
temperature sensitive.
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.
60
Briffa’s Cargo Cult
Briffa et al: 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.
61
Briffa et al 2001 was an IPCC TAR reconstruction,
but spaghetti graph does not show it reverting to
early 19th century levels.
IPCC truncated the Briffa et al 2001 reconstruction (green) in 1960.
Thus no visible “divergence”. Also truncated in AR4 (pale blue).
62
“Divergence” Problem – NAS and IPCC
NAS Panel: Cook et al. (2004), who subdivided long tree
ring records for the Northern Hemisphere into latitudinal
bands, and found …that “divergence” is unique to areas
north of 55°N,
IPCC AR4: “‘divergence’ is apparently restricted to some
northern, high-latitude regions, but it is certainly not
ubiquitous even there…the possibility of investigating
these issues further [a limit on the potential to reconstruct
possible warm periods in earlier times] is restricted by the
lack of recent tree ring data at most of the sites from which
tree ring data discussed in this chapter were acquired.” (p.
473)
63
Updating Almagre: the Starbucks Hypothesis
Almagre CO (about 35 miles west of Colorado Springs CO) is a
bristlecone pine site with a Graybill chronology going back to
AD1000. We took 64 cores (36 trees), of which 38 cores (20 trees)
at or near Graybill site. Highest tree ring millennium chronology in
the world!
64
http://picasaweb.google.com/Almagre.Bristlecones.2007/
Exact Graybill Trees
We located 16 tagged trees of which 8 have been sampled. We
reconciled the tags to the ITRDB archive (before co-operation
ceased). Only 3 of the 8 sampled trees had been archived. It
appears that Graybill sampled 42 trees, of which only 21 are
65
archived. Reasons for selective archiving unknown at present.
Very Low Recent Growth in Many Trees
In mm/100.
66
Strip Bark Trees
NAS panel said that strip bark trees should be “avoided”.
However, this information not recorded in bristlecone and
foxtail (or other) archives. Graybill said that he sought out
strip bark. (In mm/100)
67
Bizarre Strip Bark Forms
Brunstein, C. USGS.
68
Updated Almagre Chronology
Decline in recent ring widths – which are obviously not at
levels “teleconnecting” with high NH temperatures.
1840-50s are a very “loud” phenomenon in chronology.
In dimensionless chronology units, basis 1.
69
Strip Bark At Graumlich Sites
From the plot below, I asked Andrea Lloyd whether this tree,
with the characteristic discrepancy between cores, was strip
bark. She consulted her field notes – the answer was yes. (In
mm/100)
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White Mts very arid
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Ababneh Sheep Mt Update
Left - Graybill 1987 and Ababneh 2006 (PhD thesis) for Sheep Mountain
(Chronology units minus 1). Right – Both re-scaled on 1902-1980 showing
that Graybill dilates relative to Ababneh after 1840s. (s.d. units) Inset – Weights
of Mann and Jones 2003 PC1, showing Sheep Mt dominance.
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More Low Latitude “Divergence”
A statistician, considering this as an “out of sample” test of the hypothesis
that there is a linear relationship between ring width and temperature,
would conclude that this refutes the hypothesis. In the literature, this is
referred to as the “Divergence Problem”. (In sd units)
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Miller et al 2006
Deadwood tree stems scattered above treeline on tephra-covered
slopes of Whitewing Mtn (3051 m) and San Joaquin Ridge (3122 m)
show evidence of being killed in an eruption from adjacent Glass Creek
Vent, Inyo Craters. Using tree-ring methods, we dated deadwood to
815-1350 CE, and infer from death dates that the eruption occurred in
late summer 1350 CE. Using contemporary distributions of the species,
we modeled paleoclimate during the time of sympatry [the MWP] to
be significantly warmer (+3.2 deg C annual minimum temperature)
and
74 slightly drier (-24 mm annual precipitation) than present,
Tornetrask: Grudd 2008 is drastic revision of
earlier chronologies. Questioned standardization
methods of prior studies.
Grudd Fig. 12 The thick blue curve is the new Tornetrask MXD
lowfrequency reconstruction of April–August temperatures, with a
95% confidence interval (grey shading) adopted from Fig. 5. The
thin red curve is from Briffa et al. (1992) ; the hatched curve is
from Grudd et al. (2002) and based on TRW.
75
Polar Urals
Left – red- Briffa et al (Nature 1995) reported that 1032 was the “coldest
year of the millennium”. 11th century was based on only a couple of poorly
dated cores. New tranche of data (green -1998 in Esper et al 2002)
showed very warm 11th century – but Briffa never published this. Instead
he did his own analysis on Yamal site (right –red ) about 100 miles away.
Like Sheep Mt, dilation of post-mid 19th century results in Briffa version.
Briffa’s Yamal version used in all but one subsequent study without any
attempt
76 to reconcile to Polar Urals update. (In sd units)
Shiyatov and Naurzbaev
Shiyatov 1995: From the middle of the 8th to the end of
the 13th, there was intense regeneration of larch and
the timberline rose up to 340 a.s.l. The 12th and 13th
centuries were most favorable for larch growth. At this
time the altitudinal position of the timberline was the
highest, stand density the biggest, longevity of trees the
longest, size of trees the largest, increment in diameter
and height the most intensive as compared with other
periods under review…
Naurzbaev et al 2004: Trees that lived at the upper
(elevational) tree limit during the so-called Medieval
Warm Epoch (from A.D. 900 to 1200) show annual
and summer temperature warmer by 1.5 and 2.3
deg C, respectively, approximately one standard
deviation of modern temperature. Note that these
trees grew 150-200 m higher (1-1.2 deg C cooler)
than those at low elevation but the same latitude,
implying that this may be an underestimate of the
actual temperature difference.
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dO18 in Ice Cores: no global pattern


Guliya (3rd) is
supposedly evidence of
global warming, while
Mount Logan attributed
to “regional circulation
changes”;
NAS Panel: “no
Antarctic sites show
medieval warming” –
ahem, what about Law
Dome?
78
All centered on mean.
Dunde Ice Core: versions are inconsistent and
sample data unarchived
How can interannual climate be calculated when one ice core
yields a spaghetti graph? The purple series strongly influences
the Yang composite, one of the extreme IPCC Box 6.4 series.
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Question: is there a rational
way of choosing (a) or (b)?
Left: NRC panel. Right: Variations of standard reconstructions
using Polar Urals update instead of Yamal and Sargasso Sea SST
instead of G Bulloides wind speed proxy and Yakutia instead of
problematic bristlecones/foxtails
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Econometric References:
http://www.climateaudit.org/?page_id=2709
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END
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