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EAS Seminar, Georgia Tech


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Title: EAS Seminar, Georgia Tech

EAS Seminar, Georgia Tech
  • Stephen McIntyre
  • Toronto Ontario
  • Atlanta Feb 8, 2008

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

  • 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
  • Ive never asserted or implied that AGW policy
    stands or falls on the HS.
  • Ive never suggested that perfect certainty is
    needed to make climate decisions. People make
    decisions under uncertainty all the time.
  • Ive avoided all policy discussions other than
    archiving. If I had a big policy job, I would be
    guided by official institutions. Ive never
    suggested that any of the issues that Ive been
    involved should affect climate policy decisions.
  • Conversely, the big picture doesnt excuse
    using poor methods or poor dislosure.
  • Even if the HS is irrelevant to climate policy,
    Ive become interested in the statistical and
    historical issues in 1000-year climate

The Hockey Stick
  • Left John Houghton at IPCC TAR WG1 Press
    conference right - Al Gore, Inconvenient Truth

The iconic hockey stick
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

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/ONLINE
    -PREPRINTS/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
    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
  • 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

  •   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 N79 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
    NgtNeofs (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 i1,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.

Statistical Skill
  • IPCC TAR reconstruction which had significant
    skill in independent cross-validation tests.
    Self-consistent estimates were also made of the
  • MBH98 ß or RE correlation (r) and
    squared-correlation (r2) statistics are also

Robustness to presence/absence of dendro proxies
  • Mann et al. 2000 possible low-frequency bias due
    to non-climatic influences on dendroclimatic
    (tree-ring) indicators is not problematic in our
    temperature reconstructionsWhether 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
  • 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
  • their reconstruction was not robust to the
    presence/absence of all dendro proxies. It was
    not even robust to the presence/absence of
  • 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
  • Data decentered against post-1902 mean.
    Preferentially adds weight to hockey stick-shaped
    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.

The Defense
  • Our criticisms were wrong because
  • They could get an HS without using principal
  • 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 cant 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.

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

Wegman Report 2006
  • The debate over Dr. Manns 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. Manns 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
    McIntyres claims or accept them. The situation
    was ripe for a third-party review of the types
    that we and Dr. Norths 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 doesnt matter because the answer is
    correct anyway. Method Wrong Answer Correct
    Bad Science.

NAS Panel Schizophrenic
  • Agreed with our point that the MBH PC method was
  • 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
  • On no occasion did they contradict any explicit
    MM statement.

NAS Panel
  • Concluded that things were murky as you went
    further back.
  • Overall result was plausible showing other

North at the House Committee
  • CHAIRMAN BARTON. Dr. North, do you dispute the
    conclusions or the methodology of Dr. Wegmans
  • DR. NORTH. No, we dont. We dont 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.

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.

Norths Texas AM Seminer
  • At a Texas AM seminar, North said that they
    didnt 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
    thH264.mp4 minute 55 or so
  • We did not dissect each and every study in the
    report to see which trees were used.

Why hasnt this been settled?
  • the issue isnt 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
  • still some intellectual work that needs to
    isolate the issues more surgically than has been
    done to date.

  • Reconstructions in a statistical context
  • Econometric thoughts on spurious regression
  • Some important data sets

A. Reconstruction Methods Jones and Mann 2004
  • Composite-plus-scale (CPS)
  • 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
  • Climate Field Reconstruction (CFR)
  • 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
  • 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

Multivariate Calibration Cook (Briffa, Jones)
  • 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 1082415449,030 coefficients
    from only 7941532,785 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.

MBH Method
  1. Standardize gridcell temperatures by
    area-weighting and standard deviations
  2. Calculate temperature PCs
  3. Estimate transfer coefficients for proxies to
    PCs in calibration period by over-determined
  4. Estimate reconstructed PCs in reconstruction by
    over-determined optimization
  5. Re-scale reconstructed PCs to observed PCs
  6. Expand back to gridcell temperatures
  7. Calculate NH average temperature

Advantage of MBH Method
  • MBH98s 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.

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
- Reconstructed NH temperature index
- Reconstructed TPCs
- Gridcell eigenvalues, eigenvectors (EOFs)
- Gridcell standard deviations
- Gridcell area weights
These are the weights (?) for each reconstructed
temperature PC in NH temperature reconstruction
All operations in reconstructed Temperature PCs
are linear. Optimizations are Regressions
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
- 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)
S,V from temperature SVD, s, µ are gridcell
standard deviations, cosine latitude area weights
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)
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)
Weights can be shown graphically
Prominent weights are for the NOAMER PC1
(bristlecones), Gaspé, Tornetrask and Cooks
Tasmania tree ring. There are 22 weights in this
picture in total.
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.
Different weights yield different
reconstructions. Plausible ex ante methods yield
different weights and results.
Burger and Cubasch 2006
MBH and Scaled-Composite Reconstructions
  • standardize, average and inflate so variance
    matches target variance
  • With correlation weights
  • MBH (AD1000, AD1400 steps)

CPS with Correlation Weights One-Stage Partial
Least Squares
Bair et al 2004.
  • OLS regression coefficients are a rotation (and
    dilation) of the PLS coefficients in

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

Phillips 1998 Figure 4. n x2 in interval pi to
pi, repeated periodically. The regression using
1000 observations and 125 white noise regressors
Wahl and Ammanns no PC case a near-OLS
regression 79 years long against 65-90
predictors. Calibration residuals are
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
If you insert synthetic HS series plus low-order
red noise, you get recons that look like the
no-PC recons
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
You can get the same verification results using
tech stocks instead of the Bristlecone PC1Gaspe.
In deg C
Ridge Regression is not a magic bullet
  • Stone and Brooks 1990 Continuum Regression
    Ridge regression coefficients can be arranged as
    a 1-parameter continuum between OLS and PLS

Borga et al 2000 Taxonomy
  • Solutions to
    for cases below

Two-parameter mixing
  • You can do one-parameter mixing of and
    identity matrix to get to CCA (Canonical
    Correspondence Analysis).

OLS gets cute with coefficients with values all
over the place. In this network, simple is better.
How do you test reconstructions the problem of
spurious regression? Is there a valid
statistical relationship between climate field
(the temperature PC1) and bristlecones?
Yule 1926 - this is RE-resistant
Mortality per 1000 (points) and proportion of
Church of England marriages per 1000 marriages
Hendrys Theory of Inflation 1980
Hendrys 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 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.
Canonical reconstructions fail
All multiproxy reconstructions, except MBH99,
fail Durbin-Watson statistic (minimum 1.5).
Passing a DW test is a necessary but not
sufficient test of model validity.
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.
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.

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.
IPCC Box 6.4 Figure 1
The most stylized and repetitively data mined
series are shown in IPCC AR4 Box 6.4 Figure 1.
Manns incorrectly calculated PC1 is even shown.
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.

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.  

The Divergence Problem
The graphs below show results from the only
large-population (387 sites) survey
Schweingruber sites chosen ex ante as temperature
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
Briffas 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
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).

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
55N, IPCC AR4 divergence is apparently
restricted to some northern, high-latitude
regions, but it is certainly not ubiquitous even
therethe 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)
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!
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 archived. Reasons for selective archiving
unknown at present.
Very Low Recent Growth in Many Trees
In mm/100.
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
Bizarre Strip Bark Forms
Brunstein, C. USGS.
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.
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)
White Mts very arid
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.
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)
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 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
AprilAugust 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.
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. Briffas Yamal version
used in all but one subsequent study without any
attempt 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

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?

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
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

Econometric References 
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