An Analysis of European Vineyard Data
[Those who have followed the story of
Mann's Hockey Stick and the fraudulent manipulation of data which
that episode revealed, will be interested in the following analysis
by Douglas Keenan of a paper published in Nature on vineyard
records of grape harvests in Europe. The paper purported to demonstrate
that current warming is unprecedented and thus in accord with
IPCC claims. Keenan found otherwise. Since The Lavoiser Group
listed this article, we have received an interesting, short response
from Graham Due. It has been added at the foot
of this page.]
On 18 November 2004, Isabelle Chuine and
co-workers published a research paper on global warming. The
paper appeared in Nature,
the world's most highly-regarded scientific journal. And it gathered
some publicity. Chuine et al. claimed to have developed
a method for estimating the summer temperature in Burgundy, France,
in any given year back to 1370 (based on the harvest dates of
grapes). Using their method, the authors asserted that the summer
of 2003 was the warmest summer since 1370, in Burgundy.
I had been following global warming studies
only as a disinterested outside spectator (and only occasionally).
Someone sent me the paper of Chuine et al., though, and
wondered what I thought of it from a mathematical perspective.
So I had a look.
To study the paper properly, I needed to
have the authors' data. So I e-mailed Dr. Chuine, asking
for this. The authors, though, were very reluctant to let me
have the data. It took me eight months, tens of e-mails exchanged
with the authors, and two formal complaints to Nature,
before I got the data. (Some data was purchased from Météo
France.) It is obviously inappropriate that such
a large effort was necessary.
Looking at the data made it manifest that
there are serious problems with the work of Chuine et al.
In particular, the authors' estimate for the summer temperature
of 2003 was higher than the actual temperature by 2.4 °C
(about 4.3 °F). This is the primary reason that 2003
seemed, according to the authors, to be extremely warm.
There is also another reason. The three
warmest years on record, prior to 2003, were 1945, 1947, and
1952. (The instrumental record goes back to 1922, or even 1883
if we accept some inaccuracies.) The estimate of Chuine et al.
for the summer temperature in each of those years was much lower
than the actual temperature.
That is, the authors had developed a method
that gave a falsely-high estimate of temperature in 2003 and
falsely-low estimates of temperatures in other very warm years.
They then used those false estimates to proclaim that 2003 was
tremendously warmer than other years.
The above is easy enough to understand.
It does not even require any specialist scientific training.
So how could the peer reviewers of the paper not have seen it?
(Peer reviewers are the scientists who check a paper prior
to its publication.) I asked Dr. Chuine what data was sent
to Nature, when the paper was submitted to the journal.
Dr. Chuine replied, "We never sent data to Nature".
I have since published a short note that
details the above problem (reference below). There are several
other problems with the paper of Chuine et al. as well.
I have written a brief survey of those (for people with an
undergraduate-level background in science). As described in that
survey, problems would be obvious to anyone with an appropriate
scientific background, even without the data. In other words,
the peer reviewers could not have had appropriate background.
What is important here is not the truth
or falsity of the assertion of Chuine et al. about Burgundy
temperatures. Rather, what is important is that a paper on what
is arguably the world's most important scientific topic (global
warming) was published in the world's most prestigious scientific
journal with essentially no checking of the work prior to publication.
Moreover---and crucially---this lack of
checking is not the result of some fluke failures in the publication
process. Rather, it is common for researchers to submit papers
without supporting data, and it is frequent that peer reviewers
do not have the requisite mathematical or statistical skills
needed to check the work (medical sciences largely excepted).
In other words, the publication of the work of Chuine et al.
was due to systemic problems in the scientific publication process.
The systemic nature of the problems indicates
that there might be many other scientific papers that, like the
paper of Chuine et al., were inappropriately published.
Indeed, that is true and I could list numerous examples. The
only thing really unusual about the paper of Chuine et al.
is that the main problem with it is understandable for people
without specialist scientific training. Actually, that is why
I decided to publish about it. In many cases of incorrect research
the authors will try to hide behind an obfuscating smokescreen
of complexity and sophistry. That is not very feasible for Chuine
et al. (though the authors did try).
Finally, it is worth noting that Chuine
et al. had the data; so they must have known that their
conclusions were unfounded. In other words, there is prima facie
evidence of scientific fraud. What will happen to the researchers
as a result of this? Probably nothing. That is another systemic problem
with the scientific publication process.
See also Peer
review and the IPCC
Chuine I., Yiou P., Viovy
N., Seguin B., Daux V., Le Roy Ladurie E. (2004), "Grape ripening as a past climate indicator",
432: 289c290. doi: 10.1038/432289a.
Keenan D.J. (2007), "Grape
harvest dates are poor indicators of summer warmth",
Theoretical and Applied Climatology,
87: 255c256. doi: 10.1007/s00704-006-0197-9.
Addendum to Keenan's Critique of Grape
Harvest Date Analysis
by Graham Due
Keenan's critique is complete and
requires no further elaboration.
It is noteworthy that any editor
of a scientific journal could believe, even in a moment of weakness,
that such an arbitrary and elaborate procedure as the growing
and harvesting of grapes should constitute a reliable measuring
Such publication demonstrates the
politicisation of science---not a new phenomenon, of course,
(eg. the "science" of eugenics).
I studied grape harvest and other
phenological data in Australia using a data set involving roughly
12 each of varieties, sites and years. The study was published
in Ag. and For. Met. (Due et al., 1993).
Detailed multivariate statistical
analysis showed little relationship between weather and any phenological
However, the belief that warm weather
and earlier harvest seems to be set in the cement of the popular---and
A recent CSIRO publication builds
on the belief and tells us all how to cope with the "impact"
of global warming on the production of quality wine. This work
generated money for the CSIRO and its researchers.
Regarding tree rings, given the major
and well-documented effect of CO2 on plant
physiology, and the well accepted rise in recent CO2
levels, it seems amazing that tree ring data are accepted without
adjustment for higher CO2 levels. There
is no public discussion of the effect of CO2
on increased plant growth. I wonder if a major increase in plant
growth been measured and associated with increased CO2
levels. This would be the biggest "field experiment"
of all time.
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