"Matt Barrow" wrote in message
...

The Hockey Stick has got to be the joke of the 90's environuts.

The infamous "Hockey Stick" graph was featured prominently in the IPCC TAR
Summary for Policymakers. It was important in that it overturned the concept
of a global Medieval Warm Period warmer than the 20th century and a
pronounced Little Ice Age, both long time (cautiously) accepted features of
the last 1000 years of climate history.

This caused quite an uproar in the sceptic community, not least because of
its visual efficacy. Two Canadians, an economist and a petroleum geologist,
took it apon themselves to verify this proxy reconstruction by getting the
data and examining the methodology used for themselves. They found that
there were errors in the description of data used as published in Nature.
Mann et al., the Hockey Stick's creators, published a correction in Nature,
noting where the description of the study did not match what was actually
done. The Canadians, McIntyre and McKitrick, then proceeded to publish a
paper that purported to uncover serious methodological flaws and problems
with data sets used.

Everything from this point on is hotly disputed and highly technical.

All the claims made by M&M have been rebutted in detail by many other
climatologists and they insist that these folks are completely in error.
This of course fits nicely with the expectations of both sides of the Global
Warming issue, the conspiracy theorists as well as the champions of peer
review. All the rebuttals have been objected to and the objections denied
and the denials rejected. The issues are highly technical and require
considerable time and energy to truly investigate. Steve McIntyre has a
website devoted to his continued probe of this study and Michael Mann is a
contributor to Real Climate which devotes considerable web space to refuting
the attacks. In short, M&M raise many specific and technical objections and
the climate scientists seem pretty unified in denying the charges. To my
knowledge, the worst indictment from the climate science community came from
a study led by Hans Von Storch that concluded M&M was right about a
particular criticism of methodology but correcting it did not change the
study results.

If you want to try to evaluate this issue fairly you must read the copious
material at the sites mentioned above. You must also be prepared to get into
dendrochonolgy and statistical analysis.

Where does that leave the rest of us?

For myself, I will confess immediately that the technical issues are over my
head, I don't know PCA from R^2 from a hole in the ground. But I think the
most critical point to remember, if you are researching this in the context
of determining the validity of AGW theory, is that this row is about a
single study that was published 8 years ago. This is starting to be ancient
history. If you feel it is tainted (as I prefer to just assume, because as I
said I do not want to put the required effort into unraveling it all for
myself) then simply discard it.

The fact is there are dozens of other reconstructions. These other
reconstructions do tend to show some more variability than MBH98, ie the
handle of the hockey stick is not as straight, but they *all* support the
general conclusions that the IPCC TAR came to in 2001: the late 20th century
warming is anamolous in the last one or two thousand years and the 1990's
are very likely warmer than any other time in the last one or two thousand
years.

Here is a nice superimposition of numerous global, hemispheric and regional
reconstructions for the last 2000 years and the last 12000 years together
with an average. References are all presented at the bottom of the pages.
Regional variations are of course greater than global, so don't be surprised
by how wavy some of the lines in there are. Does the 20th century stand out?

(Disclosu one of the reconstructions used in those pages is by the same
team that did the infamous hockey stick, but it is not the same study. To
the best of my knowledge, M&M have claimed no problems with that one, though
they have expressed some concerns that span the entire field of
dendrochronology).

I have read as much about this controversy as I ever will, and I have come
to the firm conviction that I do not have the technical background and/or
time required to make a scientific judgment on this issue one way or
another. That is the best objective opinion I can offer you. I suspect 95%
of the people you will come across arguing about this have chosen their
position ideologically.

And while MBH, in my mind, are in no way guilty of fraud or incompetence
until solidly proven to be so (many of the accusations do go this far), the
judgement of their research must be approached in reverse: given a reason to
doubt, I will not accept it until it is proven to me that the criticisms are
invalid. Neither case can I decided for myself until I devote the required
time to both the statistical background and the technical details of M&M vs
MBH98.

So where does that leave me? With the dozens of other proxy reconstructions,
some by the same team or involving members, some by completely different
people, some using tree rings, some using corals, some using stalagtites,
some using borehole measurements, all of which support the general
conclusions. And it is that general conclusion which is important to me, not
whether or not one Bristlecone pine was or was not included correctly in a
single 8 year old study.

The general conclusion is:


"Although each of the temperature reconstructions are different (due to
differing calibration methods and data used), they all show some similar
patterns of temperature change over the last several centuries. Most
striking is the fact that each record reveals that the 20th century is the
warmest of the entire record, and that warming was most dramatic after
1920."
http://www.ncdc.noaa.gov/paleo/globa...paleolast.html

I also urge anyone worried about this study and what its conclusion means
for the theory of Anthropogenic Global Warming to remember this: the study
of the past can be very informative, but it is not explanatory of the
present or predictive of the future.

The scientific basis for the dangers we face and their cause is about much
more than a few tree-rings and the temperature during the Medieval Warm
Period.

--
Coby Beck
(remove #\Space "coby 101 @ bigpond . com")