Oh brother...

http://www.desmogblog.com/wegman-wiggles-out-of-hockey-stick-accountability

Isn't this Wegman, I suppose, one of the world's leading authorities on statistics?

from
http://www.aaas.org/spp/cstc/stc/Archive/stc06/06_07_stcnewsletter.htm

QUOTE
During the hearing, Edward Wegman, a statistician at George Mason University, testified on behalf of the mathematicians who reviewed the Mann papers. Wegman stated, “The proxy data exhibiting the hockey stick shape are actually decentered low.” Wegman showed that the procedure used by Mann was in principle capable of distorting the shape of a graph, though he did not provide an alternative reconstruction of the original Mann data. Surprisingly, there was no actual dispute over the shape of the famous hockey stick graph after all, since nobody argued that its shape would be altered through the use of different techniques. Wegman additionally advocated that “evaluation by statisticians should be standard practice” in the grant applications of any scientific study with policy implications.


At Chairman Boehlert’s request, the National Academy of Sciences recently reviewed this issue. In a report released on June 22, entitled Surface Temperature Reconstructions for the Last 2,000 Years, the Academy concluded that, while Mann’s statistical procedures weren’t optimal, the procedure did not unduly distort his conclusions, which the Academy reinforced. “The basic conclusion of Mann et al. was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2,000 years.” Due to the degree of uncertainty in the temperature estimates from many centuries ago, the Academy did not support Mann’s specific claims that the 1990s was the hottest decade and 1998 the hottest year in the past millennium.

UNQUOTE


So much ado about nothing. This hockey stick seems to be still valid.

Hope I don't seem obsessive. Just want to get to the bottom of this.

http://news.bbc.co.uk/1/hi/sci/tech/5109188.stm
QUOTE
The new report, carried out by a panel of the US-based National Research Council (NRC), largely vindicates the researchers' work, first published in 1998.
UNQUOTE

So what does Wegman have to say now? Can both "sides" be right?

Hopefully me last post on this HS subject...

quote:

Originally posted by JL(SFC58,AFCB):


If my memory serves me right (and I concede it might not), M&M did attempt to challenge in either Nature or Scientific American, but were told that their article was too complicated! I think LKW will know for sure whether this was the case.

Too complicated for the world's most respected scientific publication? I find that somewhat unlikely, but no doubt Steve_M or John_M can comment?

Lots of links for further reading at the bottom of
http://en.wikipedia.org/wiki/Hockey_Stick_graph

One thing I'd like answering, though: if the Hockey Stick or AGW in general are on such shaky ground why do the "sceptics" so often find it necessary to use fake and misrepresented information? Why not stick to the facts? They should be enough, but we get stuff like the Beck graph and the ones used in TGGWS (actually without watching it again I'm not sure that TGGWS didn't use the Beck graph anyway)?
http://www.realclimate.org/index.php/archives/2007/05/the-weirdest-millennium/

quote:

Originally posted by realprimate:
Hope I don't seem obsessive. Just want to get to the bottom of this.

http://news.bbc.co.uk/1/hi/sci/tech/5109188.stm
QUOTE
The new report, carried out by a panel of the US-based National Research Council (NRC), largely vindicates the researchers' work, first published in 1998.
UNQUOTE

So what does Wegman have to say now? Can both "sides" be right?

Hopefully me last post on this HS subject...

I hope not! The claim that MBH98 has been discredited keeps reappearing on forums like this. Of course the people claiming this don't mention the NRC report on the same subject, which clearly states that although there were flaws in the statistical methods used by MBH, they are insignificant and do not alter the outcome.

BTW I find it makes a post more readable if I use italics for quotes from external sources, but that's JMO.

It has been discredited for a whole list of reasons. Sheesh, you guys tie yourself up into knots on this.

What McIntyre & McKinrick achieved was to gain a corrigendum to be issued by Nature on the MBH98/99 papers. There should have been a further corrigendum issued but that would have been too embarrassing for a publication which has published its fair amount of fraudulent papers in the last few years due to its editorial policy to go for the exciting and new.

There is also the problem that the supposed validation by Wahl & Ammann 2006 paper actually agrees with McIntyre & McKinrick on the r2 statistic (W&A 0.16/M&M 0.14). Pretty meaningless correlation with which to base a reconstruction of past climates.

There also the problem with the supposed independent studies which agree with MBH98/89 as the data used by them is the same small data set that give a hockey stick shape. In fact some of these "independent" studies use the MBH outputs as an input for their analysis.

The fact remains that palaeoclimatology remains a somewhat wishy-washy science. I agree with the conclusion of the NAS North Panel that the proxies just are not reliable to construct past climate conditions. Especially if you have to rely on vaguely supernatural concepts such as "teleconnections".

Indeed, if I can find the link to the press conference of the NAS report, you'll hear the panel state that MBH98/99 studies were flawed and shouldn't have been used in the IPCC TAR. If you read the report carefully, you see a recommendation to avoid the usage of proxies such as bristlecones as these are not a temperature proxy. And its the bristlecones which give MBH98/99 its hockey shape.

Personally, its not the relative merits of this paper that should concern people but the behaviour of Mann. Once you publish something, your study should then be open to others to replicate. This means that data, methodology and source codes should be available via the journal that your study is published in. This is just good scientific practice. Passing peer review doesn't a scientific hypothesis make. Its surviving the attention of your peers trying to replicate or disprove the results that count. This is easier in disciplines such as mathematics or physics as you have to literally write the equation out.

The problem to me is that for a paper which states that the methodology used was novel, its usage in the TAR was politically motivated (the graph turns up 6 times in the Summary for Policy-makers).

There a whole lot more I can say on this but my lamb roast smells almost done.

Thanks LKW. That puts it all into context.

And the r2 statistic is just what I wanted; but what I don't know is what the variables were that were correlated (or not!). Was it model output and real world observations? If so, then in any normal science, the model would simply be ditched as having little explanatory value.

quote:

Originally posted by JL(SFC58,AFCB):
Thanks LKW. That puts it all into context.

And the r2 statistic is just what I wanted; but what I don't know is what the variables were that were correlated (or not!). Was it model output and real world observations? If so, then in any normal science, the model would simply be ditched as having little explanatory value.

Er. hmmmmm.


http://www.realclimate.org/index.php/archives/2006/08/f...ockeystick-hearings/

emeritus Stanford Physics Professor David Ritson who has identified significant apparent problems with the calculations contained in the Wegman report,

This whole issue has virtually nothing to do with the Hockey Stick at all really. It's more an attack on the peer review process. There might be valid points here given the increasing importance of getting the science right, but the attack is hardly being carried out in the most constructive manner. Having spent a couple of weeks at climateaudit.org I can understand the modus operandi a bit more clearly.

It all started with a bunch of mostly European-centric anecdotal evidence suggesting existence of a medieval warming period and little ice age. When the proxy evidence was looked at, the MWP and LIA turned out not to have been extreme as was understood (within the limits of knowledge). As an aside, the authors suggested that 1998 was possibly the hottest year, and the 1990s the hottest decade of the last millennium.

The degree of qualification of these final statements is probably not strong enough given the statistical basis, but even so, in a normal scientific process this would have been successfully tested and either falsified or confirmed by later studies.

Instead, some minor statistical flaws plus more doubt being thrown at the proxy data have been inflated into a massive row. Given that the hockey stick graph is hardly the cornerstone of the AGW debate, it is a distraction. And it's a standard political technique, where you point out one flaw, and when that flaw is dealt with you say "yes, but really the flaw was symptomatic of another flaw" and so on. So while evidence for a globally coherent MWP is non-existent, the argument has moved onto suggesting, without evidence, that the "flaws" in MBH98/99 are symptomatic of the AGW debate as a whole.

The Wegman report was nothing more than an attack on the peer review process based on a load of psychological mumbo-jumbo about "social network analysis". There was no effort in this report to check whether the Hockey Stick was a reasonable result, and when asked about that, Wegman side-stepped the question saying he didn't have the time to do it. If he had done so, it would have weakened the political force of his report considerably.

Good old Steve to the rescue. Yeah I was about to ask whether Wegman had done a curve of his own based on the same data as Mike Mann. I'd probably need to use my dad's magnifying glass to see the difference IMHO.

And as for the LIKW's opinion of Mike Mann's behaviour. Compared to the sceptics (beginning to feel the term delusionists more appropriate, deniers too loaded etc) Mike Mann's the driven snow.

quote:

Originally posted by realprimate:
Good old Steve to the rescue. Yeah I was about to ask whether Wegman had done a curve of his own based on the same data as Mike Mann. I'd probably need to use my dad's magnifying glass to see the difference IMHO.

And as for the LIKW's opinion of Mike Mann's behaviour. Compared to the sceptics (beginning to feel the term delusionists more appropriate, deniers too loaded etc) Mike Mann's the driven snow.

And you wonder why you find it difficult to convert sceptics???????????

quote:

Originally posted by JL(SFC58,AFCB):

And you wonder why you find it difficult to convert sceptics???????????

Cut's both ways JL. One side has a mountain of scientific peer reviewed evidence. The other's reduced to sniping from the sidelines.

quote:

Originally posted by realprimate:
Good old Steve to the rescue. Yeah I was about to ask whether Wegman had done a curve of his own based on the same data as Mike Mann. I'd probably need to use my dad's magnifying glass to see the difference IMHO.

And as for the LIKW's opinion of Mike Mann's behaviour. Compared to the sceptics (beginning to feel the term delusionists more appropriate, deniers too loaded etc) Mike Mann's the driven snow.

I've always said that "sceptic" is inappropriate. "Denier/denialist" is too loaded as it implies a similarity to holocaust denial. I think "contra", short for contrarian, works quite well. I think some contras are delusional about this, especially the ones that go on about lefty/greeny conspiracies to tax, tax, tax, but to call them all delusional is going too far.

BTW ExxonMobil accept that GW is happening, although they disagree with Kyoto about how to deal with it.
http://business.guardian.co.uk/story/0,,2103541,00.html
ExxonMobil criticised Greenpeace, the Kyoto treaty and the European carbon trading system yesterday but insisted it was not a "climate change denier" and said it wanted to play a constructive role in countering global warming.
What do the contras make of that?

Steve M

quote:

Given that the hockey stick graph is hardly the cornerstone of the AGW debate

So temperatures rising between 1850 and 1998 (and a suppressed MWP) is hardly the cornerstone of AGW - then what is? It seems pretty important given the amount it's used as a graphic to illustrate the AGW case.

quote:

Originally posted by Steve_M:
So while evidence for a globally coherent MWP is non-existent, the argument has moved onto suggesting, without evidence, that the "flaws" in MBH98/99 are symptomatic of the AGW debate as a whole.

Hardly Steve - its more a comment on the limitations of palaeoclimatology.

The NAS panel got it right when they stated that the limitation of proxies means that its a 50/50 bet whether the mediaeval period was cooler or warmer than today. Effectively it a case where a science has been stretched beyond its limitations.

The statistical methodology used in MBH98/99 had the problem that random noise generated hockey sticks shapes. This was the corrigendum issued by Mann in Nature. Correcting this meant that only 8% of the data used generated a hockey stick signature - the rest is noise (moving the hockey stick shape from being the dominant Principle Component or PC1 to PC4). This signature was from the bristlecone data collected by Graybill.

Mann knew that the bristlecones were a dominant data-group because he ran an analysis without them which gave merely noise. The fact that when faced with this result, he merely censored the file and carried on to publish MBH98 doesn't reflect well on him. The ironic thing is that when Mann eventually sent data to McIntyre, it included the censored file.

Also, the problem for M&M, Wegman and anybody else is that Mann has never produced the actual data and methodology he specifically used. So no-body has been able to replicate the results in MBH98/99. There are still methodological questions to answer.

I note Steve that you don't argue against Wegman's statistical analysis or the NAS panel's comments on the bristlecones. Why not accept that palaeoclimatology is not worth paying attention to and that the IPCC shouldn't be including it in their reports.

quote:

Originally posted by realprimate:

quote:

Originally posted by JL(SFC58,AFCB):

And you wonder why you find it difficult to convert sceptics???????????

Cut's both ways JL. One side has a mountain of scientific peer reviewed evidence. The other's reduced to sniping from the sidelines.

And I think we've seen what peer-review is worth. Get your mates to do it.

And I'm not trying to persuade you - I'm just a sceptic, not a denialist.

quote:

Originally posted by TrueSceptic:

ExxonMobil criticised Greenpeace, the Kyoto treaty and the European carbon trading system yesterday but insisted it was not a "climate change denier" and said it wanted to play a constructive role in countering global warming.
What do the contras make of that?

I have no problem with that. I also accept that temperatures have risen by 0.8 degrees (perhaps a bit less, but that's not worth arguing about) in the past 150 years. Let's all panic.......

quote:

Originally posted by Lost in Kate Winslet:
Also, the problem for M&M, Wegman and anybody else is that Mann has never produced the actual data and methodology he specifically used. So no-body has been able to replicate the results in MBH98/99. .

Well whaddaya know.

Surfed and got this:-

http://timlambert.org/2005/06/barton/

Tim Lambert Says:
June 29th, 2005 at 4:03 am
Sigh. Mann’s data and algorithm is here. His results have been independently reproduced, see here.

http://www.nature.com/nature/journal/v430/n6995/extref/nature02478-s1.htm

http://www.ucar.edu/news/releases/2005/ammann.shtml

Any comments LIKW? Is that the data? After all if you look at my previous posts I got some outstanding questions on the whole issue. Now gotta work.

quote:

Originally posted by JL(SFC58,AFCB):

I have no problem with that. I also accept that temperatures have risen by 0.8 degrees (perhaps a bit less, but that's not worth arguing about) in the past 150 years. Let's all panic.......

Also another 0.6degs "in the pipeline". So from non peer reviewed arithmetic that's 1.4degs which is getting ominously close to that "must not exceed 2degs" dictum from someone.

quote:

Originally posted by realprimate:

quote:

Originally posted by Lost in Kate Winslet:
Also, the problem for M&M, Wegman and anybody else is that Mann has never produced the actual data and methodology he specifically used. So no-body has been able to replicate the results in MBH98/99. .

Well whaddaya know.

Surfed and got this:-

http://timlambert.org/2005/06/barton/

Tim Lambert Says:
June 29th, 2005 at 4:03 am
Sigh. Mann’s data and algorithm is here. His results have been independently reproduced, see here.

http://www.nature.com/nature/journal/v430/n6995/extref/nature02478-s1.htm

http://www.ucar.edu/news/releases/2005/ammann.shtml

Any comments LIKW? Is that the data? After all if you look at my previous posts I got some outstanding questions on the whole issue. Now gotta work.

Aarrgghh... Not Tim Lambert...

Sorry realprimate but I don't take Tim seriously in this debate. Tim has his own field of focus on the AGW debate but I have found him dogmatic and subject to getting hooked on a pedantic level in order to promote his AGW position.

Also I said that in the above post:

quote:

Mann has never produced the actual data and methodology he specifically used.

The reason is that you cannot replicate Mann's results using that data set and there remains unanswered questions about the precise statistical methodology used. Perhaps if Mann provided the computer code then it might be that the data set is the correct one but until that happens, the statement that nobody has been able to replicate the results in MBH98/99 stands.

The Wahl and Ammann article you linked is interesting because they agree with my comment in the above paragraph. The key quote to note is:

quote:

reproduced the MBH results using their own computer code.

They were not able to replicate it using Mann's computer code.

There is also something you should be aware of when they say that:

quote:

They found the MBH method is robust even when numerous modifications are employed.

Its not the r2 statistic which they are using here (they agree with M&M using r2) but rather the R statistic. Now note the following from the article:

quote:

Their results appear in two new research papers submitted for review to the journals Geophysical Research Letters and Climatic Change.

This is important to note because W&A split the argument for MBH being robust into their Climate Change article while the proof that R gives a robust result was in their GRL article.

The GRL article was never published because it failed peer-review. Yet Climatic Change published their article despite knowing that this had occurred. The GRL article was the foundation on which they built their argument. If this hasn't been published then the claim that Mann's results have been independently reproduced is invalid.

Hope that helps.

Son of Mulder

quote:

So temperatures rising between 1850 and 1998 (and a suppressed MWP) is hardly the cornerstone of AGW - then what is? It seems pretty important given the amount it's used as a graphic to illustrate the AGW case.

Clarification. The shaft of the hockey stick is not the cornerstone of AGW science. I think I've already said that I think the graphic is used a lot because it struck a chord with politicians - I don't know whether that's true or not. The NAS panel says the following (which also justifies keeping the science in the IPCC report):

quote:

Surface temperature reconstructions for periods
prior to the industrial era are only one of multiple
lines of evidence supporting the conclusion that
climatic warming is occurring in response to human
activities, and they are not the primary evidence.

It's not correct to say that the NAS report suggested there was a 50-50 chance that the MWP was warmer than now. Here are their conclusions:

quote:

It can be said with a high level of confidence
that global mean surface temperature was
higher during the last few decades of the 20th
century than during any comparable period
during the preceding four centuries. This
statement is justified by the consistency of the
evidence from a wide variety of geographically
diverse proxies.

Less confidence can be placed in large-scale
surface temperature reconstructions for the
period from A.D. 900 to 1600. Presently available
proxy evidence indicates that temperatures
at many, but not all, individual locations were
higher during the past 25 years than during any
period of comparable length since A.D. 900.
The uncertainties associated with reconstructing
hemispheric mean or global mean temperatures
from these data increase substantially backward
in time through this period and are not yet fully
quantified.

Very little confidence can be assigned to state-
ments concerning the hemispheric mean or
global mean surface temperature prior to about
A.D. 900 because of sparse data coverage and
because the uncertainties associated with proxy
data and the methods used to analyze and com-
bine them are larger than during more recent
time periods.

...

The basic conclusion of Mann et al. (1998,
1999) was that the late 20th century warmth in the
Northern Hemisphere was unprecedented during
at least the last 1,000 years. This conclusion has
subsequently been supported by an array of evi-
dence that includes both additional large-scale sur-
face temperature reconstructions and pronounced
changes in a variety of local proxy indicators, such
as melting on icecaps and the retreat of glaciers
around the world, which in many cases appear to be
unprecedented during at least the last 2,000 years.
Not all individual proxy records indicate that the
recent warmth is unprecedented, although a larger
fraction of geographically diverse sites experienced
exceptional warmth during the late 20th century
than during any other extended period from A.D.
900 onward.