Global Warming Debate: Refuting Common Arguments

[Bored Wombat]

I referred to the exact title in the first part of the sentence; in the same sentence I referenced it again. Sorry for the confusion.

Well, I'm big enough to accept the apology, but I still suspect that you were trying to overstate your case. If you use an abbreviation for a term you should use it when you first use the term. But in this case it would look better for full disclosure if you explicitly mentioned that it did appear in the technical summary. Or at least that the term "summary" wasn't a good description for the summary for policy makers, especially to an audience interested in physics, who would be more familiar with the other summary.

And yes I'd say it is fair to say that some of the key ideas reflected in the MBH 98 hockey stick, namely that there was little or no medieval warming period, has indeed lost favour;

Well other northern hemisphere reconstuctions can have a slight bump around 1000 AD, but certainly not all of them.

The consensus is that it is certainly not as pronounced as might have been suspected from early, one site based studies. And the suspicion is that this would be further ameliorated if the southern hemisphere were included.

But the National Academies review found nothing wrong with Mann et al's treatment of the data at that time. It was the very recent end that they found that the statistical mistreatment resulted in Mann et al. under-reporting the expected error.

In what way do you mean "fallen out of favour"? Probably we can agree that any medieval warm period was likely at least half a degree cooler than temperatures this decade if we are talking about global mean surface temperature?

that this is reflected by its removal from the Summary for Policy Makers and its subsequent embedding in the graph in the Paleo section with several other competing studies that show a substantial medieval warming, comparable with today's warming.

Disagree. It's removal from the report was because it wasn't new, and had been covered in the 2001 report.

It speaks volumes for the respect that it is still held in that it nevertheless occurred twice in a report that is supposed to be about the findings since the previous report.

 

[Bored Wombat]

Perhaps I misunderstood. By 'ecological communities' that 'dont exist anymore' do you mean a species extinction? I took that to mean human communities. This another good reason for cites - in addition to the data, they avoid ambiguity.

Population extinction of many species, sometimes including total extinction.

No, I wasn't talking about human communities. I don't even know what a sub antarctic human community might mean. And we're talking about global warming, not Godzilla.

I will endeavour to cite more, but I have spoken in the last few years to ecologists looking at Australian freshwater communities, Australian desert communities, European amphibians, and Australian wetlands affected by dry land salinity, and only the last one did not speak with grief of the destruction of their studied area.

And the devastation of various sub-Antarctic communities by invasion by temperate species is now, I am told, well represented in the scientific literature. The concern seems to be now that Antarctic communities may soon fall by the same mechanism.

 

[Bored Wombat]

[my bold] Yes I've been all through it. I think you misread? Your first sentence directly contradicts the box:
One can not draw that conclusion from MBH 98, hence its disfavour.

Please cite a source for this claimed "disfavour".

 

[Andre]

One can not draw that conclusion from MBH 98

Please cite a source for this claimed "disfavour".

The http://republicans.energycommerce.house.gov/108/home/07142006_Wegman_Report.pdf

Overall, our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis.

 

[Andre]

Population extinction of many species, sometimes including total extinction.

No, I wasn't talking about human communities. I don't even know what a sub antarctic human community might mean. And we're talking about global warming, not Godzilla.

I will endeavour to cite more, but I have spoken in the last few years to ecologists looking at Australian freshwater communities, Australian desert communities, European amphibians, and Australian wetlands affected by dry land salinity, and only the last one did not speak with grief of the destruction of their studied area.

And the devastation of various sub-Antarctic communities by invasion by temperate species is now, I am told, well represented in the scientific literature. The concern seems to be now that Antarctic communities may soon fall by the same mechanism.

Where is the peer reviewed source?

 

[Bored Wombat]

The http://republicans.energycommerce.house.gov/108/home/07142006_Wegman_Report.pdf

The Wegman report raised some issues, and was certainly harsher than the more transparent and peer reviewed National Academies report.

It doesn't really stand for scientific opinion though. Do you have a peer reviewed source?

 

[Andre]

The Wegman report raised some issues, but and was certainly harsher than the more transparent and peer reviewed National Academies report.

What is your peer review resource to make that assessment?

 

[Bored Wombat]

Where is the peer reviewed source?

"The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-Antarctic sites." - http://www.frontiersinzoology.com/content/2/1/9" , Peck, Frontiers in Zoology 2005, 2:9 doi:10.1186/1742-9994-2-9

Perhaps for example: "Warming is likely to remove
physiological barriers on lithodid crabs that currently place a
limit on the invasion of shallow waters of the high Antarctic;
a scenario that is especially likely for waters oV the Antarctic
Peninsula" - http://epic.awi.de/Publications/Tha2008c.pdf"
Thatje et al, Polar Biol (2008) 31:1143–1148 DOI 10.1007/s00300-008-0457-5

(http://www.independent.co.uk/enviro...life-threatened-by-crab-invasion-782989.html", as the popular press put it)

http://www.telegraph.co.uk/science/science-news/3325543/Antarctic-seabed-ecosystems-invasion-threat.html" is another popular press write up, this time about a presentation at the AAAS conference in 2008:
"Unique Antarctic seabed ecosystems are under threat from invasions of species taking advantage of global warming, scientists have warned.

Predatory giant crabs, sharks and other fish are poised to make a return to the rapidly warming shallow waters around the South Pole for the first time in tens of millions of years.

Their come-back will disrupt the make-up of ancient communities of unusual animals such as sea spiders, brightly-coloured brittle stars, thin-shelled muscles and giant relatives of the woodlouse called isopods."

But, again, this is hardly controversial. The fact that species range changes is contributing to the 30% biodiversity drop over the past few decades is well marked in ecology.

 

[Bored Wombat]

What is your peer review resource to make that assessment?

It's not controversial that the National Academies Report's peer review process was transparent and the Wegman reports wasn't.

I have provided the news at nature's article that Mann et al. was vindicated. That is also what was reported in the popular press, and it was also the response of scientists. It is you who are making the controversial claims that needs peer reviewed support.

 

[mheslep]

Well, I'm big enough to accept the apology, but I still suspect that you were trying to overstate your case.

Im little interested in what you suspect about me.

If you use an abbreviation for a term you should use it when you first use the term. But in this case it would look better for full disclosure if you explicitly mentioned that it did appear in the technical summary. Or at least that the term "summary" wasn't a good description for the summary for policy makers, especially to an audience interested in physics, who would be more familiar with the other summary. Well other northern hemisphere reconstuctions can have a slight bump around 1000 AD, but certainly not all of them.

[...]

The consensus is that it is certainly not as pronounced as might have been suspected from early, one site based studies. And the suspicion is that this would be further ameliorated if the southern hemisphere were included.

But the National Academies review found nothing wrong with Mann et al's treatment of the data at that time. It was the very recent end that they found that the statistical mistreatment resulted in Mann et al. under-reporting the expected error.

In what way do you mean "fallen out of favour"? Probably we can agree that any medieval warm period was likely at least half a degree cooler than temperatures this decade if we are talking about global mean surface temperature?
Disagree. It's removal from the report was because it wasn't new, and had been covered in the 2001 report.

It speaks volumes for the respect that it is still held in that it nevertheless occurred twice in a report that is supposed to be about the findings since the previous report.

By disfavour I only refer to MBH 98/Mann99, not any broader topic in AGW, or paleo reconstruction. Perhaps I should say instead that it has been updated in 2007 w/ reconstructions considered more accurate? Anyway I see Vanesch has spoken more clearly here on the subject.
https://www.physicsforums.com/showpost.php?p=1926328&postcount=11

 

[mheslep]

The http://republicans.energycommerce.house.gov/108/home/07142006_Wegman_Report.pdf

Thanks Andre, though I think the National Academies report itself, when read in detail also does a good job of pointing out limitations.
Edit: In particular, I mean what the Academy has to say about:

...the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium.

from

• Mann, M.E and Bradley, R.S. (1999), Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations, in Geophysical Research Letters, Vol. 26, No. 6, p.759

...Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.

from

• Surface Temperature Reconstructions for the Last 2,000 Years, Report in Brief, The National Academies, June 22, 2006

http://dels.nas.edu/dels/rpt_briefs/Surface_Temps_final.pdf

 

[Andre]

It's not controversial that the National Academies Report's peer review process was transparent and the Wegman reports wasn't.

I have provided the news at nature's article that Mann et al. was vindicated. That is also what was reported in the popular press, and it was also the response of scientists. It is you who are making the controversial claims that needs peer reviewed support.

Really amazing, anyway, apparently the transcripts to the senate hearings of Oliver North seem to have disappeared; however his exact answer in testimony was recorded on numerous places, -when asked if he disputed the methodology conclusions of Wegman's report- he said:

No, we don’t. We don’t disagree with their criticism

 

[Monique]

The http://republicans.energycommerce.house.gov/108/home/07142006_Wegman_Report.pdf

This is a link to policy makers, but not to the real science. We all know political parties are colored, that's why there's an objection to the source.

 

[Andre]

It would be nice if examples can be given in the Wegman report to demonstrate that the sciencific conclusion is not supported by rigid unbiased reproduceable science especially when the NAS committee agreed with that conclusion as I showed in my previous post.

 

[Andre]

Anyway, let's do a quick recap. So here was the hockeystick in the Third Asssesment report of the IPCC of Mann Bradley and Hughes form 1999 (MBH99) which showed a flat temperature from 1000 Bc up intil about 1850 AD with suddenly rising temperatures. McIntyre and McKitrick demonstrated that MBH had used improper statistic methodologies.

So it was asked to the NAS and to http://www.galaxy.gmu.edu/stats/faculty/wegman.html to verify the critisism of McIntyre and McKitrick. Wegman confirmed that. The NAS with Oliver North in the chair had a more subtle approach. They had misgivings about the procedures of MBH but it would not matter because they stated that other research came to similar conclusions.

So in this thread it is now assumed that Wegman wrote something politcal (which seems to be threated here as biased/spin/fraud) while it also is assumed that the NAS endorsed MBH99. They did not. Because in the hearings of the Committee on Energy and Commerce of the House of Representatives, these were some of the statements of members of the NAS:

CHAIRMAN BARTON. I understand that. It looks like my time
is expired, so I want to ask one more question. 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. But again, just because the claims are made, doesn't
mean they are false.
CHAIRMAN BARTON. I understand that you can have the right
conclusion and that it not be--
DR. NORTH. It happens all the time in science.
CHAIRMAN BARTON. Yes, and not be substantiated by what you
purport to be the facts but have we established--we know that
Dr. Wegman has said that Dr. Mann's methodology is incorrect. Do
you agree with that? I mean, it doesn't mean Dr. Mann's
conclusions are wrong, but we can stipulate now that we have--and if
you want to ask your statistician expert from North Carolina that
Dr. Mann's methodology cannot be documented and cannot be verified
by independent review.
DR. NORTH. Do you mind if he speaks?
CHAIRMAN BARTON. Yes, if he would like to come to the
microphone.
MR. BLOOMFIELD. Thank you. Yes, Peter 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.

Now what to say about the discussion/allegations in this thread? like:

It's not controversial that the National Academies Report's peer review process was transparent and the Wegman reports wasn't.

I have provided the news at nature's article that Mann et al. was vindicated. That is also what was reported in the popular press, and it was also the response of scientists. It is you who are making the controversial claims that needs peer reviewed support.

I leave the conclusions to the readers.

 

[mheslep]

This is a link to policy makers, but not to the real science. We all know political parties are colored, that's why there's an objection to the source.

Edit:
The Wegman report in this link happens to be hosted on a policy maker's website.
Wegman is a scientific report, non-peer reviewed unless one counts the publicly documented statements on Wegman by the authors of the National Academies North report. On the other hand, the Nature News report post https://www.physicsforums.com/showpost.php?p=2419819&postcount=58" up thread on the subject is not peer reviewed material either.

 

[Xnn]

Of course science marches on and these past reports and reconstructions did not have the following available:

http://www.ucar.edu/news/releases/2009/arctic2k.jsp

https://www.physicsforums.com/attachment.php?attachmentid=21606&stc=1&d=1257469597

From the above perspective, it appears that the MWP (950 to 1100) was only minor warming period superimposed on a 1900 year cooling trend that was distinctly interrupted around 1900.

 

[Xnn]

Notice, that now we can say the following authority:

Arctic temperatures in the 1990s reached their warmest level of any decade in at least 2,000 years, new research indicates.

and it has nothing to do with tree rings or Michael Mann.

 

[Bored Wombat]

Im little interested in what you suspect about me.

You miss the point if you think I was discussing our personal relationship.

MBH 99 appeared in what most people here would consider the summary of the IPCC 2007 WG1 report.

By using the term "Summary" to refer to the SPM, you misrepresent the respect in which MBH is held.

By disfavour I only refer to MBH 98/Mann99, not any broader topic in AGW, or paleo reconstruction. Perhaps I should say instead that it has been updated in 2007 w/ reconstructions considered more accurate? Anyway I see Vanesch has spoken more clearly here on the subject.
https://www.physicsforums.com/showpost.php?p=1926328&postcount=11

I certainly agree that there is more data out there now, and that that increased the confidence that we have in these reconstructions. And that the more modern ones have had a many more datasets included in the analysis, and this also increases confidence in the results.

But MBH 1999 is not an outlier amongst reconstructions, and certainly the current view is nearer the MBH view than the pre-MBH view. So I don't think that it has fallen into any "disfavour".

 

[Bored Wombat]

...Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.

from

* Surface Temperature Reconstructions for the Last 2,000 Years, Report in Brief, The National Academies, June 22, 2006

Less confidence than the confidence that we have that the "Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium."

That's a fairly complete vindication of MBH, which has the average for the 20th century to be within the error bars on the temperature reconstruction for most of the time prior to about 1600.
http://en.wikipedia.org/wiki/File:Hockey_stick_chart_ipcc_large.jpg"

So, despite the phrase "even less confidence" this is exactly in line with the findings of the MBH 99 paper, for someone who has understood the error analysis in MBH 99.

 

[Bored Wombat]

It would be nice if examples can be given in the Wegman report to demonstrate that the sciencific conclusion is not supported by rigid unbiased reproduceable science especially when the NAS committee agreed with that conclusion as I showed in my previous post.

No the NA report found the same methodological flaws.

They, however, found that the conclusions were largely sound. Partly because the flaws did not affect the shape of the reconstruction, but only lead to an understating of the errors. And partly because those conclusions were supported by later work.

 

[Bored Wombat]

Edit:
The Wegman report in this link happens to be hosted on a policy maker's website.
Wegman is a scientific report, non-peer reviewed unless one counts the publicly documented statements on Wegman by the authors of the National Academies North report. On the other hand, the Nature News report post https://www.physicsforums.com/showpost.php?p=2419819&postcount=58" up thread on the subject is not peer reviewed material either.

The news at nature is not controversial.

It noted that the NA report found that there were methodological errors, but that these were not material, and it criticised the way the report was used.

But the claims from outside the scientific field were that the whole shape of the hockey stick was due to incorrect methodology, and this was shown not to be the case.

The Wegman report didn't focus so much on the fact that the methodological problems didn't make any material difference, and spent several pages looking at who in the field has published papers with each other ... Which I think is difficult to justify in the absence of any analysis as to what difference this makes to scientific publishing nor the peer review process.

Claiming that Mann et al is in a state of "disfavour" is controversial, because its findings have been nearly completely vindicated. So you need to provide a peer reviewed source to back that up. The Wegman report doesn't establish that "disfavour", certainly not amongst the scientific community. (About whom I assume we are talking about. Certainly there is disfavour from the aforementioned Jo Nova dot com, and other semi-professional science deniers.)

Does the IPCC 2007 report, which reproduces Mann et al 1999 twice, mention anything about its results being questionable?

 

[Bored Wombat]

Of course science marches on and these past reports and reconstructions did not have the following available:

http://www.ucar.edu/news/releases/2009/arctic2k.jsp

https://www.physicsforums.com/attachment.php?attachmentid=21606&stc=1&d=1257469597

From the above perspective, it appears that the MWP (950 to 1100) was only minor warming period superimposed on a 1900 year cooling trend that was distinctly interrupted around 1900.

Yes. Global warming is exaggerated at the poles, because CO2 overlaps with H2O, and there's not much atmospheric H2O concentration at the poles.

This gives more evidence that the warming is a greenhouse warming, but it is a little unfair to compare it with temperature reconstructions for the whole hemisphere, because it is stronger than the warming for the whole hemisphere.

 

[Xnn]

Yes. Global warming is exaggerated at the poles, because CO2 overlaps with H2O, and there's not much atmospheric H2O concentration at the poles.

This gives more evidence that the warming is a greenhouse warming, but it is a little unfair to compare it with temperature reconstructions for the whole hemisphere, because it is stronger than the warming for the whole hemisphere.

I agree. However, the reconstructions and analysis that have been done in the past did not have this new source of information available. It's not dependant on tree rings or Michael Mann. So, if a reconstruction of NH temperature history were to be constructed today, it should include this new data, which shows the MWP in an entirely different perspective.

For example, the period 950 to 1100 was not the warmest period prior to 1900 within the Arctic and we can say that the 1990's appear to be the warmest decade for the Arctic over the last 2000.

 

[mheslep]

The news at nature is not controversial.

Yes, it can be as it's news, but that matters not. It is not an peered reviewed source.

It noted that the NA report found that there were methodological errors, but that these were not material, and it criticised the way the report was used.

The mistakes were as I detailed https://www.physicsforums.com/showpost.php?p=2426834&postcount=81", which state that Mann deserves little "confidence" beyond 400 years (their word, not mine). I'd appreciate it if we stick to direct quotes from the sources (Mann and NA), and not other summaries.

But the claims from outside the scientific field were that the whole shape of the hockey stick was due to incorrect methodology, and this was shown not to be the case.

Not interested in claims from non scientific sources for discussion here, hopefully we can dispense with reference to those as well.

Claiming that Mann et al is in a state of "disfavour" is controversial,

Disfavour was a poor word choice on my part, as it smacks of a reliance on some community somewhere. I corrected it above.

because its findings have been nearly completely vindicated.

There's no room for 'completely' in that sentence regarding Mann 99, given the actual source material presented in this thread.

...So you need to provide a peer reviewed source to back that up. The Wegman report doesn't establish that "disfavour", certainly not amongst the scientific community.

As has been discussed in this forum, it's not useful to try and speak for the sentiment of the scientific community. Argument based on the sources is the way to go.

 

[mheslep]

But MBH 1999 is not an outlier amongst reconstructions, and certainly the current view is nearer the MBH view than the pre-MBH view. So I don't think that it has fallen into any "disfavour".

We mean here Mann et al 1999, the millennial reconstruction covering the MWP and featured in the Summary For Policy Makers 2001, not MBH 98's 400 year reconstruction. And yes I think Mann et al 1999 deserves little "confidence" further back than 400 years as the NA report states, and yes I think there's a significant difference between what Mann et al shows around 1000AD, basically showing no MWP to my eye, and what is said in the IPCC 2007

mean temperatures during medieval times (950–1100) were indeed warm in a 2-kyr context

Based on this, other reconstructions shown in IPCC 2007, and my glance at http://en.wikipedia.org/wiki/File:Hockey_stick_chart_ipcc_large.jpg" , I qualitatively call Mann 1999 wrong about the MWP.

 

[mheslep]

Of course science marches on and these past reports and reconstructions did not have the following available:

http://www.ucar.edu/news/releases/2009/arctic2k.jsp

https://www.physicsforums.com/attachment.php?attachmentid=21606&stc=1&d=1257469597

From the above perspective, it appears that the MWP (950 to 1100) was only minor warming period superimposed on a 1900 year cooling trend that was distinctly interrupted around 1900.

The actual paper and abstract:

• Kaufman, D.S. et al, 2009. Recent Warming Reverses Long-Term Arctic Cooling, Science 4 September 2009, Vol. 325. no. 5945, pp. 1236 - 1239. DOI: 10.1126/science.1173983

Abstract:

The temperature history of the first millennium C.E. is sparsely documented, especially in the Arctic. We present a synthesis of decadally resolved proxy temperature records from poleward of 60°N covering the past 2000 years, which indicates that a pervasive cooling in progress 2000 years ago continued through the Middle Ages and into the Little Ice Age. A 2000-year transient climate simulation with the Community Climate System Model shows the same temperature sensitivity to changes in insolation as does our proxy reconstruction, supporting the inference that this long-term trend was caused by the steady orbitally driven reduction in summer insolation. The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2000-year-long reconstruction occurring between 1950 and 2000.

http://www.sciencemag.org/cgi/content/abstract/325/5945/1236

I wonder what type of proxies are available at those latitudes. Reading to come.

 

[Bored Wombat]

I agree. However, the reconstructions and analysis that have been done in the past did not have this new source of information available. It's not dependant on tree rings or Michael Mann. So, if a reconstruction of NH temperature history were to be constructed today, it should include this new data, which shows the MWP in an entirely different perspective.

For example, the period 950 to 1100 was not the warmest period prior to 1900 within the Arctic and we can say that the 1990's appear to be the warmest decade for the Arctic over the last 2000.

Good point.

 

[Bored Wombat]

Yes, it can be as it's news, but that matters not. It is not an peered reviewed source.

I’m not saying that news can’t be controversial; I’m saying that in this particular case isn’t controversial.

The NA report was a vindication of Mann et al. The only people saying otherwise are not only not peer reviewed, they’re on website’s whose editorial position is explicitly counterscientific.

The mistakes were as I detailed https://www.physicsforums.com/showpost.php?p=2426834&postcount=81", which state that Mann deserves little "confidence" beyond 400 years (their word, not mine). I'd appreciate it if we stick to direct quotes from the sources (Mann and NA), and not other summaries.

They do not state that Mann deserves little confidence.

They state that less confidence can be placed in the statement that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” than the statement that “the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium.”

The previous paragraph talks more specifically about Mann et al: “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 evidence that includes the additional large-scale surface temperature reconstructions and documentation of the spatial coherence of recent warming described above (Cook et al. 2004, Moberg et al. 2005b, Rutherford et al. 2005, D’Arrigo et al. 2006, Osborn and Briffa 2006, Wahl and Ammann in press) and also the pronounced changes in a variety of local proxy indicators described in previous chapters (e.g., Thompson et al. in press).”

As I have pointed out already, the error bars in Mann et al 1999 also show that there is not strong confidence in the conclusion that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium”. So again the NA report, is in full agreement with Mann et al on that point.

This is why those secondary sources are all explaining that the NA report backed the hockey stick graph. Now they are not peer reviewed, but neither is your own opinion that they said “that Mann deserves little "confidence" beyond 400 years”. You're misreading the report to get that, you're taking the paragraph about "confidence" isolated, out of context, and claiming it refers to Mann et al (1999) in general. In this case respected secondary sources such as news at nature can be useful, because they make it clear that your analysis is an outlier.

 

[Bored Wombat]

http://en.wikipedia.org/wiki/File:Hockey_stick_chart_ipcc_large.jpg" , I qualitatively call Mann 1999 wrong about the MWP.

It agrees within the error with other reconstructions.

So it's right.

 

[mheslep]

Ah, finally a new page! Guys let's shrink those image posts that explode the page width?

Okay, here's the entire tail end of the http://dels.nas.edu/dels/rpt_briefs/Surface_Temps_final.pdf" without omission. I think it is helpful to post here.

[...]
o Very little confidence can be assigned to statements 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 combine them are larger than during more recent time periods.

The main reason that our confidence in large-scale surface temperature reconstructions
is lower before A.D. 1600 and especially before A.D. 900 is the relative scarcity of precisely
dated proxy evidence. Other factors limiting our confidence in surface temperature reconstructions include the relatively short length of the instrumental record (which is used to calibrate and validate the reconstructions); the fact that all proxies are influenced by a variety of climate variables; the possibility that the relationship between proxy data and local surface temperatures may have varied over time; the lack of agreement as to which methods are most appropriate for calibrating and validating large-scale reconstructions
and for selecting the proxy data to include; and the difficulties associated with constructing
a global or hemispheric mean temperature estimate using data from a limited number of sites and with varying chronological precision. All of these considerations introduce uncertainties that are difficult to quantify.

Despite these limitations, the committee finds that efforts to reconstruct temperature histories for broad geographic regions using multiproxy methods are an important contribution to climate research and that these large-scale surface temperature reconstructions contain meaningful climatic signals. The individual proxy series used to create these reconstructions generally exhibit strong correlations with local environmental conditions, and in most cases there is a physical, chemical, or physiological reason why the proxy reflects local temperature variations. Our confidence in the results of these reconstructions becomes stronger when multiple independent lines of evidence point to the same general result, as in the case of the Little Ice Age cooling and the 20th century warming.

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 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. 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.

Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. The substantial uncertainties currently present in the quantitative assessment of large scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.

In addition to this text, the NA report includes Figure S-1 showing other well known reconstructions in which at least two, Moberg et al and Esper et al, are showing circa 1000AD was the warmest part of their proxy reconstructions in the last 1000 years (though they may end in 1980?)

Then note the last part I bold faced. The 'less confidence' in that sentence from the NA does not refer to the wide error bars Mann et al associated with its prior to 1600AD estimates, but rather it refers to the high time resolution claims made in Mann et al's use of the terms 'decade' and 'year', i.e., because not all of the proxies record "information on such short timescales." Specifically on this point of making claims re short timescales, NA is not in agreement with Mann et al.

NA also prefers the word "plausible" over "likely" about the warmest period in a 1000 years. As an amateur, I agree.

 

[Bored Wombat]

In addition to this text, the NA report includes Figure S-1 showing other well known reconstructions in which at least two, Moberg et al and Esper et al, are showing circa 1000AD was the warmest part of their proxy reconstructions in the last 1000 years (though they may end in 1980?)

But less than the temperatures in the 1990s.

Then note the last part I bold faced. The 'less confidence' in that sentence from the NA does not refer to the wide error bars Mann et al associated with its prior to 1600AD estimates,

That's right.
Mann et al's error analysis is independently in agreement with the NA report on this.

but rather it refers to the high time resolution claims made in Mann et al's use of the terms 'decade' and 'year', i.e., because not all of the proxies record "information on such short timescales." Specifically on this point of making claims re short timescales, NA is not in agreement with Mann et al.

Largely it is. Mann et al says nearly exactly the same thing materially.

NA also prefers the word "plausible" over "likely" about the warmest period in a 1000 years. As an amateur, I agree.

No, they don't compare "plausible" to any other term. But if that's the basis of your claim that Mann et al. "deserves little confidence", that Mann et al used the word "likely" whereas the NA used the word "plausible", then you make too much of the language and not enough of the error analysis in Mann et al.

 

[Andre]

"The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-Antarctic sites." - http://www.frontiersinzoology.com/content/2/1/9" , Peck, Frontiers in Zoology 2005, 2:9 doi:10.1186/1742-9994-2-9

Perhaps for example: "Warming is likely to remove
physiological barriers on lithodid crabs that currently place a
limit on the invasion of shallow waters of the high Antarctic;
a scenario that is especially likely for waters oV the Antarctic
Peninsula" - http://epic.awi.de/Publications/Tha2008c.pdf"
Thatje et al, Polar Biol (2008) 31:1143–1148 DOI 10.1007/s00300-008-0457-5

(http://www.independent.co.uk/enviro...life-threatened-by-crab-invasion-782989.html", as the popular press put it)

http://www.telegraph.co.uk/science/science-news/3325543/Antarctic-seabed-ecosystems-invasion-threat.html" is another popular press write up, this time about a presentation at the AAAS conference in 2008:
"Unique Antarctic seabed ecosystems are under threat from invasions of species taking advantage of global warming, scientists have warned.

Predatory giant crabs, sharks and other fish are poised to make a return to the rapidly warming shallow waters around the South Pole for the first time in tens of millions of years.

Their come-back will disrupt the make-up of ancient communities of unusual animals such as sea spiders, brightly-coloured brittle stars, thin-shelled muscles and giant relatives of the woodlouse called isopods."

But, again, this is hardly controversial. The fact that species range changes is contributing to the 30% biodiversity drop over the past few decades is well marked in ecology.

and the times, they are a changing:

http://www.sciencemag.org/cgi/content/summary/326/5954/806

Over the past decade, several models have been developed to predict the impact of climate change on biodiversity. Results from these models have suggested some alarming consequences of climate change for biodiversity, predicting, for example, that in the next century many plants and animals will go extinct (1) and there could be a large-scale dieback of tropical rainforests (2). However, caution may be required in interpreting results from these models, not least because their coarse spatial scales fail to capture topography or "microclimatic buffering" and they often do not consider the full acclimation capacity of plants and animals (3). Several recent studies indicate that taking these factors into consideration can seriously alter the model predictions (4–7).

 

[mheslep]

and the times, they are a changing:

Interesting what happens at higher resolution. More from Willis and Bhagwat:

[...]
In one study, Randin et al. assessed the influence of spatial scale on the accuracy of bioclimatic model predictions of habitat losses for alpine plant species in the Swiss Alps (4). A coarse European-scale model (with 16 km by 16 km grid cells) predicted a loss of all suitable habitats during the 21st century, whereas a model run using local-scale data (25 m by 25 m grid cells) predicted persistence of suitable habitats for up to 100% of plant species.
[...]
Many studies have indicated that increased atmospheric CO2 affects photosynthesis rates and enhances net primary productivity—more so in tropical than in temperate regions—yet previous climate-vegetation simulations did not take this into account.

 

[Bored Wombat]

Interesting what happens at higher resolution. More from Willis and Bhagwat:

That is interesting.

And it helps explain why the "Extinction Risk" paper poorly modeled extinction over the end of the last glaciation.

But an isolated community with a small gene-pool is still on the road to extinction. It can be wiped out by a small land use change, or flood or fire, and has little capacity to adapt to change or disease.

So, while it improves modelling I don't think that it genuinely affects the observed facts such as: "The fact that species range changes is contributing to the 30% biodiversity drop over the past few decades is well marked in ecology."