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jethro

New Research

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The theory for AGW has been around for some time now, the last IPCC report was released a couple of years ago, what new research has questioned, refined, augmented the theory?

Please only post peer reviewed papers, abstracts from science journals or links to academic research in this thread.

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It doesn't provide answers regarding the question "how much of the global warming is natural and how much is AGW", but NCDC has May 2010, March-May 2010 and January-May 2010 combined as the warmest on record globally, just ahead of 1998:

http://www.ncdc.noaa.gov/sotc/?report=global&year=2010&month=5&submitted=Get+Report

I disputed the prior assertions from Sunny Starry Skies and a few others based on GISS data that stated that Winter 2009/10 was the warmest globally, since NCDC and CRU didn't agree, but the spring is another matter, with NCDC coming into agreement, and CRU had March/April combined coming close to being the warmest on record.

Given that the recent El Nino was weaker than the 1998 one, yet global temperatures have exceeded 1998 levels, the implication is that we are continuing to see an underlying warming trend, with high confidence limits that the overall trend is in the range of 0.1 to 0.3C per decade (higher values will assume a significant negative influence from PDO/solar, lower values will not).

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Here's a wealth of information about plants, crops and the Rain Forest.

Intensive farming may not be all bad:

http://www.newscientist.com/article/dn19042-intensive-farming-massively-slowed-global-warming.html

Hope that the increasing demand for Palm oil may be able to be managed sustainably:

http://www.pnas.org/content/107/24/11140.abstract

How plants utilise the increased CO2 levels together with indications that they sequester the extra carbon in the soil:

http://www.pnas.org/content/107/24/10938.full.pdf

The importance of the Rain forest in absorbing CO2 emissions and how this may be incorperated into the international climate accord:

http://www.pnas.org/content/107/24/10821.abstract

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It's a little old (so not quite in keeping with the spirit of this thread) but this (PDF), it seems to me, is an excellent starting point, structured as a scientific review, for those wishing to delve deeper into the details.

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It's a little old (so not quite in keeping with the spirit of this thread) but this (PDF), it seems to me, is an excellent starting point, structured as a scientific review, for those wishing to delve deeper into the details.

Hi V.P,

Thanks for posting the above. I am afraid that I don't share your enthusiasm for the linked paper however.

Much of Michael Mann's temperature reconstructions have been discredited (just finished reading a book entitled' The Hockey stick illusion)', or you can go to Climate audit (google it) and see the various papers and saga surrounding the use of various data and mathematical techniques that Mann and others have used in regards to the use of proxy data.

I know that this paper is a general overview, but accepts and includes an aweful lot of discredited data and references that should not have been.

I think V.P with your mathematical background you should check this out. The use of dubious verification statistics (criticised by the US congress and various expert pannels), the use of short-centering, and effective mining the data for 'Hockey stick' shapes is quite shocking in a lot of the data that appears in this paper also.

In the linked paper, the data series incorporated uses data from Bristlecone pines - which have been heavily critised as not being reliable. The location data from Tornetrask, the Polar Urals and Northern tree line come for considerable critisism. The paper referenced in the Table from page 15 includes references to Briffa 1992 and 1995 in which there were updates to the Polar Urals data available at the time but which Briffa did not use (if he had it would have changed the whole shape and outcome the series data ..... basically confirming a medieval warm period and LIA).

All of Mann's data uses a predominance of American tree ring proxies and use of Bristlecone pines.

Apparently there are only a handful of series data that allow a 'hockey stick' shape to present itself through Mann's and Briffa data series. All their papers include the same sets of flawed proxies and Mann's poor statistical management of the data has been discredited by peer review publications and indeed by an expert review pannel set up by the US congress.

I would advise all readers to indeed read the linked paper but be very wary of its contents and conclusions .... as it is in fact not what it appears to be (an effort to show that the Medieval warm period and Little Ice age were localised and not global in nature). In fact McIntyre (see climate audit) has shown that most of the tree ring proxy data does in fact show both of these events, but the methods and weighting used by Mann influences the graphs shown.

In this paper the graphs on page 13 and 16 and indeed the whole of the conclusions are very questionable. Don't take my word for it, please read the book referenced above or visit the climate audit site and read some of the saga surrounding the issue of tree-ring proxies and various dubious practices of the paleoclimatology fraternity.

The below link gives the results of a recent study where 'shock / horror' temperature reconstructions show the opposite, ..... that in the Indo Pacific, there is a signal for both the medieval warm period and also LIA.

https://darchive.mbl....pdf?sequence=1

For those wondering what the 'hockey-stick' debate is all about, here is a little background:

http://www.uoguelph.ca/~rmckitri/research/APEC-hockey.pdf

Anyway, its all good for starting a debate !!

Y.S

Edited by Yorkshiresnows

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Here's a paper which some of you may find interesting: http://www.springerlink.com/content/n567324n1n3321h3/fulltext.pdf

Abstract FutureGreenland temperature evolution will affect melting of the ice sheet and associated global sea-level change. Therefore, understanding Greenland temperature variability and its relation to global trends is critical. Here, we reconstruct the last 1,000 years of central Greenland surface temperature from isotopes of N2 and Ar in air bubbles in an ice core. This technique provides constraints on decadal to centennial temperature fluctuations. We found that northern hemisphere temperature and Greenland temperature changed synchronously at periods of ∼20 years and 40–100 years. This quasi-periodic multi-decadal temperature fluctuation persisted

throughout the last millennium, and is likely to continue into the future.

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Nice update to the area guys. In the spirit of trying to keep to the best peer-reviewed science, with data and original references, and in the spirit of not getting personal, here's some more info on 'hockey sticks':

In defence of Mann's work - the 'hockey stick' has been statistically verified by independent parties, and reproduced using different statistical methods. The National Research Council found some minor statistical errors, but also found that they had little bearing on the final result Papers proposing to discredit it (McKitrick/Macintyre/Soon/Baliunas etc) themselves have been discredited for using poor statistical methods among other things (see references below).

Books such as the opportunistic 'Hockey Stick Illusion' have no scientific bearing as they are not peer-reviewed in any way, and so merely reflect an opinion. In this case the opinion is wildly off the mark, but the book was clearly written to feed on the media frenzy of the unfounded hackergate allegations. Since several reports (quite apart from a bit of common sense) have shown there to be no substance behind the scientific allegations, it's clear that this particular book is hardly going to stand the test of time). Anyone can write, and publish, a book on aliens, crop circles, global warming and black helicopters...

A much better book to read would be the excellent: "Noise: Lies, Damned Lies, and Denial of Global Warming " by statisitician Grant Foster, who not only can debunk many fallacious arguments, but provide you with the logical reasoning as to how to interpret noisy datasets. But of course it's a book, and not subject to the rigours of peer review...

Some independent and some non-tree-ring verifications of all or part of the "Hockey Stick":

Possibly the most important?

Committee on Surface Temperature Reconstructions for the Last 2,000 Years, National Research Council, 2006: Surface Temperature Reconstructions for the Last 2,000 Years, entire report available here:

http://www.nap.edu/c...676#description

[great detail about different methodologies, reconstructions etc, copious references, and that's only till 2006]

Wahl and Amman 2007: Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence. Climatic Change, pdf here: http://www.cgd.ucar....mChange2007.pdf

Huang et al, 2000: Temperature trends over the past five centuries reconstructed from borehole temperatures. Nature, pdf here:

http://www.ldeo.colu...Nature%2700.pdf

Smith et al 2006: Reconstructing hemispheric-scale climates from multiple stalagmite records. International Journal of Climatology, abstract here:

http://www.ncdc.noaa.../smith2006.html

Oerlemans 2005: Extracting a Climate Signal from 169 Glacier Records. Science, pdf here:

http://www.martinkod...10995712675.pdf

Mann et al 2008: Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. PNAS, abstract here:

http://www.ncdc.noaa...8/mann2008.html

[this one's particularly useful as it takes on board the findings of the reviews regarding the statistical criticisms of Mann et al 1998, No tree rings, so no bristlecone pines here YS!, many more proxies, different stats]

Some Mann et al context on the LIA and MWP here:

Mann et al, 2009: Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science, abstract and figures here:

http://www.sciencema...t/326/5957/1256

http://www.sciencema...y/326/5957/1256

Quoting John Cook of Skeptical Science on the Mann et al non-controversy:

"While many continue to fixate on Mann's early work on proxy records, the science of paleoclimatology has moved on. Since 1999, there have been many independent reconstructions of past temperatures, using a variety of proxy data and a number of different methodologies. All find the same result - that the last few decades are the hottest in the last 500 to 2000 years (depending on how far back the reconstruction goes). "

http://www.skeptical...ockey-stick.htm

I'll end on a question. Given that Mann and every other respectable palaeoclimatologist happily accepts that the MWP exists, just that they debate whether or not it is a global phenomenon, and given that there are some studies that suggest climate anomalies (both of temperature and rainfall) occurring worldwide (YS refers to one or two), why should we be extra worried if the MWP turns out to be a global, not regional, warm phenomenon? Similarly, why should we all be glad that the best global estimates of climate show relatively little global temperature variation through the MWP/LIA episodes?

sss

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Nice update to the area guys. In the spirit of trying to keep to the best peer-reviewed science, with data and original references, and in the spirit of not getting personal, here's some more info on 'hockey sticks':

In defence of Mann's work - the 'hockey stick' has been statistically verified by independent parties, and reproduced using different statistical methods. The National Research Council found some minor statistical errors, but also found that they had little bearing on the final result Papers proposing to discredit it (McKitrick/Macintyre/Soon/Baliunas etc) themselves have been discredited for using poor statistical methods among other things (see references below).

Books such as the opportunistic 'Hockey Stick Illusion' have no scientific bearing as they are not peer-reviewed in any way, and so merely reflect an opinion. In this case the opinion is wildly off the mark, but the book was clearly written to feed on the media frenzy of the unfounded hackergate allegations. Since several reports (quite apart from a bit of common sense) have shown there to be no substance behind the scientific allegations, it's clear that this particular book is hardly going to stand the test of time). Anyone can write, and publish, a book on aliens, crop circles, global warming and black helicopters...

A much better book to read would be the excellent: "Noise: Lies, Damned Lies, and Denial of Global Warming " by statisitician Grant Foster, who not only can debunk many fallacious arguments, but provide you with the logical reasoning as to how to interpret noisy datasets. But of course it's a book, and not subject to the rigours of peer review...

Some independent and some non-tree-ring verifications of all or part of the "Hockey Stick":

Possibly the most important?

Committee on Surface Temperature Reconstructions for the Last 2,000 Years, National Research Council, 2006: Surface Temperature Reconstructions for the Last 2,000 Years, entire report available here:

http://www.nap.edu/c...676#description

[great detail about different methodologies, reconstructions etc, copious references, and that's only till 2006]

Wahl and Amman 2007: Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence. Climatic Change, pdf here: http://www.cgd.ucar....mChange2007.pdf

Huang et al, 2000: Temperature trends over the past five centuries reconstructed from borehole temperatures. Nature, pdf here:

http://www.ldeo.colu...Nature%2700.pdf

Smith et al 2006: Reconstructing hemispheric-scale climates from multiple stalagmite records. International Journal of Climatology, abstract here:

http://www.ncdc.noaa.../smith2006.html

Oerlemans 2005: Extracting a Climate Signal from 169 Glacier Records. Science, pdf here:

http://www.martinkod...10995712675.pdf

Mann et al 2008: Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. PNAS, abstract here:

http://www.ncdc.noaa...8/mann2008.html

[this one's particularly useful as it takes on board the findings of the reviews regarding the statistical criticisms of Mann et al 1998, No tree rings, so no bristlecone pines here YS!, many more proxies, different stats]

Some Mann et al context on the LIA and MWP here:

Mann et al, 2009: Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science, abstract and figures here:

http://www.sciencema...t/326/5957/1256

http://www.sciencema...y/326/5957/1256

Quoting John Cook of Skeptical Science on the Mann et al non-controversy:

"While many continue to fixate on Mann's early work on proxy records, the science of paleoclimatology has moved on. Since 1999, there have been many independent reconstructions of past temperatures, using a variety of proxy data and a number of different methodologies. All find the same result - that the last few decades are the hottest in the last 500 to 2000 years (depending on how far back the reconstruction goes). "

http://www.skeptical...ockey-stick.htm

I'll end on a question. Given that Mann and every other respectable palaeoclimatologist happily accepts that the MWP exists, just that they debate whether or not it is a global phenomenon, and given that there are some studies that suggest climate anomalies (both of temperature and rainfall) occurring worldwide (YS refers to one or two), why should we be extra worried if the MWP turns out to be a global, not regional, warm phenomenon? Similarly, why should we all be glad that the best global estimates of climate show relatively little global temperature variation through the MWP/LIA episodes?

sss

If you took a closer look at some of the references you yourself have quoted you would see a striking similarity to the contents that make up the conclusions .... essentially the same flawed proxie data (Bristlecone pines, Polar Urals (without the updated data) and various other discredited data that has been shown and proven (expert scientific pannel) to be wrong.

Mann has been discredited ..... that is a fact (minor discrepancies my bottom). Please point me to the minor points that would not affect the outcome of his conclusions ?

Also all of the subsequent papers that you have quoted use the Bristlecone data that has been universally (say that again ..Universally) discredited. Most of the authors have affilitaions with Mann and the 'hockey-stick' team of original authors. His statistical techniques have been shown in per reviewed papers to be fatally flawed (short centering, and use of strange correlation statistics not used in any other field). Bore hole proxies and even most of the tree ring proxy data show ...... no hockey stick.

In previous posts you have ridiculed that the medieval warm period was as warm as now if not warmer and scoffed at the idea there could possibly have been less ice than now in polar regions ................. yet now accept the MWP and LIA ......???

Also, given that Mann was put in charge of mediating and writing the final IPCC Third assessmement report (essentially vetting his own data !!!) you have to wonder at the peer review process in the IPCC ..... A VERY worrying situation .....

I respect your view, but please do not rubbish various books .... are you saying that they are somehow mistaken. Why not look at Climate audit's web site and check out the various published data that clearly shows that the hockey stick is so fatally flawed, that there is nobody serious in science now willing to seriously defend it.

Most of the proxy data used stops at around 1980. None of the tree ring data has been updated since. McIntyre, himself queried this and looked at the data used from the western United states, taking additional data from the same set of trees from one of the proxy series........ which showed .......... no Hockey stick !!

Move away from tree ring proxies, say boreholes and ice cores or even the Indio Pacific ocean warm pool (see previous reference) and what do you clearly see ...... a global signal for the MWP and LIA. Not regional ...... but Global ...... which if to me is just plain common sense given the dramatic recorded Northern Hemisphere historic and recorded temperature records.

Y.S

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Bristlecone pine data are in one paper (as a very small part) and part of one chapter of the NAS report. All other references I included are not based on bristlecone pines. Note the distinct lack of bristlecone pines in boreholes, glaciers, stalagmites, or Mann et al 2008, namely most of the papers I cited. The weaknesses in the Mann et al methodology have been rectified by subsequent papers using different methodologies and different proxies, with and without tree rings.

Mann has been discredited by... who, exactly? Official inquiries by Penn State and the NAS cleared him (see report linked in previous post). Given that his results have been verified independently many times over, and he's been cleared of wrongdoing, you're just plain wrong on that one. Oh, wait, do you want to use the discredited Wegman Report? The one that has a whole host of distortion and plagiarism, as exposed by Deep Climate's articles "Wegman (and Rapp) on tree rings: A divergence problem" and subsequent articles. I'll leave readers to find the article and assess whether they think the Wegman report stands up to scrutiny. Do you have any other official reports that have discredited Mann, Y.S.?

On the MWP/LIA, how many times do I have to say that they are perfectly acceptable regional events, most pronounced in the North Atlantic region. Nobody disputes this. I do not, and never have, disputed this. People dispute whether it was global, and there the evidence is doubtful at best. "Warm periods" of various flavours have been identified in many places, but not always at the same time. Such spatio-temporal discrepancies, along with the lack of strong evidence from many non-north Atlantic sites means the MWP cannot be comfortably considered a global event.

Jethro asked for evidence to be presented. You can read the NAS report, you can read Wahl and Ammann (2007), which showed McKitrick and Macintyre's results to be "without statistical and climatological merit", and shows Mann's result to be basically sound.

Edited by Paul
You are walking a tightrope SSS - have removed the childish sniping from this post, but it will be the final time this happens - please read the code of conduct and ensure you abide by it.

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Bristlecone pine data are in one paper (as a very small part) and part of one chapter of the NAS report. All other references I included are not based on bristlecone pines. Note the distinct lack of bristlecone pines in boreholes, glaciers, stalagmites, or Mann et al 2008, namely most of the papers I cited. The weaknesses in the Mann et al methodology have been rectified by subsequent papers using different methodologies and different proxies, with and without tree rings.

Mann has been discredited by... who, exactly? Official inquiries by Penn State and the NAS cleared him (see report linked in previous post). Given that his results have been verified independently many times over, and he's been cleared of wrongdoing, you're just plain wrong on that one. Oh, wait, do you want to use the discredited Wegman Report? The one that has a whole host of distortion and plagiarism, as exposed by Deep Climate's articles "Wegman (and Rapp) on tree rings: A divergence problem" and subsequent articles. I'll leave readers to find the article and assess whether they think the Wegman report stands up to scrutiny. Do you have any other official reports that have discredited Mann, Y.S.?

On the MWP/LIA, how many times do I have to say that they are perfectly acceptable regional events, most pronounced in the North Atlantic region. Nobody disputes this. I do not, and never have, disputed this. People dispute whether it was global, and there the evidence is doubtful at best. "Warm periods" of various flavours have been identified in many places, but not always at the same time. Such spatio-temporal discrepancies, along with the lack of strong evidence from many non-north Atlantic sites means the MWP cannot be comfortably considered a global event.

Jethro asked for evidence to be presented. You can read the NAS report, you can read Wahl and Ammann (2007), which showed McKitrick and Macintyre's results to be "without statistical and climatological merit", and shows Mann's result to be basically sound.

Hi Sunny Skies,

Okay, lets take a closer look at one of your earlier references:

"Mann et al 2008: Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. PNAS, abstract here:

http://www.ncdc.noaa...8/mann2008.html

[this one's particularly useful as it takes on board the findings of the reviews regarding the statistical criticisms of Mann et al 1998, No tree rings, so no bristlecone pines here YS!, many more proxies, different stats]"

See you have posted the abstract and not the full paper (have you read the full paper by any chance ? Did you download the supplementary data and check which proxy series were being used ?)

This paper was an attempt by Mann to take on board some of the critisism levelled at his earlier papers and to resurrect the Hockey stick. But I am afraid that this paper has been exposed to the following flaws:

1) It still uses a load of tree ring proxy data (relying on no less than 112 Oak tree proxies):

"Doug Keenan has received a favorable decision from the FOI Commissioner in his lengthy FOI/EIR battle for tree ring data collected by Mike Baillie of Queen’s University, Belfast. The data is from Irish oaks and was collected mostly in the 1970s"

"Baillie and Wilson argued that oak chronologies were “virtually useless†as temperature proxies and “dangerous†in a temperature reconstruction. Nonetheless, as I report below, no fewer than 119 oak chronologies (including 3 Baillie chronologies) were used in Mann et al 2008 without any complaint by Wilson or other specialists"

And of the author of the original oak tree study that was used In Mann 2008:

"Although ancient oaks could give an indication of one-off dramatic climatic events, such as droughts, they were not useful as a temperature proxy because they were highly sensitive to water availability as well as past temperatures"

“It’s been dressed up as though we are suppressing climate data, but we have never produced climate records from our tree rings,†Professor Bailee said.

“In my view it would be dangerous to try and make interpretations about the temperature from this data.â€

2) Almost all of the non tree proxy data do not even show a 'modern warming', one major exception being a group of four lake sediment series from Finland known as the Tiljander proxies.

However, again, the original paper was written by a pHD student (a thesis paper), author Mia Tiljander. It turned out that the 20th century up-tick (hockey shape) in these proxies was actually caused by artificial disturbance of the sediment caused by ditch digging rather than anything climatic.

Mann acknowledges this fact but rather than reject the series, he stated that the disturbance did not matter. He provided a 'sensitivity' analysis, showing that he still could get a 'hockey stick without the Tiljander proxies.

The BIG selling point of this paper was exactly this point. You could get a hockey stick shape even if you looked at non-tree ring proxies. And here is the slight of hand:

This claim rests on a circular argument:

Mann had shown that the Tiljander proxies were valid by removing them from the database and showing that you still got a hockey stick. However, when he did this test, the hockey stick shape of the final reconstruction came from ...... BRISTLECONES (universally accepted as flawed). Then he argued that he could remove the tree ring proxies (including the Bristlecones) and still get a hockey stick ......... and of course he could, because in this case the hockey stick shape came from the Tiljander proxies.

His arguments therefore rested on two sets of flawed proxies in the database but only removing one at a time and arguing that you get a hockey stick either way !!!!

3) Briffa's discredited tree ring proxy series is also included in this paper, with the same inconvenient divergence in the latter part of the 20th century truncated down to 1960. The data series actually shows a down-tick therafter (there's a lot on this from previous publications - see Climate audit for more information).

4) One of the 'new' proxy series included is a documentary record of temperatures in East Africa dating back to 1400. If true, this would have overturned everything known about the history of the continent ....... but it was discovered that Mann had inadvertantly swopped the the latitude and longitude, and the series should have been located in Spain. It became farcically apparent that the proxy was not a documentary record at all ...... but a rainfall record.

To be fair to Mann on this point, once this error had been made public, he corrected the data, with the effect of a change in 0.5 degrees C in the 18th century.

5) McIntyre and McKitrick published (late 2008) in the same journal a short comment dealing with the major flaws as they saw them:

a) The use of confidence levels in the statistics used - they pointed out that using conventional statistical methods, they could show that Mann's uncertainty bounds were infinately large prior to 1800 ..... in other words that his new reconstruction was of no use prior to that date.

:) the calibration process producing hockey sticks from 'red-noise'

c) the Tiljander issue

d) the use of proxies which were not responding to temperature, including Bristlecones.

There's a load more, but I think you get the point !!

Yes I do read the stuff you post (I've already looked at a lot of these in anycase).

I could also go through the Wahl and Ammone 2007 paper....... as there is an aweful lot on that as well, but this post is already very long, so perhaps I'll add a separate reply later on.

The thing is Sunny Skies, the Hockey stick in the grand scheme of globval warming is neither here nor there. It was used by the IPCC to get round a problem in selling the story of 'unprecedented global warmth from human activity' ....... when you have a ruddy great MWP that is apparent for the Northern hemisphere and up until the late 90's was universally believed as Global ..... and the same fro the LIA, there's going to be a selling problem.

Then 'hey-presto' we have Mann 98 / 99 and now Mann 2008 providing the 'Hockey stick' ...... based on a whole set of flawed data, truncated data series, heavily critisised statistical techniques and proxy data only going to 1980 (most of it limited to before) and then addig by splicing, current 20th century instrumentaltemperature records.

I also love the way that there is still currently widespread use of bristlecone proxy data even though there is widespread agreement that they do not provide reliable temperature proxies.

Also, have you any comment on the Indo -Pacific warm pool proxies that have not been criticised (as far as I can tell) and which provide a clear GLOBAL signal for both the MWP and LIA ?

Y.S

P.S Some of the problems with tree ring proxies (referencing a particular series of 'Yamal' used ina lot of papers can be seen here:

http://wattsupwiththat.com/2009/09/28/mirror-posting-of-climate-audit-article-on-yamal-a-divergence-problem/

Edited by Yorkshiresnows

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I've always found attempts to discredit proxy data per se confusing...When attempting to put together ANY picture of past climate, construct theories and attempt predictions, the vast bulk of the data used is 'proxy'...Do we have any non-proxy (first hand) support for the much-vaunted warmth of the MWP, for example? I suspect not. But we're all supposed to accept it nonetheless?

IMO, all proxy data needs treated with a degree of caution. Not just that with which we happen to disagree.

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I've always found attempts to discredit proxy data per se confusing...When attempting to put together ANY picture of past climate, construct theories and attempt predictions, the vast bulk of the data used is 'proxy'...Do we have any non-proxy (first hand) support for the much-vaunted warmth of the MWP, for example? I suspect not. But we're all supposed to accept it nonetheless?

IMO, all proxy data needs treated with a degree of caution. Not just that with which we happen to disagree.

Hi Pete,

Yes, good point.

But not all proxy data is prone to such problems as Tree-ring data and in particlular Bristlecones. I would agree with Starry skies that non-tree ring proxy data (ice cores / Bore hole drills and ocean water pool assessments) would be preferable (the Mann 2008 paper however, is full of tree ring data)

The main problem as I see it is that the tree-ring proxy series has not been well updated. There are lots of issues that can be resolved and corrected (for example an update to the Polar Urals proxy series was made), but as this does not show an 'Up-tick' in the 20th century it seems to have been dropped for another location, or, worse, the old data is still used. Most papers on this issue contain the same key proxy series data.

The other thing that is stiking to me, is that the majority of data does indeed show a MWP and LIA ...... you have to go to some lengths to get rid of it by lots of manipulations of the data...... always very suspicious !!

Y.S

P.S Take a look at this which illustrates the 'selective' way in whicha lot of the data has ben presented:

http://www.climateaudit.info/pdf/mcintyre-scitech.pdf

Edited by Yorkshiresnows

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Y.S., have you got any better data than one book (not peer-reviewed), and one blog site (Jethro, were we not only supposed to be posting data of academic value?) Bristlecone pines are old hat, the science has moved on, and you're wrong about Mann et al 2008 - they specifically do the reconstruction without tree rings, as well as with. It does not change the conclusions. "Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used." [Mann et al, 2008]

MacIntyre's methods were discredited by Wahl and Ammann, amongst many others, and his submission to the CRU enquiry was found to be without merit by the enquiry. Why are you so doggedly keen to support MacIntyre when he's provided nothing of significant academic merit? He's also made to look a complete fool by other bloggers (fight bad blog science with good blog science? you don't need a science paper to show he's deliberately wrong - see Deep Climate's recent post and his two "how to be a climate science auditor" or "let the backpedalling begin" posts). The trouble is, Macintyre is so desperately wrong about tree ring data, their use, the concepts involved and the analysis techniques required that he can't bring himself to admit it, or to admit that the tree ring data isn't even required to prove the original point!

Pete, you're absolutely right about all proxy data to be treated with caution, and it remains entirely possible that a series of records will somehow show the MWP to be both global and as warm as at present, but so far multiple different methodologies and proxy types are not showing this to be the case. If it's subsequently shown to be global and significant through data that has academic merit, I'll change my opinion on its global significance. I'll also be even more worried about AGW than I was before...

Why is it not likely to be global despite individual sites sometimes showing a MWP? How about this: you can argue that proxy A (20deg S), proxy B (50 deg S) and proxy C (40deg S) all show a warm period somewhere in the Medieval. When was it? Was it a uniform, significant event? If 'A' peaked around 8-900AD, 'B' around 1000 to 1100AD, and 'C' around 1200-1300AD what happens? The average signal from the three sites, particularly if one or more show relative coolness at other times, may be a rather muted, or even absent "MWP." As the time loosely described as Medieval covers >500 years, each individual paper could describe finding a MWP at their location, but the MWP is still not global. What happens in the real world is that many NH, and especially the N Atlantic reasonably clearly show a MWP (though there are temporal discrepancies even across the Atlantic), and on the whole the regional warm periods match with each other, indicating widespread regional warmth. Elsewhere, the periods are either absent or do not line up, and when you add all those signals together with the European/Atlantic ones, the global MWP is less impressive than you first thought from a Eurocentric view.

As a conjecture, I think this is what you'd expect from a solar-driven climate anomaly - very modest in overall magnitude, but regionally strong, absent or even reversed depending on the patchwork of heat redistribution driven by weather systems. The recent research linking cold European winters to solar minima supports that (think last year!), showing a change in the redistribution of heat around the globe driven by the Sun (though little reduction in radiative forcing), while the globe overall was at near-record high temperatures. So I suggest that solar forcing's most important effect is to alter the patterns of weather, leading to patchworks of warm/cool/little change. Greenhouse warming occurs relatively evenly ovear all the globe due to the mixing of CO2, and observations show that is what is distinct about the late 20th Century, as opposed to the MWP. What does everyone think?

sss

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One interesting thing about global warming is that it hasn't been even. Any trawl through the CRU or NCDC data will reveal that the landmasses have warmed more than the oceans and the Northern Hemisphere has warmed more than the Southern Hemisphere.

However this in itself isn't inconsistent with CO2/AGW because landmasses are more sensitive to temperature changes than oceans and the Northern Hemisphere has more land than the Southern. Apart from some anomalies over Antarctica temperature changes are considered broadly in line with AGW expectations.

One source: http://www.ncdc.noaa.gov/oa/climate/globalwarming.html

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MacIntyre's methods were discredited by Wahl and Ammann, amongst many others, and his submission to the CRU enquiry was found to be without merit by the enquiry. Why are you so doggedly keen to support MacIntyre when he's provided nothing of significant academic merit?

Perhaps you would like to check out the NAS expert pannel report conclusions, or indeed the Wegman report commisoned to look into the affair:

"The report commissioned by the House Energy Committee, backs up and reinforces that conclusion. The three researchers - EdwardJ. Wegman of George Mson University, David W.Scott of Rice University and Yasmin H. Said of John Hopkins University are not climatologists; they're statasticians. Their task was to look at Mr Mann's methods from a statsitical perspective and assess their validity. Their conclusion is that Mr Mann's papers are plagued by basic statistical errors that call his conclusions into doubt. Further, professor Wegman's report upholds the findings of Messrs. McIntyre and McKitrick that Mr Mann's methodology is biased towards producing 'hockey stick' shaped graphs"

The Wegman report conclusion:

"In general we found MBH98 and MBH99 to be somewhat obscure and incomplete and the criticisms of McIntyre and McKirick to be valid and compelling"

As for the last part of your above statement ...... They have uncovered a slur on Science and shown what a complete load of old tosh, the Hockey stick papers were / are. You can make your own mind up. I believe I have illustrated my own point of view with sufficient references.

You still have not commented on the Indo-Pacific warm pool paper that I posted ................ showing a MWP and LIA signal ...... Global, not Regional !

Y.S

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Just thought that I would add a little on the Eugene Wahl and Ammon Caspar 'discreditation':

The authors submitted two manuscripts for publication (in Climatic Change) in which they reportedly showed the hockey stick could be replicated.

The first papers conclusions were:

"The claim by McIntyre and McKitrick that a spurious 'hockey-stick' climatic reconstruction is introduced by data trasformation is unfounded"

They then went on to discuss principal component (PC) retention policies (the methods used by Mann to screen out the useful data from the proxies) but also claimed that in their second paper they had shown that no matter how you standardised the data, you would still get a hockey stick provided you retained sufficient PC's.

For the second paper Ammon (unlike) Mann had published his computer code so that McIntyre and McKitrick could see how the data was being used (they were claiming that they had replicated Mann's findings).

McIntyre and McKitrick observed that Ammon's emulation of the hockey stick was in fact nearly exactly the same as their own and confirmed that the same fatal flaws they had uncovered in Mann's original paper were there in the Ammon paper also. Namely that the R squared verification tests that linked the temperature reconstructions to the proxy data were so low as to indicate no meaning at all !! Mann's own RE correlation statistics were used (which were one of the main critisisms of that paper) to pass the data through.

McIntyre was actually appointed reviewer and pointed out these flaws (amongst many others) to the publishing editor at Climatic Change. The Paper was rejected and has not been published to date.

The replication of the Hockey stick was / is in tatters !!

Unfortunately, a pre-release press release from the UCAR was not withdrawn and many folks (including the IPCC) still refer to these authors work as evidence of support for the Mann Hockey stick, and evidence that McIntyre and McKitrick had been refuted ........ when in fact, it is just the opposite !!

Here's is a letter written to Ammon stating the main issues:

http://climateaudit.files.wordpress.com/2005/09/reply.ammann.pdf

Y.S

Edited by Yorkshiresnows

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er, Y.S., I hate to inform you, but Wahl and Ammann was published by Climatic Change in volume 85 (1-2), pp33-69...

Wegman has been discredited as I already alluded to in the earlier post. Here are some critiques of that so-called impartial report.

http://www.desmogblog.com/sites/beta.desmogblog.com/files/plagiarism%20conspiracies%20felonies%20v1%200%201.pdf - report by John Mashey

http://desmogblog.com/wegmans-report-highly-politicized-and-fatally-flawed

http://deepclimate.files.wordpress.com/2009/12/wegman-bradley-tree-rings.pdf

So far you've provided sources from a book and a very biased blog, plus a load of allegations regarding the honour of several scientists and their methods. Nothing that stands up to scientific scrutiny. So as far as that is concerned, I'm no longer bothered with replying in detail to unsubstantiated material. You never did explain how bristlecone pines affect speleothems... or quite how boreholes, glaciers and speleothems don't qualify as 'non'-tree-ring proxies. Just a load of unsubstantiated suggestions, for which you provide either no reference at all, or Macintyre's blog...

You fail to spot that I dealt with your pointing out other random sites showing warmth in some detail in my last post, and acknowledged that if the proxies improve and subsequently show globally uniform MWP/LIA, I'll revise my view. So far they haven't shown that at all, and you have utterly failed to show that.

If the MWP was global, and warmer than today... I'll be even more worried about AGW effects.

Papers like this one, show exactly why:

http://geology.gsapubs.org/content/38/7/603.abstract

Arctic temperatures in the Palaeocene ~19C warmer than present with 390ppm CO2. Care to think about the consequences of this for methane release and sea level?

sss

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There's quite a lot of evidence which shows the MWP and LIA were not restricted to Europe.

http://agwobserver.w...econstructions/

http://www.co2scienc...es/mwpchina.php

http://news.bbc.co.u...ech/4636115.stm

Hi Jethro, your last link's European? But yes, you're right in that there are other sites that show a climate anomaly of some sort, some time between 800 and 1300AD - hence the debate about whether the MWP was global or not! The key challenge is whether the ones that show warm temperature anomalies (not precipitation etc) are all occurring at the same time, and showing a uniform warm episode.

This is not so clear - for example the Ma et al 2003 paper, as a random example, has three or four data points showing a warm MWP, according to what I can read of the abstract. That's fair enough, but what's happening between the data points? For example a similar stalagmite sampled at 100 year intervals, where the intervals approcimately corresponded to the 1660s, 1760s, 1860s, and 1960s might suggest that temperatures wer relatively cold in the UK? For the most part they would be right, but there's scope to miss data between the points. And if the warm and cold episodes in different locations don't match, the aggregated signal is not necessarily one of significant warmth. The Ma et al paper is entirely justified in suggesting Medieval warmth in China, but is it really the same warmth at the same time as elsewhere? My own feeling, [which I stress is separate from defending the work of someone like Mann from the spurious allegations of someone like MacIntyre] is that it would be surprising if the MWP was not at least hemispheric in extent, due to weather teleconnections. But in a parallel to my conjecture I put out earlier, I find it rather interesting that of all places China is reporting anomalous Medieval warmth. Were they not also anomalously afflicted by the cold winter (while the rest of the world was doing it's best to break high temperatures)? It should highlight in the minds of everyone that individual locations identifying a warm episode are not enough - most locations with a records capable of identifying the warm episode need to record it, or the warmth can be an artefact of patchy heat redistribution rather than a uniform climatic signal.

And if the spaghetti diagrams of modern palaeoclimate evolve with new data towards one showing more pronounced Medieval warmth... then woe betide us in the implications for planetary climate sensitivity.

TWS - fair point, but the key thing is that basically the whole globe is warming, not cooling, albeit at rather differing rates. That is as expected from the well-mixed CO2 (which is generall a little higher in the NH).

Any thoughts on Eocene climate and Arctic sensitivity from the paper I linked to? Should we be worried about a 19C Arctic temperature rise? It sounds mad but anomalies over the Arctic are already pretty large.

sss

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SSS - I have vague memories of a paper linking a shift in monsoon patterns to temperature changes on a global scale??? If I get time and remember to do so, I'll see if I can find it again.

I think when it comes to discerning an aggregated signal on a global level, I think you're looking for more information than it is possible to achieve with any degree of certainty, from any proxy measure. Demanding that that the warmth should be universal in time from such sparse information is to my mind, an impossible ask. As you say yourself, China was cold this winter, we were cold this winter and yet globally the thermometers showed the world was a warm place; will proxy measures a thousand years hence register thermometers or sediments, what would they reveal about this winter past?

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SSS - I have vague memories of a paper linking a shift in monsoon patterns to temperature changes on a global scale??? If I get time and remember to do so, I'll see if I can find it again.

I think when it comes to discerning an aggregated signal on a global level, I think you're looking for more information than it is possible to achieve with any degree of certainty, from any proxy measure. Demanding that that the warmth should be universal in time from such sparse information is to my mind, an impossible ask. As you say yourself, China was cold this winter, we were cold this winter and yet globally the thermometers showed the world was a warm place; will proxy measures a thousand years hence register thermometers or sediments, what would they reveal about this winter past?

Good question! I only used this winter to try and get the idea of a spatially heterogeneous pattern across, and the concept that Britain and China might show one thing, but the globe may not. Over one year the pattern wouldn't show, but over 30 or 50 years it might.

Indeed discerning a signal is tricky, hence why the TAR 'hockey stick' had significant error bars! But I was imagining those timeseries that are reasonably continuous - they often have highs and lows, even within the same century. I think that's why Mann's global graphs have mostly come out flat - because those highs and lows didn't always match. But other aggregations have a bit more synchrony and show something of a MWP (e.g., NH-only timeseries). It's clearly not an issue where the 'science is settled', to use an ugly phrase, but so far nobody has done better than the recent hockey sticks of Mann or the other 'spaghetti plots' that show more variation, but still the 20th Century uptick. And none of this particular debate changes the cause of the 20th Century rise of course!

sss

EDIT: I think I've read several on monsoons, but a few years ago now and I don't remember the contents - if you find anything interesting, it might be good for a post!

Edited by sunny starry skies

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I remember a paper on rising sea temps impacting the monsoon. If you lessen the degree of temp difference from land to sea you impact the monsoon?

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er, Y.S., I hate to inform you, but Wahl and Ammann was published by Climatic Change in volume 85 (1-2), pp33-69...

Wegman has been discredited as I already alluded to in the earlier post. Here are some critiques of that so-called impartial report.

http://www.desmogblo...0v1%200%201.pdf - report by John Mashey

http://desmogblog.co...-fatally-flawed

http://deepclimate.f...-tree-rings.pdf

So far you've provided sources from a book and a very biased blog, plus a load of allegations regarding the honour of several scientists and their methods. Nothing that stands up to scientific scrutiny. So as far as that is concerned, I'm no longer bothered with replying in detail to unsubstantiated material. You never did explain how bristlecone pines affect speleothems... or quite how boreholes, glaciers and speleothems don't qualify as 'non'-tree-ring proxies. Just a load of unsubstantiated suggestions, for which you provide either no reference at all, or Macintyre's blog...

You fail to spot that I dealt with your pointing out other random sites showing warmth in some detail in my last post, and acknowledged that if the proxies improve and subsequently show globally uniform MWP/LIA, I'll revise my view. So far they haven't shown that at all, and you have utterly failed to show that.

If the MWP was global, and warmer than today... I'll be even more worried about AGW effects.

Papers like this one, show exactly why:

http://geology.gsapu.../7/603.abstract

Arctic temperatures in the Palaeocene ~19C warmer than present with 390ppm CO2. Care to think about the consequences of this for methane release and sea level?

sss

Sorry Starry skies,

See your highlighted text. ...... er .... yes I know (paper 1 from my post above !!!!!!). Paper 2 which is referenced in paper 1 and is the main technical report was rejected ...... because its a load of crap !!

As such, paper 1 is irrelevant !!!

You have obviously not read or looked at the data in your own quoted references.

I have read around 20 papers in detail ..... and that includes looking at the proxiy data they have used. Perhaps you might like to do the same and then come back on here and tell me that the vast majority of the key papers that are used in this 'Hockey stick' debate do not use tree-ring data.

In fact I will go further, most use the same tree ring data, that has been discredited. MANN 2008 USED BRISTLECONE TREE RING DATA as well as oak tree ring data (and that makes your earlier post incorrect).

You obviously do not take much credence in the written book ? That's your look-out. I challenge you to purchase the book and read it, then check out the references it contains online, then come back to me and say ... its all a load of rubbish.

The point of the multi-proxy data is how the author deals with the weighting of the proxy mix. The Mann 2008 paper as I stated above used tree-ring data as well as non-tree ring data. The point (repeating myself here) is that the non-tree ring data was flawed ... fact. Without the non-tree ring data, Mann was relying on Bristlecone proxies to generate the hockey stick shape ...... none of the other tree ring data did !!!

As for climate audit being a biased blog ...... well so what, they are questioning the science and that a good thing as far as I am concerned. What exactly makes your references more reliable than mine?

There is also a key difference between e.g. Mann's work and the published data from McIntyre and that is that Mann will not release his computer code or indeed how he calculated his confidence intervals. The climate audit site has all the information available for all the work that McIntyre has done for anybody to take a look at. Go on ... have a look !

The Hockey stick is dead and always was. If you need to invent new statistics, cut, amend, truncate and discard the majority of the data to obtain a certain shape .... well your on a hiding to nothing in my view.

ONCE MORE, WHY HAVE YOU NOT COMMENTED ON THE INDO-PACIFIC WARM POOL PAPER I POSTED EARLIER ??????? IS IT BECAUSE IT SHOWS A MWP AND LIA BEING GLOBAL EVENTS ? Is this not a non tree ring proxy study that provides evidence that you need?

https://darchive.mblwhoilibrary.org/bitstream/handle/1912/3188/ppnature08233_with_fig%26supple.pdf?sequence=1

Y.S

Edited by Yorkshiresnows

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[[which I stress is separate from defending the work of someone like Mann from the spurious allegations of someone like MacIntyre] is that it would be surprising if the MWP was not at least hemispheric in extent, due to weather teleconnections. But in a parallel to my conjecture I put out earlier, I find it rather interesting that of all places China is reporting anomalous Medieval warmth. Were they not also anomalously afflicted by the cold winter (while the rest of the world was doing it's best to break high temperatures)? It should highlight in the minds of everyone that individual locations identifying a warm episode are not enough - most locations with a records capable of identifying the warm episode need to record it, or the warmth can be an artefact of patchy heat redistribution rather than a uniform climatic signal.

Hi Starry Skies,

Please explain 'spurious allegations'. Why are they 'spurious' when the guy (and others) have spent 10 years looking at data from many studies and have published and won expert pannel review hearings? They don't seem spurious to me, thoughtful, considered, accurate ...yes, could see that .......

What makes MacIntyre's work 'spurious' Are you qualified to make that judgement (I know that I am not).

Y.S

Edited by Yorkshiresnows

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MacIntyre's methods were discredited by Wahl and Ammann, amongst many others, and his submission to the CRU enquiry was found to be without merit by the enquiry. sss

Edited by Yorkshiresnows

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