Bishop Hill Rand Simberg reviews the Yamal story
May 18, 2012 Climate: MWP Rand Simberg at PJ Media reviews the Yamal story, quoting extensively from yours truly.
But at a minimum [Yamal] should be the final blow to the hockey stick, and perhaps to the very notion that bristlecone pines and larches are accurate thermometers. It should also be a final blow to the credibility of many of the leading lights of climate “science,” but based on history, it probably won’t be, at least among the political class. What it really should be is the beginning of the major housecleaning necessary if the field is to have any scientific credibility, but that may have to await a general reformation of academia itself. It would help, though, if we get a new government next year that cuts off funding to such charlatans, and the institutions that whitewash their unscientific behavior.
Reader Comments (62)
The timber experts always knew trees weren't good thermometers. There own literature said so and documented how there were many variables that affected growth. It was only the climate science people that arbitarily decided treeometers were the evidence they needed. That or upside down varves ;-) ). I wouldn't hold my breath for the clearing out of the establishment either. There are too many people with their reputations at stake.
Unfortunately, I think the best we can hope for is that it will slowly fade away, just like global cooling did in the 70s. Oh, that was the same people.
All proxies have their strengths and limitation. Understanding these limitations is key to palaeoclimatology and deriving estimates of past climate.
Trees are not thermometers or rain gauges, but when sampled in appropriate locations (high latitude/elevation for temperature for example) the ring-width (or maximum density) parameters can provide fair estimates of past temperature variation. If you are expecting explained variance close to 100%, then you will not get this from any proxy archive.
Don’t forget, these are proxies and much effort is now focussed on estimating error.
Rob Wilson’s logic is faulty- as is much of the “thinking” in climate “science”.
They never document that the trees ONLY respond to temperature, but in addition, they assume that if it responds to temperature now it will have done so in the past. Is this true? No.
Case 1: a stand is currently well-drained soil and growing well, but 200 yrs ago a beaver pond made the site soggy and they were growing poorly irrespective of the weather.
Case 2: currently the trees are widely spaced and growing well, but 200 yrs ago the stand was crowded until insects killed half of them. During the crowded period ring widths were narrow until the insect attack.
Case 3: when young the trees were widely spaced and grew well for 100 yrs, the stand became crowded and they grew poorly for 200 yrs, then gradually trees died and they grew better.
Case 4: (documented in a recent paper): the oldest trees in an area are genetically slower growing than average (because slower growing live longer) so a sample of trees will show faster recent growth than long ago growth because only the slow growing trees are the old ones.
Case 5: trees also respond to precip (duh) and precip changes do not correlate with temperature changes over 1000 yrs.
In no case does the screening of trees to pick only those that correlate with 20th century temp prevent these problems.
(H/T Craig Loehle)
Imagine this argument in the hands of a drug trial. Let’s suppose that they studied 36 patients and picked the patients with the 10 “best” responses, and then refused to produce data on the other 26 patients on the grounds that they didn’t discuss these other patients in their study. It’s too ridiculous for words.
Finally the Wegman report stated that the “Climate” community did not have much interaction with mainstream statisticians.
If they did they would realise that by selecting data to reflect a hypothesis is a classic way to generate a Type 1 statistical error, also known as a false positive (a result that indicates that a given condition is present when it actually is not present). In this case a spurious correlation of tree ring width/density with temperature.
This is something we teach our first year undergraduates.
My statement was short and clear and is a simple rule of thumb that has come from many decades of physiological work studying the environmental influences on tree-growth. There is a new generation of tree-growth models that take into account both temperature and precipitation etc. I agree that from one year to the next, there is an amalgam of factors that influence tree growth. But, you fail to miss the point that sampling is NOT random. Sampling to “optimise” the climate signal must go to environments were one factor is mostly limiting – i.e. the tree-line situation. Of course, there are multiple influences from one year to the next, but averaged over say the instrumental period (20th century), we are really interested in the mean response – i.e. the one dominant parameter. All the other factors you mention are random effects through time and have different influences form between each year – as studied from any model residuals.
Don – your arguments – for a single site - are entirely relevant, but there is so much data out there that individual site nuances can be overcome through simple averaging without having to muck around with screening or using more advanced statistical techniques. My work in Scotland:
http://www.st-andrews.ac.uk/~rjsw/ScottishPine/
is a good case in point. We are sampling ALL remnant pine woodlands – some sites are better temperature proxies than others. This might be down to varying elevations, tree-ages, site ecologies or past management effects. I could average all the data into one regional series, I could use principal component analysis and use the 1st eigenvector, or I could “cherry pick” the data and use only those sites that have had minimal management disturbance and are closest to tree-line – and then average. The outcome from each methodological scenario would be very similar.
What you assume – “….. responds to temperature now it will have done so in the past” – is actually a hypothesis which can be tested by comparing to other independent proxy records. I don’t know what more you could expect from the palaeoclimate community in this regard.
It would be nice to if someone could build a time machine and send a temperature logger back to the medieval – that would be a true test of our proxy estimates.
'much effort is now focussed on estimating error'. Error? The error was in not actually eliminating the Medieval Warm Period. Who ever thought they could change the past with a graph? Pikers.
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'using more advanced statistical techniques'. I don't know whether to laugh or cry.
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please understand that there is no goal to delete/remove/eliminate the Medieval Warm Period by anyone I know.
now I must get back to marking but might come back for some more procrastination later
Rob
Thanks for looking in again
If you analyse all ancient sites at northern/upper treelines then presumably you can get a handle on the variability within and between sites. How much is this going to tell us about the error bars on sites where subfossil material is being used?
'estimating error', 'advanced statistical techniques'. Rob, let me give you a little unsolicited advice. No matter how rigourous it gets, paleodendrochronology is never going to have much public credibility until it addresses the Hockey Stick, and the Yamal, and loudly and publicly repudiates those responsible. This is not science, this is a mob of suckers sold a pig in a poke.
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'by anyone I know'. Heh, it's always somebody else.
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Rob - ta for dropping in.
As an aside - there is also a problem in selecting trees close to the tree-line, because those trees have an even shorter growing season? Even at sea level in Scotland the growing season is only 5 months at best, at the tree-line it will only be 4 months? As I write the pines out my window have still to produce new needles, and I am down in the strath next to the river, only 75m above sea level. This compounds the problem with using trees as a proxies, not only do they make poor thermometers due to growth rates being dependent on a range of environmental factors, but they only 'measure' the temperatures in the short summer season. As others have suggested, determining actual tree-lines (which were higher in Siberia in the MWP) is a better guide than slicing up old and highly variable trees, and applying statistical jiggery-pokery. Sediment reconstructions are surely a better bet as they will reflect annual and not just the short summer season temperatures, and the thermal mass of the sea water itself will be more likely to smooth out seasonal variations and noise? Interestingly, the Loch Sunart reconstruction suggests nothing unprecedented about the late 20th Century spike, and clearly shows a warmer period from 900 to 1050, a similar spike in the 12th century, and another warm period in the 1500s before a gradual descent into the LIA.
"...use only those sites that have had minimal management disturbance and are closest to tree-line – and then average. The outcome from each methodological scenario would be very similar."
The question is: how would you *know * which site has had minimal disturbances? Without a gold-standard, there can be *no* valid inter-comparison of supposed proxies.
Simple limitations cannot be overcome by 'advanced' methods.
"It would be nice to if someone could build a time machine and send a temperature logger back to the medieval – that would be a true test of our proxy estimates."
Exactly. Although I'm not sure paleoclimatologists appreciate the implication of the sentence.
Hi Andrew,
Assessing within site error (between series) is relatively straight forward by calculating the standard error (standard deviation for each year divided by the square root of n- number of series) and plotting the 2-sigma either side of the annual index value. However, the ambiguities come in w.r.t. the data processing of the TR data – the detrending of the biological age trend. Error will be greater when an RCS approach is used compared to when series are detrended individually using a series specific fitted function (e.g. negative exponential etc). RCS is noisier, but the final chronology should be closer to the “truth” (w.r.t capturing potential longer term (> centennial) variability) although we don’t know what the truth is of course. Lots of data is needed for RCS to work properly.
Comparing between site chronologies can help in this regard so long as the sites are from the same climatically homogenous zone. However, there really are not that many millennial temperature sensitive length chronologies to do such comparison – if the focus is the medieval. Scandinavia is perhaps one of the few regions where long 1000+ yearlong chronologies have been compared between northern Norway, Sweden and Finland and on the whole the chronologies (ring-width, maximum density and even stable isotopes of C and O) agree quite well. Torneträsk is perhaps the most anomalous of the records (w.r.t the MXD record), but it depends on which “version” you use – multiple published versions related to increased replication and differing processing methods over the last 20 years. The latest version (Grudd 2008) for example, shows a warm medieval period (warmer than 20th century) which does not agree with other Scandinavian records. However, replication is really quite low pre-1300 and from own playing with the data, I think this is simply a bias related to differing processing methods and highlights that the error estimates for the MWP are simply much greater for this period. New studies are in the pipeline for both Sweden and Finland to address this issue.
Another good case in point is the differences between the Polar Urals and Yamal data. They are from a similar climatological region and should agree. The high to mid frequency variation between the series is very similar – as would be expected - but when looking at longer term trends, then there are marked differences. This certainly needs resolving, but caution is needed as the living, historical and sub-fossil data-sets are from different species (spruce and larch) so need to be treated differently. Steve Macintyre gave me some flack when I used Yamal for DWJ06 instead of the Polar Urals data. The problem was that the PU data I had access to at that time had spruce in the living period and larch in the historic data-set which resulted in odd variance changes through time that resulted in a biased final product. Yamal did not have these issues. At that time, we were not aware of the low replication at the recent end and Yamal also calibrated locally more strongly than the PU data anyway.
I am not overtly concerned with Yamal. If it was removed from the DWJ06 data-set, I doubt the NH record would change significantly. If I find some time next week, I’ll do the analysis send you a figure. However, perhaps the time is ripe for a new NH tree-ring based reconstruction, using the many updated version of many many records. We definitely need more data for the medieval period – I’ll be there in a few years for Scotland if everything goes well.
'ripe for a new NH tree ring based reconstruction'. Look, Rob, I know you're a good guy and all, but you really should be clued in to the fact that numerous reconstructions since MBH 98-99, even including varves and speleo, have shown the fundamental validity of the Piltdown Mann's early work. So why bother?
Now, if you could actually reconstruct natural paleo variability with tree rings, I'd be impressed. But sadly, Rob, who else would believe you?
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Rob
Thanks for your helpful and constructive comments. The bit about "bristlecone pines and larches are accurate thermometers" is a bit of a straw man, I don't think anyone has claimed that.
The main issue is of course is the reasons for the selection of certain data sets rather than others - and you've given one reason here.
Re your comment about the MWP, can we deduce that you don't know the 'major researcher' who told Deming 'we have to get rid of the MWP'? :)
"and Yamal also calibrated locally more strongly than the PU data anyway"
Rob, by this do you mean Yamal apparently matched recent temperatures better?
Do you use this as a basis for selection or weighting at all?
Good to see your further contribution.
Rob,
Thank you for pitching in here. Have you or has anyone you are aware of analysed the ring data wrt presence of signals in the data themselves without regard to alignment of those signals with the temperature records? If so, could you share any speculation as to what such signals might express?
This idea was suggested by Brandon Shollenberger at Lucia's a week or so ago and seemed fascinating to me. He reported that Mann had mentioned that the data contained other signals but apparently had never pursued them.
When I commented above, I had not discovered the discussion of signal detection in ring data here: http://climateaudit.org/2012/05/15/new-data-from-hantemirov/
@Rob Wilson "I am not overtly concerned with Yamal. If it was removed from the DWJ06 data-set, I doubt the NH record would change significantly."
I would be if I were you. Why not have a conversation with Steve McIntyre (Climate Audit). He has already done the analysis.:-)
"But, you fail to miss the point that sampling is NOT random. Sampling to “optimise” the climate signal must go to environments were one factor is mostly limiting "
Basically you have your hypothesis and you sample to "optimise". That's cherry-picking in common parlance. If trees are at the treeline then they state they are ultimately temperature limited. So why not average all, rather than those select few that meet your preconceived hypothesis?
I also concur with others bloggers comments about treelines. Altitudinal and Latitudinal treelines can be accurately dated (dendrochronology- rather than the pseudoscience of dendroclimatology).
and show rather different patterns to tree rings- e.g.
Rashit M. Hantemirov* and Stepan G. Shiyatov (2002)
A continuous multimillennial ring-width chronology in Yamal, northwestern Siberia.
The Holocene 12,6 pp. 717–726.
Cheers.
It's also quite possible that it was one of those throwaway lines — "of course the easiest way to convince people of the seriousness of the situation would be if we could get rid of the mediaeval warm period" - that sort of thing.
A bit like "will nobody rid me of this turbulent priest?", which Henry may (or may not) have meant his lickspittle courtiers to take literally.
But the point is that, within a few years, along comes this still wet-behind-the-ears, newly frocked PhD with a piece of research that — whoopy-do — just happens to get rid of the mediaeval warm period!
Forgive some of us for not being just sceptical but cynical with it!
But then 3 years later Esper et al (2002) came along with a new analysis and brought the MWP back - as have many other studies.
Too much time has been wasted picking Mann et al. (1999) apart. Yes - it dominated IPCC TAR, but at that time, there was no other large scale synthesis for the last 1000 years - except Jones et al. (1998) and Briffa (2000) – which were mentioned in TAR. AR4 rightly brought all the different flavours together and I am sure AR5 will do something similar. Almost every other year a new flavour of large scale NH temperatures is developed:
http://www.ncdc.noaa.gov/paleo/recons.html
the basic message has not changed. I personally believe we still need many more records to derive a better large scale estimates for the MWP, but the recent multi-proxy Ljungqvist work has been a good stab in the right direction to address the spatial signature of the MWP which is very much likely to be more spatially heterogeneous than the warming of the last 100 years.
'very much likely to be more spatially heterogeneous'. With the right 'advanced statistical techniques' you can see what you already believe to be there.
Marvelous straight lines, Rob; you missed your calling.
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Rob
You might well be right but if sceptics hadn't picked MBH98 apart we'd still be stuck with the erroneous idea that the MWP didn't exist and that climate had in essence not changed for 1000 years and suddenly warmed up in the 20th century.
There is more than enough evidence left behind by those who lived it that there was a mediaeval warm period as there was a little ice age. I can't see that trying to refine its parameters, interesting though that exercise may be in the interests of some branch of pure science, is telling us anything about the behaviour of climate in the 21st century, in particular whether it is behaving in any material way differently from what it has in the past.
Given that both temperatures and CO2 levels have been higher (and lower) in the past I'm inclined to the view — absent any convincing empirical evidence to the contrary — that the climate is doing what it always does: changing, with anthropogenic contributions to that change extremely small and on balance beneficial given that we are, or a least should be, concerned with the well-being of our own species and that we are considerably better off by any measurement you care to apply than we were 100, 500, or 2,000 years ago.
Incidentally, you will probably not be surprised that I take the ncdc link with a pinch of salt. It seems overburdened with such names as Mann, Jones, Wahl, Ammann, Briffa, D'Arrigo, Hegerl ...
I'm sorry, Bob, we just don't believe these people any more!
Shh, don't tell Rob, but there's another active thread discussing 'advanced statistical techniques'. Some randy, dandy, reviewer has been wasting 'too much time' picking Mann up. Now why would he do that?
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Rob Wilson might not know anyone wanting to get rid of the MWP, but someone did, as reported by David Deming,
See the HSI, p.28
It's all about attribution, and the wonderful irony here is that attribution was used to create guilt, when in fact, no matter how paltry Man's effect, attribution should, and someday will, evoke praise. That wondrous, thunderous, dissonance resounds as the laughter in the clouds.
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Rob,
Some of us who visit this blog on a daily basis are also what I call 'CA lifers'. I use this term because we've been following the whole denroclimatology debarcle for years on ClimateAudit and tAV and in particular your self-serving comments on various dendroclimatology threads on CA.
As a UK taxpayer I personally find it extremely annoying that I have no choice but to continue funding researchers like yourself who can't even acknowledge bad science when it hits them right in their faces. Mann's MBH 98/99 and subsequent work has repeatedly been shown at best to be very poor and at worst totally freudulent yet researches like yourself in the same field continue to give it a 'pass'.
When are you going to admit Rob that dendroclimatology (attempting to divine past climate from tree rings) is an utter waste of my hard earned UK taxes.
[Snip. Calm down, please. BH]
KevinUK
Time to remind people again that Rob Wilson is one of the Goodies. He has communicated with Steve McIntyre (though has difficulty spelling his name!) which upset Clare Goodess (who spied on the two of them talking to each other) and Ed Cook. In email 4241.txt Rob tried to explain to some of the others how screening proxies by whether they match recent temperature rise generates spurious hockey sticks, even if you use random data for your 'proxies'. He got a bizarre cryptic response from Cook.
Rob Wilson:
Thanks for stopping by, and for your interesting comments.
Let me outline the problems dendroclimatology will have in regaining the trust of earth scientists outside your specialty.
First, the Hockey Stick graph is so laughably wrong, you guys look like, hmm, [polite euphemism here] for defending the indefensible. The graph itself, with current instrumental temperatures grafted on to proxy records, is so *obviously* apples vs oranges, that it's hard to believe any serious scientist would defend it -- proxies *aren't* thermometers. Yet there it is, making a mockery of basic principles of presenting scientific data every time it's used.
Second, your field is *still* not observing the basic principles of transparency and data-sharing that got your specialty into trouble in the first pace -- and led to the Climategate release of behind-the-scenes emails, which I hope you realize makes the leaders in your field look pretty bad -- as do the obvious whitewashes that followed, presented as "independent investigations." No one with any serious interest in the field accepts these results -- they were for political cover, sfaict. I strongly recommend that you read Clive Crook's outside look at the investigations, cited below.
Which leads to the third point -- the leaders in your specialty have decided to put politics ahead of science. Leading to a fatal loss of credibility with decision-makers and the general public. In how many other fields can the head of a major climate agency -- GISS -- be repeatedly arrested for civil disobedience and still keep his job? Can anyone believe his agency's results are presented objectively? Again, a glance at GISS's Gavin Schmidt's remarkable fulmination re the Yamal data at Real Climate will confirm this problem.
I'll close with a quote from the Atlantic magazine's Clive Crook: "The climate-science establishment ... seems entirely incapable of understanding, let alone repairing, the harm it has done to its own cause." http://www.theatlantic.com/politics/archive/2010/07/climategate-and-the-big-green-lie/59709
Peter D. Tillman
Consulting Geologist, Arizona and New Mexico (USA)
Specialties: geochemical sampling theory and practice
Application of statistical techniques to geochemical sampling
Bish and Paul M,
IMO Rob Wilson is far from one of the 'good guys'. Over the years I'm been following CA and have read prety much all of Rob's comments I haven't come a single one of his posts that has dissuaded me from my first impressions of him. He is IMO (and until such time as he condones the extremely poor science espoused by his fellow activist colleagues like Gabi Hergerl always be) a typical self serving academic who is never going to be prepared to admit that he has been wasting his entire academic career thus far on a fruitless tax wasting activity namely trying to divine past climate from tree rings.
Skeptics like myself get labelled 'deniers' yet Rob thinks he can get a way with delusional statements like
"the basic message has not changed. I personally believe we still need many more records to derive a better large scale estimates for the MWP, but the recent multi-proxy Ljungqvist work has been a good stab in the right direction to address the spatial signature of the MWP which is very much likely to be more spatially heterogeneous than the warming of the last 100 years."
KevinUK
Kevin
Please could you watch your tone.
I'm not sure that classifying people as 'goodies' or 'baddies' in this context is very helpful.
My experience of scientists — not being one but well-acquainted with several — is that as a group they tend to be somewhat self-centred and very sure of themselves but also in many cases insecure and even desperate for approval.
But then that applies to a lot of us, no?
They need reassurance that their work is valuable because (a) laymen don't understand half of what they are doing, and (b) research tends to throw up more dead ends than live possibilities and if they're not careful they start worrying that their work is not valuable.
The difficulty I have — and this is where I tend to side with Kevin — is that while I wouldn't go so far as to say that palaeoclimatology is worthless I don't see it as anything which in the present state of its development is a practical tool. Highly esoteric and on a par with the study of ancient civilisations which may have something useful to impart to us in the future but not a study from which it is safe to draw conclusions about climate in the 21st century or to make any judgement as to what action (if any) needs to be taken to adapt to likely climatic changes, still less unlikely ones.
Since we already know that dendrology has failed miserably to match the warming of the late 20th century (this being the very warming that the pessimists tell us is unprecedented and about which we need to take action) to expect us to believe that prior to 1960 treemometers were a reliable source of temperature data is behaviour which defies all logic. As well read the entrails of long-dead chickens.
At the other end of the scale the soothsayers are busy creating numerous computer models which they think we are stupid enough to believe tell us something other than what they are programmed to tell us.
Amd mightily shirty they get when we don't.
With very few exceptions none of these people takes his/her nose out of the trees or away from the computer screen and looks at what the world has done, is doing, and in all probability will do again. And like a lot people (scientists are as susceptible as any and more than some) they never, ever take a step back and apply the theories of William of Ockham. Only when those fail is it necessary to look for complex and unlikely reasons for things.
Unless, of course, you have some vested interest in things being the way you want them to be. But that, as they say, is a whole new argument!
Whilst you can debate the merits or lack thereof of dendrochronology, there are some basics that first should be understood. Fieldwork collection of tree cores is great, as you get to play in the big outdoors. From then its all downhill. In order to reconstruct climate you have firstly to carefully record the ring widths of each tree. This step is mind numbingly boring. There is nothing worse than staring down a microscope for hours and hours and hours. Why would anyone spend there time collecting data in such a manner for the sole aim of creating fake data. It doesn't make sense to me. However, as the internet proverb goes: haters gotta hate.
I am genuinely confused with the posts which equate Rob Wilson to Michael Mann. In much the same way as anyone can have their flaws, it is simply ridiculous to assume that as one Scientist was wrong (granted, in a fairly major fashion) that all Science is wrong.
The evolution of knowledge is the basis of Science - at one point it was believed that the Earth was flat, now look how we have moved on. Sadly, to further push the boundaries of information, it is no longer adequate to simply look at the world and state "Oh, wait a minute, this looks a lot rounder than completely flat.".
The advancement of techniques to quantify the world in which we live is something which, "IMO" tax money is well spent.
If I was cited on a web site that features Obama birther loons, I wouldn't be boasting about it.
MarkB
I'd be careful if I were you. Blogs are not responsible for the people who choose to infest their sites. As I'm sure you well know. You cannot, for example, hold the Bishop responsible for your presence here.
4yth year student
Nobody is suggesting that tree-ring data is fake. Just meaningless as a proxy for .....just about anything actually.
It's difficult to get this point across. If it didn't match post-1961 observed data then the fact that it matched pre-1961 observed data means nothing and if it's all you've got (pre-reliable temp records) it means even less unless you can come up with a sensible explanation for the discrepancy. Until you can why should I believe that your tree-rings tell me anything at all except that that was a good year for growth or a bad year for growth? It does not tell me why.
TEAMPhys
When exactly was it believed that the earth was flat? Aristotle certainly thought the earth was round in 330BC and apart from the Chinese until the 17th century — and they have always been a law unto themselves — only very primitive societies have even been suspected of such a belief and then only because they had no reason to think otherwise.
Come on guys... seriously? Rob Wilson is damned if he does and damned if he doesn't. He is at least trying to engage with you. He is as you say a goodie... Although branding scientists as heroes and villains isn't going to do much for the quality (or apparent lack thereof) of the science.
The whole argument has spiraled out of control. There is no conspiracy, they are doing the best with what they've got. There are uncertainties, problems, limitations of course there are... such is the nature of science it is always evolving... but I don't think that means you can say the science is wrong. I'm very happy for my tax money to be spent trying to IMPROVE these techniques.
I do think if you engaged a little more in the literature, rather than writing it off because of who the author is you might realize where the issues really are and that the people who actually do this science are trying to overcome them. And sure, the scientists should do a better job of making uncertainties clearer to the broader public, but given the response Rob Wilson etc. has got during his forays into the blog world, why would they bother?
Mike... you're cherry picking. I'm fairly certain there are some reconstructions that do follow recent warming relatively well. And many of them need updating... so we shall see.
@ 4th year student:
I can think of far worse jobs than that.
My only personal knowledge of dendroclimatology comes from a neighbouring forestry professor (retired). He mentioned that his PhD was an attempt to reconstruct historic climate from ancient English oaks. I asked how he got on, the answer was nowhere; he spent years on it and completely failed to detect any meaningful signal from the tree-rings.
@lapogus
some species at some sites will not have a meaningful temperature signal.
Question: Can a categorical statement about the homogeneity of warming, 1850 onward, be made?
I think not. Anyone who knows even a little about thermometer coverage during the 1800s would agree.
But apparently, Rob Wilson, doesn't think so. Apparently the whole globe homogenously warmed up during the modern period and the sparse thermometer network is interpreted with this view.
By the same token, you can bring any number of proxies into the mix for the medieval period. But it would always add to a heterogeneity.
All this amounts to a shifting, weaving and bobbing in logic, and nothing more. Even in the modern period, we see heterogeneity year after year. Russia was very warm in 2010. Alaska, Europe and large parts of Asia were brutally cold in the winter of 2011. Similarly, there is a lack of centennial-scale warming in several locations. Yet, all of these are averaged to produce a single warming trend under a global average temperature. The same concept becomes anathema as soon as warming in the Medieval period is under question. Suddenly, everything is spatially and temporally heterogenous, things warm and cool at different times, and there is apparently no unified picture.
It is just smoke-and-mirrors crap.
@Lapogus
That failure at reconstruction does not surprise me. For the purpose of reconstruction of cliamtic variability from tree rings there is the necessity that the tree be stressed either due to climate or due to water availability. This is why reconstructions are taken from high elevations and lattitudes when trying to reconstruct temperature, or from warm regions for the reconstruction of precipitation. Unless a tree has an excess of one and a lack of the other there is no signal within the growth trend of the tree. English oak trees are temperate trees, they do no really occur in areas of stress within the UK, probably because we cut them all down! As such this reconstruction attempted will not have a strong climatic signal.
@ Mike
I was using a facetious commonly heralded "fact" to exemplify the development of Scientific knowledge, and how ridiculous many arguments on this blog appear to me.
"only because they had no reason to think otherwise" - This argument could be extrapolated back to this whole debate, and therefore I am of the opinion you have stabbed yourself in the foot. (I feel the need to reflect this debate and be pedantic enough to state that this is, of course, metaphoric stabbing)
4th year student - that may be so. But how much more extreme are the conditions which Rob's pines experience than those typically experienced by English or Argyll oaks? I remain to be convinced that dendroclimatology is not just a vast opportunity for cherry-picking; some species don't have a signal; some do, but only from some areas, and only if they have suffered some severe environmental stress...
No offence, and I appreciate that you are contributing here and not making an arse of yourself down the Grassmarket like most students did in my day, but it's Friday night and I am having a beer, so I will say what I am thinking:
Dendroclimatology is bollocks.
@lapogus
I'm also a 4th year and I've just completed a dissertation using some of those very same pine sites.
They are at/near tree-line which is by definition the ecological limit of the species so is more 'extreme'.
I don't know if you are familiar with Fritts... but there are sensitive series and there are complacent series. Sampling must be focused on sensitive regions, because as has been pointed out there are many factors which affect tree growth. So in order to maximize the signal being investigated they go to tree-line because trees are growing in their ecological margin and will be sensitive to environmental change. At elevation tree line they are likely to be sensitive to temperature because that is the limiting factor affecting tree growth in those conditions. The other factors get averaged out when the series are averaged together.. many trees and many sites mean a robust climate signal can be generated from sensitive series.
Spacey - ok, I can see the reasoning for the tree-line selection (though my argument that these trees are only reflecting the short summer season temperatures and not the annual average still stands).
And I will moderate my previous statement to: Dendroclimatology is mostly bollocks.
But as I suggested in my first comment on this thread earlier today (directed at Rob), why all this emphasis on trees? The Loch Sunart sediments have given a seemingly comprehensive and credible reconstruction which confirms the MWP, the 16th Century warm period, the descent into the LIA and the long slow thaw from the end of the LIA.
I think trees are useful because there are a lot of them and is much less expensive than other proxies. Which is always a plus when people don't want their tax money being used on such things.
I agree other proxies are useful and I think that's the way things are beginning to/going to go... using many different types of proxies and creating multiproxy reconstructions. But I think tree rings will still be valuable as part of that.
You might be interested to know that part of what Rob is doing with the pine in Scotland as part of the relic project (see his webpage) is also going to be using lake sediments.
spacey - the growing season for trees is quite short, which raises the question of how you can correlate rings to global annual temperatures, but also, I understand that many trees only grow when the temperature (or other factors) are within a certain range. So if the rain factor swamps the tree, the tree stops growing, which means an attenuated temperature response. But, even if you sample trees at higher altitudes where water is not the limiting factor, if the temperature exceeds the upper bound of the tree's reponse, how do you get a reliable temperature signal? The signal will be flattened to within the limits of the tree's desired temperature.
Re: Tree rings as reliable temperature proxies
Many recent tree-ring proxies *don't* track current temperatures -- the well-known "divergence problem", which is hand-waved away (in public) by the dendros, as if such mistrackings couldn't have happened in the past. If the dendros hand-selected tree-ring cores can't track the known instrumental temperatures nearby....
Which problem led directly to the snipping-out of such results on public hockey-stick graphs -- the notorious "hide the decline" deception, again hand-waved away by the leaders of the field, as if any serious scientist wouldn't see through these transparent and inept excuses. As Richard A. Muller observed in a devastating critique of "hide the decline", “I now have a list of people [Michael Mann, Phil Jones and others] whose papers I won’t read anymore.”