New poster bender has written some very thoughtful posts, including some comments on Gaspé which I I’d like to recover from deep in a political thread. The growth pulse in Gaspé cedars seemed very improbable to me as a temperature proxy; bender has some detailed knowledge on the topic.
Bender Post #1:
Re: #233 Have you yet seen the threads discussing the relationship of tree ring width to temperature ? As in, it is not a linear relationship, but an inverse quadratic; i.e., in really hot years, trees don’t grow well, so hot years do not show up in the tree ring record. Any thoughts on this?
The oft-cited Ste-Anne Gaspé “northern treeline” Thuja occidentalis tree-ring chronology used by MHB98, which is hockey-stick shaped, is only one of three for this species from eastern Canada. The other two (S. Ontario, AD 594-1990 and Duparquet, Quebec AD 1186-1987), not used by MBH98, indicate exactly what you describe: a *negative* response to warm temperatures during the 20th century (Kelley et al. CJFR 24: 1049, Archambault & Bergeron CJFR 22: 674). The reason these chronologies were ingnored by MBH98 is probably that they were not “20th century treeline”, and they exhibit significant precipitation sensitivity. (But they also are not hockey-stick shaped either.)
But because the position of the treeline varies over time, so the temperature response function coefficients of a given tree in a fixed location should vary accordingly. This point has been made by: Cook, E.R., Esper, J. and D’Arrigo, R.D. 2004. Extra-tropical Northern Hemisphere land temperature variability over the past 1000 years Quaternary Science Reviews 23:2063-2074. who describe a “loss of climate sensitivity in the northern boreal zone” in the 20th century.
And the reason this is relevant because it is exactly the point picked up on by Wegman et al. p. 28:
In MBH98/99 the authors make a simple seemingly innocuous and somewhat obscure calibration assumption. Because the instrumental temperature records are only available for a limited window, they use instrumental temperature data from 1902-1995 to calibrate the proxy data set. This would seem reasonable except for the fact that temperatures were rising during this period.
Although Wegman et al. don’t say as much, a change in a tree’s temperature sensitivity coefficient over time will bias a tree-ring based temperature reconstruction. I realize the above question was probably rhetorical. I just thought I would supply a concrete and relevant example of how such a quadratic response to temperature is not only real, but could lead to time-series nonstationarity that violates assumptions made in the inferential leap one takes in going from calibration to reconstruction.
Bender Post #2:
Re #272 Jacoby’s lost Gaspé cedars (posting from 25 April 2005 in a different thread) from Riviere-Ste-Anne, Quebec would most likely be located in the high-elevation Parc Quebecois de la Gaspésie, south of Ste-Anne-des-Monts – in which case these trees were probably never cut down. (They’re likely protected, and of no commercial value.) Granted, this is not a GPS pin-pointing, so you could not revisit the exact stands sampled in 1983. But you wouldn’t need to. All the cedars in that whole area should be responding similarly to temperature, if that is what they are responding to.
But one has to wonder about the possible release of these Gaspé cedars under heavy defoliation by spruce budworms in the 1950s and 1980s. One look at that chronology will confirm sharp spikes in growth during those two well-documented outbreaks of unprecedented severity – spikes which account for much of the hockey-stick shape of that chronology. (Maybe that’s what the sampler was doing there in 1983 – checking out the incredible damage during the peak of that outbreak?) Unfortunately the ITRDB stand metadata are insufficient to determine if the sampled trees were growing in mixed stands that could have been subject to release by insect disturbance. Possibly a moot point if it was a barren “treeline” site. Light is not usually limiting in those circumstances, but – come to think of it – these growth pulses could be a result of increased nitrogen (which is severely limiting in the boreal alpine environment) from insect frass. That might explain why the other cedar chronologies (from low-elevation cliffsides in Ontario and rocky lakeshores in northwestern Quebec; see #272) do not show the hockey-stick shape: no budworm, no frass, no nitrogen, no 20th century release.
All this to say: MBH98 is based on at least one tree-ring chronology whose local ecology and dynamics were never formally studied. Archiving data for future use is one thing. Understanding it is quite another. Does it make sense to publish based on archived data which have never actually been analyzed?
Re: #15
Short answer: Weather influences insect population dynamics significantly, but the degree and form of the effect varies from system to system. Statistical evidence is hard to come by, but that’s not surprising given the way these systems work. There is no “one size fits all” answer.
Longer: People have tried to make the link between all kinds of weather indices and insect outbreaks and they usually don’t pan out. It is thought that this is because of the action of other variables in the system (the forest, insect predators, etc.) – that weather is far from the only driver, such that the correlations are typically weak. That being said, there are many systems, and situations, where drought can act as a trigger to insect outbreak. The idea is that (1) insects like the warm weather, and (2) they do well on the weakened, drought-stressed trees. The spruce bark beetles currently in Alaska are a great example. All insects are cold-blooded and in temperate areas are limited by temperature, so as we move out of the Holocene most forest-dwelling species are expanding their range with the retreat of the glaciers.
Dendrochronologists like Tom Swetnam know all about this, and so people trained in dendrochronology at LTRR and elsewhere generally have a good appreciation for the potential importance of insects in affecting ring width, density, and character. (In fact his 1993 published work on western spruce budworms tried to make the link between budworm outbreaks and wet summers.) But I would not say that the appreciation for millenial-scale variability in outbreak dynamics is very good. Insects are viewed as a random noisy nuisance which they are happy to be rid of (usually by cherry-picking hypothetically insect-free sites). One problem is that the signal associated with some insect species, often periodic, has a way of fading in and out in time and space.
The argument against insects as a key driver of ring characteristics goes like this: we’ve never seen any on this tree species in this particular site type in the 20th century, so therefore they were never here, and therefore weather is the primary driver. The problem is that we now know that climates vary naturally. We know that insects move in when a region warms up (spruce beetles in Alaska, mountain pine beetle in British Columbia, hemlock wooly adelgid in the NE US). So in theory it is possible that these insects, though absent now from the system, were at one time prevalent.
A dendroclimatologist will argue that the proof is in the pudding: weather variable correlates with ring width/density, therefore it causes it. The problem is, as you know, that these correlations are never all that strong, and they even go through phases of strengthening and weakening. Maybe the weakening is the result of some other limiting factor kicking into play? Who knows what. But where there’s uncertainty, there’s doubt.
I can’t comment on the specific case of BP as it is a system I don’t know anything about. But I was interested to learn about 10 year cyclic outbreaks on cedar leaf miners on northern white cedar in eastern Canada (Jacoby’s lost Gaspé cedars). The outbreaks can be quite intense and are triggered by drought – such as the most recent outbreak from 2000-02 in Ontario. Dead cedars in Guelph not 10km from where Kelly et al did their cliffside cedar studies. This insect has never been seen at high elevations in Gaspé in the 20th century. But that doesn’t mean it wasn’t there during the MWP.
I’m not suggesting insects everywhere are the major driver and that dendroclimatologists are in gross error. I’m suggesting that they shouldn’t be so quick to dismiss insects, as there is a chance they could be compromising reconstruction quality during some parts of the tree ring record.
Given the importance of BP to MBH98 it might be interesting to know something about the insects of BP. As I say, I don’t know thing myself. High elevation sites are often too cold for defoliating insects. On the other hand, climates do vary
(On the uptick of BP growth in the 20th century: has a nitrogen pulse been excluded yet? That it is only in the NE US BP is interesting. Looks like there are actually two upticks – 1950, 1980 – coinciding with eastern spruce budworm outbreaks.)
This is one of my areas of research (but NOT BP), and so I can say firsthand that the state of knowledge evolves continually.
Long answer to a simple question. Wish that nature were simpler.
Climate Audit 
41 Comments
A couple of quick comments:
1) Nitrogen has definitely not been ruled out in connection with bristlecones. In our EE 2005 article, we cited a reference mentioning nitrogen increases for bristlecones at Niwot Ridge near UCAR world headquarters. The NAS panel also mentions nitrogen as an issue.
2) the Duparquet cedars were listed in the original MBH SI. These are one of the 32 series that were said to have been used, but not used (a statement was issued in the Corrigendum). The stated reason for exclusion in the Corrigendum was totally false. I notified Nature i advance that the reason provided was false, but they didn’t care. The Corrigendum was not peer reviewed.
Self-correction. I read “White Mountains” and thought “New Hampshire” and leaped to a speculation about eastern budworms & BP. Of course BP are in the west, not the east, so this line is absurd. Just a microcosmic example of the danger of confirmatory pattern seeking, and why we need rigorous check & balances in this business. Especially when the “submit” button is so easy to press.
Now why would trees spontaneously lose their ability to respond to climate? It’s a miracle.
Re bender’s post
bender, this paragraph is the reason I was asking about the effect of insects. It seems to be saying the growth spikes are during the budworm outbreaks, which I would have expected to be bad for the trees. What am I missing ?
I assume you know who the “H” is in MBH? It is Malcom Hughes, who is currently at LTRR. I would assume since he is a well known dendro guy that he knows something about dendro.
Re #4
You aren’t missing anything.
Re #5
Malcolm Hughes knows more than just “something” about dendro. He knows a heck of a lot. Maybe even more than anybody. If you think he has something to add to the discussion, let’s hear it.
Hmmm, if Hughes knows that much about dendro., then why all the f*@#%%@* cherry-picking in the MBH stuff. Maybe he didn’t read it?
Great post, bender. As you explain, even if growth varied linearly with temperature, there are still far too many variables affecting tree growth to find a consistant “temperature signal” in tree rings over a long period of time. Surely Hughes knows that, too.
A similar mistake was made by most people looking at mortality of red spruce in New England during the ’80s. The acid rain scare was going full-bore at the time, so all mortality was ascribed to that agent. There was even a book I recall titled Last Stand of the Red Spruce which purported to prove the link (written by a lawyer, natch).
Ultimately, it was shown that a periodic spruce beetle outbreak was the cause:
Worrall, J. J., T. D. Lee, and T. C. Harrington. 2005.
Forest dynamics and agents that initiate and expand canopy gaps
in Picea-Abies forests of Crawford Notch, New Hampshire, USA.
J. Ecology 93:178-190.
This is not to say that acid precipitation did not and is not affecting northeastern forests – but in the political and scientific climate of the time other agents were largely ignored, (the degree of mistaken assumptions, of course, grew as information moved from the scientific to the political and press arenas)and the effect was routinely overstated. Bad policy was proposed and scientists lost credibility.
Bravo to Steve and the others contributing to this site for asking hard (though in retrospect, obvious) questions about climate science early in the debate. It seems you are already having an effect on both the scientific and political discussion.
Re: #8 Supporting footnotes.
(1) Moreover spruce beetle is another one of those insects that comes and goes over extremely long time-scales. Used to be a huge problem in the 1920s in … the Gaspé. You don’t hear anything about it any more. Now budworm is the 20th century threat. Why? Maybe it has something to do with the conversion of the commercial forest from spruce to fir? So much for the idea that “insects aren’t there now, therefore they never were, therefore the climatic signal is the dominant one”. Maybe. Maybe not.
(2) Since you mention it, acid rain has also been ruled out as a primary factor in the 1980s decline of hardwoods in the east. The mechanism has been worked out to a remarkable level of detail in yellow birch, and the cause is: fine root breakage during “false spring” thaw-freeze events, such as the one that happened in March 1981, where ice lenses form in the rooting zone in clay soils. Apparently, this happened in 1933 as well. Took alot of careful experimentation to get the error bars small enough to prove their case, but they did it:
Cox, R.M.; Zhu, X.B. 2003. Effects of simulated thaw on xylem cavitation, residual embolism, spring dieback and shoot growth in yellow birch. Tree Physiology 23: 615-624.
(I wonder if something like that could have happened during the multicentennial MWP?)
And now, the same is hypothesized to explain 1980s sugar maple decline as well:
http://www.biology.mcgill.ca/undergra/c465a/biodiver/2001/sugar-maple/causes.htm
and literature cited therein.
I guess the anti-coal lobby promoted the wrong science on that one. Doh.
What have I learned from these examples? Nature is so variable and nonlinear and tricky that it takes a lot of effort to get the uncertainty down to the point where you can exclude everything but your pet hypothesis. Don’t play policy-maker pretending you’re there when you aren’t. Just do the science. And when someone smarter than you points out an error, come clean on it. Maybe you’ll learn something.
RE 4:
fFreddy, I’m guessing that the cedars’ growth is reduced during the insect outbreaks. Then the insects cyclically “crash” (while bug-crap has accumulated under the tree canopies). The trees, no longer chomped on & now fertilized, have growth “pulses”, which then settle down after a few yrs until the next outbreak.
RE #9:
bender, perhaps Sugar maple is declining in general, but here locally (mountainous MD) it’s actually spreading aggressively into the oak forest, particularly along flood-plains (rather surprising), and up the inclines from there. I obviously can’t observe much area, but I’ve seen this situation in a number of localized areas in the western MD mountains where S. maple seems anything but declining, especially if the particular area has been “left alone” for some time.
The local S. maple could have some genetic differences from the “New England” phenotype, and may not respond to or be subject to the same stresses. Annual temp’s here now are about the same as they were in the 30s & 40s.
Is there any evidence that the insect infestation/tree growth cycle follows a preditor/prey relation like the Lotka-Volterra equations?
Not being an expert or having read anything in the area I’d think it would depend on the type of insect. For instance locus I think would be a good example as a case that the Volterra equation might hold.
I’m wondering if it is possible to detect insects based on comparing two different trees. If the response of one tree is abnormally different then another perhaps that is an indicator that the other tree likely had an insect outbreak or some other disease.
Re #10: Cedar is a non-host of the budworm. Spruce and fir a host. So if the two species were mixed in a stand, cedar would exhibit a (+) response, spruce/fir (-). [My suggestion of a linkage here was pure speculation. But it is a neat coincidence that the chronologies were collected in 1983 in an area at or near where the budworm was wreaking havoc (RiviàÆà⧲e Ste-Anne is a long river). No one could have missed the budworm’s presence during the spring and summer 1983. But maybe if the sampling was done in the fall … when the mosquitoes & blackflies were gone … you might not notice the budworm. Suggestion: get more cedar samples.]
Re #11:
When I said “decline” I should have used quotes. It was more a temporary crown dieback situation, where not all stands declined. And yes, in Québec too maple are doing very well. They are invading, along with beech, many commercial forest stands. Noble hardwoods indeed. Thanks for the correction.
Re #12:
Swetnam & Lynch (1993) wrote the book (Ecological Monograph) on insect outbreaks being cyclical and easily evidenced through stem analysis. Dendrochronologists such as H in MBH, and anyone trained at LTRR, knows the story well and will back it up.
Re #13:
There is good reason to believe that many tree ring signals are not only first order autoregressive, but second order as well, because many forest insects cycle due to predator-prey, insect-plant, and insect-disease interactions. Citations far too numerous too provide. Probably easier to cite systems that do not have periodic outbreaks of some type. But a few examples include:
eastern spruce budworm on spruce in eastern North America (Blais 1983, Jardon et al. 2003, Boulanger & Arsenault 2004)
autumnal moth on mountain birch in Sweden (Tenow 1970, Bylund et al. 1998)
western spruce budworm on Douglas-fir (Swetnam & Lynch 1993, Ryerson et al. 2003)
larch budmoth in the Swiss Alps (Weber 1995)
larch sawfly in sub-arctic Canada (Jardon et al. 1994)
Pandora moth on ponderosa pine in Oregon (Speer et al. 2000)
All of these are tree-ring studies.
When these systems are cycling, the 2nd order autocorrelation in ring width parameters is strong and NEGATIVE. When they’re not, you can not really detect their presence, and must rely on direct population sampling methods. The reason they’re negative is because a predator-prey cycle requires delayed negative feedback. Schema: herbivores go up in year t, predators follow in year t+1, herbivores decline year t+2. This is of course, a drastic oversimplification intended to illustrate to a generalist audience qualitatively what happens.
Dendroclimatologists will argue that their samples and systems have been cherry-picked to avoid drastic insect problems. Maybe. But what is that old line about “absence of evidence”?
bender, you’ll be amused by Jacoby’s mention of insects here . He selected the 10 most "temperature-sensitive" of 36 sites sampled and refused to archive the other data, on the basis of their funded mission:
I think that this is trumped by Esper:
As I say, my suggestion of a possible link with insects in the case of sub-alpine cedar is pure speculation. I don’t want to lead you astray on this. That bit about temperatures in the rooting zone seems like a worthy avenue of investigation as well, but it too is wild speculation.
If I knew the location of the Riv-Ste-Anne cedar chronology I could tell you based on historical records if and when those exact stands were defoliated or not. We could go there and resample. As it stands, TCO is right – all the cedars above ~750m should give you the same climatic signal – IF that is indeed how those cherries are to be picked. The problem is: the site selection criteria are unspecified in papers, undocumented in the database, so how do you know when you’re replicating their sampling method? How does the replicator know when he’s replicating the design, when the methods are secret? How do they know, a priori, which stands are going to give “the signal”? If they only know a posteriori, and are cherry-picking from among the chronologies, then they are creating a real epistemological problem for themselves. Hindsight is 20/20.
Did I mention that cedar needle miner, Argyresthia spp., outbreaks occur at ~10 year intervals in southern Québec? I wonder if they knew that, and if so, how they knew to avoid the kinds of areas where needle miners are prevalent.
I’m sure Jacoby is brilliant at what he does. Just as Hughes is. They are fine people, as most people are, as all dendrochronologists are. I’m just not convinced that the reconstructions are as statistically robust as they need to be to support the claims that are being made. I mean, it’s one thing to *postulate* in the academic literature a climate link based on a posteriori cherry-picking of chronologies. It’s quite another to fast-track an analysis to the level of a policy tool while downplaying the uncertainty in it all. Policy-makers like things simple, but they sure as heck don’t want to be embarrassed by something that has been rendered overly simplistic.
TCO was right. TCO was right.
Umm…and to answer your question, you consult the dendro experts, get their best take on how to select a stand, document that rationale, select the stand and then publish the result. If it turns out to be a different sort of stand, fine. You’ve opened up the debate of how to pick stands and of why one versus the other is favored.
Re:#18
That’s the hard part, TCO!
No, it’s not. just pick your own set of experts. ask for criteria. Write them down. Use them. Publish.
RE #4 fFreddy,
See first paragraph of bender’s comment 15. A budworm attack on spruce/fir may allow a growth spike among other species, such as cedar, if they had been competing for nutrients, sunshine, or whatever.
Of course TCO was right (on ocassion); he can’t be wrong all of the time. 🙂
It is intersting to note the close approximation of the treeline on the west side of Hudson Bay with the 10°C summer isotherm and the lack of approximation on the east side of the Bay in Northern Quebec. It is possible variations of ice conditions in the Bay are one factor. These are quite well reconstructed for parts of the 18th and 19th centuries from Hudson’s Bay Company ship records by Faurer and Catchpole. I also recall research done on the correlation of insects in the boreal forest and the southern limit of permafrost. Sorry I don’t have a reference for the latter but believe it was federal forestry people.
We need Al Gore down here in Southern Oregon. It’s abnormally hot so far this summer, and we have broken some records. But most of the records were set in 1928.
Could the national heat wave have anything to do with Al Gore’s speaking tour ? Maybe NASA should monitor the temperature of the air leaving his gullet.
FYI
LA Times
Global Warming — Signed, Sealed and Delivered
Scientists agree: The Earth is warming, and human activities are the principal cause.
By Naomi Oreskes, NAOMI ORESKES is a history of science professor at UC San Diego.
July 24, 2006
AN OP-ED article in the Wall Street Journal a month ago claimed that a published study affirming the existence of a scientific consensus on the reality of global warming had been refuted. This charge was repeated again last week, in a hearing of the House Committee on Energy and Commerce.
[snip]
Re: Oreskes article
Oreskes, in the LA Times op-ed continues to use the sleight-of-hand she used in her “proof” of consensus.
I watched the hearings, which were about NAOMI ORESKES. They really went ON and ON about NAOMI ORESKES, just wouldn’t shut up about NAOMI ORESKES.
I recall Steve being interupted by Barton… “What’s all this about ‘centering’, what do you think about NAOMI ORESKES?”
Funny how nobody cries about Oreskes as “not a climate scientist.” I feel pretty certain that if someone with Oreskes’ credentials said the issue of AGW was unsettled, there would be cries from the AGW crowd about her not being a climate scientist.
I have less problem with “consensus,” howvever Dr Oreske’s screed shouted/implied/was mis-characterized as unanimity, by an uninformed media.” With calculated (to deceive) author design, the media regurgitate headlines that humans are the leading (and sometimes the only) cause. Many know that to be unproven, and the continued bludgeoning by some AGW-proponents will not forge that into unanimity.
Dr Von Storch has already commented on the gatekeeper restrictivity of the post-MBH’9x journal acceptance process, and this continues today. This has always skewed the basis for the Oreske’s study in the first place. And she is clearly a Mannian-like drumbeater for such restrictiveness, for without it her study(?) would smoldering in the same ashes as the hockey stick. Perhaps it soon will be anyway.
I also register my objection to her deliberate and personal literary assassination of Dr Lindzen, and of course the calculated use of the invective “denier.” The not-so-veiled ageism of Dr Oreskes and others is obvious. Sadly, she too will meet the same ultimate fate as Sir Harold Jeffreys, only the subject will be different.
Correction: Oreskes’ study
Here are some fascinating papers, including the best “reconstruction” I’ve seen (hope the link works).
Re: 32
Nope. The link doesn’t work. Post the comlplete URL. Doesn’t screw up my browser’s pages at this site.
On a lighter note…
The 2006 hurricane season is getting off to a good start 🙂
Here is ace reporter Jerry Petree on the hurricane that never was, Hurricane Alberto, and the devastation it inflicted upon Myrtle Beach.
Hurricane Alberto Video
re: 32
By searching on “climate” at right on esnip page, I clicked on the 1st link and got: Loehle(2005)MathGeol.pdf which does a some interesting periodic reconstruction plots. I presume that is one of the .pdf files you wanted to pass on?
On the topic of insect signals confounding temperature reconstruction, has anyone read this paper, and found it odd that reconstructed temperatures should cycle every ~30 years? (see their Fig. 8)
D’Arrigo, R, Mashig, E, Frank, D, Wilson, R.J.S. and Jacoby, G. 2005. Temperature variability over the past millennium inferred from Northwestern Alaska tree rings. Climate Dynamics 24: 227-236.
Click to access DArrigoetal2005c.pdf
I’m not saying that it’s primarily an insect signal they’ve extracted, but aren’t those Alaskan spruce currently being destroyed by spruce beetles? Don’t spruce budworms cycle every ~30 years? How can these authors prove that insects are not the major factor limiting growth?
#36 That sounds like a very good explanation to me. BTW, does the fit look odd at 2000? It looks like they drew in the hockey stick by hand.
JC,
By “fit”, you are referring to the late 20th century uptick in their Fig. 3A? If you zoom in on that time-series ca. AD2000 you see that the dark band that looks something like an uptick is actually the bootstrap confidence interval, which widens enormously just before 2000 to include both positive and NEGATIVE trends as late 20th century possibilities. i.e. “Divergence” due to “loss of climate sensitivity”. (OR what would yield the same effect: an increasing impact of insects?) If that’s the “fit” you’re referring to, no, I don’t think this is odd. Just telling.
Overlooking the obvious looking for AGW,
link
Here is a story that look to me like researchers walking around the stumps of bristlecone pines that are above the current tree line and looking for evidence of global warming but not asking why there are dead bristlecones above the treeline.
Faithfully? Hmmm.
My search for spruce budworm indicated your site, but I could not see anything related to budworms. nevertheless, if you are interested in the spruce budworm, or have any ideas on that problem, visit my site loneresearcher.blogspot.com
I would be interested in any comments that you care to make as I really don’t know whether I am right in my speculations or where to go with my thoughts on the subject.
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