New isotope based temperature reconstruction using McIntyre's 'Starbucks hypothesis' tree core samples

A new paper in GRL published Sep 6th Secular temperature trends for the southern Rocky Mountains over the last five centuries makes use of some tree core sample data gathered by Steve McIntyre and Mr. Pete. Readers of WUWT and Climate Audit may recall that in the summer of 2007, Steve left CA in my attendance for a couple of weeks while he went to Colorado to visit his sister, and to prove or disprove his ‘Starbucks hypothesis’ which asks:

…could a climate scientist have a Starbucks in the morning, collect tree rings through the day and still be home for dinner?

This came about because apparently RealClimateScientists™ don’t have the funds or time to get out of the office and gather new tree core samples, such as cores that would fill in the last 25 years that seems to be part of that “tricky” divergence problem. In A Little Secret (Oct 2007) Steve wrote:

Don’t you think that someone on the Team might have been a little curious as to what bristlecone ring widths have done during the past 25 years? For this, we have the classic excuse of Michael Mann and the Team for not updating bristlecone and proxy records is that it’s not practical within the limited climate budgets:

While paleoclimatologists are attempting to update many important proxy records to the present, this is a costly, and labor-intensive activity, often requiring expensive field campaigns that involve traveling with heavy equipment to difficult-to-reach locations (such as high-elevation or remote polar sites). For historical reasons, many of the important records were obtained in the 1970s and 1980s and have yet to be updated.

This new paper proves that you can do field science on vacation, while visiting Starbucks, and in a single day. It also has a thing or two to tell us about the accuracy of tree ring width and wood density records and their value as a temperature proxy.

First, the calibration of the d18Oc data with instrumental temperature data from the nearby Cheesman USHCN station.

image

Figure 1A. Timeseries of temperature anomalies reconstructed from d18Oc and that observed at the Cheesman meteorological station. Error bars represent the uncertainty in the temperature timeseries that arises both from the spread of tree-to-tree values and the uncertainty in the slope of the transfer function.

Abstract:

Pre-instrumental surface temperature variability in the Southwestern United States has traditionally been reconstructed using variations in the annual ring widths of high altitude trees that live near a growth-limiting isotherm. A number of studies have suggested that the response of some trees to temperature variations is non-stationary, warranting the development of alternative approaches towards reconstructing past regional temperature variability. Here we present a five-century temperature reconstruction for a high altitude site in the Rocky Mountains derived from the oxygen isotopic composition of cellulose (d18Oc) from Bristlecone Pine trees. The record is independent of the co-located growth-based reconstruction while providing the same temporal resolution and absolute age constraints. The empirical correlation between d18Oc and instrumental temperatures is used to produce a temperature transfer function. A forward-model for cellulose isotope variations, driven by meteorological data and output from an isotope-enabled General  Circulation Model, is used to evaluate the processes that propagate the temperature signal to the proxy. The cellulose record documents persistent multidecadal variations in d18Oc that are attributable to temperature shifts on the order of 1C but no sustained monotonic rise in temperature or a step-like increase since the late 19th century. The isotope-based temperature history is consistent with both regional wood density-based temperature estimates and some sparse early instrumental records.

Berkelhammer, M.,and L. D. Stott (2012), Secular temperature trends for the southern Rocky Mountains over the last five centuries, Geophys. Res. Lett., 39, L17701, doi:10.1029/2012GL052447.

image

Figure 3. (top) Reconstructed (JJA) max. temperature anomalies based on the d18Oc from two long cores (blue and green) at the Almagre Mt. site. The mean of the reconstruction was smoothed with a 20-year bandpass filter (black) to accentuate low frequency trends. (top middle) Reconstructed AMJJAS max. temperatures for the same site based on variations in annual growth [LaMarche and Stockton, 1974]. (bottom middle) Reconstructed AMJJAS max. temperatures for the region based on variations in wood density variations [Briffa et al., 1992]. (bottom) Difference between the temperatures reconstructed from d18Oc and ring width variations (purple) and the difference between temperatures reconstructed from wood density [Briffa et al., 1992] and ring width variations (green).

Discussion

During the 20th century, the summer surface temperatures in this region are characterized by a broadly parabolic trend, with minima during the 1930s and early 1980s

and a period of relative warmth during the late 1940s to early 1960s (Figure 1). The temperature reconstruction based on d18Oc suggests that in terms of mean temperature and multidecadal variance, the 20th century is largely comparable to

the preceding 4 centuries (Figure 3).

Despite the seemingly good correspondence between tree ring width (Figures 3 and S5) and d18Oc proxies during the instrumental period, over much of the previous 400 years

the two records exhibit very different climate histories (Figure 3). Prior to the mid 19th century the width-based reconstruction indicates temperatures at this site were

approximately 0.7C cooler than during the instrumental era while the d18Oc reconstruction suggests that temperatures have remained stable. The residual between these two reconstructions (Figure 3) is sufficiently large and sustained to suggest the existence of a significant bias in one or both of these two proxies that cannot likely be explained as arising simply from random errors in the linear transfer function.

Daux et al. [2011] also note an apparent divergence between width and isotope based temperature reconstructions in Larix decidua from France. They attribute the divergence

possibly to changes in the soil hydrology (i.e., plant utilization of soil water enriched by evaporation) or moisture stress. At this site, soils are thin and the trees are characteristically shallow-rooted and it is thus unlikely that deeper, low-residence time water would be available. Further no indication of anomalous 20th water stress or abundance is seen in either d13C from pinyon pine trees across the region [Leavitt et al., 2007] or widths from lower elevation drought-stressed trees [Cook et al., 1999].

To help resolve this enigma, an additional temperature proxy that is based on a regional composite of wood density measurements is considered [Briffa et al., 1992] (Figures 3 and S5). This temperature proxy is independent of both tree growth rate and the isotopic composition of cellulose and is shown to have high skill as a growing season temperature proxy in this region (Figure S5). To test the consistency between density and isotope-derived temperatures we look at the cross-wavelet [Grinsted et al., 2004] between the records (Figure S6). In the multi-decadal window, the density and isotope reconstructions are consistently in-phase with one another through the last 400 years, implying that the two proxies are likely being influenced by a common climate parameter, which we assume to be growing season surface temperature variations. With respect to the cross-wavelet between widths and isotopes, the two appear to only be commonly forced during the 20th century (Figure S6).

Further confirmation of this is garnered by looking at early instrumental data from the region (not shown), which indicate that surface temperatures between 1850–1870 were, on average, as warm as those of the 1930s–1960s [Wahl and Lawson, 1970], which is consistent with the relative thermal stability implied by the isotopic and

density reconstructions. Taken together, the d18Oc and wood density records provide a fairly consistent perspective on multidecadal temperature variations, which suggest a cool bias in the width-based temperatures prior to the mid 19th century.

Conclusions

The isotope temperature record from this site indicates relatively stable summer season temperatures amidst decadal to multidecadal temperature fluctuations. Although

the isotope reconstruction is associated with several significant sources of uncertainty that arise from the transfer function and tree-to-tree heterogeneity, the results highlight the need for, 1) additional efforts to extend a processbased network of temperature reconstructions across the region and 2) develop pre-instrumental forward model simulations (for both widths and isotopes) that could be used to test the assumptions of linearity that underlie the proxy reconstructions.

The main points of the paper are:

  • Temp. trends in the SW US can be reconstructed using isotopes in tree rings
  • A process model of the proxy can be used to characterize uncertainty in proxy
  • Temperature trends in SW US have been relatively stable over last 5 centuries

Acknowledgments. The authors thank M. Zhu, G. Kleber and

M. Rincon for invaluable assistance in sample preparation and analysis;

Z. Gedalof and J. Franks for cross dating the samples used in this analysis;

V. Bommarito, L. Holzmann, P. Holzmann, R. Lee, N. McIntyre S.

McIntyre, L. Thomas for sample collection; A. Ballantyne for feedback

on an earlier version of the paper; K. Yoshimura for providing outputs

from the IsoGSM simulations; 2 anonymous reviewers for suggestions

on improving the manuscript and the ITRDB for tree ring data. Funding

was provided by NOAA Award NA10OAR4310129 to LDS.

Mr. Pete, Steve M., wives, and Steve’s sister test the Starbucks Hypothesis in Colorado Springs in summer 2007

This effort, peer reviewed paper, and results just goes to show that citizen science can do what RealClimateScientists™ can’t or won’t, and do it just as effectively. For those who worry about such things, it should be noted that Steve applied for, and got permission for the core sampling of the Bristlecone pines in Colorado.

h/t to Dr. Leif Svalgaard who has the full paper on his website: http://www.leif.org//EOS/2012GL052447.pdf

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Louis Hooffstetter

“This effort…just goes to show that citizen science can do what RealClimateScientists ™ can’t or won’t, and do it just as effectively.”
They can do it more effectively, as they obtain reproducible results!

I could never do research like that.
I don’t have the knees for shorts. 😉

“this is a costly, and labor-intensive activity”
Sheesh !!
What are under grads for????

Ged

And remarkably, not a single influence of man was seen.

DaveA

…expensive field campaigns that involve traveling with heavy equipment to difficult-to-reach locations (such as high-elevation or remote polar sites).

Reminds me of that Dr Seuss book “Scrambled Eggs Super” where the kid fantasizes about collecting all kinds of exotic eggs from around the world. If memory serves it did include high-elevations and remote polar sites.

Don K

OK, what have you scoundrels done with my hockey stick?

Caleb

I remember my delight when Steave pulled this off, back in 2007.
How long is the growing season at that altitude? I always thought this proxie might be good for summer temperatures (in Colorado,) but left a total blank in terms of fall-winter-spring temperatures.
Another question people wondered about back in 2007 was whether or not higher levels of CO2 might make these trees grow a little faster. In which case increased recent growth would hide cooling, and make cooling look like warming. Has this issue been discussed?

“With respect to the cross-wavelet between widths and isotopes, the two appear to only be commonly forced during the 20th century (Figure S6).”
So here instead of a divergence problem we have convergence.
Lots of lines of evidence (although not warming) point to a 20th century game change. Human CO2 may be doing other stuff, like removing a constraint on photosynthesis. I’d love to see the 13C profiles of those rings.

RHS

One question about the Cheesman USHCN station. How well situated is the site considered?
From the image here: http://gallery.surfacestations.org/main.php?g2_itemId=50424
It looks like a typical mountain setting with a low tree density.
However, it is less than nine meters from a large concrete pad, a maintenance building, and in between two dirt roads.

Richard M

You have to remember it takes a lot more work to find those special trees like YAD061. You never know when any particular tree might be skeptically inclined or paid to grow by fossil fuel companies. 😉

Jimbo

…expensive field campaigns that involve traveling with heavy equipment to difficult-to-reach locations (such as high-elevation or remote polar sites).

I do feel for these poorly funded calamatologists.

November 21, 2002
Four big international companies, including the oil giant Exxon Mobil, said yesterday that they would give Stanford University $225 million over 10 years for research on ways to meet growing energy needs without worsening global warming.
Exxon Mobil, whose pledge of $100 million makes it the biggest of the four contributors,
http://www.nytimes.com/2002/11/21/us/exxon-led-group-is-giving-a-climate-grant-to-stanford.html

Bob

I would think that tree ring size would be more closely related to the length of the growing season than the temperature. That might mean the same thing in terms of average summer temperature, but it makes a big difference for inhabitants.

Ged says:
September 11, 2012 at 8:40 am
“And remarkably, not a single influence of man was seen.”
Aren’t you missing an ‘n’?
Kurt in Switzerland

Note the absence of a Little Age Age dip in temperatures…

jorgekafkazar

“While paleoclimatologists are attempting to update many important proxy records to the present, this is a costly, and labor-intensive activity…”
Yeah, those Starbucks lattes would have cost Mike a lot of bucks.
“…often requiring expensive field campaigns…”
Campaigns? This isn’t exactly D-Day, Mike.
“…that involve traveling with heavy equipment…”
Like an auger, a coring bit, and Michael Mann’s hat.
“…to difficult-to-reach locations (such as high-elevation or remote polar sites). For historical reasons, many of the important records were obtained in the 1970s and 1980s and have yet to be updated.”
Historical reasons: a scientist’s place in history depends on nobody getting newer data. /sarc

Jimmy Haigh

Leif Svalgaard says:
September 11, 2012 at 9:22 am
“Note the absence of a Little Age Age dip in temperatures…”
But why? Was there no Little Ice Age? Or is it because trees are just not good thermometers?

John A

I always thought that the most likely correlation would be between amount of snowpack and treering width, observing that apart from snowmelt, those trees get precious little water in the form of precipitation

Note the absence of a Little Ice Age [LIA] dip in temperatures…
No sign of Maunder and Dalton minima…

Jimmy Haigh says:
September 11, 2012 at 9:41 am
But why? Was there no Little Ice Age? Or is it because trees are just not good thermometers?
Several possibilities:
1) perhaps LIA was not global
2) perhaps trees no good for temperatures
3) perhaps solar activity was not a low as thought
Pick your poison.

“Tree rings generally grow wider during warm periods and narrower during cold ones”. It seems that tree rings would grow wider during wet years and narrower during dry years. As a lay person not schooled in dendrochronology, how do you tell the difference? Seems like tree rings could tell you 30″/yr vs 10″/yr of rain. How does this work for temperature?

tonyb

leif said;
“Note the absence of a Little Age Age dip in temperatures…”
Surely the reason for that is that trees grow only during the summer and many LIA summers were as hot as today. It is the winters and nights that have got warmer in recent centuries.
tonyb

I planted about a dozen saplings in my yard in 2000, most are about the same size now, but the largest is 20 feet away from the smallest which is about 60-70% of the size of the larger one. I can explain why they are different, but if the wood was harvested in 50-100 years no one else would be able to.

John West

There’s another possibility Leif.
4) That even though the LIA was global it wasn’t evenly distributed throughout all locales, in other words, some places wouldn’t have had a temperature drop even if most places did.
http://www.co2science.org/data/mwp/qualitative.php

David A. Evans

Yes Leif, I noticed that too and offer…
4) Summer temps don’t change much.
DaveE.

John W

Leif Svalgaard says:
September 11, 2012 at 9:46 am
No sign of Maunder and Dalton minima…
———-
Are you saying that it did not happen?

zefal

The “heavy equipment” needed in collecting tree ring samples Mann refers to, I’m guessing, is his feedbag.

John W says:
September 11, 2012 at 10:05 am
Are you saying that it did not happen?
Not necessarily, just introducing some caution in interpreting proxies. Of course, when the proxies confirm one’s pet theory they are good, right? And when not, they are bad [or other effects corrupt the data], right?

Don Keiller

But this work is only representative of one small location.
It cannot and does not have relevance/teleconnect to the global situation.
Unlike Yamal.
RC (sarc)

Jimbo

While reading this:

The record is independent of the co-located growth-based reconstruction while providing the same temporal resolution and absolute age constraints.

It brought back memories of this:

Bristlecone Pines: Treemometers or rain gauges?
http://wattsupwiththat.com/2008/03/19/treemometers-or-rain-gauges/

Jeff D.

I now understand why the climate guys are moving to Colorado. It would seem from the graphs that this area is immune to any climate change! Guess this begs the question is the science really settled? Just another pin in the hat of the more we learn the less we really understand.

“McIntyre S.”

Comma missing (from the original paper).

Don Keiller says:
September 11, 2012 at 10:13 am
But this work is only representative of one small location.
It cannot and does not have relevance/teleconnect to the global situation.

Yet people are falling all over each other to trumpet the relevance of this series. If it is not relevant, then why laud it?

Michael

Why not update Yamal? Because the science is settled, don’t you know that! /sarc

Forgive me, but I thought the 1930’s were way hotter than the 1950’s?

“Not necessarily, just introducing some caution in interpreting proxies. Of course, when the proxies confirm one’s pet theory they are good, right? And when not, they are bad [or other effects corrupt the data], right?’
amen to that Leif. Sometimes proxies are an inkblot test.
Notice the following: X cannot warm the planet because lts cool here and there. Or one could say that X cannot cool the planet because its warm here or there. Same basic argumentative structure.
A lowering of solar activity cannot cool the planet, because during the LIA summers were just as hot. C02 cannot warm the planet because its cold in my neighborhood.

Tom in Florida

MiCro says:
September 11, 2012 at 9:58 am
“I planted about a dozen saplings in my yard in 2000, most are about the same size now, but the largest is 20 feet away from the smallest which is about 60-70% of the size of the larger one. I can explain why they are different, but if the wood was harvested in 50-100 years no one else would be able to.”
Agreed. When I purchased my house in 2001 there was a terribly neglected tangerine tree in the front yard. I have nursed it back to health, it has grown into a beautiful tree that produces lots of excellent fruit. If someone wanted to use that tree to support AGW they might have a very good proxy for their point of view but would not really know the reason why there was increased growth since 2001. Unless one knows the nutritional history of a tree, it doesn’t seem logical to use it solely for a temperature proxy.

SanityP

Anthony Watts says:
September 11, 2012 at 10:39 am
Maybe WUWT needs to launch a Yamal expedition.

I would donate to such an expedition.

D. Patterson

The charting doesn’t go back far enough to tell us much of anything about the Maunder Minimum other than its tail end. The Dalton Minimum seems to have some presence, but the wood density suggests there would have been other confounding factos such as moisture and cloud cover which would tend to make the trees not so good as temperature recording instruments.

If a Yamal expedition is launched, tthey should look for this tree. It’s influence is astounding!

The Institute for Climate Seance Truthiness

This is clearly all wrong. First of all, the deniers who wrote this are not members of the Climate Seance Club (TM). Secondly, they did not use the right trees, only certain magic trees work as proxies, and you have to be a member of the Climate Seance Club (TM) to get the secret decoder ring which allows one to pick the right trees. The PROPER research for a paper like this requires large amounts of money, and ours is all being spent on Climate Seance Communications to ensure the public is aware of the truthiness of Climate Seance. Clearly you have never been to a Climate Sceance or you would know all of this.
(sarc)

Anthony Watts says: September 11, 2012 at 10:39 am
Maybe WUWT needs to launch a Yamal expedition.
Shedloads of sponsorship money available if you know the right people.
http://www.yamaloilandgas.com/en
I say, do it.

SanityP

Leif Svalgaard says:
September 11, 2012 at 9:46 am
Note the absence of a Little Ice Age [LIA] dip in temperatures…
No sign of Maunder and Dalton minima…

To me that indicates the uselesness of treating trees as proxies for temperatures.

Mark and two Cats

Anthony Watts said:
September 11, 2012 at 10:39 am
Maybe WUWT needs to launch a Yamal expedition.
————————————–
Are you going to row there? 😉

Just curious Did this year’s huge fire near Colo Springs affect this site?

Anthony Watts says: September 11, 2012 at 10:39 am
“Maybe WUWT needs to launch a Yamal expedition.”
Maybe you can get some grant money for that!
…sarc.

Steven Mosher says:
September 11, 2012 at 10:49 am
A lowering of solar activity cannot cool the planet, because during the LIA summers were just as hot.
Yes and no.
I’ve been pointing that for some years now.
http://www.vukcevic.talktalk.net/CETsw.htm
– Yes, because the TSI doesn’t vary much and the N. Hemisphere gets most of it in summer and least in the winter, and yes the winters are that have the 300 year uptrend.
– No, because temperature natural variability is caused by geomagnetic activity, which lasts longer during the night, and the winter nights are much longer than the summer nights.
See you. 🙂

Was this area affected by the huge fires near Colorado Springs this year?
Not the Starbucks, the pines.

David Jones

Matthew W says:
September 11, 2012 at 8:39 am
“this is a costly, and labor-intensive activity”
Sheesh !!
What are under grads for????
And what are the GRANTS for? I assumed the grant was to pay the cost of the research, not just to put into the pocket of the “researcher.”

Berényi Péter

So, you say collecting this kind of data is cheap. On the other hand, it does not support computational climate model ensemble projections. While running such models is extremely expensive, for they need supercomputers and development of several million lines of code.
Therefore cheap datasets like this are useless, they should be thrown out ASAP, on purely economic grounds. Let real scientist conduct their costly, labor-intensive activity instead, with expensive field campaigns that involve traveling with heavy equipment to difficult-to-reach locations (like Starbucks), until those few lucky trees are found, whose record is consistent with the models, that is, they lend support to science, amply demonstrating their worth.
/sarc (needless, but required)