To: Bo Vinther <firstname.lastname@example.org>
Subject: Re: Arctic2k update?
Date: Sun, 6 Sep 2009 06:31:35 -0700
Cc: Nick McKay <email@example.com>, Caspar Ammann <firstname.lastname@example.org>, David Schneider <email@example.com>, Jonathan Overpeck <firstname.lastname@example.org>, "Bette L. Otto-Bliesner" <email@example.com>, "Raymond Bradley" <firstname.lastname@example.org>, Miller Giff <email@example.com>, "Keith Briffa" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>
Bo and others:
Regarding the annual data: You're correct that we only use 10-year means throughout our
calculations (Fig 2 shows annual values, but are not used in any calculation/conclusion).
In his e-mail to me, McIntyre requested the annual data that we say are not publicly
available as a footnote to Table S1.
Unless anyone has another suggestion, I will reply and send him the 10-year data (which is
already posted at NOAA-Paleoclimate) and explain that they were the basis for all of the
calculations. He might want the annual data that the mean values were based on. I suppose
we'll cross that bridge when we get to it.
On Sep 6, 2009, at 5:42 AM, Bo Vinther wrote:
Sorry to hear that you are getting trouble for doing such a nice paper....I by the way
agree completely with Peck that we should not be rushed and that a correction probably
should go into Science.
Anyway, let me answer the two questions you had for me:
2) Correcting ice core data for upstream effects should not be controversial (while not
correcting in areas of flow should be highly controversial indeed!).
Upstream correction of delta-18O was in fact already done 30 years ago for the Milcent ice
core - a quick quote from Hammer et al. 1978, page 14:
"The delta values are corrected for decreasing deltas up-slope at the site of formation of
the individual layers"
Hammer, C. U., H. B. Clausen, W. Dansgaard, N. Gundestrup, S. J.
Johnsen and N. Reeh, Dating of Greenland ice cores by flow models,
isotopes, volcanic debris, and continental dust, J. Glaciol., 20, 326,
So upstream correction of delta data from ice cores 8using ice flow models9 has in fact
been performed since the year I was born.....
5) I will suggest that we release the 1860-2000 section of the annually resolved ice core
data, as these are the data that go into figure 2 in the paper.
Such a limited release I can permit immediately.
Releasing everything is something different and I can't see the need - as far as I rememver
we are not presenting/using the 1-1859 part of the series in annual resolution anywhere in
the paper - or am I wrong?
Darrell Kaufman wrote:
I received my first hate mail this AM, which helped me to realize that I shouldn't be
wasting time reading the blogs.
Regarding the "upside down man", as Nick's plot shows, when flipped, the Korttajarvi series
has little impact on the overall reconstructions. Also, the series was not included in the
calibration. Nonetheless, it's unfortunate that I flipped the Korttajarvi data. We used the
density data as the temperature proxy, as recommended to me by Antii Ojala (co-author of
the original work). It's weakly inversely related to organic matter content. I should have
used the inverse of density as the temperature proxy. I probably got confused by the fact
that the 20th century shows very high density values and I inadvertently equated that
directly with temperature.
This is new territory for me, but not acknowledging an error might come back to bite us. I
suggest that we nip it in the bud and write a brief update showing the corrected composite
(Nick's graph) and post it to RealClimate. Do you all agree?
There's other criticisms that have come up by McIntyre's group:
(1) We cherry-picked the tree-ring series in Eurasia. Apparently this is old ground, but do
we need to address why we chose the Yamal record over the Polar Urals? Apparently, there's
also a record from the Indigirka River region, which might not have been published and
doesn't seem to be included in Keith's recent summary. If we overlooked any record that met
our criteria, I suggest that we explain why. Keith: are you back? Can Ray or Mike provide
(2) The correction for Dye-3 was criticized because the approach/rationale had not been
reviewed independently on its own. Bo: has this procedure now been published anywhere?
(3) We didn't publish any error analysis (e.g., leave-one-out ), but I recall that we did
do some of that prior to publication. Would it be worthwhile including this in our update?
The threshold-exceedence difference (O&B-style) does include a boot-strapped estimate of
errors. That might suffice, but is not the record we use for the temperature calibration.
(4) We selected records that showed 20th century warming. The only records that I know of
that go back 1000 years that we left out were from the Gulf of Alaska that are known to be
related strongly to precipitation, not temperature, and we stated this upfront. Do we want
to clarify that it would be inappropriate to use a record of precip to reconstruct
temperature? Or do we want to assume that precip should increase with temperature and add
those records in and show that the primary signals remain?
(5) McIntyre wrote to me to request the annual data series that we used to calculate the
10-year mean values (10-year means were up on the NOAA site the same AM as the paper was
published). The only "non-published" data are the annual series from the ice cores
(Agassiz, Dye-3, NGRIP, and Renland). We stated this in the footnote, but it does stretch
our assertion that all of the data are available publicly. Bo: How do you want to proceed?
Should I forward the annual data to McIntyre?
Please let me -- better yet, the entire group -- know whether you think we should post a
revision on RealScience, and whether we should include a reply to other criticism (1
through 5 above). I'm also thinking that I should write to Ojala and Tiljander directly to
apologize for inadvertently reversing their data.
Other thoughts or advise?
On Sep 4, 2009, at 5:24 PM, Nick McKay wrote:
The Korttajarvi record was oriented in the reconstruction in the way that McIntyre said.
I took a look at the original reference - the temperature proxy we looked at is x-ray
density, which the author interprets to be inversely related to temperature. We had
higher values as warmer in the reconstruction, so it looks to me like we got it wrong,
unless we decided to reinterpret the record which I don't remember. Darrell, does this
sound right to you?
This dataset is truncated at 1800, so it doesn't enter the calibration, nor does it
affect the recent warming trend.
The attached plot (same as before) shows the effect of re-orienting the record on the
reconstruction. It doesn't change any of our major or minor interpretations of course.
On Thu, Sep 3, 2009 at 4:45 PM, Nick McKay <email@example.com> wrote:
I haven't checked the original reference for it's interpretation, but I checked the code
and we did use it in the orientation that he stated. He's also right that flipping
doesn't affect any of the conclusions. Actually, flipping it makes it fit in better with
the 1900-year trend.
I've attached a plot of the original, and another with Korttajarvi flipped.