Tuesday, May 8, 2012

4005.txt

cc: Keith Briffa <k.briffaatXYZxyz.ac.uk>
date: Wed, 20 Dec 2006 17:07:31 +0000
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: Re: Guiot, Schweingruber data
to: t.kleinenatXYZxyz.ac.uk

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Hi Thomas,

the gridded Guiot data do exist. I don't have a copy, though I could
ask Joel for them and I'm fairly sure he would send them. However I
don't think that they are appropriate to use, since values are
computed even where no proxy values are available, and grid boxes
with proxy data in them also include information from other proxies,
if I recall his method correctly. For the Guiot reconstruction,
therefore, I suggest just using the area-mean time series.

For the Schweingruber data, calibrated regional-mean time series from
Briffa et al. (2001) are available under plates 2 and 3 here:
http://www.cru.uea.ac.uk/cru/people/briffa/jgr2001/
and are useful because the averaging enhances the signal to noise
ratio and because we have estimated the error ranges (note that the
error ranges are not available on Keith's webpage, so I'll email
those to you separately).

We have also gridded the Schweingruber data and then calibrated it to
represent April-September temperatures. These data are available in
the attached text-format file. Because every grid box contains a
tree-ring chronology, there is less extrapolation/interpolation and
therefore it's more appropriate for comparison with
models. Unfortunately we haven't yet published the details of how
the gridding and calibration were done. Also we have applied a
completely artificial adjustment to the data after 1960, so they look
closer to observed temperatures than the tree-ring data actually were
-- don't rely on the match after 1960 to tell you how skilfull they
really are! Finally, note that the files gives the latitudes and
longitudes of the centre of each box above each column (which is the
time series for that box). +ve longitude is East of Greenwich
meridian, -ve is west. The time series run from 1400 to 1994.

Finally, finally, we (Keith and I) were wondering what more you
wanted to discuss about proxy data/reconstructions on Thursday
morning, and whether we could instead cover things via
emails? Please let us know what you had in mind to cover at the meeting.

Cheers

Tim

At 10:38 11/12/2006, Thomas Kleinen wrote:
>Hi Tim and Keith.
>
>I have had a quick look at the Guiot and the Schweingruber data on the SOAP
>website.
>
>In his paper Guiot writes that his aim was to extend the CRU 5� gridded
>temperature series, but on the SOAP page only the European mean timeseries is
>available. Does the gridded timeseries exist, and do we have access somehow?
>
>The Schweingruber data is more like what I had in mind, but density / ring
>width doesn't really help, ideally I'd still need to translate that into
>temperature changes, and I had hoped I wouldn't need to go into the theory on
>that... So do you have that database as temperature changes as well, or
>should I rather use that as "qualitative" data (little growth = rather cool,
>much growth = rather warm)?
>
>Thanks.
>Thomas

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Attachment Converted: "c:\eudora\attach\schweingruber_mxdabd_grid.dat"
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Dr Timothy J Osborn, Academic Fellow
Climatic Research Unit
School of Environmental Sciences
University of East Anglia
Norwich NR4 7TJ, UK

e-mail: t.osbornatXYZxyz.ac.uk
phone: +44 1603 592089
fax: +44 1603 507784
web: http://www.cru.uea.ac.uk/~timo/
sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm


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