date: Wed Jul 20 16:58:40 2005
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: Re: crowley
to: Keith Briffa <k.briffaatXYZxyz.ac.uk>, Tom Wigley <wigleyatXYZxyz.ucar.edu>
as a followup to Keith's email, it might be quite likely that one of the series you plot is
replaced by the instrumental record after 1960, because the file from Crowley and Lowery
that is available at the WDC-Paleoclimate contains such a record. The header states:
Crowley and Lowery 2000 (Ambio 29, 51)
Northern Hemisphere Temperature Reconstruction
Modified as published in Crowley 2000
(Science v289 p.270, 14 July 2000)
Data from Fig. 1, Crowley 2000:
Decadally smoothed time series of Crowley-Lowery reconstruction
spliced into smoothed Jones et al instrumental record after 1860
(labeled CL2.Jns11), and a slight modification (labeled CL2)
of the original Crowley and Lowery reconstruction to 1965.
The URL of this file is:
and it is listed here:
At 12:22 18/07/2005, Keith Briffa wrote:
as a first quick response - the Crowley numbers came from his paper with Lowery. I seem
to remember that there were 2 versions of the composite that he produced - certainly we
used the data that did not include Sargasso and Michigan site data. I presume the other
(from the CRU web site) were the data used by Phil and Mike Mann that they got from him
(where exactly did you pick then up from?)and could be the other data set (with those
sites included). It seems odd that the values are so high in the recent period of this
series and could conceivably be instrumental data , but would have to check. The scaling
of the data we used to produce the Crowley curve that formed one of the lines in our
spaghetti diagram (that we put on the web site under my name and made available to
NGDC), was based on taking the unscaled composite he sent and re-calibrating against
April - Sept. average for land North of 20 degrees Lat., and repeating his somewhat
bazaar calibration procedure (which deliberately omitted the data between 1900-1920 that
did not fit with the instrumental data (remember his data are also decadal smoothed
values). In fact , as we were using summer data we calibrated over 1881-1900 (avoiding
the high early decades that I still believe are biased in summer) and 1920 - 1960 ,
whereas he used 1856-1880 and 1920-1965. Of the precise details might differ - but the
crux of the matter is that I suspect one of the Figures you show may have instrumental
data in the recent period - but not ours. If you say exactly where these series came
from I can ask Tim (who will have done the calibrations) to check.
As for the second question , the QR data are averaged ring widths from relatively few
site chronologies in the high north (mostly N.Eurasia - Scandinavia,Yamal,Taimyr),
though with a few other site data added in as stated. The 2001 data are the MXD data
from near 400 sites and provide the best interannual to multidecadal indication of
summer temps for land areas north of 20 degrees than any of the true proxy (ie not
including instrumental ) data. No idea what the correlation over the common 600 year
period is - but I have never said that the ring width is anything other than summer
temps for the area it covers .
At 20:38 15/07/2005, you wrote:
Look at the attached. Can you explain to me why these plots
differ -- particularly after 1880?
Could you also explain why the Briffa data in QR 2000 are so poorly
correlated with the Briffa 2001 data?
I think I know the answers, but I want an independent and spontaneous
answer from you.
Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.