cc: m.hulme@uea.ac.uk
date: Fri, 01 Oct 1999 10:18:41 +0100
from: Phil Jones
subject: Paper 980G by Luterbacher et al
to: b.d.mcgregor@bham.ac.uk
Dear Glenn,
I've tried to ring you to talk about this paper that IJC has rejected
on 21/9/99. My interest is that I'm one of the et al's. I've talked to
Mike here about it and he suggested I contacted you about the decision.
Your decision has been made on the basis of one reviewer only. I know from
Jurg Luterbacher that you've had difficulty getting a second reviewer to
respond.
We (me, Mike and the Swiss) think we have a real grievance and are
questioning the decision. Fortunately Mike didn't attend the last IJC
meeting otherwise I might have been able to find out who this well
respected referee is. I know I shouldn't have asked Mike but I was so
annoyed with the two main comments that I asked him !
His two points are basically wrong !
1) 'Patterns during the 20th century are applicable to earlier epochs'.
This assumption applies to all paleo reconstruction papers ever written.
OK, it is an assumption called the 'Principal of Uniformitarianism' and
we could have stated it clearer, but it is one that has been made by
countless thousands before us. If it is not valid we might as well give up.
The method used in the paper is not the same as infilling SST fields to get
complete fields, a technique that I would question ( this technique is
usually used to get complete fields to drive GCMs). Our paper uses real
data for the past and attempts through a calibration/verification exercise
to derive circulation patterns for earlier periods. The only real
requirement for the technique to work properly is that all the long
time series used in the reconstructions are homogeneous.
2) 'Changes in climate forcing through time invalidate such statistical
relationships'. Here the reviewer's concern is completely wrong as he/she
intimates because 'year to year variability is much greater than long-term
climate change'. It is not just greater is at least one order of magnitude
greater, maybe more. The regression-type relationships derived in the
paper are almost entirely based on high-frequency relationships. Longer
timescale variability is relatively small in this regard. Longer timescale
change over the 1675-present is not that great anyway (the 1730s for
example are only slightly cooler than the 1980s).
Global average sea level pressure can't change but patterns will change in
different periods and it is these that influence the surface temperature
and precipitation patterns. The drawback of using surface temperature
and precipitation patterns to reconstruct circulation indices is that you
can't then go and look at changes in circulation/surface climate
relationships as these have been used in the reconstructions. However,
using methods like this produces far more reliable reconstructions than
proxy data (trees, ice cores etc) as we can derive indices on a monthly
basis and not just for a season or year. (By the way proxy data
reconstructions of circulation indices suffer the same problems as
it is temperature and precipitation and not the circulation that alters
tree ring widths/densities and ice core composition). With the earlier
paper from the same EU project (Jones et al, IJC 19, 347-364), pressure
reconstructions were derived from station pressure data, so here from
1780 we will be able to look at the change in the strength of circulation/
surface climate relationships through time (I'm doing this in another
paper).
Finally, and I didn't mean to get into all this detail, but it seemed to
just flow, the reconstruction technique does use gradients and not just
the station data. The canonical correlation technique relates PC-based
patterns of real cirulation data to PC-based patterns of station temperature
and precipitation and one pressure site at Paris. The regression
relationships are based on the patterns, hence gradients are used
implicitly.
In conclusion, I'm hoping you will reverse your decision and allow us to
resubmit a slightly revised, and reduced in size ( it was too long) paper
and send it out to reviewers who will respond in a reasonable time frame.
The problems raised by the reviewer are no problems and we can easily
address them. They don't invalidate the results.
Cheers
Phil
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email p.jones@uea.ac.uk
NR4 7TJ
UK
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