subject: Review Received by Geophysical Research Letters
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B2.11; Q2.03) Date: Mon, 15 Jan 2007 13:55:14 UT Message-Id: <116886931486@gems2>
Dear Dr. Jones:
Thank you for your review of "Warming in the High Arctic: Evidence from an instrumental
record spanning 125 years" by G.W.K. Moore and Aarti Motala [Paper #2006GL028883], which we
have safely received. A copy of this review is attached below for your reference.
Thank you for your time and effort!
Geophysical Research Letters
Science Category: Science Category 4
Presentation Category: Presentation Category C
Annotated Manuscript: No
Review of Moore and Motala
This paper has some potential, but needs a major rewrite in order to be worthwhile. As I
see this as a very major revision, I'm recommending rejection, but suggesting that the
author's submit a massively revised version. I have come to this conclusion for several
reasons, outlined in the major changes section below. Although the authors acknowledge the
assistance of four colleagues, they have shown themselves (particularly with regard to
reanalyses) to be relatively na�ve and not fully aware of the climatological literature.
1. The instrumental record at Alert extends back to 1950/51. You cannot ignore 29 years of
modern instrumental data. You are only using monthly mean temperatures and these data are
readily available. With the Arctic showing recent warming, larger-scale averages indicate
warming since the 1960s and a warm epoch in the 1930s and 1940s. Either way there is a lot
more data - of a potentially cooler period, for which modern measurements exist. The
earlier expedition/exploration data might still be unusual but it is vital to also show the
full Alert record (the most northern 'manned' site in the world) compared to the full
Arctic record for the land areas north of 65�N.
2. The aim of the paper was to compare the late 19th century years with the full Alert
record on Ellesmere Island. My next point will discuss the poorest part of the paper - the
use of reanalyses - but there is a much simpler way of assessing the unusualness of the
early data. There are a number of series from Greenland, which extend back to the period
and some to much earlier periods (see Vinther et al., 2006). Apart from not being aware of
this work, the arguments used by the authors from Rigor et al. (2000), especially for the
winter season where the authors' differences are largest, mean that they can make a direct
comparison with the homogenized record from Upernavik (~73�N). I realise this site is
someway south, but correlation decay lengths are large in winter. The winters around the
expedition period do appear cool, but there are other winters that are much milder. The NW
Greenland record shows considerable decadal variability in winter.
3. To use reanalyses like this there needs to be more awareness of what input data are
used. If the regional reanalysis of Mesinger et al. (2006) is based on the same system as
NCEP (NNR, i.e. Kalnay et al., 1996), then the whole exercise is pretty pointless. The
authors should read the paper by Simmons et al. (2004) where the quality of the ERA-40
reanalysis is compared with observational data and NNR. ERA-40 is a second generation
reanalysis and the surface temperature measurements are assimilated. This is not the case
in NNR. This might explain why the real observed data at Alert only are only poorly
explained by the regional reanalysis. I think the use of the reanalysis in this instance is
pointless and I remain to be convinced that their use serves any purpose or that they are
giving any useful information as to the comparison of temperatures measured at Alert and
the expedition sites.
4. When using reanalysis data for comparison to real observations near coastal areas, it is
vital to know whether the model grid box being used is land or ocean. This may not matter
much for most of the year, but may in summer months. The resolution of the regional
reanalysis needs to be stated and perhaps the grid-box size shown on a figure, such as
Figure 2. What is the resolution?
5. The discussion of exposure issues on p4 needs to bear in mind where the observations
were made and when. These papers about exposure need to be read. Stevenson screens and
their variants were in widespread use in the UK, Canada and the USA in the 1880s. No north
European location has problems due to exposure in this period. Problems come earlier -
prior to the 1860s - see discussion in Moberg et al. (2003). The warm bias in summer is
clear for European locations, but that in winter is much less marked. The biases of the
order of 0.2�C are an order of magnitude smaller than those that might be due to different
locations on Ellesmere Island. The authors are right to raise the issue, but it is likely
unimportant, 0.2�C is likely the wrong value, but the real one isn't known.
6. The authors should comment on the best way to make use of the early expedition records
like those being analyzed. This is to use the approach of Klingbjer and Moberg (2003).
Here, early measurements some distance from a modern station were adjusted by means of
modern measurements taken with a data logger. This might have been impossible, but is
relatively unexpensive, just requiring a little forethought.
7. Two small final points. The Greenland data will show whether these years in the 1870s
and 1880s are unusual. Earlier north Canadian expedition data have been assessed by
Overland and Wood (2003) and found not to be that unusual compared to modern conditions.
This was for different periods and different regions though. It may just show that you
can't take as representative a few years of measurements.
8. Related work to that discussed in the authors has been undertaken in the Antarctic with
expeditions and exploration data (see Jones, 1990). There are likely other datastes in
other parts of northern Canada, which along with the much earlier Greenland data could be
combined in a far more informative paper. The paper is timely with respect to the upcoming
IPY, but there were many more Arctic expeditions in 1882/3 during the first IPY. Many of
these have been recently reconsidered in the light of the upcoming period.
9. There may also be some proxy data for Ellesmere Island from lake cores, but these mostly
reflect summer conditions. Ray Bradley has written frequently on this area.
References (not used by the authors)
Klingbjer, P. and Moberg, A., 2003: A composite monthly temperature record from Tornedalen
in northern Sweden, 1802-2002, Int. J. Climatol. 23, 1465-1494.
Moberg, A., Alexandersson, H., Bergstr�m, H. and Jones, P.D., 2003: Were south Swedish
summer temperatures before 1860 as warm as measured?, Int. J. Climatol. 23, 1495-1521.
Overland, J.E., and K. Wood, 2003: Accounts from 19th century Canadian Arctic explorers'
logs reflect present climate conditions, EOS, 84, 410-412.
Simmons, A.J., P.D. Jones, V. da Costa Bechtold, A.C.M. Beljaars, P.W. K�llberg, S.
Saarinen, S.M. Uppala, P. Viterbo and N. Wedi, 2004: Comparison of trends and low-frequency
variability in CRU, ERA-40 and NCEP/NCAR analyses of surface air temperature. J. Geophys.
Res., 109, D24115, doi:10.1029/2004JD006306.
Vinther, B.M., Andersen, K.K., Jones, P.D., Briffa, K.R. and Cappelen, J., 2006: Extending
Greenland temperature records into the late-18th century. J. Geophys. Res. 111, D11105,