Sunday, June 3, 2012

4860.txt

cc: "Kevin Trenberth" <trenbertatXYZxyzr.edu>
date: Mon Sep 22 12:25:40 2008
from: Phil Jones <p.jonesatXYZxyz.ac.uk>
subject: Re: climate
to: Wibj�rn Karl�n <wibjorn.karlenatXYZxyztgeog.uu.se>

Wibjorn,
I'll attach a couple of papers. In the first from 1994 you can see that I have
calculated the global average from land stations based on a limited network (172
stations). This reveals much the same course of temperature change as
the full network (~3000). The reason this works is that there aren't 3000
spatial degrees of freedom across the world's land areas - on the monthly and upwards
timescale. The number of spatial degrees of freedom reduces as the timescale
increases out to decades, centuries etc. This is the reason why a limited number
of proxy locations around the world can produce longer millennial-scale NH series.
There are numerous long-term stations around the world. I don't know where
you've been looking but they are very numerous. It is generally not of much use
going to many Met Services, even in Europe, as many haven't put together their
long records. Most are only interested in weather forecasting and putting up sondes.
Italy is the classic example here. The Scandinavian met services have made
good efforts, however, and these are now being extended to Germany, Holland,
France and Spain. As I said earlier we have all the NORDKLIM data in our database.
We also have all the good work undertaken in Canada, Australia, NZ and Japan,
as well as Austria, Switzerland, Spain and work done outside the met service in Italy.
Australia is an interesting example. Here exposure issues before the mid-1910s
are an issue to developing much longer series. Most of the Australian provinces
did not introduce Stevenson screens until this time, so their records before the
change are too warm. NZ in contrast put Stevenson screens into operation at all
their sites in the 1870s, so their series are much longer and homoegeneous
throughout. Neville Nicholls knows how to adjust the Australian sites before about 1915,
but can't get anyone interested in supporting the work there.
A barely read paper on this issue is
Nicholls, N., R. Tapp, K. Burrows, and D. Richards, 1996. Historical thermometer exposures
in Australia. Int. J. Climatology, 16, 705-710.
As I mentioned earlier, Anders and I are aware of the same exposure issue with
summers in Sweden before the 1860s. I'm involved with a group at the Austrian Met
Service, who have developed a technique for adjusting the pre-1870 records (mainly
in the summers) for exposure issues of direct sunlight on the instruments. The paper
is in peer-review. It results from about 15 years of overlapping measurements
of the old pre-1870 exposure and modern exposure at one site in Austria. This will
result in central European temperatures being reduced by about 0.5 deg C for
summers before about 1870. If the long Adelaide comparisons were applied
across Australia it would result in a similar sort of change. Australia is a large
country though and Adelaide is not a very typical climate.
I'm attaching a more recent paper on Chinese temperature trends. In this I
use examples from London and Vienna to show that urban sites in Europe,
while having Urban Heat Islands, are not getting any warmer than their rural
surrounding sites during the 20th century. The situation is different in China.
For many European cities and maybe some others in other developed regions
city centre sites are not getting any warmer. There is a reference in the paper
to New York City as well.
I realise that none of this answers your questions, but in many cases
you're asking the wrong questions, or not aware of work that has already
been done.
Cheers
Phil

At 08:51 19/09/2008, you wrote:

Uppsala 19 September

Dear Phil,

Thanks for offering to calculate temperature for boxes for Scandinavia. However, I
repeat what Bradley said some years ago: I prefer to calculate a global mean on seven
good stations than to use thousand not so good stations. It is hard to know which
stations that is good but for the Nordic countries the meteorological institutes have
done a screening.

The area with the trend in climate I think is typical is not small. It includes
Greenland and at least western Russia and northern Siberia. Also it includes US (not my
calculation, see below), Africa (few long term stations but the same trend. Only three
stations are published for Australia. These indicate a cooling since late 1800s. So do
southern South America.

In most areas there are no stations which have operated over a long period.

Personally, I think it is time to rethink about global warming. Splicing is risky and
particularly using short records. The quality of many stations is poor. As I am sure you
know, US is no sorting out many stations because of poor location. Wherever I have
travelled, I have seen surprising examples which can lead to erroneous records. It would
be better to use a few station, carefully checked in field than a lot of records.

Wibj�rn


[]

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.jonesatXYZxyz.ac.uk
NR4 7TJ
UK
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