cc: "Kevin Trenberth" date: Mon Sep 22 12:25:40 2008 from: Phil Jones subject: Re: climate to: Wibjörn Karlén 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. Wibjörn [] 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 ----------------------------------------------------------------------------