From	Phil Jones	Date	Mon Sep 6 11:10:47 2004
To	Tom Wigley
CC	Professor David Taplin, Ben Santer
Subject	Re: question
Tom, Ben should have seen the ERA-40 Report # 18. You can forward the JGR paper. WRT 1, it is difficult to say as it depends who's produced the values. For HadCRUT2v, I think I've convinced the HC that the globe is (NH+SH)/2. If Peter Thorne did the calculations then this will be the case. There is another issue. Sometimes the trends over Jan79-Dec03 are calculated from the 300 months rather than the 25 years. Christy does this, I think. NCDC's Globe is probably the one domain. I've been doing some work with Russ Vose at NCDC, which he's still to write up. Most of the differences were due to how the globe was calculated. It is more informative to also include NH and SH as well as globe in such tables. I'll forward a plot Tom Peterson produced a week or two ago. ERA-40 (2 )comparisons are discussed in the ERA-40 report # 18 and the JGR submitted paper. This also has comparisons by continent, which again are more informative. There is a plot in that work from the full globe vs the CRU coverage. I wouldn't believe their tropics. Also Antarctica is way off as well - at least where the surface data are located, so I wouldn't have much faith in their values for the unmonitored parts. On (3) I did some comparisons ages ago with Jim Angell's surface data from sondes. Jim's data was just noisier and I suspect LKS would be also. I've not done anything like this for ages. The closest would be the ERA-40 comparisons, which is much more extensive than the LKS network. I might have a chance to do an LKS comparison if Dian sends me the co-ordinates. Comparisons over 1958-2003 will be much more realistic, but the ERA-40/NCEP degrade prior to the 1960s. LKS would be better here. All sonde data look odd in the late 1950s to the early 1960s. The jump around 1976/77 has always intrigued me. It is bigger in some regions than others - I think it gets more credence because it is large over western North America. Kevin had a paper on this in BAMS in the late 1980s. Cheers Phil At 15:57 04/09/2004, Tom Wigley wrote: Phil, On Sept. 13-17 I will be at a meeting at the Met Office to do with a report we are writing on trends in vert temp profiles as part of the US Climate Change Science Program (CCSP). It involves all the usual suspects. Seven chapters, the last of which is equivalent to a summary for policy-makers -- for which I am the lead author. Various people are updating data sets and doing calculations of trends, etc. Some of the surface numbers I found to be a bit disturbing -- so I am asking for your opinion. These are trends per decade for Jan. 1979 thru Dec. 2003 ...... SOURCE GLOBE 30S-30N HadCRUT2v 0.169 0.127 NCDC 0.151 0.146 ERA40 0.113 0.032 LKS 0.074 0.056 (1) CRU and NCDC are consistent within the noise, but I have one question -- how do both calculate GLOBE? (2) ERA40 is marginally OK (relative to CRU) in GLOBE, but the tropics is alarmingly different. (The diff here accounts for the GLOBE difference.) Why is this? Which is better? Is this discussed in your paper with Adrian? (3) LKS is the surface data from the corrected LKS radiosonde data set. The difference here must be partly due to coverage issues. But I recall that years ago we saw a difference between surface sonde and CRU data. Have you done a like with like comparison (i.e., selecting the LKS sonde sites and extracting the corresp CRU (and NCDC, and ERA40 -- and (if possible) NCEP) data? This seems to be a pretty basic sanity check on the sonde data -- so, if you have not done this already, could you do it for me please? I think there is a nice little GRL paper here. For the CCSP we are also giving trends, etc. over 1958-2003. So the real need is for a full time series comparison over this period -- i.e., not just trends. In other words, what I would like you to produce is the monthly time series for the various data sets for the LKS coverage. If you don't know the LKS site locations, I can get these for you. Re going back to 1958, the sonde trop data have a well known (but not well explained) problem over roughly 1958 to 1964/5. I am curious as to whether this shows up in the LKS surface record. I am also curious about the apparent 1976 jump -- some people have made a lot of noise about this, but I don't see it as a major item in the global surface data. So the Q here is, is is apparent in the restricted coverage of the sonde data? I hope you can help. I am leaving here on Sept 7 to spend a few days with a friend of mine in Plymouth -- you could contact me thru him (I am copying this to him so you can see his email). Thanx, Tom. 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 ----------------------------------------------------------------------------