From: "Malcolm Hughes" To: Keith Briffa , "Malcolm Hughes" , Tim Osborn , "Michael E. Mann" Subject: Re: J. Climate paper - in confidence Date: Tue, 20 Jan 2004 10:27:09 -0700 Cc: Scott Rutherford , mann@virginia.edu Mike - you are right that we should probably leave the network uncahnged for this mss. In fact, however, as Keith indicated, the Vaganov data probably retained a fair amount of low frequency because of the use of the corridor method (i.e. were not "heavily standardized"). CHeers, Malcolm On 20 Jan 2004 at 7:58, Michael E. Mann wrote: > Thanks Keith, > > I agree w/ this--I think the Vaganov chronologies were pretty heavily > standardized, and the other issues you raise are important. In the > future, we would (and will) be a bit more circumspect about the use of > some of these data. > > In the present case, however, I think we are forced to use the exact > same network. > > Re, the omission of some results. I think we can probably keep them. > Simply by cleaning up the text, removing redundancy, etc. I've > shortened and tightened the manuscript considerably, and I think I've > improved the logical flow a bit in the process. So my feeling is that > we will not have to split this up, but I'll leave this to all of you > to decide after you see the revised draft from Scott and me... > > Thanks, > > mike > > At 09:45 AM 1/20/2004 +0000, Keith Briffa wrote: > Malcolm seems to have done a good job sorting out these > constituent sets , and I don't have anything to add other than > agreeing that as a general principal , where possible, original > chronologies should be used in preference to reconstructed > temperature series ( the latter having been already optimized > using simple or multiple regression to fit the target temperature > series ). This applies not only to our western US reconstructions > (which it should be stressed are based on very flexible curve > fitting in the standardisation - and inevitably can show little > variance on time scales longer than a decade or so) but also to > the Tornetrask and Polar Urals reconstructions (each of which was > based on ring width and density data , but standardised to try to > preserve centennial variability - though the density series had by > far the largest regression coefficients). There is though a > question regarding the PCs of the Siberian network (presumably > provided by Eugene?) . The correlation between density and ring > width can get high in central and eastern parts of the network , > so even though these are different variables , it might not be > strictly true to think of them as truly independent > (statistically) of the density chronologies we use from the > Schweingruber network ( there may also be a standardisation issue > here , as the density chronologies were standardised with > Hugershoff functions for our initial network work (as reported in > the Holocene Special Issue) whereas your PC amplitudes may be > based on "Corridor Standardisation" - which likely preserves less > low frequency? ) . These remarks are simply for clarification and > discussion , and I too will wait on your response draft , though I > would throw in the pot the fact that omitting the time dependent > stuff would simplify the message at his stage. cheers Keith > > At 01:42 PM 1/19/04 -0700, Malcolm Hughes wrote: > Mike - there are the following density data in that set: > 1) 20 Schweingruber/Frttss series from the ITRDB (those that > met the criteria described in the Mann et al 2000 EI paper) > 2) Northern Fennoscandia reconstruction (from Keith) > 3) Northern Urals reconstruction (from Keith) > 4) 1 density series for China (Hughes data) and one from India > (also Hughes data) - neither included in Keith's data set, I > think. 5) To my great surprise I find that you used the Briffa > gridded temperature reconstruction from W. N. America > (mis-attributed to Fritts and Shao) - of course I should have > picked up on this 6 years ago when reading the proofs of the > Nature sup mat. It was my understanding that we had decided not to > use these reconstructions, as the data on which they were based > were in the ITRDB, and had been subject to that screening process. > So depending on whether you used the long or the shorter versions > of these, there will have been a considerable number of density > series included , some of them twice. It means that there is > considerably more overlap between the two data sets, in North > America, than I have been telling people. I stand corrected. > Cheers, Malcolm . .Malcolm Hughes Professor of Dendrochronology > Laboratory of Tree-Ring Research University of Arizona Tucson, AZ > 85721 520-621-6470 fax 520-621-8229 > > -- > Professor Keith Briffa, > Climatic Research Unit > University of East Anglia > Norwich, NR4 7TJ, U.K. > > Phone: +44-1603-593909 > Fax: +44-1603-507784 > > http://www.cru.uea.ac.uk/cru/people/briffa/ > > ____________________________________________________________ > __ > Professor Michael E. Mann > Department of Environmental Sciences, Clark Hall > University of Virginia > Charlottesville, VA 22903 > ______________________________________________________________________ > _ e-mail: mann@virginia.edu Phone: (434) 924-7770FAX: (434) 982-2137 > http://www.evsc.virginia.edu/faculty/people/mann.shtml Malcolm Hughes Professor of Dendrochronology Laboratory of Tree-Ring Research University of Arizona Tucson, AZ 85721 520-621-6470 fax 520-621-8229