date: Wed, 09 Feb 2005 11:14:17 -0500
from: "Michael E. Mann" <mann@virginia.edu>
subject: Fwd: Re: CLIVAR abstract
to: Keith Briffa <k.briffa@uea.ac.uk>, Phil Jones <p.jones@uea.ac.uk>, Tim Osborn <t.osborn@uea.ac.uk>

   just to clarify, the "calibration period" (i.e., the period over which the composite is
   standardized to the actual model series) is 1856-1980, as in Mann and Jones, and MOberg et
   al...
   mike

     Date: Wed, 09 Feb 2005 11:09:57 -0500
     To: Keith Briffa <k.briffa@uea.ac.uk>
     From: "Michael E. Mann" <mann@virginia.edu>
     Subject: Re: CLIVAR abstract
     Cc: Tim Osborn <t.osborn@uea.ac.uk>, Phil Jones <p.jones@uea.ac.uk>
     Dear Keith, Phil, Tim:
     I'm attaching a preliminary result. Let me first explain what I've done. I've adapted to
     the Mann and Jones composite scheme and applied to pseudoproxies from Caspar's forced
     CSM1.4 coupled model experiment.
     The Pseudoproxy experiments and "Composite-Plus-Scale" scheme are described in more
     detail in the attached paper (provisionally accepted as letter in J. Climate, but likely
     to change a bit in response to reviewers). I've also attached the "supplementary
     information" from the paper.
     I've attached the result of an experiment using an average SNR=0.25, and I've compared
     the standard composite scheme (i.e., the Mann and Jones approach, but really the way
     we've all done this sorts of composites in the past, more or less), and the "Moberg"
     scheme.  I've implemented the MOberg scheme in the following way. All pseudoproxies are
     initially decadally-smoothed since this is the typical starting point (e.g. Crowley and
     Lowery, Bradley and Jones, and Mann and Jones are all based on decadal resolution
     proxies)   I choose half of the 12 pseudproxies for the low frequency calibration (>80
     year periods), and the other half for the high-frequency calibration (<80 year periods).
     To emulate their use of low-resolution proxies, I first lowpass (at 40 year period) the
     proxies to be used in the low-frequency calibration (this approximates the smoothness of
     the sed cores, boreholes, etc.). This turns out to be the essential step. Because,
     Moberg et al standardized all proxies by their nominal standard deviation. This means
     that the low-res proxies (which have almost most of their variance at multidecadal
     timescales), get near unit weight in any compositing, while the high-res (i.e.,
     "tree-ring" proxies), get downweighted because they have significant variance in both
     bands, so they get only a fraction of a unit weight. In short, the Moberg et al
     standardization procedure overweights the low-res proxies by design.
     Indeed, my experiment demonstrates this. I use their scheme, standardizing all proxies
     by nominal sd first, then separately composite the high f and low f components,
     recombine, and then standardize by the target (NH) series (i.e., I apply same mean and
     decadal standard deviation to composite as in the target true model NH series).
     The attached comparison shows a comparison of actual model NH series (red),  Mann and
     Jones (e.g. standard) compositing approach w/ the 12 pseudoproxies (black), and the
     Moberg et al scheme (blue). As discussed in our J. Climate letter, CPS will
     underestimate the low f variance at low SNR, and that's clear here (red curve lies a bit
     colder than black).  But what really jumps out here is the spurious low f  variability
     (in this case, anomalous multidecadal cooling periods) w/ the Moberg scheme.
     This is just one example. I need to try some more, but the answer that is emerging is
     that their scheme imposes spurious low-frequency variability.
     Will update you when I have more complete results. Let me know what you think...
     Thanks,
     mike
     At 10:07 AM 2/9/2005, Keith Briffa wrote:

     thanks for this . I have to say that I do not think the Moberg paper advances the
     Science much. Need to see supplementary information , but my initial thought is that
     there are real problems with their treatment of the "low frequency data" . We are
     weighed down with trying to put a large European proposal together , but Tim and I are
     toying wit the idea of writing a response. I find it a bit irritating that they couch
     their piece as a specific criticism of the M+J series and virtually ignore the other
     reconstructions , hence setting up a straw Mann (ha ha) . Problem is that thsi
     juxtaposition of boreholes ,Echo-G and their series will create a new "state of the art"
     of (apparently) mutually reinforcing evidence.  At 12:49 09/02/2005, you wrote:

     Hi Keith,
     Thanks for the clarification.
     I have seen the zero order draft and have looked over it, though not yet in full detail.
     On the whole appears quite fair, and balanced, and comprehensive. Very nice job!
     I still think the borehole discussion is a bit unbalanced. It sounds a lot like Henry
     Pollock to me. The Gonzalez-Rouco simulation is, as we know, somewhat questionable, and
     there is no discussion of the GISS simulation by Mann and Schmidt which suggests a
     likely low-frequency bias. So I'm likely to comment on this in my "official" remarks as
     a reviewer for the chapter (seems a bit odd that I'm both a contributor and reviewer,
     but as long as you all don't mind, I don't either). Other than that, I think my comments
     will probably be minor (you know how rare that is!).
     I see that the comments are due in early April, so I'll probably wait until it gets
     close so that I can provide an update on the status of in-review/in-press manuscripts.
     For example, I'm hoping to work w/ Phil on a sort-of response to Moberg et al, which
     should be quite clarifying (we can get the same result as them, basically, using the
     Mann and Jones series and a similar approach to what they did, but I think I can show
     that the approach does very poorly w/ pseudoproxies). By the way, the Mann et al J.
     Climate letter on the CCSM Pseudoproxy experiments in now provisionally accepted. Will
     keep you updated.
     Thanks again for keeping me updated, and congratulations on a wonderful job w/ the ZOD.
     Its an improvement on what we had in the TAR for sure, and I really like the fact that
     it gives justice to the large amount of work that has been done by the community since
     then...
     thanks again,
     mike
     (At 03:50 AM 2/9/2005, you wrote:

     Sorry !!!!!!!!!!!!!!!!   You can see that I am in "headless chicken mode"  - no idea how
     this message got reworked into my inbox!    Have you seen the zero order draft ?  Where
     are we with balancing views?
     Keith
     At 16:54 08/02/2005, you wrote:

     HI Keith,
     Thanks--this is a very old message. I think we provided this abstract many months ago
     already. SO, unless I misunderstand, nothing for us to do here, I think??
     Mike
     At 11:33 AM 2/8/05, Keith Briffa wrote:

     Mike
     just seen this email - please forward their request again and I will look again
     cheers
     Keith
     At 22:43 12/11/2003, you wrote:

     Dear Keith,
     No doubt you got the reminder that the CLIVAR folks want a (400 word) abstract from us
     by Dec 15th for the June meeting.  Did you want to take the first stab at this, then we
     can iterate back and forth a bit?
     let me know how you want to proceed w/ this...
     Thanks,
     mike
     ______________________________________________________________
                         Professor Michael E. Mann
                Department of Environmental Sciences, Clark Hall
                           University of Virginia
                          Charlottesville, VA 22903
     _______________________________________________________________________
     e-mail: mann@virginia.edu   Phone: (434) 924-7770   FAX: (434) 982-2137
              [1]http://www.evsc.virginia.edu/faculty/people/mann.shtml

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [2]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) 924-7770   FAX: (434) 982-2137
            [3]http://www.evsc.virginia.edu/faculty/people/mann.shtml

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [4]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) 924-7770   FAX: (434) 982-2137
              [5]http://www.evsc.virginia.edu/faculty/people/mann.shtml

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [6]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) 924-7770   FAX: (434) 982-2137
              [7]http://www.evsc.virginia.edu/faculty/people/mann.shtml

   ______________________________________________________________
                       Professor Michael E. Mann
              Department of Environmental Sciences, Clark Hall
                         University of Virginia
                        Charlottesville, VA 22903
   _______________________________________________________________________
   e-mail: mann@virginia.edu   Phone: (434) 924-7770   FAX: (434) 982-2137
            [8]http://www.evsc.virginia.edu/faculty/people/mann.shtml

