cc: "Tim Osborn" <t.osborn@uea.ac.uk>
date: Thu Dec  1 10:42:18 2005
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: ENSO and Hadcm3
to: "Rob Wilson" <rob.wilson@ed.ac.uk>, "Brohan, Philip" <philip.brohan@metoffice.gov.uk>

   Rob et al
   this looks good on the surface and would have been well worth including -  IF - as you say
   , the Cook and the Mann reconstructions had been independent. I do not believe they are.
   Surely Mann included the Texas/Mexico tree-ring data (produced largely by Stahle) in
   predictors - perhaps in the form of major PC amplitude series ? We need to check this . I
   am sure these are the major contributer to Ed's reconstruction .
   At 14:26 30/11/2005, Rob Wilson wrote:

     Hi Philip, Tim and Keith,

     if you have a minute, any comments on my musings below would be greatly appreciated.
     thanks
     Rob
     ----------------------

     in trying to address some of Mike Evans' comments, I am going to add an extra section to
     the paper - essentially comparing the reconstruction and models to ENSO.

     Spectral analysis (MTM) of the coral recon, and the ALL run for HADCM3  identifies
     significant (99%) spectral peaks at secular (>~90 yrs) scales and within the ENSO
     bandwidth. ECHO-G does not show any ENSO equivalent spectral peaks at this high
     confidence limit, although some spectral peaks are identified at the 95% level.

     In general the MTM spectra for the coral recon and HADCM3 ALL are surprisingly similar -
     see attached.

     However, after high pass filtering the time series with an 8 yr Gaussian filter, there
     is little coherence between the coral recon and HADCM3 (r = -0.03)

     I chose Ed's NINO3 TR based reconstruction for comparative analysis - he reconstructed
     Dec-Feb NINO3 SSTS back to 1408. This reconstruction is completely independent to the
     coral recon. I thought this better than Mann's NINO3 recon as it included some coral
     data.

     Anyway, after high pass (8 yr) filtering, over the 1870-1978, the correlation between
     instrumental annual tropical SSTs and Dec-Feb NINO3 SSTs = 0.76.

     The correlation between the coral recon and TR NINO3 recon over the same period = 0.47.
     Weaker, but the series are after all independent.

     Again, there is no coherence between HADCM3 and Ed's NINO3 recon.

     So - if I interpret these results correctly, HADCM3 does portray variability at the ENSO
     time-scale, but this variability has NOT been 'tuned' to the real world - i.e. the model
     all run does not correlate with reality. I am sure I am not the first to notice this -
     is there any relevant references?

   --
   Professor Keith Briffa,
   Climatic Research Unit
   University of East Anglia
   Norwich, NR4 7TJ, U.K.

   Phone: +44-1603-593909
   Fax: +44-1603-507784
   [1]http://www.cru.uea.ac.uk/cru/people/briffa/

