date: Wed Nov  2 13:35:27 2005
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: optimal detection
to: Gerard van der Schrier <schrier@knmi.nl>

   Gerard
   just a note to say I am reading these messages and happy you are continuing along the lines
   you are - and especially appreciate the continuing work on the long PDSI data sets.
   Keith
   At 13:19 02/11/2005, you wrote:

     Keith & Tim,
     I've applied the optimal detection to the observed trend in sea-level over the 1990 as
     observed from satellites. The routine comes up with a best-guess estimate, which is
     negative, suggesting that the meridional heat transport at 30N decreased. This is
     consistent with some of the results we heard at the RAPID science meeting. The heat
     transport is still normalized, so I can't say yet how large (in percentage) the decrease
     is.
     The problem is: the best-guess amplitude is too small (or the error bars too large) to
     say with some confidence that the result is significantly different from zero.
     I actually expected the sea-level variability in HadCM3 to be less strong compared to
     the real world, feeding my hope that we might be able to detect a response significantly
     different from zero, but this turns out not be true.
     There are still one-or-two things I could try. E.g., I've taken now the *difference* in
     heat transport between 30N and 70N. Heat transport at 70N is ca. 10% of that at 30N.
     Moreover,  the HadCM3 model seems to overestimate meridional heat transport at high
     latitudes. It might be a good idea to relate sea-level changes to heat transport at 30N
     only.
     Cheers, Gerard

   --
   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/

