date: Wed Nov 2 13:35:27 2005 from: Keith Briffa subject: Re: optimal detection to: Gerard van der Schrier 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/