cc: Keith Briffa ,jason.lowe@metoffice.gov.uk, jonathan.gregory@metoffice.gov.uk date: Fri, 30 Jun 2006 17:08:06 +0100 from: Tim Osborn subject: Re: Global vs Regional data, a question of mm? to: Alex Wright Keith, Jason and Jonathan - I've attached the figure that Alex sent comparing sea level from HadCM3 near Connecticut with global sea level, because of his concerns (copied below) about the differences. Hi Alex, I've just repeated this for Connecticut(Wright) series that I sent you and it looks to be correct. The units of both local and regional are definitely mm. I think that it really is the result of global averaging (or looking at it the other way, the effect of regional/local variability superimposed on the global changes). But the local sea level goes down!! The reason I think is changes in the Atlantic THC which seem to be reflected closely in the sea level off the east coast of the US. Please see attached PDF, series 5 is Connecticut sea level from 'all', and series 1 is THC/MOC from 'all' (multiplied by minus 30). The big sea level drop after 1900 is clearly related to a big increase in Atlantic THC then. See THC time series from 'all' and 'nat' here: http://www.cru.uea.ac.uk/cru/projects/soap/pw/data/model/hadcm3/hadcm3_moc.htm So, units are correct and cause seems to be big variations in this region related to ocean circulation changes. So... eastern US may not be good in this model for estimating global sea level, but perhaps useful for monitoring THC (but there are *many* caveats that limit this use in the real world!). Cheers Tim At 14:44 30/06/2006, you wrote: >Hi Tim, > >Last Q for today..... probably...... >Attached is a comparison between Global vs Regional (for Connecticut >as an example, all are pretty much the same) simulated SL. >As you can see, the difference is quite..... striking. >My biggest concern is the scale, they are both supposed to be in mm, >however I would hazard a guess that this is not the case for the >regional data set. >Any thing I may have missed???? >Unless this really IS the result of globally averaging the data sets!!! > >Cheers >Alex > > > Attachment Converted: "c:\eudora\attach\Global sim vs CT mm.jpg" Attachment Converted: "c:\eudora\attach\moc_vs_connectivcutsealevel.pdf" Dr Timothy J Osborn, Academic Fellow Climatic Research Unit School of Environmental Sciences, University of East Anglia Norwich NR4 7TJ, UK e-mail: t.osborn@uea.ac.uk phone: +44 1603 592089 fax: +44 1603 507784 web: http://www.cru.uea.ac.uk/~timo/ sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm **Norwich -- City for Science: **Hosting the BA Festival 2-9 September 2006