cc: Keith Briffa <k.briffa@uea.ac.uk>,jason.lowe@metoffice.gov.uk, jonathan.gregory@metoffice.gov.uk
date: Fri, 30 Jun 2006 17:08:06 +0100
from: Tim Osborn <t.osborn@uea.ac.uk>
subject: Re: Global vs Regional data, a question of mm?
to: Alex Wright <alex.wright@falw.vu.nl>

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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
>
>
>

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Attachment Converted: "c:\eudora\attach\Global sim vs CT mm.jpg"

Attachment Converted: "c:\eudora\attach\moc_vs_connectivcutsealevel.pdf"
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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

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