Friday, December 30, 2011

1500.txt

cc: "Keith Briffa" <k.briffaatXYZxyz.ac.uk>, <sandy.tudhopeatXYZxyzac.uk>
date: Fri, 10 Dec 2004 09:49:52 -0000
from: "Rob Wilson" <rjwilson_dendroatXYZxyzeyonder.co.uk>
subject: Re: e-mail problem?
to: "Tim Osborn" <t.osbornatXYZxyz.ac.uk>

Hi Tim,

here are some updated correlations of the 'mean' generated coral reconstruction with
the Hadley and Echo models.

The correlations are substantially higher with the Echo all model (nb. air temp and not SST
at the moment).
Although I have been in contact with Philip and Simon, I have not sent them these
results just yet.
I have restricted the analyses to the post 1750 period as this is where we have some
confidence in the reconstruction. As you say, the recent period correlations are likely
driven by the long term increasing trend. If the series are 1st differenced, then
correlations are generally non-significant and the sign changes in some cases.
You mentioned that there might be data from your MAGICC model. When will these data be
ready?

anyway, I hope to cobble together the beginnings of a paper before Christmas

Rob

----- Original Message -----

From: [1]Tim Osborn

To: [2]Rob Wilson

Cc: [3]Keith Briffa ; [4]sandy.tudhopeatXYZxyzac.uk

Sent: Tuesday, November 30, 2004 10:37 AM

Subject: Re: e-mail problem?

Hi Rob,
thanks for the reports which I've just read. The recons look very
promising! A few comments below, but first an answer to your request:
At 09:00 30/11/2004, you wrote:
>if you have the data, could you send me the ECHO-G 'NAT' and 'ALL' runs
>for tropical (30N-30S?) annual SSTs.
>They are not available on the SOAP website.
Julie Jones is still working on sending the SST for the ECHO-G "Erik" run
(which has "ALL" forcings for 1000-1990) so I can't send them yet.
Irina Fast has, however, sent SST from the ECHO-G "Enat" run (which has
"NATURAL" forcings only for 1750-1990). I've computed the tropical means
which are available for "Enat" here:
[5]http://www.cru.uea.ac.uk/cru/projects/soap/pw/data/model/echo-g/echo-g_sst___ts.htm#t
ro
I'm not sure when Julie will finish the "Erik" SST data - they are causing
her many problems. In the meantime, however, you might consider looking at
the 2m air temperature over the oceans. For the tropical mean and with
30-year smoothing, this looks almost identical to the SST for HadCM3:
[6]http://www.cru.uea.ac.uk/cru/projects/soap/pw/data/model/hadcm3/hadcm3_airtm_ts.htm#t
ro
compare with
[7]http://www.cru.uea.ac.uk/cru/projects/soap/pw/data/model/hadcm3/hadcm3_sst___ts.htm#t
ro
and it is ready computed for ECHO-G "Erik" here:
[8]http://www.cru.uea.ac.uk/cru/projects/soap/pw/data/model/echo-g/echo-g_airtm_ts.htm#t
ro
Now to some brief comments:
(1) The calibration and verification statistics appear to improve for
1635-1702 for the simple means method. I first thought that this was
because of the Palmyra data, but then I couldn't think how it could improve
the stats when it doesn't overlap with the instrumental data against which
the skill is measured. Also, in your simple means method, do you average
the O18 data themselves, or do you normalise/anomalise each series first
and then average them. If the latter, what did you use for a reference
period, and how did you cope with the difficulty of different record
lengths - especially the Palmyra data?
(2) I don't have the corrections yet for removing the artificial step
between the HadCM3 "all" and "nat" runs. I hope to have it soon from
Simon. But I guess it won't be large in the tropics, since it arose from
an incorrect surface roughness in regions where there had been an
anthropogenic change in land use (cropland, deforesting, pasture etc.)
between 1750 and 1990 - hence mainly the mid latitude land areas. Still, I
guess there could be a response of the oceans.
(3) The comparison with HadCM3 seems excellent - r(ALL,RECON)=0.54
!!! This seems a very publishable result. I guess much of it is related
to the warming trend, though? Both the model and recon will contain forced
variability and internally-generated variability (plus model will contain
errors in forcing, and recon will contain errors), but ONLY the forced
variability should be in common, r=0.54 is very high - this supports
Simon's analysis that the relative contribution of forcing is greatest in
the tropical oceans! It would be interesting to correlate the
reconstructions with a combination of NAT for pre-1750 with ALL for
post-1750, because this is (supposedly) the best representation of reality.
(4) As well as the correlation, a comparison of the magnitudes of
variability and trends is important. Allowing for the different vertical
scales, these seem qualitatively similar, with perhaps stronger variations
in the model - but wouldn't you expect that, given the recons don't capture
all the variability (or have you subsequently scaled them to have the same
variance as the actual data?).
(5) It would be nice to see the comparison and correlations with the ECHO-G
runs. Also, Sarah Raper and I are making runs with the simple MAGICC model
driven by the same forcings - we could provide those time series when
they're ready and compare with those too.
(6) Keith and I will talk a bit more, but Keith's already made some good
comments about whether some sub-regions of the SST might be more skilfully
reconstructed, especially with fewer corals early on.
Sorry to go on!
Cheers
Tim
Dr Timothy J Osborn
Climatic Research Unit
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, UK
e-mail: [9]t.osbornatXYZxyz.ac.uk
phone: +44 1603 592089
fax: +44 1603 507784
web: [10]http://www.cru.uea.ac.uk/~timo/
sunclock: [11]http://www.cru.uea.ac.uk/~timo/sunclock.htm

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