cc: david.roberts@metoffice.com, andy.jones@metoffice.com, jonathan.gregory@metoffice.com, jason.lowe@metoffice.com, richard.betts@metoffice.com, k.briffa@uea.ac.uk, t.osborn@uea.ac.uk, margaret.woodage@metoffice.com, p.jones@uea.ac.uk
date: Thu, 04 Sep 2003 14:20:01 +0100
from: Simon Tett <simon.tett@metoffice.com>
subject: Re: Abstract for AGU
to: Tom Crowley <tcrowley@duke.edu>

Hi Tom,
	the model may be too sensitive! I just havn't yet done the detailed
analysis. I will over the next month...

Simon

Tom Crowley wrote:
> 
> Simon,
> 
> sounds very good EXCEPT -- an alternate explanation is that the model
> sensitivity may be too high.  come on, we must keep a balanced view
> of the sources of discrepancies!  tom
> 
> >Dear All,
> >
> >     I have submitted an abstract(see below) on our simulation/analysis of
> >      the last 500 years to AGU session PP11. Phil Jones has been
> >      co-opted through his early instrumental data. You have up to 1400
> >      UTC to scream! Sorry -- I left things till late in the day.
> >
> >Simon
> >
> >============================================================
> >
> >Simulating the Last Half-Millennium
> >
> >S. Tett (1), R. Betts (2), D. Roberts(2), M. Woodage
> >(2), A. Jones (2), T. Crowley (3), K. Briffa (4), T. Osborn (4), J.
> >Gregory (5),
> >J. Lowe (1) and P. Jones (3).
> >
> >(1) Hadley Centre -- Reading, Meteorology Building  University of
> >     Reading,  Reading  Berkshire  RG6 6BB  UK
> >
> >(2) Hadley Centre, Met Office, FitzRoy Road, Exeter, EX1 3PB, UK
> >
> >(3) Dept. of Earth and Ocean Sciences, Nicholas School of the
> >     Environment and Earth Sciences, Duke University, NC, USA
> >
> >(4) Climatic Research Unit, School of Environmental Sciences,
> >     University of East Anglia, Norwich  NR4 7TJ UK
> >
> >(5) CGAM, Department of Meteorology, University of Reading, PO Box
> >     243, Reading RG6 6BB UK
> >
> >
> >To test simulated AOGCM variability and change against proxy
> >reconstructions we have simulated the last half-millennium using the
> >HadCM3 model forced with natural and anthropogenic forcings. The
> >natural forcings used were changes in orbital parameters, volcanic
> >aerosol forcings, and solar irradiance. A simulation (NATURAL) forced
> >with only natural factors and with land-surface characteristics set
> >to 1750 values and well-mixed greenhouse gases set to pre-industrial
> >concentrations was carried out. A second simulation (ALL) with both
> >anthropogenic and natural forcings was started in 1750 from
> >NATURAL. In ALL sulphate aerosols, greenhouse gases, ozone and land
> >surface characteristics also change.
> >
> >
> >The natural simulation shows general agreement between the naturally
> >forced simulation and paleo-reconstructions until the mid- to
> >late-19th century. However the simulated response appears to be too
> >large while simulated decadal variability is significantly smaller
> >than that reconstructed. In the simulations there is an anthropogenic
> >impact on climate by the mid to late 19th century. Comparison with
> >early European instrumental data appears to qualitatively confirm the
> >simulated anthropogenic cooling during the 19th century.
> >
> >
> >After correcting for long-term drift, simulated sea-level falls
> >rapidly after large volcanic eruptions (such as Tambora) then recovers
> >over several decades to pre-eruption conditions. A simple diagnostic
> >model shows maximum glacier advance during the maunder minimum and the
> >mid-19th century.  Twentieth century sea-level rise is dominated by
> >anthropogenic forcings mainly due to thermal expansion with a moderate
> >contribution from glacier retreat.
> >
> >
> >
> >--
> >Dr Simon Tett  Managing Scientist, Data development and applications.
> >Met Office   Hadley Centre  Climate Prediction and Research
> >London Road   Bracknell    Berkshire   RG12 2SY   United Kingdom
> >Tel: +44 (0)1344 856886   Fax: +44 (0)1344 854898
> >E-mail: simon.tett@metoffice.com   http://www.metoffice.com
> 
> --
> Thomas J. Crowley
> Nicholas Professor of Earth Systems Science
> Dept. of Earth and Ocean Sciences
> Nicholas School of the Environment and Earth Sciences
> Box 90227
> 103  Old Chem Building Duke University
> Durham, NC  27708
> 
> tcrowley@duke.edu
> 919-681-8228
> 919-684-5833  fax

-- 
Dr Simon Tett  Managing Scientist, Data development and applications.
Met Office   Hadley Centre  Climate Prediction and Research
London Road   Bracknell    Berkshire   RG12 2SY   United Kingdom 
Tel: +44 (0)1344 856886   Fax: +44 (0)1344 854898 
E-mail: simon.tett@metoffice.com   http://www.metoffice.com

Attachment Converted: "c:\eudora\attach\simon.tett9.vcf"
