cc: david.roberts@metoffice.com, andy.jones@metoffice.com, jonathan.gregory@metoffice.com, jason.lowe@metoffice.com, richard.betts@metoffice.com, tcrowley@duke.edu, k.briffa@uea.ac.uk, t.osborn@uea.ac.uk, margaret.woodage@metoffice.com
date: Wed, 11 Jun 2003 13:45:09 +0100 (BST)
from: Simon Tett <simon.tett@metoffice.com>
to: keith.williams@metoffice.com

Subject: Title and Abstract
BCC: simon.tett@metoffice.com
--text follows this line--

Keith (CC co-authors) -- here is my seminar title, co-authors and
abstract.

Simon

------------------------------------------------------------

Simulating  the Recent Holocene

Simon F. B Tett, Richard Betts, Keith Briffa (CRU, UEA), 
  Tom J. Crowley (Duke), Jonathan Gregory (Reading), Andy Jones, 
  Jason  Lowe, Tim Osborn (CRU, UEA), David L. Roberts and 
  Margaret  J. Woodage


  A simulation of the last 500 years using natural forcings alone has
  been carried out. The forcings considered are volcanic aerosol,
  solar irraidance and orbital changes. Greenhouse gases and
  land-surface values are set to "pre-industrial" values. On
  multi-century timescales this simulation has a stable climate though
  multi-decadal variability, driven by external forcing, is present.
  If this is correct then the recent Holocene would have been stable
  in the absence of anthropogenic influences.  Maximum changes in
  sea-level are about 2cm from 1820 to 1950.  In the simulation
  glaciers would have reached their maximum advance in the early 18\th
  and mid-19\th centuries. No evidence of an orbital influence on
  simulated climate is found.
  
  The simulation agrees well with proxy reconstructions of temperature
  though there is some evidence that the model may be over-sensitive.
  Natural forcing enhances variability. In particular tropical
  temperature decadal-variability is enhanced by a factor of two.
  Large-scale precipitation is also enhanced but only on 50-year
  time-scales is there a significant enhancement, relative to the
  control simulation, of northern hemisphere land precipitation.
 
  A second experiment from 1750 to 1999 using both anthropogenic and
  natural forcings has just completed. The anthropogenic effects
  considered are changes in sulphate aerosol, greenhouse gases, ozone
  and land-surface changes. Preliminary results from this suggest an
  anthropogenic effect as early as the late 19th century.


-- 
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
