Monday, May 21, 2012


date: Thu Sep 4 13:30:31 2003
from: Keith Briffa <>
subject: Re: Abstract for AGU
to: Simon Tett <>

though time short , thought it worth making the following suggested changes. The main
ambiguity though is your meaning about the simulated variability being too large (see
Italic remarks ) - do you mean high-frequency? This sentence is not clear. Below changes
shown in bold.
Keith and Tim
At 11:25 AM 9/4/03 +0100, you wrote:

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.
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
aerosols , and solar irradiance. One simulation (NATURAL), was run from A.D.1500 using
only natural forcing factors and with land-surface characteristics set
to A.D.1750 values and well-mixed greenhouse gases set to pre-industrial
concentrations. A second simulation (ALL), uses a combination of both
anthropogenic and natural forcings starting in 1750 . In ALL, sulphate aerosols,
greenhouse gases, ozone and land
surface characteristics also change through time.
The natural simulation shows general agreement with the paleo-reconstructions until the
mid- to
late-19th century. However, the (is something missing here?)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 confirm qualitatively the
simulated anthropogenic (do you mean sulphate aerosol and what time?) cooling during the
19th century.
After correcting for long-term drift (I would not put this previous phrase in here as
the sea level response is not dependent on this correction) The simulated sea-level
rapidly after large volcanic eruptions (such as Tambora), then recovers
over several decades to pre-eruption levels. A simple diagnostic
model shows maximum glacier advance occuring during the Maunder minimum and the
mid-19th century. Twentieth century sea-level rise, which is dominated by
anthropogenic forcings, is mainly due to ocean thermal expansion with a moderate
contribution from glacier melting.
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: [1]

Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.

Phone: +44-1603-593909
Fax: +44-1603-507784

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