date: Thu Sep 4 13:30:31 2003 from: Keith Briffa subject: Re: Abstract for AGU to: Simon Tett Simon 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. 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 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 falls 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: simon.tett@metoffice.com [1]http://www.metoffice.com -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [2]http://www.cru.uea.ac.uk/cru/people/briffa[3]/