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 subject: Re: Abstract for AGU to: Tom Crowley 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"