HR: 16:50h
AN: GC54B-05    [Abstracts]
TI: Natural and Anthropogenically forced climate change in the Tropics.
AU: * Tett, S F
EM: simon.tett@ed.ac.uk
AF: School of Geosciences, The University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh, EH9 3JW, United Kingdom
AU: Zorita, E
EM: Eduardo.Zorita@gkss.de
AF: Institute for Coastal Research, GKSS Research Centre, Geesthacht, 21502, Germany
AB: We describe results from simulations using two general circulation models (HadMC3 and ECHO-G) which are driven by changes in solar irradiance and volcanic aerosol ("Natural forcings") and with CO2 and other greenhouse gases set to pre-industrial values. We examine the importance of naturally forced variability relative to internal variability. In both models we find that, especially in the tropics outside the Pacific, natural forcings significantly enhance temperature variability on decadal time-scales. Using another simulation of HadCM3, in which both human and natural forcings were included, we find that there is a significant simulated anthropogenic effect on the tropics as early as the mid-19th century. We also find evidence of a significant change in the flow of the River Orinoco which we speculate could be due to a northward shift of the tropical rain due to aerosols. If our results are applicable to the real world then they suggest that natural forcings needs to be considered an important mechanism for tropical variability and that humans may have influenced tropical climate prior to the 20th century. Finally we suggest that tropics may be a good place to look for paleo-records to examine the responses to external forcings and thus provide strong tests of climate models used to predict future climate change.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1626 Global climate models (3337, 4928)
DE: 1650 Solar variability (7537)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting