4.4
The contribution of anthropogenic and natural forcings to recent trends in the Southern Hemisphere
PAPER WITHDRAWN
Julie M. Arblaster, NCAR, Boulder, CO
Trends over recent decades in the high latitudes of the Southern Hemisphere, in particular those involving the Southern Hemisphere annular mode, have been well documented in the literature. Stratospheric ozone losses, greenhouse gas increases and natural variability are all thought to play a part in these trends but it is difficult to separate their relative contributions in the observed record. A state-of-the-art global coupled model is used here to isolate the response of the Southern Hemisphere climate to various forcings. Ensembles of 20th Century simulations forced with observed records of greenhouse gases, stratospheric and tropospheric ozone, sulfate aerosols, volcanic aerosols, solar variability and various combinations of these have recently been completed. When all forcings are combined the model is able to reproduce the observed time series of globally averaged surface temperature of the last 100 years. The model also captures the decrease in sea level pressure in Southern Hemisphere high latitudes and relative increase in mid-low latitudes found in the observations, that has been attributed to both ozone losses and greenhouse gas increases. Over 50 twentieth century simulations have been completed with the coupled model, allowing for a thorough investigation of the Southern Hemisphere response, both at the surface and vertically, to each individual forcing.
Session 4, Climate Models: Evaluation and Projections, Part I (Room 608)
Tuesday, 13 January 2004, 8:30 AM-3:15 PM, Room 608
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