CSIRO Marine and Atmospheric Research
Past Seminars

Friday 9 January 2004, 11.30 am (Tas time)

CSIRO Auditorium, Hobart

Dr David Thompson
Department of Atmospheric Science
Colorado State University

Interpretation of recent Southern Hemisphere climate change

Climate variability in the middle to high latitude Southern Hemisphere (SH) is dominated by the SH annular mode, a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex. In this talk, I will argue that recent SH climate change can be interpreted as a bias towards the high index polarity of this pattern, with stronger westerly flow encircling the polar cap. It is demonstrated that the largest and most significant trends at Earth's surface can be traced to recent trends in the lower stratospheric polar vortex, which are due largely to photochemical ozone losses. Both the seasonality and structure of the observed climate trends are simulated in a state-of-the-art climate model run with high vertical resolution that is forced solely with prescribed stratospheric ozone depletion.

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