Scott Power, National Climate Centre, Bureau of Meteorology, Melbourne, VIC 3001, AUSTRALIA, (s.power@bom.gov.au; Fax: +613 9669 4678; Phone: +613 9669 4085)

Here we will review some of the main mechanisms which cause Australia’s climate to vary from year to year, from decade-to-decade and beyond.

Recent years have seen substantial advances in our understanding of climatic processes. This has been driven by a combination of factors – e.g., the recognition of the major contribution made by the ENSO phenomenon to global climate variability, increased concerns about global warming, along with substantially improved data collection and computing resources. This talk briefly reviews current knowledge about some of the major modes of climate variability.

• Clarify the difference between weather and climate;

- Examine some of the mechanisms which can cause climate to vary from seasonal through interannual, through decadal and centennial time-scales, and beyond;

- What ENSO is, and the mechanisms by which its effects may be felt around the world – including Australia. The effects that ocean temperatures generally can have on climate;

- Introduction to some theoretical concepts about the mechanisms responsible for climate variability, including the concept of how events normally associated with weather time-scales can trigger variability on climatic time-scales, and how ocean and land surface can enhance this effect;

- Why climate forecasts are given in terms of probabilities and chances;

- Review recent research aimed at trying to improve our understanding of variability on decadal time-scales;

- Analyse trends in air temperatures over the past century, and their relationship to global warming, and issues such as land clearing, sun spot variability, volcanic activity and urban heating;

- Outline of specific mechanisms responsible for climate variability over Australia, and a discussion of where key gaps remain in our understanding of these mechanisms.