T he impact of climate variability on Australia has been highlighted by the fluctuating events during the 1990s. While Queenslanders suffered drought for much of the first half of the decade, people in southeast Australia contended with severe spring floods in 1992 and 1993. Drought spread nationwide in 1994, but the pendulum swung the other way in 1995 and 1996 as heavy rain and flooding returned to many parts. Drought once again visited the southeast of the country during 1997 and 1998. Rural productivity, especially in Queensland and New South Wales, is linked to the behaviour of the Southern Oscillation.
Tourism is another industry vulnerable to large swings in seasonal climate.
Because climate variability can affect the Australian economy, Australians need the best possible understanding of the physical mechanisms controlling this dramatic feature of their climate. Characteristic changes in the atmosphere accompany those in the ocean, resulting in altered weather patterns across the globe. The Pacific Ocean is a huge mass of water which controls many climate features in its region. In most years the Humboldt current brings relatively cold water northward along the west coast of South America, an effect increased by upwelling of cold water along the Peruvian coast. The cold water then flows westward along the equator and is heated by the tropical sun.