Transcript

Understanding rainfall changes across Australia is generally a lot more difficult than understanding temperature changes. This is due to the large inherent natural variability in Australian rainfall patterns.

Most people understand that Australia is truly the land of droughts and flooding rains. This is principally due to the influence of the El Niño–Southern Oscillation. During an El Niño event large parts of Australia typically experience drought conditions. The opposite of an El Niño, La Niña, tends to bring very heavy rainfall across Australia. In 2010 a very strong La Niña event brought record rainfall to large parts of eastern Australia, including flooding in Queensland, Victoria, New South Wales, and Western Australia.

But despite this episode of very heavy rain, there are rainfall trends emerging of the opposite sign, principally drying across southern Australia. That drying has been experienced as a reduction in winter and autumn rainfall, particularly in the south-west of the continent, and in the south-east of the continent, and this reduction in rainfall has led to large impacts on our water storages.

While it’s difficult to characterise rainfall changes from the historical data, it’s important to note that changes to rainfall are expected under global warming. In particular, as the planet warms, climate models have consistently predicted a drying of parts of Australia, in particular across the south of the continent and through parts of the Murray Darling Basin.

Our ability to monitor the climate system improves with each day and into the future the Bureau of Meteorology and the CSIRO will continue to monitor Australia’s climate and report on emerging trends and changes which will have a significant impact on Australia, our economy, and our society.

Transcript

The ocean is a central component of the climate system. Over the last 50 years the oceans have warmed considerably, absorbing vast amounts of heat. Over 90% of the extra heat stored in the climate system is actually stored in the ocean, so if you want to understand climate change you really need to understand what’s happening in the ocean.

As a result of ocean warming the oceans are expanding and sea leave is rising. Our coastal society has developed over the last several centuries in a period of relatively stable sea levels. However, during the 20th Century sea level has been rising, the rate of rise has increased from the 19th to the 20th Century, and increased further during the 20th Century. Over the last couple of decades the rate of rise has almost doubled the average for the 20th Century. It is projected to continue to rise as a result of continued warming of the ocean and thermal expansion, and the melting of glaciers and icecaps.

A major uncertainty is how the ice sheets of Antarctica and Greenland will respond, potentially contributing further to sea level rise. Because of the long time scales associated with the oceans and the ice sheets, sea level rise will continue for centuries, and as a result our society will have to adapt to rising sea levels.