CLIMATE CHANGE

Temperature

Australia experienced its eleventh warmest year on record in 2006 following its warmest year on record in 2005. The annual average temperature for 2006 was 0.47°C above the standard 1960-91 average.

Despite record warm daytime temperatures in the drought-affected south-east, 2006 was cooler than 2005 when temperatures are averaged across the whole country. The annual mean maximum temperature was 0.60°C above average (ninth highest), while the mean minimum temperature was 0.34°C above average (seventeenth highest). Temperature anomalies varied throughout the year, but spring 2006 was particularly warm (+1.42°C), being Australia’s warmest spring season on record.

Many of Australia’s warmest years on record (such as 1988, 1998 and 2002) were influenced by significant El Niño events. However, Australia’s warmest year on record, 2005, was not accompanied by an El Niño event, making the record temperatures quite unusual.

Australian annual mean temperatures have increased by approximately 0.9°C since 1910. However, annual temperatures will continue to vary from year-to-year in association with factors such as El Niño-events. The average Australian temperature for 2006 was cooler than for 2005 (1.06°C above normal).

Since 1979, only four years have been cooler-than-average in Australia.

Globally, the average temperature for 2006 was approximately 0.42°C above average, making it the sixth-warmest year since records began in 1861.

Rainfall

Rainfall in 2006 was well below normal in the south-east and far south-west of Australia, but was close to normal when averaged over the whole country.

Preliminary data indicate that the average total rainfall throughout Australia for 2006 was approximately 490 millimetres (mm) - slightly more than the long-term average of 472 mm. This total included above-average totals across the north and inland Western Australia, cancelling out the below-average totals recorded in the south-east and far south-west. Parts of south-east Australia experienced their driest year on record, including key catchment areas which feed the Murray River and the Snowy Rivers, as did parts of the Western Australian coast, including Perth.

Conversely, record high falls were observed in parts of the tropics and inland Western Australia. It was the third-driest year on record for both Victoria and Tasmania. For the broader south-east Australian region, which takes in south-east South Australia and southern New South Wales, it was the second-driest year on record.

The dominant cause of the drought experienced throughout south-east Australia in 2006 was the development of an El Niño in the tropical Pacific Ocean.

El Niño refers to a warming of surface water over the central and eastern tropical Pacific Ocean. Combined with this warming are changes in the atmosphere (measured by the Southern Oscillation Index which measures the air pressure difference between Tahiti and Darwin) that affect weather patterns across much of the Pacific Basin, including Australia. It is often associated with reduced winter and spring rainfall.

Australian rainfall trends over the last 50 years have seen declines over southern and eastern Australia, and increases across the north-west. The pattern of rainfall during 2006 continued this trend.

The dry conditions in southern and eastern Australia in 2006 have continued the long-term rainfall deficiencies in many regions, some of which extend back more than five years. Aspects of this multi-year drought are highly unusual and unprecedented in many areas. Understanding the role that climate change has played in these anomalies is an area of continuing research.

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