Annual Australian Climate Statement 2006

Issued 3 January 2007

A year of climate contrasts

Data collected by the Bureau of Meteorology indicate that Australia's annual mean temperature for 2006 was 0.47 °C above the standard 1961–1990 average, making it the eleventh warmest year since comparable temperature observations became available in 1910. Rainfall was well below normal in the southeast and far southwest, but close to normal when averaged over the whole country.

Temperatures

Despite record warm daytime temperatures in the drought-affected southeast, 2006 was cooler than the previous year when averaged across the whole country. This was largely due to a very active tropical wet season early in the year resulting in cooler temperatures through the north, and clear skies and low soil moisture associated with the drought resulting in cold overnight temperatures from April to July. 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.

annual australian mean temperature timeseries
Australian annual mean temperature anomalies (compared to the 1961–90 average) since 1910.

Australian mean temperatures are calculated from a country-wide network of about 100 high-quality, mostly rural, observing stations. The Bureau of Meteorology has undertaken extensive data rehabilitation to ensure that the temperature records from these sites have not been compromised by changes in site location, exposure or instrumentation over time.

2006 mean temperature anomaly map
Annual mean temperature anomalies ( °C) across Australia for 2006.

Rainfall

australian total rainfall timeseries
Australian annual mean rainfall (mm) since 1900.

Preliminary data indicate that the average total rainfall throughout Australia for 2006 was about 490 mm, slightly more than the long-term average of 472 mm. However, it is unlikely that many Australians will remember 2006 as a wet year. The near-normal all-Australian total was made up of well above average totals across the north and inland Western Australia cancelling out the well below average totals recorded in the southeast and far southwest. Parts of southeast Australia experienced their driest year on record, including key catchment areas which feed the Murray and Snowy Rivers, as did parts of the Western Australian coast, including Perth. In contrast, 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, while for the broader southeast Australian region, which also takes in southeast South Australia and southern New South Wales, it was the second-driest.

Australia's area-averaged rainfall is calculated from a network of around 5000 rainfall stations, most of which are staffed by volunteer observers.

australian annual rainfall deciles
Annual rainfall deciles for 2006.

Our climate is changing

Australian annual mean temperatures have increased by approximately 0.9 °C since 1910, consistent with a global mean temperature increase of between 0.7 °C and 0.8 °C since 1900. According to a preliminary estimate released by the World Meteorological Organization (WMO) on 14 December 2006, the global mean temperature for 2006 was about 0.42 °C above average, making it the sixth-warmest year globally since records commenced in 1861.

While there has been a consistent warming trend apparent in Australian temperatures, annual temperatures will continue to vary from year to year in association with factors such as the El Niño-Southern Oscillation. Consequently, it is not surprising that the mean Australian temperature for 2006 was cooler than for 2005, the nation's warmest year on record (1.06 °C above normal).

The dominant cause of the drought experienced throughout southeast Australia in 2006 was the development of an El Niño in the tropical Pacific Ocean. However, Australia has experienced marked rainfall trends over the last 50 years with declines over southern and eastern Australia and increases across the northwest. 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 active research.