Chapter 2 - Climate Data and Monitoring

Climate Monitoring and Analysis > Climate Variability and Climate Change Detection

A high-quality temperature data set, developed jointly by the Bureau of Meteorology and the University of Melbourne, is used operationally to determine Australian annual mean temperature anomalies. This data set extends from 1910, when national coverage of high-quality data first became available, to the present. Data from a nonurban subset of 95 stations have been shown to provide the most reliable calculations of Australia’s annual mean temperature anomalies. The 1990-1999 decade was Australia's warmest in the post-1910 period, being on average 0.33ºC warmer than the average for the 1961-1990 reference period. The next warmest was the 1980- 1989 decade with a mean temperature departure of +0.22ºC (Figure 2.17). The year 1998 was the warmest on record for Australia, at 0.73ºC above the average. The most recent years, 2001 and 2002, were 0.11ºC below and 0.61ºC above the 30-year average, respectively. The latter was the fifth warmest year on record, in contrast to the rather cooler and very wet years of 1999, 2000, and 2001.

Figure 2.17 Australian Mean Temperature Anomalies (1910-2002). Anomalies are calculated with respect to the reference period (1961-1990).

Operational procedures have been developed in the NCC to extend the monitoring of climate change to the monthly timescale. High-quality temperature and rainfall anomalies computed over each state/territory and important climatological regions are generated within a few days of month’s end, and published in the CMB and distributed on the internet.

Changes in climate extremes can have a greater potential environmental and socioeconomic impact than changes in mean climate variables. The 2002-03 El Niño was characterized by unprecedented high daytime temperatures during winter/spring, at least partly reflecting the warming trend observed in recent decades (Figure 2.18).

Figure 2.18 Time series of Maximum temperature (top curve) and Rainfall for the Murray Darling Basin showing that, while the region was very dry in 2002, the high temperatures were even more unusual in a historical context.