The ACT was warmer than average during each year in the period 2000–02. Monthly mean, maximum and minimum temperatures were all above normal. Highest mean temperatures (based on monthly averages of mean daily temperatures) were recorded in 2002, with an annual average of 13.9°C (5.5 per cent above the long-term mean). Maximum temperatures were also highest in 2002, at 7.4 per cent above normal, but minimum temperatures were highest in 2000. Conditions were closer to normal in 2001 according to all these measures of temperature.
|Table 1: Annual temperature statistics in the ACT, 2000 to 2002|
|Annual mean (°C)||13.4||13.7||13.9||19.8||20.7||21.0||6.9||6.6||6.7|
Temperatures were above average during much of the reporting period, consistent with the generally drier than average conditions. The most consistently warm spell in mean and maximum temperatures extended from March 2002 to February 2003. Minimum temperatures were also above average during this period, with the exception of August-October 2002 when clear-sky conditions resulted in slightly lower than normal night-time temperatures. Overall the pattern of monthly temperatures was consistent with the generally drier than average conditions during the reporting period, particularly in 2002–03, and with the significant rainfall received in February 2002.
Figure 1. Monthly temperature anomalies (in °C) at Canberra Airport, January 2000 to June 2003, for the maximum temperatures (top), minimum temperatures (bottom) and mean temperatures (middle)
Of the 42 months from January 2000 to June 2003, only eight recorded below-average maximum temperatures, and 11 were cooler than normal in terms of mean temperatures. Minimum temperatures were below average in 17 months, consistent with the tendency for hotter conditions during cloud-free days to be accompanied by cooler conditions at night, when surface heat is lost under clear-sky conditions. February 2002 was a notable exception; the significant rainfall received in that month, and the cloudiness associated with the rainfall event, resulted in very much lower than average daytime maximum temperatures, and slightly above average minimum temperatures.
Both mean and maximum temperatures reached their highest values in January 2001, when the mean temperature of 22.8°C was 2.5°C above average. The monthly average maximum temperature that month was 31.0°C, which is 3.3°C above average. However, the biggest anomaly in both mean and maximum temperatures was in November 2002, when the monthly average maximum temperature was 4.9°C higher than normal at 27.5°C.
The lowest monthly maximum temperature was recorded in July 2000, which averaged 11.8°C (0.6°C above normal). The biggest negative anomaly in maximum temperature was 24.5°C in January 2000, which is 3.2°C below average; mean temperatures also recorded the largest anomaly in January 2000. Mean temperatures were lowest in July 2002, reaching a monthly average of 5.8°C which is 0.3°C above normal for July. Minimum temperatures were lowest in July 2002, which averaged -1.1°C (which is 0.7°C below average for the month. The largest negative anomaly in minimum temperatures occurred in May 2001, when the average minimum was 1.0°C (or 2.3°C below normal).
The temperature record at Canberra has two principal characteristics: first, it shows a marked degree of interannual variability, consistent with the interannual rainfall variability observed in this region. Wet years tend to be cooler, and dry years warmer than average. The five warmest years in the record have occurred since 1980, often in association with El Niño events (and the accompanying below-average rainfall); examples include 1982, 1988, 1992 and 1998. Secondly, temperature at Canberra has a clear upward trend since the mid-1950s.
Figure 2. Annual mean temperatures at Canberra, showing maximum (top line), minimum (bottom line) and the average annual mean temperature (in the middle)
- The period from 1960 to about 1980 experienced somewhat less interannual variability in maximum temperatures than the periods before and after those dates; minimum temperatures, however, were more variable, particularly after 1973–74.
- The early 1940s were warmer than the long-term average, but conditions during the 1950s and early 1960s were cooler. Thereafter there is a warming trend in all three measures of temperature.
- Since 1950, decadal-average mean temperatures have increased by 0.8°C; maximum temperatures have increased by 0.9°C, and minimum temperatures by 0.7°C. This equates to a warming rate of 0.2°C per decade, which is consistent with rates reported for Australia as a whole and for many other parts of the world.
The warmest year on record was 1982, with an average maximum temperature of 21.2°C, mean temperature of 13.9°C, and minimum temperature of 6.5°C; 1971, 1981 and 1983 share the same highest annual average minimum temperature of 7.7°C. The coldest year was 1956, when mean temperature averaged 11.9°C, maximum temperature 17.9°C and minimum temperature 5.8°C. The lowest annual average minimum temperature of 4.6°C occurred in 1957.
Temperature is measured principally at the official Bureau of Meteorology station at Canberra Airport. Data for this and other stations in the Territory may be made available through the Bureau of Meteorology. There may also be a number of privately-kept records in the Territory; these often contain invaluable information for otherwise sparsely-monitored areas.
The Canberra temperature record begins late in 1939. While this is a sufficiently long record for climatological analysis, it is too short for detecting low-frequency fluctuations in temperature. Long records from stations close to the ACT (in Tallaganda, Tumut and Yass shires, for example) may also provide insights into the temperature climatology of the Territory.
Information on Bureau of Meteorology weather stations and climate data can be obtained from:
|Organisation||National Climate Centre|
|Phone (BH)||(03) 9669 4082|
|Fax||(03) 9669 4515|