Long-Term Climate Variability in Australia

Variation in Australian Climate

Long-Term Global Climate Variations

Long-Term Temperature Variations in Australia

Long-Term Rainfall Variations in Australia

Other Climate Variations in Australia

Other Climate Variations in Australia

Cloud
Cloud cover trends over the past four decades show a slight increase until the mid-1970s, followed by a weak drop. This recent decline is consistent with an increased number of El Niño events in recent years.

Cyclones
Trends in tropical cyclone activity in the Australian region show that the total number of cyclones has decreased in recent decades. However, the number of intense cyclones (minimum central pressure less than 970 hectopascals) appears to have increased slightly. Tropical cyclone numbers in the Australian region are influenced by the El Niño-Southern Oscillation phenomenon, and the decrease in total cyclone numbers may be associated with an increased frequency of El Niño events.

The Importance of High Quality Climate Data

Reliable detection of long-term climate trends requires long, good quality climate records. Changes in observing instruments, site location, site condition and observational practices have led to artificial jumps in the climate records at many climate observing sites throughout Australia. These jumps can be larger than the actual changes in climate and can easily disguise any real trends. Changes in the level of urbanisation and land-use practices surrounding a site can also have an impact on the climate record. The Bureau of Meteorology keeps records of changes made at sites to allow scientists to reconstruct instrumental climate records as accurately as possible. This is particularly important for Australia's Reference Climate Stations (RCSs), stations specifically intended for studies of long-term climate trends and variability.

Where possible, comparison observation programs are undertaken for at least two years at RCSs so that the impacts of any changes such as instrumentation or position can be assessed. Special inspections are also made to ensure that RCSs are maintained to the highest possible standards.