Historical datasets of instrumental temperature, rainfall and atmospheric pressure observations have recently been developed for southeastern Australia (SEA), extending the regional climate record back to 1860. In this study we use the newly extended datasets to conduct the first multivariate examination of SEA climatic changes from 1860 to 2009.
The climate in SEA is highly variable in response to fluctuations in large-scale circulation features including El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). To examine how teleconnection patterns in the SEA region have changed over time, we then applied a path analysis over the 1871–2009 period to isolate the independent relationships between SEA climate variables, ENSO and the IOD. The extended data revealed several relatively unknown periods of 19th century SEA climate variations. Cool and wet conditions were identified in the early parts of the 1860s, 1870s and 1890s, while dry conditions were found in the late 1870s, 1880–1885, and during the well-known Federation Drought (1895–1902).
Path analysis identified a decrease in the influence of ENSO on SEA rainfall during 1920–1959, particularly in the austral winter. Increasing correlations between the IOD and annual SEA rainfall and pressure were found in the recent 1970–2009 period, but appear to be within the range of natural variability in the context of the last 140 years. Despite large changes in the correlations between SEA rainfall, ENSO and the IOD, correlations between SEA rainfall and temperature remained stable over 1871–2009. Similar results were obtained using 20th Century Reanalysis data for 1871–2009, supporting the quality of the extended historical datasets and providing verification for the reanalysis data in SEA from the late 19th century.