Temperature variations of southeastern Australia, 1860-2011

Abstract

This study presents the first quality-controlled dataset of surface air temperature observations for 1860-1909 across southeastern Australia. Long-term monthly maximum and minimum temperature records from 38 stations in Victoria, South Australia, New South Wales and southern Queensland were identified from the Australian Bureau of Meteorology observational network to provide continuous data coverage from 1860-1950. Detailed homogenisation was undertaken using metadata collected from station history files and a two-step statistical process that involved individual station adjustments and comparison with neighbouring reference series. The homogenisation process removed many non-climatic changepoints in the previously unexamined 1860-1909 period. Importantly, the impact of the systematic change to Stevenson thermometer screens at the beginning of the 20th century appears to have been minimised. The homogenisation process also reduced the variability of pre-1910 data across the station network, making it comparable with that of the current high-quality temperature record. The adjusted dataset showed very high correlations with the newly developed high-quality observational dataset currently used in Australian climate research (ACORN-SAT) for the overlapping 1910-1950 period. Combining the 1860-1950 data with ACORN-SAT data for southeastern Australia enabled temperature variations for 1860-2011 to be studied for the first time. A cooling of maximum and minimum temperatures was identified over 1872-1875 and 1891-1894, as well as high interannual variation in temperature from 1885- 1890. The link between El Niño-Southern Oscillation (ENSO) and southeastern Australian temperature was found to have fluctuated over 1860-2011, with periods of weak correlations identified in the 1890-1900s, 1920-1930s and the 1960-1970s. These fluctuations were not found to be associated with any particular phase of the Interdecadal Pacific Oscillation, previously reported to modulate the influence of ENSO on the Australian climate. Trend analysis confirmed that the 1.1 °C increase in maximum temperature and 0.9 °C increase in minimum temperature since 1960 are the largest and most significant trends in southeastern Australian temperature in the last 152 years. The new historical temperature dataset for southeastern Australia provides an additional 49 years of important temperature information for Australia's most highly populated region.