A climate reconstruction of Sydney Cove, New South Wales, using weather journal and documentary data, 1788–1791

Abstract

This study presents the first analysis of the weather conditions experienced at Sydney Cove, New South Wales, during the earliest period of the European settlement of Australia. A climate analysis is presented for January 1788 to December 1791 using daily temperature and barometric pressure observations recorded by William Dawes in Sydney Cove and a temperature record kept by William Bradley on board the HMS Sirius anchored in Port Jackson (Sydney Harbour) in the early months of the First Fleet's arrival in Australia. Remarkably, the records appear comparable with modern day measurements taken from Sydney Observatory Hill, displaying similar daily variability, a distinct seasonal cycle and considerable inter-annual variability. To assess the reliability of these early weather data, they were cross-verified with other data sources, including anecdotal observations recorded in First Fleet documentary records and independent palaeoclimate reconstructions. Some biases in the temperature record, likely associated with the location of the thermometer, have been identified. Although the 1788-1791 period experienced a marked La Niña to El Niño fluctuation according to palaeoclimatic data, the cool and warm intervals in Sydney over this period cannot be conclusively linked to El Niño- Southern Oscillation (ENSO) conditions. This study demonstrates that there are excellent opportunities to expand our description of pre-20th century climate variability in Australia while contributing culturally significant material to the emerging field of Australian environmental history.