Generally, limited data are available to assess many aspects of the Antarctic environment. This is largely a consequence of the remoteness and sparse habitation of the region. Specific information is available to assess trends and changes in the physical environment. This includes palaeoclimate records from ice cores that extend back hundreds of thousands of years, synoptic weather observations generally starting in the 1950s, and satellite remote-sensing data from the late 1970s onwards. For the various components of the ecosystem, far sparser records are available. For many species, such as baleen whales, accurate population assessments remain unavailable.

This report presents our best available assessments of the state and trends of the Antarctic environment (the area south of 60°S, the Southern Ocean and Australia’s subantarctic islands), primarily as they relate to Australia’s interests in the region. Overall, the material presented here is largely an update on the 2016 state of the environment report, primarily informed by the peer-reviewed literature that has appeared in the intervening 5 years. Consequently, almost all the assessments presented here are directly comparable to those presented in 2016. For the physical environment, many aspects of change are occurring on multiyear or longer timescales because of the nature of physical processes associated with the Antarctic atmosphere, ice sheet and surrounding oceans. Thus, the assessed changes and trends are generally identical to those presented in the 2016 state of the environment report.

The 2016 state of the environment report was prepared using the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) (IPCC 2013) which provided a comprehensive picture of the state of the Antarctic environment at its release in 2013. In preparing the present report, we have primarily used observational assessments from subsequent major reports including the IPCC special report on the ocean and cryosphere in a changing climate (IPCC in press-a), the Scientific assessment of ozone depletion: 2018 (WMO 2018) and the Sixth Assessment Report of the IPCC (IPCC 2021). In addition to other peer-reviewed literature, we have also used the opinion of experts in specific fields and, where possible, we have made use of a variety of up-to-date environmental and management data collected in support of the Australian Antarctic Program.

In general, our assessment of the confidence rating for grade and trend is graded using the 3 levels used for the 2016 state of the environment report (‘adequate’, ‘limited’ and ‘low’). At present, a finer assessment using the 2 additional grades adopted in this report (‘somewhat adequate’ and ‘very limited’) cannot be applied confidently for most of the Antarctic topics considered here.