Atmosphere

2016

Airborne emissions

Australia’s coast bears the brunt of national airborne emissions, because the vast majority of people and large cities are on the coast. In addition to these land-based sources are emissions from shipping activities, which are most significant in ports that support both domestic and international trade. Major sources of emissions in Australia are stationary energy (52 per cent), transport (17 per cent), agriculture (15 per cent) and fugitive emissions (7 per cent). Given the density of human population in coastal areas, the impacts of emissions on coastal air quality are an issue of national concern.

Airborne emissions contribute to climate change, with impacts outlined in Climate and weather (in this report) and in the Atmosphere report. On both a per-person and per-dollar-of-GDP basis, Australia’s carbon dioxide emissions are above the average for Organisation for Economic Co-operation and Development member countries.

Localised impacts of airborne pollutants can be exacerbated near the coast, because of their interaction with salt spray. Aged salt spray suspended in the air eventually breaks down into components that bind with pollutants (e.g. those from emissions), thereby creating more persistent airborne particles that can contain toxic elements.

An emerging issue in some major coastal cities is emissions from visiting cruise ships, which add fine particles and sulfur dioxide to the air. An example is the White Bay Cruise Terminal that began operating at Balmain in Sydney in 2013. There is concern about the deteriorating air quality in residential areas near the terminal, although monitoring has so far not detected impacts beyond permissible levels (Sydney Ports 2014).

See the Atmosphere report for more information about airborne emissions.

Climate and weather

Coastal Australia has experienced many extreme weather events in the past 5 years, consistent with predicted effects of climate change. Pressures associated with climate change include rising air and sea temperatures, rising sea level, altered precipitation, ocean acidification, and increased frequency and intensity of storms, floods and bushfires.

Temperatures in Australia have risen slightly faster than the global average, and extreme heatwaves are becoming more frequent (Alexander et al. 2006, Perkins & Alexander 2013). From 2011 to 2016, there were several brief but extreme climatic events, and a shift from La Niña (periodic cooling of the central and eastern Pacific Ocean associated with increased probability of wetter conditions in eastern Australia) to El Niño (periodic warming of the central and eastern Pacific Ocean associated with an increased probability of drier conditions in eastern Australia). Bushfire frequency and intensity has increased, partly because of higher air temperatures (Clarke et al. 2013). Other pressures on the coast related to climate change are the effects of flooding on water quality, including suspended sediments, and increased sedimentation in waterways when severe bushfires are followed by rain.

Since 2011, New South Wales has experienced higher temperatures, bushfires, east coast lows and storms (BoM 2011). Queensland has been struck by tropical cyclones (Marcia, Yasi, Ita, Hamish and Nathan), drought and floods, and has been heavily influenced by El Niño–Southern Oscillation (ENSO) forcing (BoM 2011, 2015). For example, the Brisbane floods of 2011 occurred during a La Niña event and caused an estimated $440 million damage, and Queensland experienced a long-term drought exacerbated by an El Niño event (BoM 2015). Both Victoria and South Australia have been relatively hot and dry (Clarke et al. 2013), and Tasmania has experienced warmer conditions than usual (BoM 2015). The Northern Territory was drier than usual during the reporting period, especially from 2013 to 2015 when the monsoon season was delayed and did not reach its normal intensity (BoM 2015). In Western Australia, there was a heatwave in Ningaloo in 2011 (Feng et al. 2013), which was at least partly driven by warm continental air being blown offshore, tropical cyclones and dry conditions in the far south-west.

Extreme heatwaves have affected both terrestrial and marine species and ecosystems (Wernberg et al. 2013). Fruit bats, for example, have a finely tuned internal body temperature (Welbergen et al. 2008), and have been observed falling from trees during heatwaves in Sydney and Brisbane. Some species rapidly evolve to tolerate heat, but the capacity of most species to adapt is unknown. Species are shifting their ranges in response to climate change, with growing evidence of range expansions and contractions in coastal ecosystems (see Rising sea temperatures). Increased temperatures also have the potential to alter ecological interactions by changing metabolic rates and relative competitive abilities (Dillon et al. 2010).

Climate change will almost certainly remain the primary global environmental pressure in both the short and long term. By 2070, atmospheric warming is predicted to reach between 1 and 2.5 °C under a low-emissions scenario, and between 2.2 and 5 °C under a high-emissions scenario (BoM & CSIRO 2014). Effects of ENSO and the Interdecadal Pacific Oscillation make prediction more difficult, adding uncertainty to predicted changes in periodicity and intensity (Collins et al. 2010).

Rainfall predictions are highly variable among models, although rainfall is expected to increase in the tropics and decrease at temperate latitudes (Head et al. 2014). More heatwaves and bushfires are predicted, but change in other processes is uncertain. Translation of large, national-scale climate change projections to small, regional scales needs to be appropriately conducted (Ekström et al. 2015). Climate change also needs to be assessed with regard to its impact on, and interaction with, other pressures on coastal systems, as is currently being done on the Great Barrier Reef.

See the Atmosphere report for more detailed information on atmospheric climate change and weather.

Clark GF, Johnston EL (2016). Coasts: Atmosphere. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/coasts/topic/2016/atmosphere, DOI 10.4226/94/58b659bdc758b