3 Atmosphere | 3 Ambient air quality and other atmospheric issues | 3.4 Resilience of Australia's atmosphere

State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.

3 Atmosphere

3.4 Resilience of Australia’s atmosphere

At a glance

Recent simulations of the continuing effects of controls under the Montreal Protocol indicate that the time for total column ozone (i.e. the ozone in a column of air between the ground and outer space) to recover to 1980 benchmark levels will vary with latitude and will occur last over Antarctica around 2045 to 2060.

The frequency, duration and severity of episodes of poor air quality in urban centres are strongly influenced by short-term meteorological conditions (principally temperature and wind conditions), in combination with local topography. Air quality is usually restored to acceptable levels once the immediate conditions change. Therefore, our urban airsheds may be considered highly ‘resilient’, in terms of the common dictionary definition of the word, but human resilience to the effects of prolonged or recurring exposure to air pollutants is limited.

3.4.1 Stratospheric ozone

A number of the key ODSs persist in the atmosphere for long periods. Therefore, despite the success of the Montreal Protocol in phasing out CFCs and other major ODSs (apart from nitrous oxide), depletion of stratospheric ozone will continue for many decades.104 The World Meteorological Organization 2006’s Scientific assessment of ozone depletion concluded that, averaged across the whole of the global atmosphere, the decline in ozone stopped around 1996.202 The 2010 scientific assessment repeated this conclusion, noting that ‘average total [column] ozone values in 2006–09 have remained at the same level for the past decade, about 3.5% and 2.5% below the 1964–1980 averages, respectively, for 90°S–90°N and 60°S–60°N’.104 Similarly, monitoring of the maximum area of the Antarctic ozone hole (Figure 3.21) shows it to have been relatively stable since the mid-1990s. Recent simulations of the continuing effects of controls under the Montreal Protocol indicate that the time for total column ozone to recover to 1980 benchmark levels will vary with latitude and will occur last over Antarctica around 2045 to 2060. This recovery will occur well before stratospheric levels of ODS-derived chlorine and bromine decline to 1980 levels.104

3.4.2 Ambient air quality

Australia’s metropolitan cities all experience episodes of poor air quality (measured in terms of particulate pollution, or pollution by ozone and its precursors NOx and VOCs). The frequency, duration and severity of these episodes are strongly influenced by short-term meteorological conditions (principally temperature and wind conditions), in combination with local topography. Air quality is usually restored to acceptable levels once the immediate conditions change. In this context, our major urban airsheds are highly ‘resilient’, in terms of the common dictionary definition of the word. In contrast, application of the ecologically meaningful terms ‘resilience’, ‘sensitivity’ and ‘adaptability’ to the atmospheres of urban places is not particularly helpful in understanding either their dynamics or the effects of localised or widespread inputs of pollutants. However, if urban air pollution is considered from the perspective of the humans who cause most of it and are impacted by it, then resilience is a more useful concept.

Human resilience in the face of prolonged or recurring exposure to air pollutants is limited. Individuals vary in their sensitivity to exposure to particular air pollutants, with those most sensitive accounting for the great majority of the observed deaths and illness attributed to poor air quality. Unfortunately, our capacity to adapt to unacceptably high levels of air pollution is inherently limited. We can leave the affected area, shelter indoors (of limited value without effective air filtering), avoid strenuous exercise, wear face masks and, in the case of asthmatics and others with respiratory ailments, take prescribed medicines. Although necessary during periods of very poor air quality, these short-term adaptive strategies are not substitutes for action to mitigate the pollution at source through a range of regulatory and nonregulatory measures.