Atmosphere: Atmospheric gases

Independent report to the Australian Government Minister for the Environment and Heritage
Beeton RJS (Bob), Buckley Kristal I, Jones Gary J, Morgan Denise, Reichelt Russell E, Trewin Dennis
(2006 Australian State of the Environment Committee), 2006

4.2 Atmospheric gases

Greenhouse gas equivalents

In 2002, Australia changed the method used to estimate greenhouse gas emissions to include land clearing, as specified in the Kyoto Protocol. The procedures also follow the Intergovernmental Panel on Climate Change reporting guidelines. All previous emissions estimates were revised, and the increase in carbon dioxide equivalents (CO2-e) between 1990 and 1998 is much less than the figure quoted in SoE2001.

Australia's greenhouse gas emissions are increasing. Net emissions are estimated to have increased by 2.3 per cent to a total of 564.7 million tonnes (Mt) CO2-e from 1990 to 2004 (DEH 2006b). While this overall increase is partly a result of population increase, the per person contribution to Australia's greenhouse gas emissions has declined during 1990 to 2004-from 32.3 to 28.2 tonnes CO2-e. Emissions per dollar of gross domestic product (GDP) have also declined from 1.1 to 0.7 kilograms CO2-e per dollar of GDP (DEH 2006b). This is largely a result of the large decline in emissions from land use and land use change during the period, improved emissions management, and structural changes in the economy, with the services sector growing faster than the manufacturing sector. While these data could be used to claim that Australia has become more 'greenhouse gas efficient', the overall increase in net emissions is still of concern.

Australia signed the UN Framework Convention on Climate Change in June 1992 and ratified it in December 1992. Although not formally bound by the Kyoto Protocol, Australia has committed to meeting a target of less than an 8 per cent increase on 1990 levels by 2012.

Sources of greenhouse gas emissions (more information on this topic) 

The largest and fastest growing source of greenhouse gas emissions in Australia is the energy sector, contributing 68.6 per cent of Australia's net emissions (Figure 16). Much of the total can be attributed to the stationary energy subsector (the main source, at 49.6 per cent of net emissions) and the road transportation subsector (12.5 per cent of net national emissions). Increasing household incomes have contributed to the increase in both sectors, with stationary energy emissions also driven by growing population and export increases from the resources sector; and transport emissions affected by the numbers of vehicles. These two sectors are responsible for much of the increase in greenhouse gas emissions since 1990.

The agriculture sector is responsible for 16.5 per cent of Australia's net emissions. Another 6.3 per cent of net emissions comes from the land use, land use change and forestry sector. This last sector includes land clearing, which was a major source of Australia's net greenhouse gas emissions in the early 1990s, but is now much reduced. This reduction offsets most of the increase in emissions in all the other sectors. Other relatively minor sources include emissions from industrial processes, such as from the manufacture of mineral products, and emissions from waste disposal (DEH 2006b).

Emissions for 2020 are projected to reach 122 per cent of the 1990 level, reflecting the impact of ongoing growth in emissions in the energy sector. This emphasises the need to focus on lowering Australia's greenhouse emissions over the longer term, while maintaining a healthy and competitive economy (DEH 2005b).

Carbon dioxide (more information on this topic) 

Globally, carbon dioxide concentrations have risen from 330 parts per million in the mid-1970s to more than 375 parts per million by the mid-2000s. This constitutes a long-term growth rate of about 1.5 parts per million per year (Francey 2005). It is largely a result of the burning of fossil fuels, and this has increased because of economic growth, accentuated by increasing global population and the industrialisation of the developing world. Australia's contribution to that proportion of the increase attributable to anthropogenic sources has been around 1.5 per cent.

Methane (more information on this topic) 

Methane concentrations increased from 1450 parts per billion in the mid-1970s to 1700 parts per billion by the mid-2000s; however, the concentration is no longer increasing as rapidly as it once did. Although methane has not yet had the impact on climate that carbon dioxide has, some researchers believe that methane release from cold wetlands could be a climate change accelerator.

The long-term growth rate of methane emissions has declined to zero over the last six years, from a high of 15 parts per billion per year in the mid-1980s (CSIRO 2005b). The reason for the trend is uncertain, but it may be because the oil and gas industry is emitting less, or the same amount, of methane than previously. As well as showing a long-term decline, the methane emission growth rate shows significant variability, the cause(s) of which remain elusive. It has recently been demonstrated that assumptions about the relationship between greenhouse and vegetation require re-examination (Keppler et al 2006). The full implications of this are yet to be tested, but this discovery demonstrates the need for flexible and adaptation-driven policy.


The amount of ozone in the stratosphere (upper atmosphere) matters because it absorbs most of the sun's harmful ultraviolet B radiation. Overall, the concentration of ozone  in the stratosphere over Australia and New Zealand may have started to increase since the year 2000 (Figure 17 and Figure 18). The ozone 'hole'  over Antarctica has been at its current size of 25 million square kilometres since the mid-1990s, following two decades of rapid growth. At the same time, there has been a 1 per cent a year decrease in the erythemal ultraviolet index  (a measure of skin cancer  potential) over the southern part of Australia since 1998 (CSIRO 2005c). These datasets show marked variability, making interpretation difficult.

Figure 18: Maximum ozone hole area (area within the 220 Dobson Unit contour)

 Maximum ozone hole area (area within the 220 Dobson Unit contour)

Note: The polynomial fit does not include the unusual data seen in 2002 and 1988.
*TOMS: Total Ozone Mapping Spectrometer
Source CSIRO (2005c)

These positive trends may be associated with the decline of about 1 per cent each year in the concentration of total stratospheric chlorine (a measure of ozone-depleting substances ) since the late-1990s (CSIRO 2005b). Australia has met all Montreal Protocol targets for reducing its consumption of ozone-depleting substances, setting accelerated phase-out requirements in some cases.

Skin cancer rates for Australians showed a steady increase from the early 1980s to the late 1990s but have since stabilised (AIHW and AACR 2003). This could be a result of improved awareness and behavioural changes in the Australian community.

Ambient air quality

Urban air quality continues to improve. Concentrations of sulphur dioxide , nitrogen dioxide  and lead  are not of concern in any urban area (DEH 2004). Carbon monoxide  has not exceeded the National Environment Protection Measure (NEPM) standard in any Australian city. Photochemical smog is still an issue in some urban areas, as indicated by high ozone levels . This is especially the case in Sydney, where the most recently available data show that maximum ozone concentrations in the lower atmosphere increased (Figure 19).

The main pressure on air quality in urban areas is the continued increase in population-more people are driving more cars. The data show this as an increase in the number of vehicles per head of population and in the total vehicle kilometres travelled  (ABS 2004e). The controls on carbon monoxide, nitrogen oxide and volatile organic compounds through fuel quality standards  indicate that total motor vehicle emissions in 2020 will probably be below those of 2006 (DoTARS 2003), but this is unlikely to be the case with total particulate matter emissions .

In rural and regional Australia, levels of most pollutants are well below actual or proposed standards (DEH 2004). Sulphur dioxide  and lead  emissions continue to be of concern in a few limited localities (for example, lead and sulphur dioxide in Port Pirie, South Australia and Mount Isa, Queensland). Particular pollutants, such as benzene  in the Pilbara, may be of local concern in specific regions. Despite the probable existence of such rural air pollution hotspots, there is insufficient monitoring to identify other areas of concerns and insufficient monitoring of air toxics at such sites (Manins et al 2001).

Dust and other fine particles , including wood-smoke, are of concern in regional areas such as Armidale and Beresfield in New South Wales, Bunbury in Western Australia and Launceston in Tasmania. Concentrations of very fine particles, smaller than 2.5 microns in diameter (PM2.5), have increased threefold in Sydney and Brisbane in the last five years (Figure 20). Some very high levels in 2001 may have been a result of bushfires. PM2.5 is of concern because the smaller particles have a greater effect on health, particularly respiratory illnesses, than the larger particles (PM10) that have been monitored in the past. Some of these health effects may arise from pollen or seeds, but Australia still does not have a systematic pollen monitoring system.

Figure 20: Highest daily average of PM2.5 for Australia's capital cities

 Highest daily average of PM2.5 for Australia's capital cities

Note: µg/m³ -  micrograms per cubic metre
Source: DEH (2004)

Issues of air quality across Australia continue to be addressed through various measures, including NEPMs, Australian Design Rules for motor vehicles, national fuel quality standards, and wood-heater replacement programmes. It is hoped that issues around air toxics at rural hotspots will be addressed with the implementation of the NEPM on air toxics, with states and territories commencing monitoring of air toxics from the end of 2006.

Indoor air quality (more information on this topic) 

Although Australians spend 90 per cent or more of their time indoors, relatively little research has been done on the quality of indoor air. A major concern with respect to indoor air quality is the use of gas cookers and un-flued gas heaters. These two sources can often contribute a large percentage of the pollutants found in domestic dwellings.

Tobacco smoke is an important aspect of indoor air quality for some households and in some workplaces. The World Health Organisation states that 'there is no safe level of exposure to environmental tobacco smoke' (WHO Regional Office for Europe 2000). This position is supported by the National Occupational Health and Safety Commission's Guidance Note on the Elimination of Environmental Tobacco Smoke in the Workplace (Commonwealth of Australia 2003).

States and territories have taken various actions to ban smoking in public places, with total indoor bans in force in Tasmania, Queensland and Western Australia, and partial bans in the Australian Capital Territory and Victoria.