Key findings from the Atmosphere Chapter of the 1996 State of the Environment Report (SoE 1996).

Climate

Australia has many climatic zones including temperate, Mediterranean, subtropical and tropical. More than three-quarters of the continent is arid or semi-arid, and it has less rainfall and less runoff from its rivers than any other inhabited continent.

Our climate is highly variable. Rainfall, temperature and wind patterns fluctuate widely from year to year as a result of natural causes. Major contributors to this variability over the eastern half of Australia are El Nio and La Nia events.

The enhanced greenhouse effect

Australia produces between 1 and 2% of global greenhouse emissions, mainly from fossil fuel burning, land clearing and agriculture. Australia has one of the world's highest per capita emission levels of the greenhouse gas carbon dioxide. The Report noted that Australia, along with most other developed countries, would be unlikely to meet the implied international target of returning emissions to 1990 levels by 2000.

Ozone depletion

Australia has reduced production and use of ozone-depleting substances such as CFCs and hydrochlorofluorocarbons (HCFCs) well ahead of international obligations and plans are in place for further reduction.

Losses of stratospheric ozone of between 2 and 4% per decade have occurred in mid-latitudes (from the Tropic of Capricorn to the Antarctic Circle) since the 1950s, including over Australia. Australia has the highest rate of skin cancer in the world. Ozone depletion means that we are now exposed to greater levels of UV radiation. The Antarctic ozone hole has increased in size since the early 1980s.

Concentrations of CFCs are now levelling off, following the implementation of international controls. However, because of time lags, ozone depletion will continue to worsen for several years, and UV radiation will increase. Trends at the time of the Report suggested that the ozone layer should begin to recover soon after the year 2000.

Regional outdoor air

There is concern in some locations about the effects of sulfur dioxide and particle emissions from power stations, smelters and oil refineries. Industry also releases fluoride and lead into the atmosphere, but levels around Australian smelters are well below the NEPM standards. However, over much of the continent, air quality is not monitored.

The largest single sources of sulfur dioxide are in arid areas, where dry deposition of sulfate aerosols takes place downwind of the source.

Away from major pollution sources, air quality is generally good, but dust and smoke can be a problem.

Urban outdoor air

Motor vehicles are the greatest source of air pollution in cities.

In general, the concentrations of common pollutants meet official health guidelines and are low by world standards. Over the last decade (1986-1996), some aspects of air quality in cities such as Sydney and Melbourne have improved. Atmospheric lead levels have declined significantly mainly because of the introduction of unleaded petrol and paints.

Major pollution problems in Australian cities are episodic and are influenced by seasonal and meteorological factors. Increasing vehicle use as Australia's population grows presents a threat to future air quality.

Indoor air pollution

Little is known of the long-term effects of indoor air quality on human health. People spend a lot of time indoors where they may be exposed to a range of pollutants.