Atmosphere

Theme commentary
Tom Beer, Michael Borgas, Willem Bouma, Paul Fraser, Paul Holper and Simon Torok
CSIRO Atmospheric Research
prepared for the 2006 Australian State of the Environment Committee, 2006

Key findings

Urban air quality continues to improve. Concentrations of sulphur dioxide, nitrogen dioxide and lead are not of concern in any urban area. Carbon monoxide is of concern in a few specific urban locations. There has been no decline in concentrations of ozone in urban areas, which indicates that photochemical smog in those areas remains an issue. This is especially the case in Sydney, where maximum ozone concentrations have increased in recent years. Dust and other particulate matter, including woodsmoke, continue to be of concern in some regions and localities. The concern has shifted to the fine particulate matter (PM2.5), which is believed to dominate adverse health effects, rather than the coarser material. Some of these health effects may arise from pollen or seeds but Australia still does not have a systematic pollen monitoring system established.

In rural and regional Australia, levels of most pollutants are well below actual or proposed standards. Sulphur dioxide and lead emissions continue to be of concern in a few limited localities. 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 such hotspots on the basis of measurements, and insufficient monitoring of air toxics at such sites.

This reflects a general concern with a range of air toxics from both urban areas and regional industry, but no indicators report the trends at this stage. It is hoped that this will be addressed for future State of the Environment reports with the implementation of a National Environment Protection Measure on air toxics.

Other issues for regional air quality include odour from agricultural activity and waste treatment, but there are no indicators to demonstrate the trends in this concern. In parts of regional Australia, bushfires (either as ‘wildfires’ or as controlled burns) will be responsible for intermittent poor air quality.

Accumulation of total chlorine from ozone-depleting gases in the stratosphere slowed during the early 1990s and levels are now declining slowly. Although there is no evidence of a significant reduction in the Antarctic ozone hole in recent years, it stopped increasing in the mid to late 1990s.

Unfortunately, skin cancer incidence may be expected to continue to increase until about 2050, even though ozone levels in the stratosphere have started to recover. The reason for this is that, even though exposure to ultraviolet radiation (as a result of ozone depletion) causes skin cancer, there is about a 50-year time lag between the two. This link has become more widely known and public action in avoiding excessive ultraviolet radiation has increased significantly.

In 2002, Australia changed the methodology used to estimate greenhouse gas emissions to follow the accounting procedures recommended in the Kyoto Protocol by including land clearing. On this basis, the increase in greenhouse gas emissions between 1990 and 1998 was 1.3 per cent. An increase of 1.1 per cent applied from 1990 to 2003. Australia, though not formally bound by the Kyoto Protocol, continues to be committed to meeting a target of less than an eight per cent increase on 1990 levels by 2012.

The Australian average surface temperature continues to rise. The warming since 1950 has been almost 0.2 °C per decade. The past decade has seen Australia’s highest recorded mean annual temperatures. Climate change modelling for Australia indicates temperature increases that range from one to six degrees by 2070. Projected changes in rainfall around the country will exhibit more spatial variability than the temperature change projections. There is expected to be markedly less rainfall in Western Australia and significantly less rainfall in south-eastern Australia as global warming manifests itself.

2005 was Australia’s warmest year on record, with the annual mean temperature for Australia being 1.09 °C above the 1961–90 average. Rainfall deficits in many parts of Australia during the first-half of 2005 followed average to below-average falls since the severe drought of 2002–03, with no prolonged period of widespread above-average falls to fully remove rainfall deficiencies. Thus, in 2005 many parts of Australia were still affected by unremitting drought. Australian Bureau of Meteorology records revealed that the Murray-Darling Basin was in the midst of its worst multi-year period of rainfall deficiencies since the 1940s.