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Atmosphere Overview

The Atmosphere Chapter reviews conditions and trends under three broad topics: variability and change; ambient air quality; and indoor air quality.

Climate Variability: The seasonal graphs for 13 Bureau of Meteorology sites hint at the complex changes that have occurred in the rainfall distribution. For example, the sites such as Sorell, Swan Island and Ormley have seen relatively high summer rainfall and relatively low winter rainfall over the last 10 to 20 years, but at Queenstown the reverse is true, at least for some of the period.

Enhanced Greenhouse Effect: There are significant variations through time of the average height of the sea that make the identification of long-term trends in sea level very difficult. Data series of many decades is probably necessary to properly identify long-term trends in sea-level. Current estimates of global sea-level rise due to the enhanced greenhouse effect are about 1 to 2 mm per year (Church et al. 2001). Robust estimates of such trends will require observations over several decades. Fort Denison in Sydney and Fremantle are viewed as important sites in global evaluations of sea-level (Lambert 2002). The average corrected sea-level rise is 1.4 mm/year from these sites (Lambert 2002 and Mitchell et al. 2001). In Hobart, the trend has been 0.62 mm/year (Mitchell et al. 2001), although the total duration of this data was less than 40 years, which is generally considered inadequate for deriving an estimate of long-term sea level change. The Port Arthur baseline, set in 1841, provides an important benchmarks for sea-level changes in Australia, and for the southern hemisphere as a whole. Analysis indicates that there has been a relative rise in sea-level of about 13 cm in the area since 1841. Once adjusted for vertical movements of the land, the rate of change is between 0.8 and 1 mm/year. Global predictions are for the rate of change to increase, such that by 2100 sea level will be between 9 and 88 cm above the 1990 global average sea-level.

Ozone Depletion: Concentrations of most ozone-depleting substances in the stratosphere are declining. Nevertheless, Tasmania will experience minimum ozone levels for the next 10 to 15 years. Although the ozone hole was greatly reduced in 2002, there is no conclusive evidence of long-term ozone recovery. Indications are that the 2003 ozone hole will be larger due to colder atmospheric conditions. Collection of CFC and HCFC data for Tasmania is lacking.

Meteorological Conditions: Temperature inversions are the most common meteorological condition that can exacerbate air quality problems by trapping pollutants near the ground, and these occur regularly in Tasmania with the amount of fog often indicating the severity.

Particulate Pollution: Between 1997 and 2002, the annual average PM10 concentration, measured at Ti Tree Bend in Launceston, has decreased from 34 to 19 µg/m3 (a 44% reduction). While there are still exceedences of the Air Quality National Environment Protection Measure (NEPM), the number of days exceeding the 24-hour standard has reduced from 51 to 14. There has been a marked improvement in the severity of poor air quality incidents, and the target of no more than five exceedences a year is much closer to being achieved. Preliminary results for 2003 suggest that there were 23 exceedences of the Air NEPM standard, reflecting the colder and wetter winter in comparison with recent years, and the 5 exceedences associated with either bushfires or planned burns. It is acknowledged that air quality in Hobart may vary due to changes in topography and micro-climate and there is some preliminary evidence to suggest that some parts of Hobart have poorer air quality than that recorded at the Prince of Wales Bay monitoring station. Little is known at present about population centres other than Hobart and Launceston, or about smaller particle concentrations.

Air Toxics: There are few data on the magnitude and location of any potential air toxics issues for Tasmania. Some information is available from the National Pollutant Inventory. It is likely that some limited measurements will be made in Launceston during 2004.

Carbon Monoxide: Historical data for Hobart suggests that there was a significant improvement of carbon monoxide concentration during the mid-1980s. A two month study in 1991 suggested that levels had gone up again. Current monitoring in Hobart has not shown any exceedences of the NEPM standard, however these measurements are aimed at characterising carbon monoxide concentrations from woodsmoke sources rather than from motor vehicles within the Hobart CBD as in the previous studies. Improvements in monitoring should allow conditions and trends to be reported in the future.

Transport Emissions: There has been virtually no direct monitoring of transport emissions in Tasmania. However, there is anecdotal information that the State's vehicle fleet is not likely to compare well to other jurisdictions in the areas of fuel efficiency and vehicle maintenance.

Commercial and Residential Indoor Air Quality: In 1997, the Australian Bureau of Statistics estimated that less than 4% of time was spent outdoors. Many common indoor air pollutants have also been shown to cause adverse health effects even at low concentrations. However, there is no trend information available on indoor air quality.

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Last Modified: 14 Dec 2006
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