Atmosphere Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Dr Peter Manins, Environmental Consulting and Research Unit, CSIRO Atmospheric Research, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06746 9

Stratospheric Ozone (continued)

Findings and implications

The accumulation of ozone-depleting substancies in the background atmosphere slowed during the early 1990s, stopped in the mid-1990s (maximum in 1994) and now is declining slowly. Australian data on ozone-depleting substances make a vital contribution to global efforts to validate the Montreal Protocol mandated emission reductions.

Southern Australian and New Zealand ozone data show statistically significant decreases in ozone in summer since the late 1970s of about 4% per decade. The rate of ozone depletion slowed in the 1990s compared to the 1980s, suggesting that ozone levels may not decline much further. Predictions of future chlorine levels suggest that ozone recovery is expected by about 2050. However, recovery may be delayed by as much as 50 years as a result of climate change and larger than anticipated use of ozone-depleting substances, in particular CFCs and halons, in developing countries.

The greatest decreases in ozone have occurred over Antarctica but ozone loss appears to have stabilised during the 1990s. Although ozone levels appear to have recovered from the effects of the Mount Pinatubo eruption, there is no evidence yet of long-term ozone recovery. Over the next decade, while stratospheric chlorine remains at near maximum levels, stratospheric ozone at mid-latitudes and polar regions is susceptible to further volcanic eruptions that deposit significant aerosol material in the stratosphere.

Data from New Zealand show a clear relationship between declining ozone and rising UV radiation levels on clear-sky days in summer. Skin-reddening UV levels appear to have risen by about 10% per decade. New Zealand and southern Australian ozone data show similar trends, implying similar UV trends for both regions.

Australian attitudes and behaviour regarding exposure to UV radiation are changing, favouring less exposure. The 20% increase in skin-reddening radiation likely to have occurred on clear-sky days in summer over southern Australia since 1980 has probably contributed to the rising incidences of skin cancer but quantifying this contribution is complicated by people's changing habits in relation to exposure to UV radiation.

Australian consumption of ozone-depleting substances, which was nearly 20 kt/year in 1986, declined rapidly after 1989 in response to restrictions imposed on the use of these chemicals. Australian consumption remained well within its Montreal Protocol limit throughout the 1990s. By 1996, consumption fell to less than 1000 t and has remained below this level. Current consumption is about 800 t which is required to service the few remaining essential uses of ozone-depleting substances allowed under Australia's ozone protection strategy.

Since 1993, Australia has collected more than 10 kt of ozone-depleting substances which have either been recycled, stored or destroyed. Significant amounts of ozone-depleting substances remain to be collected and such activities need to be encouraged if Australia is to continue to show leadership in reducing its contribution to global ozone depletion.