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Issues

Variability and Change
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        At a glance

        Cape Grim Baseline Air Pollution Station looking north

        The issue

        The greenhouse effect is a natural process where naturally occurring gases (e.g. water vapour, carbon dioxide, methane, nitrous oxide, ozone and sulphur hexafluoride) absorb energy and trap it in the atmosphere. This maintains the temperature in the biosphere within a range that is suited for life.

        Adding greenhouse gases to the atmosphere through increased emissions of natural gases (e.g. carbon dioxide) from human activities and gases manufactured by humans (e.g. chlorofluorocarbons) means that the amount of energy being trapped in the atmosphere increases, enhancing the greenhouse effect.

        The implications of an enhanced greenhouse effect are difficult to quantify, but include a range of changes to the climate, such as the rainfall and temperature patterns, and average sea-level, which are causing widespread concern. The International Panel on Climate Change has published a report on climate change impacts and adapting to climate change (IPCC 2001).

        This 'At a glance' section provides an overview of the enhanced greenhouse effect. More detailed information and references are available in the Enhanced Greenhouse Effect Issue Report. Five indicators are included within the report (see Indicators section) and two case studies are presented: Cape Grim Baseline Air Pollution Station and Measuring sea-level rise at Port Arthur.

        A specific 2003 recommendation is provided for this issue on: Reducing Greenhouse Gas Emissions.

        Favourable news

        • The National Greenhouse Strategy is currently being reviewed and Tasmania is reviewing its approach to greenhouse and climate change in order to implement an effective and enhanced response.
           
        • The 1999 Tasmanian Greenhouse Statement highlights a number of areas where Tasmania can assist Australia to meet the requirements of the Kyoto Protocol.
           
        • A National and Tasmanian Greenhouse Gas Inventories report on the historical levels of greenhouse gas emissions has been published.
           
        • It would appear that Tasmania is a net sink for greenhouse gas emissions (AGO 1998), although this issue is complex and subject to uncertainties relating to, for example, the role of land cover change. In Tasmania, the 'energy' sector (stationary and transport sub-sectors) is the largest emitter of greenhouse gases.
           
        • The first stage of Hydro Tasmania's Woolnorth Wind Farm project on the north-west tip of Tasmania has been completed. The 10.5 MW stage one with six Vestas 1.75 MW wind turbines was completed in August 2002. Construction of the Bluff Point stage began in September 2002 and is due for completion in 2003. This stage will have a capacity of 54 MW and comprise 31 wind turbines (Hydro Tasmania 2002).
           
        • Tasmania is host to one of the earliest benchmarks in the world for scientifically measuring changes in sea-level. The Port Arthur baseline was struck in 1841 and provides one of the most important benchmarks for sea-level changes in Australia, and for the southern hemisphere as a whole.
           
        • A proposed Coastal Vulnerability Project is aiming to investigate the areas vulnerable to storm surges, sea-level rises and associated events, and their potential impacts.
           

        Unfavourable news

        • Climate change is now implicated in the severity of some extreme climatic events such as the 2002 drought across Australia (Karoly et al. 2003). Much of the reason for the change points to anthropogenic effects, and in particular, the increasing level of greenhouse gases in the atmosphere (e.g. carbon dioxide, methane, nitrous oxide and sulphur hexafluoride).
           

        Concentration of carbon dioxide as measured at Cape Grim

        • Significant work is still required to meet greenhouse gas emission reduction objectives in Tasmania: there has been little advancement since the last SoE Report (1997) in the implementation of greenhouse gas emission reduction measures.
           
        • The enhanced greenhouse effect is expected to lead to a global increase in sea-level, as the upper ocean expands and land ice melts due to global warming. A 13 cm rise in average sea-level has occurred since 1841 at the Port Arthur long-term baseline site. The implications of this, and a continuing rise, for the management of various structures around the coast will have to be considered in all future planning.
           
        • Statewide figures for temperature show increases in both minimum and maximum temperatures, but these should be treated with caution. On the whole, it is likely that amongst the clear variability there has been some rise in temperature.
           
        • The data on rainfall in Tasmania also need to be considered with caution, but generally indicate relatively low levels of rainfall since the mid 1980s compared to previous decades.
           
        • Significant work is still required to investigate the potential impacts of climate change-on the environment, and economy and society-and to develop adaptation options.
           

        Uncertain news

        • There is uncertainty about the magnitude and scale of climate change impacts, particularly at local and regional scales where climate models may not have sufficient resolution. However, sufficient information is already available to anticipate and prepare for climate change impacts in Tasmania. The capacity exists through regional climate modelling, which is being undertaken at a regional scale for Tasmania by the CSIRO, to reduce uncertainty through improving understanding of climate change impacts.
           
        • There are significant uncertainties in the input data and methods associated with estimating greenhouse gas emissions from land clearing. Adding land clearing emissions to greenhouse inventories, with their greater uncertainties compared with other sectors, magnifies the uncertainty in total emissions. Consequently, emissions from this sub-sector are currently excluded from the calculation of net total emissions.
           
        • The most recent consolidated Tasmanian greenhouse gas emission data was published in 1998 for the years 1990 and 1995. The information was based on national figures, and may not accurately reflect Tasmania's actual level of emissions.
           
        • The 1999 national figures show that Australia has increased its greenhouse gas emissions since the 1990 and 1995 reports, largely due to the energy sector, and in particular, the stationary energy sector. As there are relatively fewer of these industries in Tasmania, it is unlikely that the Tasmanian figures will have increased by the same amount as the national figures, but this requires further investigation.
           
        • It is very difficult to measure trends in sea-level due to significant variation through time and between sea level monitoring stations. The very accurate SEAFRAME stations have only been in place around Australia since the early 1990s, and available data are unlikely to be indicative of the longer-term trends.
           
        • Due to the paucity of quality long-term temperature monitoring stations in Tasmania, the identification of trends in temperature change is difficult. The data available across the State are better for rainfall than for temperature, but still need to be treated cautiously as there are many regions that are not adequately represented.
           

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