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Issues

Variability and Change
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        At a glance

        The issue

        Tasmania experiences considerable natural climatic variability. It is influenced by the El NiÑo - Southern Oscillation (ENSO) phenomenon, and other more local factors. To manage the Tasmanian environment in an ecologically sustainable way, a sound understanding of how these climatic factors interact and influence the climate is required. Being able to predict the length of a drought, for example, enables planning to help avoid the worst problems.

        The natural variability inherent with the Tasmanian climate exists in the absence of any climate change. An increase in climate variability is a symptom of climate change, so that an increase in the frequency of extreme weather events in Tasmania and/or around the world is often associated with climatic or atmospheric change (see Enhanced Greenhouse Effect and Ozone Depletion Issue Reports). Care must be taken in distinguishing between natural climate variability and climate change.

        This 'At a glance' section provides an overview of the issue of climate variability. More detailed information and references are available in the Climate Variability Issue Report. Three indicators are presented in the report on the Southern Oscillation Index, rainfall and temperature. Several recommendations for Atmosphere are provided.

        Favourable news

        • Improvements are being made in our ability to understand the influences on Tasmania's climate and to observe the climatic trends. This enables improved predictions of the status of the Southern Oscillation Index (SOI) and the occurrence of El NiÑo and La NiÑa events, allowing managers to accommodate varying conditions and operate at the maximum efficiency that conditions allow.
           
        • The greater awareness of the potential problems-such as wind erosion, soil compaction, and tree decline-resulting from low rainfall periods also assists managers to better plan for such difficult times.
           

        Unfavourable news

        • During the most extreme events of ENSO, known as El NiÑo events, the Australian region experiences much drier conditions, with droughts throughout much of the country, often including Tasmania. Conversely, high rainfall can also result in flooding during La NiÑa events.
           

        • Droughts and floods in Tasmania are also affected by other factors of a more local nature, including the intensity and exact location of high- and low-pressure systems relative to the State, the influence of the surrounding oceans, and the highly variable topography.
           

        • Patterns in seasonal and annual rainfall are not always consistent, or cyclical, so all activities that rely on rainfall need to take this into account. Management regimes need to recognise the difficulties in ensuring a consistent water supply.
           

        • The limited temperature data available suggest warmer conditions now than in the past (1940s), and that there has been a general shift in temperatures, rather than a change in temperature extremes, which may be related to anthropogenic causes (see Enhanced Greenhouse Effect Issue Report).
           

        • Monitoring of the sea-level also shows the high degree of natural variability in the climate and ocean system, which makes the identification of long-term trends very difficult (see the Enhanced Greenhouse Effect Issue Report). Such variability makes it important to avoid locating houses and infrastructure in vulnerable positions on the coast, as well as identifying approaches to protect existing assets from very high tides and storm surges. Managing for such events will need to become more prominent as the predictions for sea-level are that they will rise between 9 and 88 cm above the 1990 global average sea level by 2100 (Houghton and Ding 2001). Further detail is provided in the Adapting Coastal Settlements to Climate Change Issue Report.
           

        Uncertain news

        • Our knowledge of the variation in rainfall across the State is better for some areas than for others. This is because of the uneven distribution of weather monitoring stations across the State and the variation in quality of records between the stations.
           

        • There are fewer long-term temperature records than rainfall records in Tasmania, making it harder to assess changes in climate trends through time and across the State.
           

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        Last Modified: 14 Dec 2006
        URL: http://soer.justice.tas.gov.au/2003/atm/1/issue/3/ataglance.php
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