Independent report to the Australian Government Minister for the Environment and Heritage
Beeton RJS (Bob), Buckley Kristal I, Jones Gary J, Morgan Denise, Reichelt Russell E, Trewin Dennis
(2006 Australian State of the Environment Committee), 2006
Climate change has always been a reality. The challenge is to predict how much an already variable world climate system will change as a result of human activity. While scientists debate the relative contribution of human activity to climate change, it is generally considered that continued increases in the levels of greenhouse gases, such as carbon dioxide, methane and nitrous oxide, are expected to lead to an enhanced greenhouse effect and regional climate change.
The question, then, is not ‘if’ but ‘how much’. Predictions from models of temperature increases suggest a wide range of uncertainty—ranging from 0.4–2.1°C by 2030, to 6.8°C in 2070 (CSIRO 2001, Lindesay 2003) (Figure 21); others suggest an increase of 5.8°C by 2100 (Steffen 2006). The largest increases are projected to occur in summer (CSIRO 2001). There have clearly been significant increases in sea surface temperatures of up to 0.28°C in the Australian region since 1950 (Figure 22).
Source: CSIRO (2001)
Source: BoM (2006b)
It is likely that rainfall may become even more variable across the seasons and across Australia. Southern and eastern Australia may receive less rainfall in winter and spring than it does now (CSIRO 2001, Whetton and Suppiah 2003). The situation for other areas in Australia is not as well understood. Even though some of the projected changes in rainfall appear relatively small, they should not be dismissed as unimportant.
In the face of such variability, and because global climate systems are not completely understood, it is impossible to be more certain about Australia’s future climate. For example, it is only recently that there has been recognition of the influence on Australia’s rainfall of decade-long, large-scale fluctuations of ocean surface temperature and pressure across the north Pacific Ocean (Mantua et al 1997, Power et al1999, Lindesay 2003), although it is still the subject of intense debate. Variously called the Pacific Decadal Oscillation or the Inter-decadal Pacific Oscillation, it modulates the impact of El Niņo and La Niņa on Australia’s climate. In other words, data suggest that the Pacific Decadal Oscillation accentuated the low rainfall influence of the recent El Niņo. It means that the Southern Oscillation Index is no longer seen as the only predictor of Australia’s climate. The increase in tropical storms in recent years is probably a result of changes to sea surface temperatures, but no one can yet predict the future direction of these changes.
The likely effects of climate variability and change on Australia’s urban and rural communities are well recognised. Both must adapt to survive. The history of agriculture in Australia demonstrates much success in adapting agricultural practices and technologies to better manage for a variable and dry climate in a semi-arid land (Pestana 1993, Burroughs 2003). Crop production has been improved through plant breeding, and better crop and water management. Livestock enterprises have developed better-adapted animal breeds, improved pasture species and animal husbandry, and improved drought management. These practices have sometimes resulted in resource damage, such as increased soil erosion (due to loss of soil protection) and increased salinity risk (due to loss of perennial plants). Urban Australia is being similarly challenged to conserve its limited water resources and invest in alternative water sources, especially where increasing demand is outstripping supply. Australia’s water use efficiency and water reuse and recycling rates would have to increase from their current low levels.
Equally significant is the impact on Australia’s biodiversity . Recent Australian (Howden et al 2003) and international (Thomas et al 2004) assessments suggest that climate change is among the significant emerging pressures on biodiversity. Changes in the extremes and timing of the components of climate in coming decades will further compound and intensify pressures on biodiversity, especially by affecting rainfall patterns (hence fire regimes), regeneration of vegetation, and where plants and animals can live. In the oceans, it will affect sea level and sea temperatures, with potential impacts on marine ecosystems and ocean currents.
A possible impact of climate change is a change in how often coral bleaching events occur. In 1998, and again in 2000, there was large-scale bleaching of the Great Barrier Reef, raising concerns about its long-term health. Sea surface temperatures are certainly a factor, as are other stressors in coastal and ocean systems. If maximum summer temperatures increase, an increase in the frequency of major bleaching events is very likely. The future of tropical coral reefs is causing worldwide concern (Reef Futures 2003).
If management and conservation strategies do not begin to take climate-driven variability and the likely long-term shifts into account, it may be difficult to mitigate or manage impacts effectively. The National Biodiversity and Climate Change Action Plan 2004–07 is one small step in the right direction (Natural Resource Management Ministerial Council 2004).
Many of Australia’s species and ecological communities are especially vulnerable because they are highly fragmented and many of the remnants are on areas of naturally poor soil quality. Their resistance to change and resilience to shock are likely to decline as the worst seasons or events become more extreme or more frequent. Increasing extremes, for example, of climate, fire events, total grazing pressure, intra- and interspecies competition, predation, disease, gross soil loss, soil nutrient and carbon loss, soil acidity, soil salinity or soil toxicity brought about by changing acidity can further complicate the issue. This means systems that are apparently in reasonable condition can suddenly change without hope of recovery.
Overall changes in Australian climate variability cannot be accurately predicted. What can be said is that adapting for conditions outside of people’s experiences and encouraging better management on a national and international scale is needed to secure Australia’s environmental future.
- The air quality in Australia’s human settlements continues to improve and, apart from bushfires, dust storms and localised industrial pollution, mostly meets agreed national standards.
- Australia’s greenhouse gas emissions remain high by global standards but the growth in net emissions has reduced over the last five years primarily because of reduced vegetation clearing.
- The last five years have seen lower than average rainfall over much of eastern Australia (especially Queensland) and south-west Western Australia, and higher than average rainfall over central west Australia. This is consistent with rainfall trends over the last 100 years.
- The use of ozone-depleting substances has continued to decline, the amount of ozone in the upper atmosphere has increased, and the size of the hole in the ozone layer over Antarctica has clearly stabilised.
- Although Australians spend more than 90 per cent of their time indoors, relatively little research has been done on the quality of indoor air. The banning of smoking in public places by most jurisdictions would have had a positive impact.