Living in a variable climate
Dr Greg McKeon, CRC for Greenhouse Accounting, Queensland Department of Natural Resources and Water
prepared for the 2006 Australian State of the Environment Committee, 2006
There are currently major management issues resulting from climate impacts that provide useful examples of how governments and communities are dealing with current climate variability and expected climate change. The following examples, water availability in south-west Western Australia and heat wave preparedness in Queensland, indicate that adaptation planning and responses to observed climate changes and projections are beginning to occur. Other expected climatic extremes pose major risks to human welfare, infrastructure, and conservation of natural heritage. Such examples include: increased flooding resulting from greater rainfall intensities; higher coastal storm surges associated with more intense tropical cyclones and sea level rise; and greater bushfire intensities caused by increased temperatures and lower humidity. A major concern resulting from decadal and multi-decadal variability in the climate system is that the perception of the actual risk of these extremes is reduced, or even lost from the community's memory. Preparing for future climate extremes remains a challenge for communities and governments alike.
The decline of winter rainfall in south-west Western Australia provides one of the best examples of the application of emerging climate literacy. Since the mid 1970s, winter rainfall has decreased 'sharply and suddenly' in the region of south-western Australia (IOCI 2002, Abstract). By the mid-1980s, water managers were concerned, and subsequently downgraded expected long-term average inflow (called 'derating'). Water managers also developed water sources more quickly than originally planned, and stepped up efforts to conserve water (Power et al. 2005). A five-year (1998 to 2002) programme of strategic research known as the Indian Ocean Climate Initiative (IOCI) was conducted to evaluate the likely causes of this climate shift. It indicated that both natural variability and the enhanced greenhouse effect were likely to have contributed to the rainfall decrease, and that the determination of the relative influences of natural multi-decadal variability and the enhanced greenhouse effect was a major scientific challenge (IOCI 2002, Abstract). The report recommended that 'decision-makers need to alter their decision base-lines to reflect observed and projected changes but also to include increased levels of uncertainty' (IOCI 2002, Abstract).
With other regions in Australia also experiencing rainfall declines and water restrictions over the last decade, there has been a greater need to link climate science with water planning and community education so as to correctly support changes in community attitudes to water use. Power et al. (2005) reviewed the role that climate science played in influencing the successful changes in water management from the mid-1980s onwards, at a time of growing awareness of the likely impacts of global warming (Pearman 1988). The scenarios developed at the time (late 1980s) were based on the likely global warming effects on atmospheric circulation, and 'included a 20 per cent decline in rainfall by 2040 over southern Australia' (Power et al. 2005, p. 840). Power et al.(2005, p. 840) recognised that some 'derating' would have occurred in response to the observed drying without information from climate science. Further 'derating' occurred in 1998 under the assumption that rainfall in the region had changed more as a result of a 'regime shift' than a downward trend. The useful interaction of water managers and climate scientists appears to have resulted in a continuing adaptation to the uncertain combination of climate variability and change and community support for such adaptation and investment in new infrastructure.
Heatwaves have impacts on human health, energy and water consumption, and agricultural and horticultural production. The number of hot days is expected to increase as a result of global warming. For example, in Brisbane, the current long-term annual average number of days above 35°C is three. By 2030, Brisbane could experience an average of up to six days above 35°C and by 2070, up to 35 days (NR&M 2004, p. 12). This likelihood of increasing summer daytime maximum temperatures followed by warm nights offering little relief, poses a potential threat to urban communities where housing design and services may not be appropriate.
Emergency Management Australia (2004) stated, 'In Australia during the 20th century, heatwaves have caused more deaths than any other natural hazard (except disease), yet they remain one of the least-studied and most-underrated.' Woodruff et al.(2005, pp. 20–21), using the death records from Australian cities over the period 1997–99 for the age group over 65 years of age, estimated that around 1100 people died each year due to high temperatures. More recent heatwave examples in south-east Queensland include: (1) January 2000, 22 recorded deaths and 350 injuries costing an estimated $2 million; and (2) in February 2004, 12 recorded deaths and 221 heat related hospitalisations (preliminary data) (Queensland Health 2004, p. 4).
As part of the Queensland Heatwave Response Plan, the Bureau of Meteorology now issues advice to Queensland Health when the 'heat index' is forecasted to exceed 36°C in Brisbane for at least two consecutive days. Queensland Health, in turn, forwards this advice to hospitals and other agencies, and provides public advice on managing heat stress.