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
At the time of writing (October 2005), the impact of the drought that commenced in 2001 is now stimulating much public debate on climate variability, climate change and appropriate land and water use. This so-called 'millennium' drought (Whitaker 2005, p.220) is now being compared to the historic Federation drought that started in the mid-1890s and caused so much hardship and resource damage (Anon 1901, Gibbs and Maher 1967, Condon 2002, McKeon et al. 2004).
Adding to this very public debate on what to do in response to current and projected rainfall deficits are global images of the damaging impact of climate variability on human survival, global economies, and the infrastructure of civilisation (for example, drought and famine in Niger, extreme rainfall in India, increased frequency of hurricanes in the Gulf of Mexico). The combination of these local and global images, and the immediate experience of limited water availability in rural and urban communities, raises two major public issues.
- How much of the current variability is due to human-induced effects (global warming, stratospheric ozone depletion, aerosol concentrations, and land use change) in contrast to expected variability resulting from natural fluctuations of the global climate system?
- What planning and infrastructure investment should occur to manage for both a possible repetition of historical climate variability and future projected climate changes?
In the case of global warming, the debate extends to global initiatives recognising the importance of reducing greenhouse gas emissions, and the political, social and technical difficulties of achieving these emission targets. Politically, the two issues are inter-related. The relative attribution of current climate trends and extremes (such as Karoly and Braganza 2005) to 'natural' or 'human-induced' causes should influence the urgency for planning, and community support for mitigation of greenhouse gas emissions.
Even more explicit climate-related questions for public administration of government funding are being posed: how often should 'drought' be declared; how to define 'Exceptional Circumstances'; what is the appropriate level of government financial support to the agricultural community; when should local government impose restrictions on urban water use; and what government support should there be for investment in infrastructure to deal with rural, industrial and urban water needs? Although the answers to these explicit questions are outside this commentary, these issues provide examples of the application of climate science to support improved adaptation to climate variability and climate change. Fundamental to answering these questions is the development of climate literacy that is based on: (1) the emerging understanding how the climate systems work; (2) knowledge of historical climate variability; and (3) plausible projections of future climate variation. To this end, climate science is playing a major role in informing the public and decision makers (see, for example, Power et al.2005 and Box 2).
Various responses to climate variability (mainly rainfall deficits) have been supported at different times over the last two hundred years of settlement in terms of land use policy, choice of agricultural enterprise and infrastructure investment. The public and government responses—of (1) 'defending' current land use and communities against the extremes of climate (drought, flood, cyclone damage, heat waves), and (2) 'investing' in new enterprises and closer land settlement—have developed and supported the nation. The alternative responses of 'doing nothing' or 'retreating' have, in the past, been unacceptable to community expectations and a national ethos of expansion and development. For example, the option of pastoralists 'retreating' from western New South Wales following the drought episode of the early 1940s (Beadle 1948) was, in the words of the time (post-war), regarded as 'defeatist'. Similarly recent public suggestions that unspecified areas should be withdrawn from current land use (Cullen 2005) have provoked widespread debate. Despite the emotion and pain involved, history indicates that 'retreat' will be inevitable where rainfall deficits continue, and that the continued support for inappropriate land use will result only in further land degradation (e.g. Condon 2002, McKeon et al 2004).
Climate variability and change are not the only drivers affecting the viability and performance of agricultural enterprises. The review of historical degradation and recovery episodes in Australia's rangelands (McKeon et al.2004) highlighted how the coincidence of declining commodity prices with high variability in rainfall (at decadal time scales) damaged grazing enterprises and their natural resource base. Nelson et al. (2005, p. 171) developed an index to assess 'the vulnerability of Australian farm households to structural adjustment' defined 'as their relative exposure to external events, and their internal capability to cope with external events as they occur'. Examples of external trends include declining terms of trade and climate variability. Using ABARE farm survey data, they assessed the multiple dimensions of a 'vulnerability' index, namely human, social, natural, physical and financial. They found that 'farming in a harsh environment' does not necessarily lead to a high score on the vulnerability index, indicating that 'appropriate farming systems can effectively manage the risks associated with a highly variable, low rainfall climate so long as they have adequate scale' (Nelson et al.2005, p. 178).