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2.5 Climate change

Australia's climate is changing. Changes have occurred in the past and will continue to do so in the future. Therefore, adaptation to change is unavoidable, as are the consequent changes in land use and land management. This adaptation is an essential component of sustainable agriculture. If climate change is accelerated by human activities, then adaptation will almost certainly have to be rapid, with increased risks of human suffering and environmental degradation. However, if we devise appropriate proactive strategies to adapt to climate and other environmental changes as or before they occur, then their impact will be lessened.

Global climate models are being developed within the CSIRO Division of Atmospheric Research (DAR) to model the enhanced greenhouse effect. While it is important to estimate the likely magnitude of climate change, it is also important to know what is likely to happen as climate changes. This creates a demand amongst both researchers and policy makers for estimates of regional climate changes to provide information on the possible impacts.

2.5.1 Likely impacts of Climate Change

Climate change impacts must be evaluated, a task that requires integration of research. The main objectives of DAR's Climate Impact Group are therefore:

1. to provide the best available specific regional estimates of climate change likely to be experienced in Australia, quantifying and reducing the uncertainties as far as possible, and identifying possible impact areas;

2. to provide scenario output data in the most appropriate form for use in impact studies, and to collaborate as far as possible with local or specialised groups and experts in the evaluation of such impacts.

To address the above objectives, the Climate Impact Group must critically assess all possible sources of information on future climate change. This includes historical and palaeoclimatic data, but concentrates on GCMs and limited area models. Particular attention is being paid to obtaining information at finer spatial scales, down to the small catchment scales of tens of kilometres. This requires the preferential use of higher resolution GCM results, nested limited-area models, and spatial interpolation techniques. Sensitivity studies using stand-alone limited-area models are being performed on particular synoptic events that currently are too small to be modelled in detail in GCMs.

Collaborative studies are being undertaken on a range of possible impact areas, including agricultural, hydrological and coastal impacts. Recent initiatives include the development of new climate change scenarios for Australia, and the development of OzClim, a climate scenario and impacts package for use on personal computers.

The Queensland Departments of Natural Resources and Primary Industries have been particularly active in studying adaptation to climate change. McKeon et al. (1993) suggest that adoption of new practices will require confidence that climate change can be separated from the naturally high year-to-year variability in rainfall that characterises these systems:

1. the motivation to change based on the perceived risk and opportunities of climate change;

2. development of new technologies and demonstration of their benefits;

3. protection against establishment failure of new practices during less favourable climate periods; and

4. alteration of transport and market infrastructure to support altered production.

They further propose that recently improved seasonal forecasting skill, based on increased understanding of the El Niņo/Southern Oscillation and/or the use of general circulation models in real time, can be used to adapt grassland management to climate change. By linking management decisions with respect to say stocking rate, pasture burning, forage cropping, animal supplementation and herd management to forecasts of above- or below-average rainfall, management would 'drift' in the right direction thereby adapting to a new, if uncertain, climate regime.

Given the highly variable nature of our climate, it is difficult to ascertain just what changes are likely to take place over the next 50 years. For example, the exceptionally dry period in the early 1990s over much of eastern Australia was preceded by above-average rainfall years, particularly in the 1970s. However, if one goes further back into the climate records, especially pre-European as indicated from river and lake sediments, coral cores and tree rings, one can find ample evidence of much more horrendous droughts.

There is some evidence that daily maximum, mean and minimum temperatures are increasing, but not in a uniform manner across Australia. Average minimum May temperatures have increased by 0.7ēC a decade over the past 40 years in Queensland's pastoral and cropping zone, which has significance for agriculture particularly in terms of anticipated increased growth of tropical grasses (McKeon et al. 1998).

The most probable scenario for climate change across Australia is for more extreme events in terms of droughts and flooding rains, the latter being accompanied by an increased frequency and intensity of cyclones crossing the Queensland coast. A southerly shift in our weather systems is also anticipated, the monsoonal rains and warmer weather that typifies our tropics and sub-tropics extending further south. This would be expected to be accompanied by southerly migration of tropical pests and diseases.

Specific research projects currently (or recently) being undertaken in this area include:

  • CLIMARC - Computerising the Australian Climate Archives - Mr Nick Clarkson, QCCA (LWRRDC)
  • A Century's perspective on climate variability and impacts on agriculture - Dr Bill Wright, BoM (LWRRDC)
  • Adapting to climate change on the Eyre Peninsula, South Australia, 1900-1990 - Dr Les Heathcote, Flinders University
  • Learning from history: preventing future land and pasture degradation under climate change - Dr Greg McKeon, QDNR

References

1. Gordon, H.B. (1997).Prediction of enhanced global warning. In Climate prediction for agricultural and resource management, edited by R.K. Munro and L.M. Leslie, Australian Academy of Science Conference, Canberra, 6-8 May 1997, Bureau of Resource Sciences, Canberra, pp. 69-82.

2. McKeon, G.M., Howden, S.M., Abel, N.O.J. and King, J.M. (1993). Climate change: adapting tropical and subtropical grasslands. Proceedings of the XVIIth International Grassland Congress, 13-16 February 1993, Palmerston North, New Zealand, pp.1181-1190.

3. McKeon, G.M., Carter, J.O., Day, K.A., Hall, W.B. and Howden, S.M. (1998). Evaluation of the impact of climate change on northern Australian grazing industries. Final report for the Rural Industries Research and Development Corporation (DAQ139A), 287 pp.

4. Plummer, N., Hennessy, K.J., Lavery, B.M., Nicholls, N., Page, C.M., Suppiah, R. and Trewin, B.C. (1997). Trends in Australian climate extremes indices during the twentieth century. In Climate prediction for agricultural and resource management, edited by R.K. Munro and L.M. Leslie, Australian Academy of Science Conference, Canberra, 6-8 May 1997, Bureau of Resource Sciences, Canberra, pp. 245-255.

5. Whetton, P.H., Mullan, B. and Pittock, A.B. (1994). Climate change scenarios for Australia and New Zealand. In Greenhouse: coping with climate change, edited by W.J. Bouma, G.I. Pearman and M.R. Manning, CSIRO Publishing, Collingwood, Vic. 3066, Australia, 682 pp.

6. Whetton, P.H., Rayner, P.J., Pittock, A.B. and Haylock, M.R. (1994). An assessment of possible climate change in the Australian region based on an intercomparison of general circulation modeling results. Journal of Climate 7, 441-463.

7. White, D.H. and Howden, S.M. (editors) (1994). Climate change: significance for agriculture and forestry. Systems approaches arising from an IPCC meeting. Kluwer Academic Publishers, Dordrecht, The Netherlands, 146 pp.

Contacts and institutions

Dr Hal Gordon, CSIRO Division of Atmospheric Research, PMB1, Aspendale. Vic. 3195. Ph: (03) 9239 4537; hal.gordan@dar.csiro.au

Dr Barrie Pittock, CSIRO Division of Atmospheric Research, PMB1, Aspendale. Vic. 3195. Ph: (03) 9239 4527; Fax: (03) 9239 4688; barrie.pittock@dar.csiro.au

Dr Peter Whetton, CSIRO Division of Atmospheric Research, PMB1, Aspendale. Vic. 3195. Ph: (03) 9239 4535; Fax: (03) 9239 4444; peter.whetten@dar.csiro.au

2.5.2 Greenhouse gas emissions

Components of agricultural systems act as sources and sinks of greenhouse gases, notably methane, nitrous oxide and carbon dioxide. Ruminant livestock, for example, belch up significant quantities of methane gas, whereas forest plantations can be significant carbon sinks. Many reliable agronomic models can, with only minor modification, be adapted to estimate the effects of changes in management on agricultural systems. Systems analysis approaches based around such models can therefore be used to estimate the consequences of changing management strategies on levels of emissions (Boag et al. 1994). Thus increasing stocking rates lead to higher levels of emissions. Specific examples include Howden and O'Leary (1995) for cropping systems, and Howden et al. (1993, 1994, 1996) for ruminant livestock systems. In general, it would appear that management practices that help limit greenhouse gas emissions from the agricultural sector are also more likely to be considered sustainable in terms of land management.

References

1. Barson, M. and Gifford, R. (1990). Carbon dioxide sinks, the potential role of tree planting in Australia, in Greenhouse and energy, edited by D.J. Swaine, CSIRO, Melbourne.

2. Boag, S., White, D.H. and Howden, S.M. (editors) (1994). Monitoring and reducing greenhouse gas emissions from agricultural, forestry and other human activities. Climatic Change 27, 5-11.

3. Gifford, R.M., Cheney, N.P., Noble, J.C., Russell, J.S., Wellington, A.B. and Zammit, C. (1990). Australian land use, primary production of vegetation and carbon pools in relation to atmospheric carbon dioxide concentration. In Australia's renewable resources: sustainability and global change, edited by R.M. Gifford and Barson, M.M., International Geosphere-Biosphere Programme Australian Planning Workshop, October 3-4 1990, Bureau of Rural Resources Proceedings No. 14, AGPS, Canberra, pp. 151-188.

4. Hassall and Associates (1997). Greenhouse gas implications of sustainable land management practices. Report prepared for the National Landcare Program, Department of Primary Industries & Energy, 130 pp.

5. Howden, S.M. and O'Leary, G.J. (1995). Evaluating options to reduce greenhouse gas emissions from an Australian temperate wheat cropping system. Proceedings of the International Congress on Modelling and Simulation (edited by P. Binning, H. Bridgman and B. Williams), 27-30 November 1995, The University of Newcastle, Australia, 2, pp. 45-50.

6. Howden, S.M., White, D.H. and Bowman, P.J. (1996). Managing sheep grazing systems in southern Australia to minimise greenhouse gas emission: adaptation of an existing simulation model. Ecological Modelling 86, 201-206.

7. Howden, S.M., McKeon, G.M., Scanlan, J.C., Carter, J.O. and White, D.H. (1993). Changing stocking rates and burning management to reduce greenhouse gas emissions from southern Queensland grasslands. Proceedings of the XVIIth International Grasslands Congress, pp. 1203-1205.

8. Howden, S.M., White, D.H., McKeon, G.M., Scanlan, J.C. and Carter, J.O. (1994). Methods for exploring management options to reduce greenhouse gas emissions from tropical grazing systems. Climatic Change 27, 49-70.

Contacts and institutions

Dr Michele Barson, Bureau of Resource Sciences, PO Box E11, Kingston ACT 2604. Ph: (02) 6272 4347; michele.barson@brs.gov.au

Dr Mark Howden, Global Change Research, Resource Futures Program, CSIRO Wildlife and Ecology, PO Box 84, Lyneham, ACT 2602. Ph: (02) 6242 1679; Fax: (02) 6241 2362; mark.howden@dwe.csiro.au

Dr Roger Gifford, CSIRO Division of Plant Industry, GPO Box 1600, Canberra City, ACT 2601. Ph: (02) 6246 5441; roger.gifford@pi.csiro.au

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