TRAPPING OF HEAT by the atmosphere is a natural phenomenon that has been occurring ever since the atmosphere formed billions of years ago. However human activities since the Industrial Revolution in the mid-eighteenth century have increased the concentrations of 'greenhouse gases' in the atmosphere. Current carbon dioxide levels in the atmosphere are 30% higher than in pre-industrial times. Methane and nitrous oxide have increased by about 145% and 15% respectively in the same period.
According to the Intergovernmental Panel on Climate Change, the Earth may become 1.4-5.8[degrees]C warmer by the year 2100. CSIRO's climate change projections for Australia ([dagger]) indicate that our continent will warm at a slightly faster rate than the global average, reaching -0.4-2.0[degrees]C above average by the year 2030 and 1-6[degrees]C by 2070. Modelling also suggests that associated with this warming will be marked reductions in rainfall over southern and eastern Australia, more evaporation and a global sea level rise of nine to 88 centimetres.
A whole range of impacts are tied in with these changes: a marked decrease in snow in the Australian Alps; more severe tropical cyclones and storm surges; more fires; and an increase in 'moisture stress' due to reduced water availability for Australia as a whole.
This may be bad news for skiers, coastal communities and some ecosystems, but is it necessarily bad news for farmers?
According to Dr Mark Howden of CSIRO Sustainable Ecosystems, climate change may reduce the amount and the quality of produce, as well as the reliability of production and the sustainability of the natural resource base on which agriculture depends.
But in a report (1) commissioned by the Australian Greenhouse Office, Dr Howden and his colleagues argue that there are practical and financially viable options which are immediately available that can reduce the risks of negative impacts and take advantage of opportunities.
'The first requirement is that farmers accept that climate change really is happening,' says Dr Howden. 'Then they will be motivated to avoid risks, and also to look out for opportunities. Farmers are already adapting to the reduction in frost frequency that has occurred over much of Australia in the past 50 years, reducing risk of frost damage and increasing productivity.'
This positive aspect of climate change needs to be balanced with the prospect of significant reductions in growing season rainfall across the southern Australian cropping zones, coupled with higher temperatures and evaporation--a recipe for reductions in crop yields, as seen in the 2002-2003 drought.
'Of course there will always be uncertainties in future climate scenarios, because we can't predict how quickly future greenhouse emissions will rise, and we are still coming to grips with the global climate system,' he says. 'However it is certain that there will be ongoing technological, cultural and institutional change.
'This means that it is essential that we develop management systems which can adapt to change as the change happens, in effect learning as we go along,' he says.
'Seasonal forecasting will become very much more important,' says Dr Howden. 'Forecasts such as those based on El Nino, La Nina and ocean temperatures around Australia will be vital to help farmers, industry and policy makers incrementally adapt to climate change while managing for climate variability, especially when these forecasts are linked to on-ground measurements, market information, and systems modelling.'
Successful adaptation to climate change will need both strategic preparation and tactical responses, according to Dr Howden, including proven technologies to allow change to occur, as well as support for agriculturalists during periods of transition.
'Transport and market infrastructures will have to be as flexible and ready to …