The IPCC Third Assessment report (2001) concludes that Australia has significant vulnerability to the changes in temperature and rainfall projected over the next decades. Climate change will add to the existing pressures on Australia's grape and wine industry sector. Vineyards have a life of thirty plus years so urgent consideration of the changing climate is prudent for this industry.

Expected shifts in annual average temperature between present day and the year 2030 will be in the order 0.2 to 1.1°C in many of the Australian viticulture areas. By 2050 the projected increase in annual average temperature in these areas is 0.4 to 2.6°C. Projections uncertainty is covered in this spatially sensitive, continental scale, impact study by including a range of greenhouse gas emission scenarios, climate sensitivity levels and global and regional climate models.

Projected impacts on grape vine phenology have been modelled for six representative wine growing regions. Impacts to budburst day vary from region to region. Cabernet Sauvignon budburst in Coonawarra is earlier by 4 to 8 days in the year 2030, and 6 to 11 days by 2050. Some regions may be adversely affected by the chilling requirement not being met in future warmer climates. For instance in Margaret River the budburst is later. Season duration (from budburst to harvest) is compressed in all regions studied and harvest is earlier in most cases. Given the highest warming scenario, harvest could be 45 days earlier in the Coonawarra by 2050. Not only is the harvest earlier in the season and therefore in a warmer period, but it is in a warmer projected climate. There is a ‘double’ warming impact due to the earlier harvest. This affects the wine industry in that harvesting in warmer temperatures can negatively impact grape quality.

A model is created that determines the impact of climate change on the quality of grapes (found to be variety specific) in a particular region. These regional impacts can be scaled to the national level by summing the production-weighted cost to quality across each region. Overall, projected greenhouse gas induced climate change will negatively impact grape quality for the Australian wine industry. Grape quality will be reduced nationally by 7 to 23 percent by 2030 and 12 to 57 percent by 2050 (we assume that no adaptive strategies are implemented).

Impact on vineyard gross returns identify some regions as winners and some as losers. The regions producing the bulk of Australian wine tend to have reductions in production value ($/ha), as well as quality, with projected warming. In 2030 the impact range is between 4.5% to 16% decreased gross returns (nationally). By 2050 the impact is between 9.5 to 52% decrease in gross returns (assuming other no adaptive strategies are implemented).

Varietal suitability may change in future. Overall a southward and altitudinal shifting of suitability will result from projected climate change. The area available in Australia for cool variety grape growing could be severely reduced. In fact, if the overall quality of grapes is to remain equivalent to that of the present day, the area suitable for viticultural production may reduce by 40% by the year 2050.

Climate model variation reduces certainty of rainfall projections, but it is likely we are heading for a higher degree of aridity in future climates. Preliminary results of rainfall and evaporation projections indicate future increased irrigation requirements for all but one region.

Thesis URL: http://eprints.infodiv.unimelb.edu.au/archive/00003030/