Effect of potential atmospheric warming on temperature based indices describing Australian winegrape growing conditions

Background and Aims: This paper describes the changes in temperature based indices used to classify viticultural climates in Australia for three warming scenarios produced by the CSIRO: Mk3.0 global climate model for the years 2030, 2050 and 2070.Methods and Results: Temperature indices that describe grapevine growing season temperature, ripening period temperature, accumulated biologically effective degree days and growing season length were calculated to produce maps of Australia for each warming scenario. Summary statistics of each index's median and range are presented for each Australian wine region under each warming scenario. The greatest change in growing season temperature (above the 1971-2000 mean) was modelled to occur for the Perth Hills region, increasing by 1.0°C by 2030, 1.9°C by 2050 and 2.7°C by 2070. The least change in growing season temperature was modelled to occur for the Kangaroo Island region, increasing by 0.5°C by 2030, 0.9°C by 2050 and 1.3°C by 2070.Conclusion: Of the 61 recognised wine regions, a median growing season temperature of over 21°C (an indicator of the limit of quality wine grape production conditions) was found for 3 regions for the period 1971-2000, for 8 regions for the 2030 scenario, 12 regions for the 2050 scenario and 21 regions for the 2070 scenario. Significance of the Study: Without appropriate adaptations, some established viticultural regions of Australia may become less suitable for quality winegrape production, whereas regions that were once considered unsuitable for quality winegrape production may become more suitable.