TEMPERATURE

2009 was Australia's second warmest year since high quality records began in 1910 and was marked by record-breaking heatwaves, extreme bushfires and dust storms. Record maximum temperatures in parts of Victoria were a major contributing factor in the Black Saturday bushfires on and around 7 February 2009.

2009 also marked the end of Australia's warmest decade on record. The mean temperature anomaly for the decade was 0.48^oC above the long term average (1961-90). Since the 1940s each decade has been warmer than the preceding decade, indicating a shift to a long term trend to warmer temperatures. There is a clear upward trend in the number of hot events, and a downward trend in the number of cold events from 1960 (BOM 2010a).

While climate change can occur naturally, there is now widespread belief that global warming over the last half century is very likely the result of human activity, specifically the emission of greenhouse gases into the atmosphere. Australia has warmed by 0.9^oC since 1950, and the average temperatures are projected to rise by a further 0.6 to 1.5 degrees by 2030, and by 1 to 5 degrees by 2070, depending on rates of greenhouse gas emissions. Different regions of Australia are expected to experience different rates of warming, with northern and inland areas most likely to experience greater warming (CSIRO 2009b).

Apart from increasing risks of bushfires and heat related illnesses, higher temperatures have other important impacts, such as increased water demand for agriculture in response to higher evaporation rates, and major peaks in electricity demand in summer.

Two-thirds of Australian homes now have coolers (mainly air conditioners) (ABS 2008a). In the summer of 2008-09, peak electricity demand was significantly higher than the peak winter demand because of greater use of air conditioners during hot days. Catering for major spikes in electricity demand requires expensive additional generating capacity and, in extreme weather conditions, electricity utilities may have to interrupt power supplies to customers to balance supply and demand (AER 2009).

Over the longer term, continued global warming would accentuate such problems and introduce major new challenges such as rising sea levels which will threaten low-lying coastal areas with inundation, mosquito-borne illnesses spreading southward, and increased coral bleaching in the Great Barrier Reef (CSIRO 2009b).