Climate Extremes: Indicators for State of the Environment Monitoring
Australia: State of the Environment Technical Paper Series (The Atmosphere), Series 2
N Nicholls, B Trewin and M Haylock
Department of the Environment and Heritage, 2000
ISBN 0 642 19477 7
About the Technical Paper
Various indices for monitoring variations in Australian climate extremes have been developed and calculated. Considerable efforts have been expended to ensure that the data used to construct the indices were not affected by inhomogeneities likely to result in biased trends. It is feasible to calculate the annual values of these indices each year. The indices selected provide a good overview of variations in extreme weather conditions relevant to many sectors of Australian society.
Most of the trends in the various indices of climate extremes investigated were relatively weak and lacked statistical significance. The main exceptions were trends in rainfall extremes in south-western Australia and trends in temperatures over the entire Australian region especially overnight minimum temperatures, where stronger warming trends were evident. At least in the case of annual temperature, however, the strong trend simply reflected a shift in the mean, with little evidence of changes in the frequency distribution about the mean. Overall, the results presented here do not provide strong evidence of a climate becoming more extreme or variable. However, it must be stressed that, while countrywide indices may show no trend, significant changes could possibly have occurred at the regional level. Also, while the indices examined in this paper provide a good selection of indicators of extremes, they are in no way comprehensive and the possibility of changing climate variability cannot be discounted on the basis of this paper.