Trends in Australia's climate means and extremes: a global context

Using a standard set of annual and seasonal climate extremes indices derived from daily temperature and precipitation data, relationships between mean and extremes trends across Australia and the globe are analysed. Extremes indices are calculated using station data from Australian high-quality daily temperature and precipitation datasets and pre-existing high-quality datasets of climate extremes for the globe. Spatial correlations are calculated between the trends in means and extremes both annually and seasonally for maximum and minimum temperature and precipitation across Australia, and annually for precipitation across the rest of the globe. In Australia, trends in extremes of both temperature and precipitation are very highly correlated with mean trends. Annually, the spatial correlation between trends in extremes and trends in the mean is stronger for maximum temperature than for minimum temperature. However, this relationship is reversed in winter, when minimum temperatures show the stronger correlations. Analysis of the rate of change of extremes and means across Australia as a whole shows most stations have greater absolute trends in extremes than means. There is also some evidence that the trends of the most extreme events of both temperature and precipitation are changing more rapidly in relation to corresponding mean trends than are the trends for more moderate extreme events. The annual relationships between means and extremes of precipitation in Australia are consistent with all other global regions studied.