Recent apparent changes in relationships between the El Niño - Southern oscillation and Australian rainfall and temperature

High quality historical temperature and rainfall data sets have been used to produce time series of annual rainfall and temperature, averaged over Australia. The relationships between these series, and with the Southern Oscillation Index, have been examined. A change in the relationships between the variables appeared in the early 1970s. Since then, for any value of the SOI or rainfall, maximum temperature has tended to be higher than previously. Likewise, rainfall, for any value of the SOI, has tended to be greater than would have been expected for such an SOI value in previous years. Artificial changes, such as changes in instrumentation, seem unlikely to account for these observed changes in relationships. Model experiments have duplicated some of the changes in the relationships. Increased Indian Ocean temperatures may be the causal factor underlying these changes.