 However, it is probable that by then global warming and possibly Asian aerosols were influencing Australia's climate and thus these are "not" natural variability, which the record 1950 rainfalls above undoubtedly are.Using a normal distribution one can estimate the return period of 1950-level annual rainfall for the Dubbo region as around 375 years, or about three times the length of instrumental rainfall data.For areas even a little further west, however, the skewness is too high to use this method, but there can be little doubt that the return periods are similar.