Applying the Rhoades and Salinger Method to New Zealand’s “Seven-Station” Temperature Series
There is recent renewed interest in the accuracy of long-term trends in New Zealand temperature records. In December 2010, NIWA published a report documenting temperature adjustments for site changes at seven locations across the country, and derived an average “seven-station” New Zealand warming trend of 0.91°C per century over the period 1909 to 2009. This report updated temperature adjustments that had previously been based on a methodology published in Rhoades and Salinger (1993). Some controversy surrounding the effect of the different adjustment methods in 1993 and 2010 is the motivation of this paper. A number of examples are provided of the application of the Rhoades and Salinger method, and its strengths and weaknesses highlighted. A key conclusion is that four years before and after a site change is the minimum period that should be used when estimating an adjustment, in order to ensure both reasonable stability and statistical significance of the estimate.