A structural time series approach to the reconstruction of Tasmanian maximum temperatures

Structural time series modelling was applied to the problem of reconstructing maximum temperatures from three regional Phyllocladus aspleniifolius tree-ring data sets from Tasmania, Australia. The resulting maximum temperature reconstructions span the past 190 years, and show considerable improvement over reconstructions produced by the more traditional technique of Principal Component regression. Reconstructions covering the period 1810–1990 reveal increased amplitude in all three time series in the 20th as compared to the 19th century. Consistency between reconstructions also decreases in the 20th century. Such changes are suggestive of differences in atmospheric circulation patterns of the two centuries. At a general level similarities between the Phyllocladus aspleniifolius and the much publicised Lagarostrobos franklinii reconstructions are apparent. However, some significant differences exist between the two, and are most likely attributable to biological differences between species and to the higher elevation of Lagarostrobos franklinii tree-ring sites.