Climatic change over the last millennium in Tasmania reconstructed from tree-rings

Abstract

Tree-ring widths from millennium-old Huon pine (Lagarostrobos franklinii) trees have been used to reconstruct warm season (November-April) temperatures back to AD 900 for Tasmania. The reconstruction indicates that the most recent 100 years of climate have been highly unusual, with the coldest and warmest 25-year periods occurring from 1890 to 1914 and 1965 to 1989, respectively. Although the most recent 25-year period is warmer than any comparable period over the past 1090 years, it is not yet statistically unprecedented. Some evidence for the Medieval Warm Period and the 'Little Ice Age' can be found in the reconstruction, especially during the twelfth and seventeenth centuries respectively. However, the latter is weakly expressed compared to many records from the northern hemisphere, suggesting that the southern oceans may have significantly moderated its effect on Tasmania. Regular oscillations on the order of 30, 56, 80 and 180 years in length have been identified in the reconstruction using spectral analysis. These oscillations cannot be easily linked to climatic forcing functions related to solar or volcanic activity. Thus, they are best regarded as arising from the internal dynamics of the ocean-atmosphere-cryosphere system.