Lack of cool, not warm, extremes distinguishes late 20th Century climate in 979-year Tasmanian summer temperature reconstruction

Abstract

Very few annually resolved millennial-length temperature reconstructions exist for the Southern Hemisphere. Here we present four 979-year reconstructions for southeastern Australia for the austral summer months of December-February. Two of the reconstructions are based on the Australian Water Availability Project dataset and two on the Berkeley Earth Surface Temperature dataset. For each climate data set, one reconstruction is based solely on Lagarostrobos franklinii (restricted reconstructions) while the other is based on multiple Tasmanian conifer species (unrestricted reconstructions). Each reconstruction calibrates ∼50−60% of the variance in the temperature datasets depending on the number of tree-ring records available for the reconstruction. We found little difference in the temporal variability of the reconstructions, although extremes are amplified in the restricted reconstructions relative to the unrestricted reconstructions. The reconstructions highlight the occurrence of numerous individual years, especially in the 15th−17th Centuries, for which temperatures were comparable with those of the late 20th Century. The 1950−1999 period, however, stands out as the warmest 50-year period on average for the past 979 years, with a sustained shift away from relatively low mean temperatures, the length of which is unique in the 979-year record. The reconstructions are strongly and positively related to temperatures across the southeast of the Australian continent, negatively related to temperatures in the north and northeast of the continent, and uncorrelated with temperatures in the west. The lack of a strong relationship with temperatures across the continent highlights the necessity of a sub-regional focus for Australasian temperature reconstructions.

Six Centuries of Upper Indus Basin Streamflow Variability and Its Climatic Drivers

“…We find that BR typically, but not always, produces slightly wider uncertainty intervals. Commonly used statistical approaches for tree ring reconstructions of past streamflow and climate include PCR (e.g., Allen et al, ; Anchukaitis et al, ; Cook et al, , , ; Palmer et al, ; Stahle et al, ), a Bayesian framework (Devineni et al, ; Luterbacher et al, ; Steinschneider et al, ; Tingley & Huybers, ), along with other statistical methods (e.g., Bracken et al, ; Gangopadhyay et al, ; Woodhouse et al, ). Our results suggest that for a one predictand variable case at the Partab Bridge gauge, both PCR and BR methods produce comparable reconstructions in terms of their estimates, uncertainties, and reconstruction skill statistics.…”

Scientific Merits and Analytical Challenges of Tree‐Ring Densitometry

“…These studies have predominantly been conducted in Australia uncovering significant climate information imprinted in various density and tracheid dimensions, for trees where ring width has been unusable (Allen et al, 2013;Drew et al, 2012). O'Donnell et al (2016) and Allen et al (2018) reconstructed temperature, and Allen et al (2015) explored stream flow in Tasmania using density data. Outside of Australia, SilviScan wood density has been used in reconstructing summer temperature (Wood & Smith, 2015) and partially involved in reconstructing Glacier mass balance (Wood & Smith, 2013) in Canada.…”

Two climate‐sensitive tree‐ring chronologies from Arnhem Land, monsoonal Australia

“…As the temperate southern and monsoonal northern regions are subject to very different climate regimes, and the roles played by the various ocean‐atmosphere processes differ between the two regions, the southern tree‐ring chronologies cannot be expected to reflect climatic variability in the north (Allen et al . ).…”