Australia: The Land Where Time Began

A biography of the Australian continent 

A 950 Year Reconstruction of Temperature from Duckhole Lake, southern Tasmania

According to the authors¹ the ability to examine current trends within the context of natural climate variability in the long-term is limited by a lack of qualitative data from the Southern Hemisphere. In this paper the authors¹ present a temperature reconstruction of the Southern Hemisphere that they based on a sediment core they obtained from Duckhole Lake 43.365^oS, 146.875^oE. The authors¹ developed a calibration-in-time reflectance spectroscopy-based temperature model by the use of the relationship between whole-core scanning, that was non-destructive, reflectance spectroscopy measurements in the visible spectrum (380-730 nm) and the instrumental temperature record (AD 1911-2000). A trough in reflectance from 650-700 nm, representing chlorophyll and its derivatives, was shown to be correlated significantly to annual mean temperature. ... A calibration model was developed and applied to and was applied down-core to reconstruct annual mean temperatures over about 950 years in southern Tasmania. Temperatures were indicated by this to be initially cool at about 1050 AD, though it increased steadily until the late AD 1100s. In the AD 1200s there was a brief cool period, after which temperatures increased again, then decreased steadily during the AD 1600s, following which they remained relatively stable until the start of the 20th century, then decreased rapidly, then from the 1960s on they increased. When comparisons are made with high resolution temperature records from western Tasmania, New Zealand and South America some similarities were found, though there were also temperature variability differences across the Southern Hemisphere mid-latitudes. According to the authors¹ these are likely to result from a combination of factors that includes spatial variability in climate between and within regions, and differences between records documenting seasonal (i.e., warm season/late summer) verses annual variability of temperature. The need for further Southern Hemisphere records from the mid-latitudes is highlighted by this in order to constrain past natural spatial  and seasonal/annual temperature variability in the region, as well as to accurately identify and attribute changes to variability that is natural and/or anthropogenic activities.

Sources & Further reading

1. Saunders, KM, M Grosjean, and DA Hodgson. "A 950 Yr Temperature Reconstruction from Duckhole Lake, Southern Tasmania, Australia." The Holocene 23, no. 6 (June 1, 2013 2013): 771-83.