I have previously posted comments about this paper, published in the Journal of Quaternary Science that provides evidence for the generally cooler period known as the Little Ice Age being a global phenomenon rather than being limited to the Northern Hemisphere:
Five centuries of climate change in Australia: the view from underground
Henry N. Pollack 1 *, Shaopeng Huang 1, Jason E. Smerdon 2
1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA
2Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
Published Online: 27 Sep 2006
palaeoclimate • borehole temperatures • Australia
Summary and conclusions
We have analysed 57 borehole temperature profiles from across Australia to reconstruct a ground surface temperature history for the past five centuries. The five-hundred-year reconstruction is characterised by a temperature increase of approximately 0.5 K, with most of the warming occurring in the 19th and 20th centuries. The 17th century was the coolest interval of the five-century reconstruction, perhaps representing a muted expression of the Little Ice Age widely observed in the Northern Hemisphere. Because most of the boreholes were logged prior to 1976, the observed subsurface temperatures do not show the strong warming experienced by Australia in the last two decades of the 20th century. Comparison of the geothermal reconstruction to the high-quality Australian annual SAT (Surface Air Temperature) time series in their period of overlap shows excellent agreement. The full geothermal reconstruction also shows excellent agreement with the low-frequency component of dendroclimatic reconstructions from Tasmania and NewZealand. The warming of Australia over the past five centuries has been about two-thirds that experienced by southern Africa, and only about half that experienced by the continents of the Northern Hemisphere in the same time interval.
This paper provides evidence for different regional responses to global climate change and illustrates the fact that the world has warmed since the end of the LIA, with half of the warming occurring in the 20th century.