It is amazing to think Tasmania had a near-tropical climate so recently – just 45-55-odd million years ago.

Near-tropical Early Eocene terrestrial temperatures at the Australo-Antarctic margin, western Tasmania
Raymond J. Carpenter, Gregory J. Jordan, Mike K. Macphail and Robert S. Hill

Geology, March 2012, v. 40, p. 267-270, doi:10.1130/G32584.1

Abstract

A worldwide greenhouse warm climate prevailed in the Early Eocene, and nowhere was warming more dramatic than at high latitudes. Sea-surface temperatures of ∼34 °C have been estimated for a site at paleolatitude 65°S on the East Tasman Plateau of the southwest Pacific Ocean, but these estimates require independent validation, including from terrestrial proxies.

Here we determine a near-tropical terrestrial mean annual temperature estimate of ∼24 °C at sea level for an Early Eocene site in Tasmania, Australia, using three proxies based on well-dated estuarine plant fossils. This estimate is lower than the nearby sea estimates to the east, but similarly suggests that, as in the southwest Pacific, Early Eocene climates in the eastern Australo-Antarctic region were warmer than inferred elsewhere at high latitudes, including on the Antarctic Peninsula. Such data are essential for improving our understanding of climatic and biotic evolution in the Southern Hemisphere.

As Eastern Australia including Tasmania were separating from Antarctica around 45-55 million years ago, there would have been stretching of tectonic plates and the release of magma, plus Co2. Could these events have had a local impact on climate, as does the Gulf Stream on Western Europe?