Known for its expansive glaciers and the coldest temperatures on Earth, the Antarctica of today is a far cry from its tenure as a subtropical paradise 53 million years ago, replete with palm trees, summer highs near 25°C (77 F), and frost-free winters sitting near 10°C (50 F) despite the endless darkness.

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Describing a recent study lead by Jörg Pross, Jason Palmer writes about the anomalous warm bubble known as the Eocene, noting that soaring atmospheric carbon dioxide levels drove the global average temperature to increase by 5°C.

Drilling into an offshore site near Wilkes Land, a part of eastern Antarctica that lies south of Australia, Pross and his team collected sediment from deep below the sea floor that was laid down and subsequently buried over the past 53 million years. In that ancient material, says Palmer, the researchers found “pollen and spores and the remains of tiny creatures.”

With the sediment came pollen grains from palm trees and relatives of the modern baobab and macadamia.

Palmer writes that in this much-warmer Antarctica, “the lowland coastal region sported palm trees, while slightly inland, hills were populated with beech trees and conifers.”

Though scientists think the atmospheric carbon dioxide levels at the beginning of the Eocene period 55 million years ago were as high as 1000 parts per million, trumping today’s value near 400 parts per million, they’ve not quite worked out what triggered this lurch.

As to whether Antarctica will ever return to such a lush clime given modern global warming, the proposition is rather unlikely. Palmer, again:

Dr Bendle said that as an analogue of modern Earth, the Eocene represents heightened levels of CO2 that will not be reached any time soon, and may not be reached at all if CO2 emissions abate.

It’s not only carbon dioxide that needs to be taken into account, either. During the early Eocene when these palm fronds lined the shore, Antarctica and Australia were still connected at the surface. It wasn’t until millions of years later that the powerful Antarctic Circumpolar Current took shape, a strong ocean current that essentially prevents energy or heat from moving in and out of Antarctica, and one of the major reasons why the polar continent is so cold today.

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