According to a study published in the journal Nature, the frozen continent was home to a "near-tropical" rainforest 52 million years ago, when temperatures measured about 68 degrees Fahrenheit.
The sediment found in the Antarctic seabed may be more relevant during a summer when drought, record heat and violent storms are being connected to climate change trends.
"It shows that if we go through periods of higher CO2 in the atmosphere it's very likely that there will be dramatic changes on these very important areas of the globe where ice currently exists," study participant Kevin Welsh told AFP. The Australian scientist was on the 2010 expedition that brought up fossil-rich sediment from Wilkes Land on the east coast of Antarctica. "If we were to lose a lot of ice from Antarctica then we're going to see a dramatic change in sea level all around the planet," he said.
Even a small rise in sea levels could swamp major coastal cities from New York to Hong Kong.
University of Glasgow scientist James Bendle said in the London Evening Standard that the sediment samples "are the first detailed evidence we have of what was happening on the Antarctic during this vitally important time."
Noting that the drilling expedition worked through "freezing temperatures, huge ocean swells, calving glaciers, snow-covered mountains and icebergs," Bendle said, "It's amazing to imagine a time-traveler, arriving at the same coastline in the early Eocene, could paddle in pleasantly warm waters lapping at a lush forest."
The study found that sediment cores were studded with pollen from two different environments much warmer than present-day Antarctica. There was evidence of palms, ferns and other trees typical of warm, lowland rainforests like that of Madagascar. There were also samples from beech trees and conifers of the kind found in mountain forest regions.
Scientists involved in the study warned that Antarctica could become ice-free again. Already, rising levels of carbon dioxide, or greenhouse gases, and other environmental factors have led to reports of melting ice and regional warming.