Roughly 50 million years ago, palm trees once swayed on the green shores of Antarctica, while temperatures soared above 20C, recent discoveries have revealed.
In order to collect proof of the continent's tropical heritage, scientists undertook an epic expedition, drilling a kilometre into the ocean floor to collect samples of fossilised pollen that have lain undisturbed for millions of years since the Eocene epoch.
During that time – between 48 and 55 million years ago – high levels of greenhouse gas in the atmosphere forced up temperatures, with the UK being roughly 15C warmer than it is today and a steaming rainforest covering the site of London.
It's amazing to imagine a time-traveller, arriving at the same coastline
Dr James Bendle, from the University of Glasgow, said that the crucial samples are the first detailed evidence of what was happening on the Antarctic during this "vitally important time" of Earth's history.
He said it was a strange contrast to discover the continent's balmy past amidst "a backdrop of freezing temperatures, huge ocean swells, calving glaciers, snow-covered mountains and icebergs.
"It's amazing to imagine a time-traveller, arriving at the same coastline in the early Eocene, could paddle in pleasantly warm waters lapping at a lush forest," he said.
Pollen found in the sediment cores showed two past environments – one being a lowland, warm rainforest, dominated by tree-ferns, palms and trees, and the other an upland, mountain forest region with beech trees and conifers.
Pollen from both regions would have been washed, blown or transported by insects onto the shallow coastal shelf where it would have settled in the mud and been preserved for 50 million years.
However Dr Bendle added that the exciting discoveries carry a "sobering message."
The new knowledge of past "greenhouse" conditions will enhance guesses about the effects of increasing CO2 levels today, providing a startling glimpse of what could be in store for the world in centuries to come if global warming continues unchecked.
He said: "Carbon dioxide levels were naturally high in the early Eocene, but today CO2 levels are rising rapidly through human combustion of fossil fuels and deforestation.
"We haven't reached Eocene levels yet but we are increasing at a rate faster than any time in Earth's history – atmospherically speaking, we are heading rapidly back in time towards the Eocene."
The scientist added that the biggest threat lies in the fact that Antarctica today is covered with ice which could potentially raise global sea-levels by 60 metres if the continent once again reached Eocene temperatures, leading to "devastating effects all over the world."
If temperatures in Antarctica ever became as warm again, sea levels could rise 60 metres (197 feet), swamping major coastal cities such as New York, Sydney and Hong Kong.
Similarly, top author Professor JÃrg Pross, from Goethe University in Frankfurt, Germany, said: "If the current CO2 emissions continue unabated due to the burning of fossil fuels, CO2 concentrations in the atmosphere, as they existed in the distant past, are likely to be achieved within a few hundred years."