Fossilised pollen shows palm trees grew on Antarctica
Climate scientists have found evidence in fossilised pollen that palm trees once grew on Antarctica.
The 50 million year old samples, taken from seabed sediment, show the continent was once home to lush forest with summer temperatures reaching 21C.
CO2 levels were naturally high during the early Eocene epoch.
Scientists who worked on the research have said it carries a "sobering message" about possible effects of man-made climate change in the modern era.
Details of the research have been published in the science journal Nature.
The University of Glasgow's Dr James Bendle is one of the authors of the paper, which is part of an international research project to examine the Earth's climate during the Eocene greenhouse period.
He said: "Our work carries a sobering message. 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 anytime in Earth's history.
"The biggest threat lies in the fact that Antarctica today is covered with ice, enough to potentially raise global sea-levels by 60 metres if the continent once again reaches Eocene temperatures, which would have devastating effects all over the world."
Dr Bendle joined 36 other scientists for the 2010 Integrated Ocean Drilling Research Program, on a ship bound for Wilkes Land on the eastern coast of Antarctica.
This saw a drilling pipe dropped through four kilometres of water, to bore 1km deep into the ocean floor to collect samples of sediment.
Detailed analysis of this period was previously impossible as Eocene sediments were destroyed by glaciation or covered by thousands of metres of ice.
The sediments collected contained tiny fossils and chemicals that gave an insight on the climate at the time they were deposited.
Dr Bendle said they show an Eocene Antarctic, which was vastly different from the one today.
"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.
Researchers found fossilised pollen in the sediments, from plants that live in two different environments.
The findings show that one plant environment was a lowland, warm rainforest dominated by tree-ferns and palms.
The other was an upland, mountain forest region with beech trees and conifers.
Pollen from both environments indicates that temperatures on Antarctica reached up to 21C in summer and were warmer than 10°C even during the coldest and darkest months of the year.
Lead author Professor Jörg Pross, paleoclimatologist at the Goethe University, Frankfurt, 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."