The study in Nature suggests Antarctic winter temperatures exceeded 10C, while summers may have reached 25C.
The rig then drilled through 1km of sediment to return samples from the Eocene. With the sediment came pollen grains from palm trees and relatives of the modern baobab and macadamia.
Crucially, they contained also the remnants of tiny single-celled organisms called Archaea.
The creatures' cell walls show subtle molecular changes that depend on the temperature of the soil surrounding them when they were alive. The structures are faithfully preserved after they die.
They are, in essence, tiny buried thermometers from 53 million years ago.
Archaea hold on to their structure through millions of years, giving hints of long-gone temperatures
Together, the data suggest that even in the darkest period of Antarctic winter, the temperature did not drop below 10C; and summer daytime temperatures were in the 20CsWhat this means is, global warming is a natural phenomenon. Even if man is the cause this time, it does not mean it will not happen again regardless of man.