An international team of researchers carried out discovery and analysis. They were led by Alfred Wegener of the Institute Helmholtz Centre for Polar and Marine Research in Germany, but also included researchers from Imperial College London.

Tina van de Flierdt, co-author of the study and from the department of Earth science & engineering at Imperial, said: "The preservation of this 90-million-year-old forest is exceptional, but even more surprising is the world it reveals. Even during months of darkness, swampy temperate rainforests were able to grow close to the South Pole, revealing an even warmer climate than we expected."

Climate in the mid-Cretaceous age

The study also shows that carbon dioxide (CO2) levels in the ancient atmosphere were higher than perviously thought during the mid-Cretaceous period, roughly 115 to 80 million years ago — contrary to existing climate models of the period.

The mid-Cretaceous was a time when dinosaurs reigned, which makes sense because it was the warmest period in the past 140 million years. At the time, tropical temperatures soared as high as 35 degrees Celsius (95 degrees Fahrenheit), and sea level 170 meters (558 feet) higher than present levels.

Little is known, however, about the environment of the Antarctic Circle at this distant time in Earth's history. But now, with evidence of temperate rainforests in the region, similar to ones in present-day New Zealand, there is something real to grasp.

All this through a four-month polar night, which means a third of every year in this ancient forest happened in the night, where no Sun shone on the trees. It's interesting to imagine an ancient rainforest in Antarctica, but perhaps cooler that life got by on the shady side of the Cretaceous period.

By Brad Bergan