 antarctica is the coldest, most desolate place on Earth, a land of barren mountains buried beneath a two-mile thick ice cap. Freezing winds batter its shores while week-long blizzards frequently sweep its glaciers.  Yet this icy vision turns out to be exceptional. For most of the past 100 million years, the south pole was a tropical paradise, it transpires.  "It was a green beautiful place," said Prof Jane Francis, of Leeds University's School of Earth and Environment. "Lots of furry mammals including possums and beavers lived there. The weather was tropical. It is only in the recent geological past that it got so cold."  Prof Francis was speaking last week at the International Symposium on antarctic Earth Sciences in Edinburgh. More than 500 polar researchers gathered to discuss the latest details of their studies, research that has disturbing implications for the planet's future. Drilling projects and satellite surveys show the whole world, not just antarctica, was affected by temperature rises and that these were linked, closely, to fluctuations in levels of carbon dioxide in the atmosphere.  "Fifty five million years ago, there were more than 1,000 parts per million (ppm) of carbon dioxide in the atmosphere," said Professor Stephen Pekar, of City University of New York. "That heated the world enough to melt all its ice caps. Sea levels would have been almost 200ft higher than today. "  at present, there are 390ppm of CO2 in the atmosphere, a rise - c 