Learn why the presence of 50-million-year-old petrified tree stumps and a variety of semiaquatic animal fossils on Canada's Ellesmere Island suggests that the Arctic was once warm swampland in these videos from NOVA: Polar Extremes. This region, about 800 miles from the North Pole, was once covered with freshwater vegetation and inhabited by creatures commonly associated with a warm, humid climate. Use this resource to examine the types of evidence that scientists use to support their understanding of Earth's climate history.