Observations of Earth's climate over the past half-century reveal a global trend in warming temperatures of land surfaces, the lower atmosphere, and the oceans. The Arctic region is warming at a rate that is at least twice that of the global average. This is particularly evident in the central Arctic, two-thirds of which is the Arctic Ocean. In contrast to the Antarctic, which is dominated by a central continent and an enormous mass of ice with an average elevation of 7,500 feet, much of the Arctic is at sea level.