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Cover: This image of glaciers on Canada's Ellesmere Island was taken 31 July 2000 using the Advanced Spaceborne Thermal Emission and Reflection Radiometer as part of an international project to map the extent of Earth's glaciers and the rates at which they are changing. To learn about those and other changes in the Arctic over the past few decades, turn to Josefino Comiso and Claire Parkinson's article on page 38. (Image courtesy of the University of Alberta, NASA's Goddard Space Flight Center, the US/Japan ASTER science team, and the Japan Aerospace Exploration Agency.)
