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You may have heard about global warming. It seems that in the last 100 years the earth's temperature has increased about half a degree Celsius. This may not sound like much, but even half a degree can have an effect on our planet. According to the U.S. Environmental Protection Agency (EPA) the sea level has risen 6 to 8 inches (15 to 20 cm) in the last 100 years. This higher temperature may be causing some floating icebergs to melt, but this will not make the oceans rise. Icebergs are large floating chunks of ice. In order to float, the iceberg displaces a volume of water that has a weight equal to that of the iceberg. Submarines use this principle to rise and sink in the water, too. However, the rising temperature and icebergs could play a small role in the rising ocean level. Icebergs are chunks of frozen glaciers that break off from landmasses and fall into the ocean. The rising temperature may be causing more icebergs to form by weakening the glaciers, causing more cracks and making ice more likely to break off. As soon as the ice falls into the ocean, the ocean rises a little. If the rising temperature affects glaciers and icebergs, could the polar ice caps be in danger of melting and causing the oceans to rise? This could happen, but no one knows when it might happen.