Doubly threatened: Ice caps and sea levels
As the world heats up, the sea levels are rising. Many experts warn that dramatic sea-level rise is global warming's biggest danger. Two main factors are behind this: thermal expansion of the ocean and melting Ice. First, as the ocean gets wanner from global warming, its volume expands. This is basic science: water expands as it heats up. Thermal expansion has raised the oceans about 10 to 20 centimeters (4 to 8 inches), according to the International Panel on Climate Change (IPCC).