Today, about ten percent of Earth's land surface is covered by ice, in the form of glaciers, ice caps, and ice sheets. These areas of ice grow and shrink in response to changing climate. (Glaciers at the height of the last ice age, some 20,000 years ago, covered much of North America and Europe.)
At the current rate of retreat, ocean levels will continue to rise no matter what we do about CO2 levels in the future. CO2 levels would not decrease at a significant level even if we suddenly stopped burning all fossil fuels. This means that current global temperatures are enough to melt all remaining glaciers within fifty years. Continuing temperature increases will force the huge Greenland ice sheet to raise sea levels by twenty feet before this century is out. The Antarctic ice sheet is showing dangerous signs of increased ice flow.
Watch a fascinating NOVA episode called "Extreme Ice":