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.
http://discovermagazine.com/galleries/2014/dec/sink-or-swim#74686
Watch a fascinating NOVA episode called "Extreme Ice":