NASA has been monitoring and measuring world's sea levels for some years and found out that in the 20th Century sea level rise was about two millimeters per year. They claim that only a quarter of this was due to expansion caused by warming of the oceans.
"We've found that the largest likely factor for sea level rise is changes in the amount of ice that covers Earth. Three-fourths of the planet's freshwater is stored in glaciers and ice sheets, or about 220 feet of sea level," said Dr. Eric Rignot, Principal Scientist for the Radar Science and Engineering Section at NASA's Jet Propulsion Laboratory.
The latest sea level research found that from 1993-2005 sea levels rose with an average of three millimeters a year. Read more about the sea level research at Physorg