There is strong evidence that global sea level is now rising at an increased rate and will continue to rise during this century.
While studies show that sea levels changed little from AD 0 until 1900, sea levels began to climb in the 20th century.
The two major causes of global sea-level rise are thermal expansion caused by the warming of the oceans (since water expands as it warms) and the loss of land-based ice (such as glaciers and polar ice caps) due to increased melting.
This image is NOT from the (excellent! informative!) NOAA site, where I found the foregoing.
But it makes you think, eh?