Please note that both the Greenland and Western Antarctic ice sheets are of concern. Recent NASA gravity measurements have indicated that both ice sheets have started to disintegrate. The rate of disintegration is likely to be non-linear and is not easily predicted. According to NASA's J. Hansen, scientific reticence prevented any account for this phenomenon being included in the IPCC sea level rise estimates.

http://www.iop.org/EJ/article/1748-9326/2/2/024002/erl7_2_024002.html

Hansen estimates if the rate of sea level rise due to ice sheet disintegration is 1 cm between 2005 and 2015 and doubles every 10 years, that sea levels will rise by 5 meters by the end of this century.

Subsidence in many low elevation areas adds to the potential effects. USGS circular 1182 describes subsidence in Southern Florida and the subsidence of much of the gulf coast area is discusses at:

http://www.agu.org/report/hurricanes/subsidence.html

A combination of subsidence, the sea level rise effects (ocean temperature increase and glacier melting) included in the IPCC report, and the early part of a nonlinear collapse of the ice sheets could lead to an increase in sea level of 0.5 to 1 meter or more by mid century.

Near the mouth of the Chesapeake Bay (my home), the lower number is likely to occur, but that would still be significant for many low lying areas. The effects of sea level change and subsidence on the Chesapeake Bay are discussed (and illustrated) by the US Geological Survey.

http://pubs.usgs.gov/fs/fs102-98/