Why will the sea level rise?
In March 2014, scientists annonced that an important glacier in Antartica is melting. If the other glaciers in Antartica follow, the long term sea rise will be several meters, which will mean that entire regions will disappear (part of Holland, the plain of Venetia, Bangladesh, Florida…) and force millions of persons to migrate.
As well as glaciers melting, the second cause of sea rise is the dilatation of the ocean: hotter water occupies more volume than colder water. As the ocean is enormous, it takes a lot of time to warm up (and also to cool down), and for this reason the ocean will continue to rise after 2100.
The scenarios of the IPCC report predict an increase of sea level between 0.2 and 1 meter in 2100, but they don't take into account the possible melting of Antartica's glaciers, as this data was not available when the report was finalized. On the long term, if global warming continues, we must expect a higher sea level rise.
The maps below show the consequence of an increase of one meter in sea level - flooded zones are shown in blue :