If it's hard to stop rising water from causing massive damage during a temporary storm surge in a single location, think of how hard it would be to prevent rising sea levels from wreaking havoc all around the world at the same time. Thankfully it wouldn't happen as fast as during a storm, but that's a small consolation considering how many vulnerable cities and ecosystems are in coastal regions.
Yet that could very well be what we'll have to deal with. The last Intergovernmental Panel on Climate Change (IPCC) report contains scientists' best estimates so far on how much sea levels could rise over the remaining decades of the 21st century. There's a lot of incertitude about the future, but the worst case scenario is not pretty and it seems like every time we improve our estimates, they get worse...
[Scientists] concluded there was a one in 20 chance that the melting ice would drive up sea levels by more than 84 centimetres, essentially saying there's a 95% chance it wouldn't go above this figure.
While ice melt is a major contributor to the height of the seas, there are other important factors especially thermal expansion caused by the warming of the waters.
This is estimated to be raising sea levels by 3 millimetres every year. Taken together with the ice melt estimate, the scientists say the overall, maximum impact on the seas by 2100 will be a rise of 69 centimetres - just ten centimetres higher than the IPCC projection in 2007, termed AR4. (source)