Comment by Y-bar

> At some point widespread desalination is probably inevitable, but that requires a lot of energy.

This might be true, but desalination is not without it's own externalities (not counting energy usage). The primary one I am thinking of is the increase in salinity and heat in the local area killing sea life. These issues may be possible to avoid with limited use of desalination today, but a significant increase in volume may reach a point where things like dilution and cooling by mixing does not have the desired effect.