Mr. Scott, the oceans have risen about 4 inches in the last 150 years.  American buildings last for some decades and then are replaced.  Any towns in danger of flooding would use the natural cycle of replacement to move inland.  The migration stuff is pure speculation.  Today there is variation of mean temperature with latitude.  We do not see mass migration from equatorial regions to cooler higher latitude locations.  
But none of this addresses the core issue of the impact of 8 billion humans on a small world.  Folks can wring their hands about global warming till the cows come home, but the reduction in standard of living necessary to impact CO2 growth is unacceptable to most.  This includes those here who bemoan global warming.  We see little personal choice toward CO2 reduction.  It is the people not the government who must change. Start a solar energy non-profit and build a plant.