Sea-level rise may rise by 50 cm due to enhanced greenhouse gases over the next 50 years, which would put millions of people in low-lying areas at risk due to inundation. Byravan and Rajan (2005) suggest that those global citizens (most from developing countries) forced to evacuate their homelands be taken in as permanent immigrants by developed countries, since industrialized countries have accounted for most of the enhanced greenhouse gases currently in the atmosphere. They recommend that the number of "climate-change exiles" to be taken in by a host country be in proportion to that country's contribution to greenhouse gas emissions. The authors calculate that by 2080 50 million to 200 million people will be displaced and that based on accumulated emissions, the US has an obligation to provide a permanent home for about 750,000 climate-change exiles.
Reference
Byravan, S. and S.C. Rajan, 2005: Immigration could ease climate-change impact. Nature, 434, 435.