Sea level rise
"The seas will rise, engulfing their ports and cities in the future. It will be a human need and calamity on a scale never seen." [1]
"“The seas will rise. Within the next century and a half, they will rise over a hundred feet. Where are you going to live? What will happen to your ports and cities and your prime farmland? What will happen to the deltas of the world and the millions who live there? Who will take them in when they must flee their nation, unable to survive there any longer? It is this you must consider. Look at a map of the world and see what will be lost. The majority of the major cities of the world will be flooded and will not be able to be protected.” [2]
"The coastal cities and ports of the world could be flooded in 30 years." [3]