During Al Gore's movie - An Inconvenient Truth, he proposes a rise in sea levels of approx 7 feet. In the not too distant future, and with some degree of likelihood. It might not happen, and it might not sound like a lot but consider this....
Gore suggests that much of Manhattan would be underwater, including the site of the World Trade Centre memorial.
As an aside for us golfers, my reckoning is that a tiny bit of the Jubilee and New courses at St. Andrews would remain above this new level, but that the rest, including the entire Old Course would be underwater.
Matthew