8. 'If the polar ice caps completely melted' - 'London? A memory. Venice? Reclaimed by the Adriatic Sea. Thousands of years from now, in this catastrophic scenario, the Netherlands will have long since surrendered to the sea, and most of Denmark will be gone too...The entire Atlantic seaboard would vanish, along with Florida and the Gulf Coast. In California, San Francisco's hills would become a cluster of islands and the Central Valley a giant bay.'

(National Geographic © September 2013 National Geographic Society / Full source info here)

'It's not clear precisely when the polar ice caps will melt completely. But if and when they do, sea levels will rise by 216 feet. This map shows what the world would look like then. Given how many people live near coastlines today, that's not good.'