By 2050 the number of people living in delta cities is set to increase by as much as 70%, experts suggest, vastly increasing the number of those at risk.
Glaciers: If the world's mountain glaciers and icecaps melt, sea levels will rise by an estimated 0.5m
Thermal expansion: The expansion of warming oceans was the main factor contributing to sea level rise, in the 20th Century, and currently accounts for more than half of the observed rise in sea levels.
Ice sheets: These vast reserves contain billions of tonnes of frozen water - if the largest of them (the East Antarctic Ice Sheet) melts, the global sea level will rise by an estimated 64m.
Rising temperatures have also caused ocean waters to expand - the main cause of sea level rise in the 20th Century.
The weakening of the Gulf Stream coupled with the gravitational effects of being closer to the North Pole mean waters in the northern hemisphere are experiencing the biggest rise.