As the climate warms, sea ice and the ice sheets in Greenland and the Antarctic continue to melt. These and other factors lead to increases in sea level and further warming of the Earth. Climate change will manifest in many many ways, including changes in weather patterns and more extreme weather events.
For some, though, rising sea levels may leave them underwater, Michael Mann said in an interview with The Guardian earlier this month.
See the disappearing islands >
According to the EPA, global sea level has risen by eight inches since 1870. This change is already affecting many low lying islands that have had to adapt. Some populations are moving to higher areas, or are trying to buy land from other countries to migrate its citizens, and some have even developed new ways of farming to protect their agriculture.
2007 estimates from the Intergovernmental Panel On Climate Change's most conservative estimates suggest that global sea level will reach increase 8 to 16 inches above 1990 levels by 2090. The National Academy of Sciences predictions from 2009 suggest that by 2100, sea level could increase by anywhere from 16 inches to 56 inches, depending how the Earth responds to changing climate.
See the islands and how they are coping with rising sea levels.
Kiribati
The president of Kiribati, Anote Tong, is in talks with Fiji's military government to buy up to 5,000 acres of land in order to relocate the 102,697 people that live in his country.
President Tong tells The Telegraph that this is their last resort: "Our people will have to move as the tides have reached our homes and villages."
Kiribati is about halfway between Hawaii and Australia and is made up of 32 low-lying atolls and one raised island. Most of its population has already moved to one island, Tarawam, after the rest of their land disappeared beneath the ocean.
Villagers on Abaiang, one of the Kiribati Islands, had to relocate the entire village of Tebunginako because of rising seas and erosion. 
Maldives
The Maldives, consisting of over 1,100 islands to the west of India, is the world's lowest-lying nation. On average the islands are only 1.3 meters above sea level. The 325,000 (plus 100,000 expatriate workers who are not counted in the census) residents of the islands are threatened by rising sea levels.
A documentary called The Island President tells the story of President Mohamed Nasheed of the Maldives as he confronts the rise of the sea level in his country. A rise of just three feet would submerge the Maldives and make them uninhabitable.
Seychelles
Seychelles consists of 115 granite and coral islands in the western Indian Ocean, with a population of 87,122.
Scuba diver Micheal Espron tells The National: "The water used to be farther out. Soon, the water will be right up into the hotel."
He also says that tourism will be affected when there are no beaches left around the islands. Locals remember that there used to be much more land for people, but now tourists are seen cramming into the small area of beaches that remain. 
A rise of just three feet would submerge the Maldives and make them uninhabitable.
See the rest of the story at Business Insider