Scientists have warned that oceans are likely to rise as much as 1.3 metres by 2100 if the Earth's surface warms another 3.5 degrees Celsius.
By 2300, ice sheets covering West Antarctica and Greenland will have shed trillions of tonnes in mass. Sea levels could then go up by more than five metres under that temperature scenario.
This will redraw the planet's coastlines reported scientists in a peer-reviewed survey of more than 100 leading experts in the international science journal, Nature.
About ten percent of the world's population today live on land less than five metres above the high tide line.
Across the 20th century, sea level rise was caused mainly by melting glaciers and the expansion of ocean water as it warms. But over the last two decades, the main driver has become the melting and disintegrating of Earth's two ice sheets.
Greenland and West Antarctica are shedding at least six times more ice today than during the 1990s. From 1992 through 2017 they lost some 6.4 trillion tonnes in mass.
The Greenland and West Antarctic ice sheets hold enough frozen water to lift oceans about 13 metres. East Antarctica, which is more stable, holds another 50 metres' worth.
Over the last decade, the sea level has gone up about four millimetres per year. Moving into the 22nd century, however, the waterline could rise ten times faster according to the UN Intergovernmental Panel on Climate Change.
While less visible than climate-enhanced hurricanes or persistent drought, sea level rise may ultimately prove the most devastating of global warming impacts.
But if humanity succeeds in cutting carbon dioxide and holding the increase in temperature to the Paris climate treaty's goal of below 2C, the rise would be a more manageable 0.5 metre.