The oceans are not rising uniformly – the Pacific, for example, will rise by 20% more than average. And while tropical islands disappear, new ones are showing up in the Arctic. Uunartoq Qeqertaq (meaning Warming Island), for example, was born in 2006, the result of the melting of an ice-bridge that formerly connected it to mainland Greenland. Groundwater extraction for fish farms in China’s Yellow River delta may be causing land to sink, with the effect that local sea levels are rising nearly 100 times faster than the global average. The atlases of the Anthropocene will have to be redrawn.
The changes could also lengthen each day by up to two-thirds of a second, because the melting of the ice caps would cause the oceanic mass to shift closer to the equator, increasing inertia and slowing the Earth’s rotation by a fractional amount.
If the ice-sheets melt rapidly – within a few decades – it will be very hard for people to adapt. Current coastal defences would be inadequate to protect our settlements from such high sea-levels. Entire cities would need to move, including power stations, administrative offices, transport hubs and millions of houses and offices. On top of this, agricultural land and water sources would be fouled by seawater incursion, hitting our food supplies. The more developed the coast, the greater the economic loss. This map shows, for example, what the US stands to lose.
People would have to move inland or to higher altitudes. Or, in the case of one New Jersey coastal town, submit plans to lift an entire downtown area several feet above its current elevation. Coastal refugees from the world's poorest countries, such as Bangladesh and Burma, would seek new homes at the same time as the richest New Yorkers and Shanghainese.
Humans are ingenious, and a variety of creative solutions will no doubt be found, such as stilted tower blocks and floating cities. For example, billionaire Peter Thiel, a co-founder of PayPal, is funding the Seasteading Institute, which hopes to create floating autonomous states. In 2008, the Institute launched a public challenge to create the world's first independent floating city by 2015. The Poseidon Award will go to the first seastead which houses at least 50 full-time residents, is financially self-sufficient, offers seastead real estate on the open market and is politically autonomous.
Bangladesh is already preparing. Several amphibious floating houses and schools are being built, so people can rise with the waters. Designs produced as part of the Low Income Flood-proof Technology project have light and buoyant foundations made of either plastic bottles, or ferrocement – a combination of cement, sand, water and wire mesh. The houses themselves are made of bamboo. They are capable of rising three feet (almost one metre) from the ground, but the architects say they could be built to be capable of dealing with higher flood levels.
In my next column I'll examine another potential global transformer. Please post your suggestions for topics on the BBC Future Facebook page.