If all Greenland’s ice melts, sea levels would rise by 7m (23 ft) which would have a major impact throughout the world. The melting caused by global warming is happening faster than expected.

It is estimated that the average temperature in Greenland needs to rise by only 3°C to melt the whole Greenland ice cap. Because, for various reasons, surface temperature is increasing twice as fast in the Arctic as at lower latitudes this is equivalent to a global average rise of about 1.5 °C. A global rise of 1.5°C by the end of the 21st century appears very likely even if manmade greenhouse gas emissions stopped tomorrow. Estimates of how long complete melting of the ice would take range from a few thousand years to a century or less depending on the dynamics of how the melt waters penetrate the ice and lubricate it at its base thereby speeding the flow of ice to the sea. In any event, if all Greenland’s ice melts it would raise sea levels by 7m (23 ft) and this would cause catastrophic coastal flooding world wide. Based on today’s population size and distribution, it would displace around half a billion people.

When ice sheets have been destabilised in the past, from smaller climate ‘forcings’ than humans are currently causing by global warming, sea level rises at rates of up to 3-5 meters per century have occurred. Today the rate of sea-level rise is less (only around 0.3 metres per century) but appears to be increasing. Scientists have recently shown that the loss of Greenland ice has accelerated over the last decade. They predict that this rate of loss could lead to sea level rises of 1 m or more by the end of the century, which is up to three times more than the average predicted by the International Panel on Climate Change (2007).

Whether green is an erroneous transcription of grunt ("ground"), which refers to shallow bays, is not known. The south-western portion of Greenland (not covered by glaciers today) is green in the summer and may have been even greener during warmer periods in the past when human habitation was more extensive.