Greenland is already losing enough ice to raise sea level by 0.8 millimetres per year (Image: Nick Cobbing) Ancient reefs in Mexico suggest the sea rose 3 metres within 100 years (Image: Paul Blanchon)

See our related editorial

FOR a few minutes David Holland forgets about his work and screams like a kid on a roller coaster. The small helicopter he’s riding in is slaloming between towering cliffs of ice – the sheer sides of gigantic icebergs that had calved off Greenland’s Jakobshavn glacier. “It was like in a James Bond movie,” Holland says afterwards. “It’s the most exciting thing I have ever done.”

Jakobshavn has doubled its speed in the past 15 years, draining increasing amounts of ice from the Greenland ice sheet into the ocean, and Holland, an oceanographer at New York University, has been trying to find out why. Scientists like him are more than a little astonished at the rate at which our planet’s frozen frontiers seem to be responding to global warming. The crucial question, though, is what will happen over the next few decades and centuries.

That’s because the fate of the planet’s ice, from relatively small ice caps in places like the Canadian Arctic, the Andes and the Himalayas, to the immense ice sheets of Greenland and Antarctica, will largely determine the speed and extent of sea level rise. At stake are the lives and livelihoods of hundreds of millions of people, not to mention millions of square kilometres of cities and coastal land, and trillions of dollars in economic terms.

In its 2007 report, the Intergovernmental Panel on Climate Change (IPCC) forecast a …