Cambridge professor Peter Wadhams has a prediction.
Wadhams has spent many years collecting ice thickness data from submarines passing below the arctic ocean. He predicted the imminent break-up of sea ice in summer months in 2007, when the previous lowest extent of 4.17 million square kilometres was set. This year, it has unexpectedly plunged a further 500,000 sq km to less than 3.5m sq km. "I have been predicting [the collapse of sea ice in summer months] for many years. The main cause is simply global warming: as the climate has warmed there has been less ice growth during the winter and more ice melt during the summer.
"At first this didn't [get] noticed; the summer ice limits slowly shrank back, at a rate which suggested that the ice would last another 50 years or so. But in the end the summer melt overtook the winter growth such that the entire ice sheet melts or breaks up during the summer months.
"This collapse, I predicted would occur in 2015-16 at which time the summer Arctic (August to September) would become ice-free. The final collapse towards that state is now happening and will probably be complete by those dates".
Wadhams knows more than I do, so I'll give him the benefit of the doubt on this. Normally, I'd think that this year's record melt is a blip on a longer, slower trend. Here's what the ice loss looks like over time:
It's possible that the black line, indicating the overall trend, could reach 100 percent by 2015, to be sure. 2012 could be an anomaly, or it could be the cliff's edge.