Warmist Mark Serreze: "It might be that natural variability is larger than assumed"

Ice loss shifts Arctic cycles : Nature News & Comment

the observed downward trend in sea-ice cover suggests that summer sea ice could disappear completely as early as 2030, something that none of the models used for the next report by the Intergovernmental Panel on Climate Change comes close to forecasting.

“There’s a tremendous spread between observations and model projections,” says Serreze. “It might be that natural variability is larger than assumed, or perhaps models don’t get the change in ice thickness right.” Uncertainty also remains over the strength of various natural ‘feedbacks’. For example, an exposed ocean is darker than an ice-covered surface and so absorbs more solar heat, causing yet more warming and melting.

A lack of fine detail about circulation patterns in the Arctic Ocean could also be throwing off the models. For example, a survey carried out in 2008 revealed 20 formerly unobserved eddies, each some 15 to 20 kilometres in diameter, in waters north of Canada.
...[Berge] points out that the Arctic Ocean has been ice-free during the summer several times during the past 2.5 million years, and that as recently as 8,000–6,500 years ago, during a period known as the Holocene Thermal Maximum, much more of the Arctic was ice-free than it is today — with no mass-extinction events known to have occurred.

Farther afield, this year’s record sea-ice melt might foreshadow a harsh winter in parts of Europe and North America.