The National Snow and Ice Data Center (NSIDC) reports that Arctic sea ice extent continues to track way below normal, despite cool temperatures over most of the Arctic Ocean in January.

Reuters quotes NSIDC director Mark Serreze:

It’s not that the ice keeps melting, it’s just not growing very fast.
We’ve grown back ice in the winter, but that ice tends to be thin and that’s the problem. You set yourself up for a world of hurt in summer. The ice that is there is also thinner than it was before and thinner ice simply takes less energy to melt out the next summer.

With thinner, more fragile ice and less cover,

You’ve got a double whammy going on.

If Arctic ice fails to build up sufficiently during the dark, cold winter months, it is likely to melt faster and earlier when spring comes.

A Canadian research project has found that climate change is happening much faster than the most pessimistic models expected.  Models predicted only a few years ago that the Arctic would be ice-free in summer by the year 2100, but the increasing pace of climate change now suggests it could happen between 2013 and 2030. Losing sea ice has impacts on everything else that goes on in the Earth’s systems.

A new study by the Pew Environment Group estimates the financial cost  to the world economy  of a warming and melting Arctic will be at least $2.4 trillion over the next 40 years. The study looks at the “social cost of carbon,” including the cost of climate change on agriculture, energy production, water availability, sea level rise, and flooding.

By the end of January, ice extent had dropped below the extent observed in January 2007. This winter continues the recent trend of slower Arctic ice growth.

The summer Arctic sea ice melt season now lasts nearly a month longer than it did in the 1980s. A later start of freeze-up and an earlier start to the melt season both contribute to the change. A recent paper by Thorsten Markus at NASA Goddard Space Flight Center suggests that the later freeze-up is the dominant factor lengthening the melt season. The analysis shows that, on average, autumn freeze-up starts nearly four days later each decade. Extensive open water at the end of the summer melt season, combined with warmer autumns, delay the autumn freeze-up. The larger expanses of open water absorb more solar energy, and before ice can form again, that heat must be released back to the atmosphere. This trend is most pronounced in the Beaufort, Chukchi and Laptev seas.