370 scientists from 27 countries around the world spent last winter on the first ship of its kind (research vessel) ever to remain mobile in the Arctic during the winter season. What they found was that Arctic sea ice is decaying "…much faster than their most pessimistic models predict". ( The Winnipeg Free Press Interview says this quote is from Dr. David Barber, University of Manitoba and lead Principle Investigator for the research mission.) In other words, their most pessimistic model is the worst-case scenario, so Arctic sea ice is decaying much worse than the worst-case scenario. Our understanding of the polar amplification effect and the actual ongoing decay of Arctic sea ice has changed radically in the last five years. Just after the turn of the century, scientists still understood that it would likely be much closer to the year 2100 before we saw ice free conditions in the Arctic. The consensus position today is between 2013 and 2030 (see here and here and here). Snow and ice are very important temperature regulators on Earth. Snow reflects almost all of the sun’s energy harmlessly back into space. Open water absorbs almost all of the suns energy and keeps it here on Earth as heat, where it can melt more ice, etc., etc.
Another major find published in December in Geophysical Research Letters shows a big mistake in the Arctic sea ice melt. Satellites are not correctly reporting rotten multi-year ice. What was reported by the satellites as solid multi-year ice or thick first year ice was in fact rotten multi-year ice, with low strength and as much as 25% open water in between flows. The paper says that the satellites see the two similarly, but that is a little hard to understand and is obviously rooted in a much more complicated understanding of how the satellite works. What the authors say is that even though we have had a slight increase in summer sea ice extent for the last two years, giving the overall impression that Arctic sea ice is recovering, the new results show that the ice conditions in the Arctic are in fact still declining. The important thing to understand about Aortic sea ice is how much multi-year ice is there. the mulit-year ice does not melt in summer. It is the open water in the summer time that contributes so highly to the feedback. The difference in reflectivity between ice and open water is nine times. This is one of those unstoppable things. It is unstoppable once it starts, barring some fantastic effort by the people of this planet to reverse the warming trend to a point some amount cooler than when Arctic Sea ice was stable. we can not just return conditions back to the stability point because we have all of this extra heat that has been added to the system that must be removed before stability can be regained.
Barber, D. G., R. Galley, M. G. Aspin, R. De Abreu, K.-A. Warner, M. Pućko, M. Gupta, S. Prinsenberg, and S. Julien (2009), Perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009, Geophys. Res. Lett.