There is great variability in ice conditions in the Canadian Arctic and perhaps in the Arctic as a region. In the years up to 2007, whatever it was, there was reduction, and suddenly a very sharp reduction, in the summertime ice coverage in the Arctic Ocean. Since then it has been increasing each year. There has been not a reduction of ice cover but an enlargement, so this is what I would call variability. Who knows where it goes from here?
Actually, there is no necessity, I think, to expect a linear continuation of what we've experienced--this would be my view. It could be that things will get significantly colder for a number of years. The fact is that basically the planet is heating, and unless that stops, sooner or later the Arctic is really going to thin out still further. But before that happens there may be cycles, cycles of greater ice cover, more preservation of old ice, and more difficulty, therefore, of shipping, and the ships will not be there.
You could also imagine, if you want to think of somewhat worst case outcomes, a reduction of the strength of the Gulf Stream, and you get a big change in the north Atlantic, where everything becomes quite a lot colder. It may be not an ice age or a little ice age, but there are things that have happened historically in only a few years. The Gulf Stream, as we call it, has suddenly stuttered and stopped, with tremendous consequences and sometimes for a very long time.
These things are not ruled out, but we can only go with what we see. I think what we see is a pattern of warming, with some variation within it, but the longer trend is toward warm. I would think that's the common-sense trend we should prepare for.