We have about 30 years of satellite data, another 30 years or so of spotty submarine records, and another 75 to 100 years of logs from ships that managed to get into Arctic WATERS. And on this paucity of information, about an environment that is at least 10,000 years old, we are trying to claim that current ice conditions are either abnormal (Greens) or just business as usual (Skeptics.)
Satellites give us pretty good systematic information on Arctic ice area. They work 24/7/365, providing continuous observations. Submarines give us spotty information on ice area and thickness. They just happen to make readings on various transects, not a basin-wide systematic survey. Ships logs provide a little additional information about those places where ships managed to get to. Everything prior to the satellite data is, effectively, anecdotal.
What hard evidence do we have that the Arctic Ocean has been continuously covered in ice 10 or 15 metres (or more) thick? A very few samples collected in a generally haphazard fashion over about 0.5% of the age of an ecosystem. If you tried to determine normalcy about say, human beings, from about 3 months of unsystematic observations of one individual spread out over 1 year with a few anecdotal yarns thrown in for good measure, your results would be next to useless as evidence of anything except the period of observation. Paleoclimate studies provide snapshots of localized conditions if they are properly tuned and consistently interpreted, but there are too many variables to be considered to make them 100% reliable.
If all the ice disappeared tomorrow, what would that tell us about the climate? If it grew enormously thick this winter, what then? Unless we can find some really old, incredibly dedicated observer who witnessed the termination of the last ice age, and spent the intervening 10 or 12 thousand years systematically measuring the surface area and volume of Arctic ice on some kind of regular basis, what we see happening on this short time scale means very little. It might mean something if we gather another few thousands of years of data, but not now.
It really is amazing that we get such a volume of hard fact from such a little amount of information. But then Mark Twain warned us about that.
Sorry for the rant, but it just seems to me that on both sides of the argument, we are grasping at some pretty short straws. All I can say, with any amount of certainty, is that 12,000 years ago it was apparently really cold. Then it got warmer. I could go out on a limb and predict that in another 5 to 10 thousand years, it will probably get really cold again.
