It always freezes in winter.

The sun stays down for months at a time. Lake Erie sometimes freezes in winter. Hell, I’ve seen ponds freeze in Tampa, for a few hours.

In summer the ice melts, and yes, multi-year ice matters. The top layers melt off, but what’s left still reflects sunlight all summer long. Snow on top of ice helps add stability, but not as much. The satellite images here don’t tell you how thin the ice is getting, although that is discussed in other places on the websites. And new satellites are using radiometers and radar to measure ice thickness. It is not only getting less in area, but in volume, too, what doesn’t melt is getting thinner every year. Multi-year ice is becoming a smaller and smaller percentage of the total ice. I’m not making this up, Tom. People are really getting scared about this.

Rising temps and albedo both play a role. As more ice melts, sunlight normally reflected off into space penetrates the sea, warming up the sea, which melts more ice from the bottom.

Of course, in the winter darkness, everything freezes, but next year, it starts melting earlier, melts more, and stops melting later. That’s what those curves are telling us. There will always be winter ice in the Arctic ocean, unless the equatorial seas start boiling, which I don’t expect will ever happen. I don’t believe in runaway scenarios. The question is what happens in summer.

As for your fishing show data, remember that as the ice breaks up, it moves around under wind and current. This is why sea ice in the Antarctic ocean goes UP as the continental glaciers calve off due to warming there. In spring, as the Titanic learned to her peril, icebergs are numerous. Other factors confuse the issue, which is why the curves are jagged, and the trend lines are noisy. Winds, currents, storms, insolation, salinity, precipitation, cloud cover, all interact to sort of maintain a balance. A lot of thick ice has been calving off the Greenland ice sheet (remember about the giant berg I posted about a few weeks ago?), but it hasn’t come close to making up for what is melting.

The point is that in spite of all those counterbalancing mechanisms, the trend is still down, down, down. Look at the archival data in NSIDC and JAXA, they all point the same way. I am no expert in ice geology or climatology, but I am a graduate geographer and an imagery expert, I think even my opinions carry some weight on this issue.

My guess is that the summer ice will be gone sometime before the end of the century, almost certainly before 2050, and possibly within the next decade or two. I believe most people who study this professionally would not object to that assessment. The result, which we are already starting to feel, and which will get worse from now on, is changes in weather patterns leading to changes in precipitation and temperature extremes all over the world, particularly the N hemisphere, and especially in the Eurasian half of the N hemisphere. The oceans will not flood the continents, but the price of grain will go through the roof.

I don’t think the world will come to an end, the thermosphere will stabilize, but large areas of earth will change substantially. N America may become like the Sahara, the Sahara may return to temperate forest and grasslands. Europe may, paradoxically, get too cold to support its current population. After all, England is as far N as Labrador. I don’t believe the oceans will rise hundreds of feet, but they will rise several feet, leaving the bulk of the world’s population on the coasts vulnerable to regular storm flooding which in the past was only an occasional nuisance.

Are we certain of this? Of course not. This is climatology, even less predictable than meteorological forecasting. But I can tell you as a professional geographer, not a political scientist, that this is as real as it can get in this field. There is always a possibility that we are seeing a short but temporary excursion in weather parameters, or that some long term trend is about to reverse itself and we will soon be back in normal times. But that only a possibility. The probability is that we are seeing the equivalent of every point N of the Tropic of Cancer, on the average, traveling south 10 degrees of latitude. And it will happen within the lifetime of people living today. It will not be a meteorological catastrophe in the sense that the USA will become uninhabitable, but it will change global agriculture in severe, yet unpredictable ways. America may become the new Sahel.

The “lots of information we don’t have” is spotty, but its out there. Look over those websites, I haven’t had a chance to exhaust them either, they have lots of data, and link to lots more. There doesn’t seem to be any good news anywhere, and the impression I get is that the investigators tend to be very conservative. Tom, I am not making this up just to disprove your politics. This is not an ideological issue or a philosophical argument. This is the global weather report, as best we can tell. And it is not good.

PS By the way, I’m really not that concerned about the polar bears, I’m worried about my life form, not theirs. Right now, dying bears are the least of our problems. But if you look at those satellite images of the Russian and Canadian Arctic, and compare them with imagery taken just a few years and decades ago, you’ll see why so many are getting shot. They can’t swim out to the seal hunting grounds on the ice anymore. They are going foraging ashore now. People are shooting them to protect their property, their livestock, and their lives.

Here’s the graph for Sept, 2011, published last October. The new graph for Sept 2012 will be released in a few weeks. The final data point will be lower than the lowest shown here, and the regression line will be recomputed to a new, steeper slope. In the chart below it is 12%/decade.