Thinking about a fun bit of mutual dissing with the notorious Lubos on his site, it occurred to the old man that it isn’t necessarily obvious why we should be interested in Arctic sea ice levels; after all, they do change all the time, and its all a long way away: why should it matter?
First is the idea that the state of Arctic sea-ice is generally considered to be an early indicator of climate change. Since very few people would even pretend that the climate hasn’t been warming over recent decades, this is sort of a moot point; we know the climate is warming, so it doesn’t signify. Less frequently discussed is the notion that the level and rate of decline might be strongly correlated to the level and rate of global warming. If this is the case, we can use the trends in the Arctic to look ahead and, in concert with other measurements of temperature and climate changes, project forward to an expected rate of increase of global temperatures. But this is fraught with complications.
Second, is the matter of the ice-albedo feedback mechanism. The presence of ice over the ocean keeps the Arctic surface temperatures down; a loss of ice implies maybe 20-40C of local atmospheric warming. The reflectivity of the ice, especially when compared to the surrounding land or ocean, even compared to snow or areas of melt water, is very high, which means that less heat from solar radiation is ‘pumped’ into the global system. There is a lot of concern that the relationship between the albedo feedback and the Polar regions is such that a relatively small change in albedo values will produce a relatively large change in other conditions, which in turn will further effect the albedo, etc. etc…
Then there’s the matter of the relationship between prevailing conditions in the Arctic and sub-Arctic regions and the surrounding land masses and oceans. There appears to be a relatively strong connection between the state of the Arctic and the state of the North Atlantic Oscillation. This in turn has an effect on weather (and, longer term, climate) conditions right across Europe into Eurasia, and, possibly, the West Pacific. It has implications for the direction and strength of the jetstream, and the important positioning of the northern boundaries of the Hadley cells., which in turn influence how much atmospheric heat is lifted from the tropic to the temperate regions.
There are, as always, lots of other influences to take into consideration, but the role of the Arctic in Northern hemisphere conditions, and vice-versa, is, whilst not completely understood, at the least known to be significant.
Finally, and more uncertainly, there’s the matter of freshwater. This isn’t ‘fresh’ in the sense that river or lake water is; it is ocean water which is less salty (saline) than average sea water. For a while now, there’s been conjecture that large changes in the amount of freshwater leaving the Arctic Ocean via the Denmark/Fram Strait, and the Labrador Sea, will have some measurable impact on the circulation of the ocean in the North Atlantic, an important area for ocean circulation, as it is one of the key areas where water is ‘circulated’ downward into the deep ocean, and heat is thereby ‘lost’. An interrupted ocean circulation might lead to a more rapid heating of the ocean surface generally, and another feedback starts to kick in. For those in the UK and Northern Europe, this has the added concern of changes to weather and climate caused by a slowing of the circulation patterns which contribute to the relatively mild conditions we currently experience.
It is important to point out here that the reasons for the changes in Arctic sea ice levels are not entirely understood. There appears to be a link to changes in atmospheric temperatures globally, but this can, by a recent study, account for no more than 40% of the observed decline. Current thinking seems to be that 60% of the decline is related to a warming (and freshening) of the waters entering the Arctic, and the water beneath the ice in general, mainly via the Bering Straits, but also via the Denmark Strait. Influx of freshwater from the Siberian and Canadian/Alaskan river systems, connected with regional warming trends over these land masses, probably also has some effect, though this is probably relatively small by comparison.
It is also important to note that sea-ice levels have always changed, sometimes rapidly, and that not all of the factors effecting its relative long-term stability are necessarily known, so the situation might improve, especially if there is a noticeable drop in solar radiation over the coming years; this might reasonably be expected to encourage some recovery of levels. Against this, we need to look at the paper I linked to yesterday, which posits a strong link between ozone levels and local temperature trends; if this is correct, then this signal may well override the solar variability completely.
Hopefully, all of this will help you understand why we look at the sea ice.
Be loved.
9 comments
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August 12, 2007 at 6:57 pm
Luboš Motl
Dear old notorious fergus,
sea ice is surely correlated with temperature although they’re not quite identical. From 1979, there’s been warming and retreating sea ice. That’s why RealClimate really likes to offer 1979 for comparison. Before, there was 30 years of cooling. The last century gave a net warming. There have been numerous net periods of warming and cooling, superimposed cycles and noise with all kinds of characteristic timescales.
20,000 years ago at the glacial maximum, there were 2-km-thick ice sheets over Manhattan and other moderate places. Ice started to retreat and the thickness change per year was much greater than today, even the average one, before it reached the holocene 10,000 years ago when there was almost certainly no sea ice in the Arctic in the summer.
These changes have been occurring all the time and the only reason for a worry would be to show that something essential about these changes today is very different, qualitatively different, from the changes centuries and millenia ago. You are parsecs away from demonstrating such a thing. Current changes look, in fact, very moderate to the reconstructed natural past.
To worry about changing sea ice or any similar kind of climate change just because it is change is completely stupid.
Best regards
Lubos
August 12, 2007 at 7:40 pm
fergusbrown
Lubos, dear fellow, what a pleasant surprise; I am not sure the cave is a scientific enough establishment for someone of your talents, so I’m flattered by your visit.
I think you’ll find the 1979 date useful mainly because it was the start of the satellite era for measuring change in the Cryosphere, rather than for any other motive. You are, of course, absolutely correct to point out that there is a huge amount of variability in both sea ice and temperature in the Arctic; added to which, it is very difficult to say how reliable historical data is for an area which has never had a large number of measuring stations.
There has also been a lot of work done on trying to establish cyclical patterns, but as far as I am aware, there is no neat solution yet, apart from the general observation that trends do appear to have been cyclical.
It is interesting that you should mention the warm period of the 1930s, as we would expect the sea-ice metric to show some correlation with the observed temperature changes, but there is no evidence for this (though that in itself is unsurprising). Which leads us to wonder whether there might be something different about the present situation when compared to the past: note this isn’t an assertion, but a speculation.
I’m not sure that current climate shifts in the Arctic need to be substantively different to historic changes for them to matter, especially if, as you have said elsewhere, these historical shifts were associated with rapid sea level changes, for example.
I’d suggest though, that it would be common sense to imagine that, with the edge of the glaciation so far South at the end of the last ice age, even a small change in the orbital tilt, or one of the other Milankovitch variations, would produce a rapid response at the extremes. It would be rather strange to imagine that such an event would not happen.
One of the principle differences between the present situation and the past is that we know that the current shift is not linked to the Milankovitch cycles. It is also fairly clear that there is no correlation between variations in solar radiation and ice sheet changes, beyond a plausible eleven year twitch.
It isn’t a matter of worrying about change because it is change – this would be dense, as you point out – it is a matter of wondering if these changes have a consequence down the line for us. And this is, I suppose, the real difference between changes in the pre-holocene and changes in the modern era: we live in largely sedentary groups, in large financially and geopolitically significant collectives; cities and megacities, pretty much everywhere where the coastal geography permits. We also, in Western Europe, The far East, and many other places, live in a way which is highly dependent on complex and interconnected production processes, for our food and water supplies.
The point of worrying about any climate change is not about the fact that the change is happening, but about the fact that much of what we take for granted can be easily affected by relatively small perturbations to the system. Another thing for those with a moral inclination to be concerned about is whether there is something that we could, collectively, do, which might help restrain the rate or severity of possible future changes.
I have tried to give four clear reasons, above, why sea-ice levels warrant careful observation. Are you willing to stick your neck out and say that none of these is significant, or a cause for at least some concern?
PS: I stopped writing on your site because my computer got hit by spam and other stuff; the comment on CS about being bored was a bit disingenuous.
Regards,
August 13, 2007 at 9:36 am
Luboš Motl
What was the real motivation of RealClimate to choose 1979 is up to them and their priests. What I really mean is an objective fact that 1979 was probably the coolest year in the last decades, so comparisons with 1979 are likely to show stronger warming trends than comparisons on a centennial time scale.
I have nothing whatsoever about people studying Arctic ice or anything else at any level of depth, and to some extent, I am doing it myself. What I protest against is the attempt of some of the people to create the impression that this concrete scientific topic or hobby of theirs is something that should be important for the whole society or even influence major policies of the countries of this world. There are millions of other topics of the same degree of importance such as D-branes on orbifolds, motors of new Boeing aircraft, Planckian cosmic rays, genetical engineering of tomatos, and so forth.
If we talk about the kind of concern that should employ people outside this overspecialized Arctic field including global policymakers, obviously, I am willing to stick my neck out and insist that none of this is significant or a cause for any concern. I’ve been doing it for quite some time. As far as I can say, the people who earn fame or fortune on this bogus pseudotopic are immoral ones and I hope that they will eventually be convincted as criminals.
August 13, 2007 at 11:51 am
fergusbrown
Small technical point, Lubos: Cryosphere Today (the the NSIDC) aren’t comparing the sea ice conditions today with those in 1979. The anomaly is measured against the 1971-2000 mean, a period when you say warming had been happening. In this case, an increase in the anomaly when compared to this mean must be at least statistically significant. This will be the fifth year out of six in which sea ice extent has been at a new record low. This does resemble a trend.
It does sound as if you are a bit of a Lomborgian; ie; there are many other things in the world which are important and worthy of concern which should be addressed before the issue of climate change. This is a legitimate point of view and has its supporters. I, too, get annoyed at the single-minded pursuit of this above all other themes in the media, at times. This, though, is a reflection of the other legitimate point of view; that the consequences of a changing climate are such that dealing with this should take priority over those other issues.
This is not a dichotomy which can be argued over; you either tend to one or other of the perspectives. What can be discussed fairly is which of these points of view is the more rational. As I don’t have a strong opinion on that today, I’d rather steer clear of it for the moment.
It is odd that you should describe climate science as a ‘bogus pseudotopic’, since it is one of the subjects on which you are allegedly so expert. This implies either that you are being disingenuous/dishonest, or that you are as much a ‘pseudoscientist’ in this field as everyone else; which is it?
You have an entertaining style of writing which aims at provocation and confrontation. No doubt this is why your blog is so much more popular than mine. I am sure that beneath this there is a genuine scepticism which is based on your own analysis of the evidence. Please continue to visit and challenge my (often clumsy) comments on climate science, but don’t bother with the provocation; it won’t work on me
Best wishes,
August 13, 2007 at 2:53 pm
john mann
Fergus: you wrote “No doubt this is why your blog is so much more popular than mine”.
Nowthen. As a part time geologist, I sometimes appreciate caves, and I must ask if you have any interesting formations in your cave, and what sort of strata it lies in.
We need to know.
August 13, 2007 at 3:51 pm
fergusbrown
Hello, John.
This particular example is probably a talus cave, wherein all that surrounds the old man seems in imminent danger of collapse at any moment. As such, there is little in the way of speleotherms. I’m probably more of a trogloxene than a troglophile, to be honest.
The cave is filled with the detritus of intellectual dilletantism and a small number of free standing sporting goods. Stratigraphically (is that right), it’s interposed between two large plates, a flat denial and a a sloping alarmism, which undercuts it.
For further detail, you might want to look at the Wiki entry for the TV episode of a similar name…
Regards,
August 15, 2007 at 5:39 am
Arvella
Oh, no. Oh, dear. I go away for a month, and come back to find that your cave has been potato-printed in a Motl-ey pattern! I hope this does not happen often.
Yours is quite a nice cave. Stratigraphically, it seems remarkably similar to mine, though we have various musical instruments in place of sporting goods, and the bassoon has begun sounding an Arctic dirge. It’s spooky. Goosebumps in Texas in August…
The current discussion on RC has inspired me to offer up a name for a creature related to the potato-printer: the cl’ostrich. This particular subspecies likes nothing better than to hide from the truth by burying its little fuzzy head in lines of code.
Blessings-
August 15, 2007 at 5:45 am
Arvella
Might I add that I enjoy your prose?
“The cave is filled with the detritus of intellectual dilletantism and a small number of free standing sporting goods.”
Marvelous, and all too rare in the world these days. Thank you.
August 15, 2007 at 9:48 am
fergusbrown
Hello, Arvella; nice to see you back.
Don’t worry about the decor; the mottling effect is a trick of the light, and a consequence of the old man vanishing off to the Czech’s republic…in other words, serves me right. I’m not really important enough to be regularly mottled, or camouflaged, thankfully.
And thank you for the bon mot about the bons mots; I put it down to the monkeys.
Be loved.