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Climate Hustle

Explaining Arctic sea ice loss

Posted on 13 October 2010 by doug_bostrom

Arctic sea ice has aptly been termed a "canary in the global warming coal mine," a sensitive indicator of climate change; because of its importance as a diagnostic of global warming, climate change skeptics struggle to explain the decline of Arctic sea ice as a natural phenomenon. 

Satellite measurements of Arctic sea ice extent reveal a rapid decline over the past 30 years, particularly at the end of each year's annual melt season.  The downward trend and the increasing difference between seasons are in keeping with predictions of the effects of global warming. As the Arctic warms, the volume of ice in the region gradually declines, making it less likely ice will survive more than one year and thus exposing more open water at the end of each melt season (Maslanik et al).

(from National Snow and Ice Data Center )

As an explanation for the decline of Arctic sea ice, skeptics hypothesize we're seeing the effects of natural cycles causing deep, decades-long swings in Arctic ice coverage and volume. Lending observational support for such cycles is much more difficult than relying on direct observations of ice extent with contemporary instruments. Still, thanks to ocean sediment cores and some other physical clues left by past climate regimes we have reasonable insight into past Arctic sea ice extent. Combining various information about past climate behavior, we can better understand why changes in ice coverage have occurred in past times, whether those natural variations are happening today, and how those changes compare to today's sea ice trend. 

While it's true that natural variations of the climate have caused significant changes in Arctic ice extent in the past, it's important to note that such such changes are not airtight arguments against anthropogenic global warming causing today's loss of ice. After all, events of the past do not describe newly identified influences by human culture on today's climate. Indeed, comparisons between past and present Arctic climate reveal different reasons for yesterday's and today's Arctic sea ice changes and strongly suggest that today's changes are largely anthropogenic (Overpeck et al).  Meanwhile, analysis of several hundred indicators of past Arctic sea ice extent tells us that recent losses appear to have no parallel in records going back many thousands of years (Polyak et al).

The past 200 years offers an example of how natural and anthropogenic influences on Arctic sea ice can be distinguished.  The Arctic appears to have undergone an unusually cool period in the early 19th century, certainly natural, with recovery to more normal conditions extending into the 20th century leading to the warming we see today. Referring to the graph above, we can see that after the earlier cool period sea ice extent in the Arctic appears to have largely stabilized, later to begin a steady decline in chorus with other emerging observations of global warming such as increasing air and ocean temperatures. This decline in ice extent is happening even though the causes for natural recovery from the unusual cold of the 19th century are no longer in play, while research strongly suggests these recent reductions in Arctic sea ice are are caused by a new, anthropogenic mechanism (Johannessen et al).  

In sum, although natural factors have always influenced the state of Arctic sea ice, research strongly suggests that today's decline is driven by the novel influence of anthropogenic C02 we've added to the atmosphere and thus is unique in Earth's history.

This post is the Basic Version (written by Doug Bostrom) of the skeptic argument "Arctic ice melt is a natural cycle".

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Comments 1 to 50 out of 60:

  1. 'While it's true that natural variations of the climate have caused significant changes in Arctic ice extent in the past, it's important to note that such such changes are not airtight arguments against anthropogenic global warming causing today's loss of ice. After all, events of the past do not describe newly identified influences by human culture on today's climate. Indeed, comparisons between past and present Arctic climate reveal different reasons for yesterday's and today's Arctic sea ice changes and strongly suggest that today's changes are largely anthropogenic....'

    A useful discussion might be something on the lines of:

    When is the past a good guide to likely present and future outcomes? When not, and if not, why not? And vice versa.

    This would help reduce the plethora of claims and counterclaims about sea ice extent, volume and thickness, and how they are best measured. I confess freely to having added to this noise over the course of my visits to this site.

    Two very interesting looking papers which I'll be digesting at leisure with great interest.
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  2. The Atlantic Multidecadal Oscillation (AMO) is a natural cycle. It is also known to have affected the arctic sea ice before. The instrumental record of the AMO goes back to to around 1860. In that period there are approximately records of two full cycles of the AMO.

    Since it is only possible to directly correlate the sea ice extent to the AMO since the satellites were able to measure it in 1978 other means are needed to determine the affect in the past.

    The opening of the Northwest passage is one possible method. While the first credited successful passage was in 1906 (while AMO was cool) by Roald Amundsen, the expedition ended with the ship trapped in ice for 3 years and it was completed on foot.

    The first open water expedition was completed in a period of 28 months starting in 1940. The AMO was in the warm phase during this period. More interesting is that the trip back in 1944 only took about 3 months indicating that the ice volume had decreased since the initial trip.

    Many trips after that have succeeded, but using modern icebreaking ships with heavily reinforced hulls. Those were needed because the passage was once again closed while the AMO was in the cool phase.

    The transition of the AMO was once again transitioning to warm phase and has been above average since 1995. The re-opening of the passage since then correlates well to the warming of the AMO.

    Even the record low extent in 2007 correlates to the longest sustained warmth of the current AMO. After that the AMO has cooled slightly and the extent has rebounded.

    Separating any change in ice from the warm phase of the AMO would be a difficult task at best and claiming that the decreasing extent is the "canary in the global warming coal mine" is scientifically irresponsible.

    I do not claim that the AMO is the only factor decreasing extent, but it is certainly a major factor in the current extent behavior.

    John Kehr
    The Inconvenient Skeptic
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    Moderator Response: AMO also is touched on by another post on Skeptical Science.
  3. doug_bostrom

    "...research strongly suggests that today's decline is driven by the novel influence of anthropogenic C02 we've added to the atmosphere and thus is unique in Earth's history."

    Typo: Earth's history, should be, Human history.

    That point aside, its not clear why the last paragraph was included, since the effect of anthropogenic CO2 on its own is not sufficient to produce these effects. Is it only coincidental that 90 percent of the world's industry is located in the northern hemisphere, and that this problem is not being seen in the Antartic? If the problem were only due to CO2 the effects would be symetrical, and they are not. In fact, the Artic is "protected" by more land and therefore should be even colder than the Antartic, and with oceans representing a truer averaging of temperatures.
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  4. John,
    For every year since 2007 unreinforced yachts have made the North West passage in less than a month. There is no ice left there. As you point out, in 1906 the passage had to be completed on foot. This summer two yachts went entirely around the arctic ice, passing through both the North West and the North East passages. No icebreakers went with them. It is certainly unprecedented that the ice be completely gone from these areas in the historical record. Your assertion that icebreakers are currently required to make the passage is simply false- the ice has melted. Whalers have been going to the Arctic since the 1700's and they never saw either passage open.

    How do you explain the complete absence of ice in both the North West and North East passages with your "warm AMO phase"?
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  5. TIS, early warming of the Arctic and associated decline of Arctic sea ice have long been conspicuous features of predicted effects of anthropogenic warming. Sorry to upset your sense of political correctness; these descriptions are supposed to lean on everyday figures of speech and in this case the term has been employed by various people involved in Arctic climate research. Maybe I should provide a reference though that seems a bit neurotic.


    RSVP, please read more carefully.

    "...research strongly suggests that today's decline is driven by the novel influence of anthropogenic C02 we've added to the atmosphere and thus is unique in Earth's history." Read the articles cited if you want to get a better grip.
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  6. RSVP
    The Antarctic is a continent, not an area of the sea. Parts of it are very high above sea level, Mt Erebus is nearly 4000m high. Both of them are about 14 million sqkm. The Antarctic is much more exposed to cold being entirely surrounded by the chilly Southern Oceans.
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  7. RSVP #3

    Wow

    "Is it only coincidental that 90 percent of the world's industry is located in the northern hemisphere, and that this problem is not being seen in the Antartic"

    Is this another of those satirical comments designed to expose the weakeness and idiocy of much of the so-called sceptic case? The antarctic ice sheet many many times bigger than greenland. The latent heat of melting of all that ice will account for a staggering amount of heat in the long run. Roughly speaking, you're comparing apples with beachballs, and your analogy is correspondingly stretched to credulity and beyond.
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  8. Excellent article.
    An ice free arctic ocean will likely be the Pearl Harbor event that will finally wake up the public, main stream media and possibly a few politicians. When that is going to happen is harder to say, but likely before 2030 and possibly before 2020.
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  9. The moderator writes: Moderator Response: AMO also is touched on by another post on Skeptical Science.

    Is it? I didn't see anything in that post about the AMO, just references to the Arctic Oscillation and the North Atlantic Oscillation. Admittedly I skimmed the page fairly quickly and might have missed it.

    That said, I'm not personally a huge fan of the various "oscillations" when used as empirically correlated explanatory variables for other aspects of climate. With enough of these oscillations (ENSO, IOD, AO, AAO, NAO, AMO, PDO, and am I forgetting any?) it's almost always possible to find one (or better yet a combination of two) that will correlate with whatever you're looking at, especially if the time frame is short enough.
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  10. RSVP writes: Is it only coincidental that 90 percent of the world's industry is located in the northern hemisphere, and that this problem is not being seen in the Antartic? If the problem were only due to CO2 the effects would be symetrical, and they are not.

    Yes, it is coincidental. The distribution of CO2 is more or less uniform but the impacts of warming are distributed irregularly due to regional atmospheric and ocean circulation. This has been understood for decades, and is not some kind of "post hoc" explanation.
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  11. kdkd #7: "The latent heat of melting of all that ice will account for a staggering amount of heat in the long run."

    The worrisome thought to me is, 'what happens with all that heat once the ice is gone?' Right now the Arctic ocean is heating up each year, but much of that heat is 'expended' melting the sea ice through the Summer (at an average rate of about 1000 km^3 per year over the past decade). There were only 4000 km^3 of sea ice left at the end of the 2010 melt season... down from the previous record low 5800 km^3 the year before. So if the average decline over the past decade continued the Arctic would be ice free in September in four years. Even the average rate of decline since 1979, 400 km^3 per year, would have the Arctic melting out in ten years.

    The Arctic ocean is going to continue accumulating heat. That heat is going to continue melting more ice each year and I can't think of any reason that the volume loss trend should suddenly change radically. Some amount of ice around the Canadian archipelago and other 'land sheltered' areas will stick around, but the rest seems clearly headed to melt out. So when the ice is gone and that heat starts building up rather than getting 'balanced out' by having to melt the ice it seems clear that it will mean a longer period before the ocean begins to refreeze. If so then the 'Arctic amplification' we've seen the last 30 years may be small potatoes compared to what is coming in the next 30.
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  12. Oh, by the way -- nice post, Doug. Very clear and well written.
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  13. Historical records of world temperatures from ice core samples over the past 410K years show rapid declines following peaks at 130K, 230K, 330K, and 410K years ago. However, in the last 15K years (not counting the industrial years), following the last dramatic temperature rise, global temperatures have remained relatively flat, with fluctuations varying by ±1.5°C or so. If history had anything to say about world temperatures, I would have expected a sharp downward trend, heading toward the next ice age.

    We see similar historical peaks in CO2. But about 15K years ago there was a small drop in CO2, only to shoot up again about 10K years ago, which might explain the stabilizing of temperatures. Are we overlooking a smaller human footprint on CO2 and global temperatures that may have extended back 10K years or so ago? When did man discover that systematic burning could be used to manage forests, and was that systematic burning more than what nature would have done alone? Put another way, has man been reducing forest stands for 10K years or more, which might be responsible for adding some CO2 to the atmosphere and stabilizing global temperatures?

    Man has also been burning coal and limited amounts of fossil fuels for thousands of years too. This would also have contributed to CO2, but maybe to a lesser extent than forest reductions.

    So, rather than nature returning Earth to the next ice age, man is turning it into a sauna. Is it a wonder that we are now seeing shrinking glaciers and ice caps when they should be growing?
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  14. Fresh thread, inconvenient timing; the copy of the Polyak article at UCAR is unavailable right now, hopefully temporarily. In the meantime Google has a cached copy here.
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  15. Roger, that's the basis of Bill Ruddiman's hypothesis (early anthropogenic influence on climate). See Plows, Plagues, and Petroleum if you haven't already read it. I am a bit doubtful.

    Also, there is at least some evidence that the present interglacial would have been relatively long even without anthropogenic meddling. A number of people think that MIS-11 (~400,000 years before present) is the closest analogue to current conditions, and it lasted much longer than the more recent interglacials. See Berger & Loutre (2002).

    It is difficult to be confident about this either way -- around 3000 years from now, summer insolation at 65 north will be very close to the value that triggered past glaciations. So while it's likely that this interglacial would have lasted another 50,000 years, if the glacial trigger is more sensitive then it's possible that the Earth would have started a slow transition into glaciation in the not too distant future. Of course, all this is out the window now, as you note, due to anthropogenic GHGs. (It also probably belongs in another thread....)
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  16. The Inconvenient Skeptic and Ned,

    The AMO is undoubtedly contributing to the current warming in the North Atlantic and likely does contribute to the loss of sea ice in the Arctic. I believe the AMO also correlates extremely well with Arctic and North Atlantic air temperatures. However the AMO cannot alone explain the significant reductions in Arctic sea ice without including an anthropogenic signal. The AMO in its positive stage represents an intensification of the THC bringing more warm water to the North Atlantic. In the past when the positive phases have occurred it is true that ice losses have subsequently occurred, but I would find it highly suspect to suggest that the Northwest passage was open fully in one year, let alone 3 in a row.
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  17. Can't help but wonder if we shouldn't be looking more at the holocene to help us determine what we are getting into now. That looks like the time humans made it to Iceland and Greenland and it was by boat from the west. Of course its a lot easier for a band of nomads to survive a gradual climate change than for 6 billion to survive a more sudden change. Now I submit that climate change is like politics in that it all comes down to local. The holocene is believed to be regional. I wonder if someone looking back 5000 years from now might say the same thing. Though changes are happening faster now it still affects regions differently. AGW is now real for Russia and Korea with major crop failures and deaths. Here in the US it wasn't a great year for crops but we can survive it. If the weather patterns change Russia may have a good wheat crop and the US could have major crop failure. So even though its a global problem by squinting your eyes you might be able to only see regional problems.
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  18. kdkd
    "The antarctic ice sheet many many times bigger than greenland. "

    Adelady
    "The Antarctic is much more exposed to cold being entirely surrounded by the chilly Southern Oceans."

    Ned
    "The distribution of CO2 is more or less uniform"

    No one can deny Artic ice thinning or the opening of "northwest" passages. (...and I assume these still close up in winter.) What can still be disputed however is the cause. In a bygone thread, the major reason forwarded to discount industrial waste heat as a significant climate forcer is how it pales numerically with the total radiative effects of incremental GHG over the entire Earth surface. What happens however when the comparison is made between the total heat output of industrial nations crouded above the 45 parallel the supposed incremental radiative forcing of GHG in that same restricted area.

    In addition, when comparing Artic and Antartic regions geographically, it is clear that one is "water" and the other "land". This apparently affects ice cumulation regardless of global temperatures (i.e. there never was 4000 feet of ice at the north pole), which means that the Artic has a built in predisposition to melting anyway due to its lower elevations. Since it doesnt take "much" to accomplish this, and waste heat is a "drop in the bucket" in the scheme of things, this may have more to do with what is really going on than is suspected.
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    Moderator Response: Given its easily quantified irrelevance in comparison to natural variability, we'll do better to continue sequestering further discussion of waste heat in the existing "Waste heat vs greenhouse warming" thread.
  19. As always, a good general approach is to first read the research, then dispute the cause based on an informed perspective.
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  20. Robert,

    As I stated I do not believe the AMO is the only factor, but there is not sufficient information of the impact on the northwest passage from the last warm AMO to know the full impact. What was the status from 1945-1955? All that can be verified is that 1944 was a low ice year. As the AMO stayed strong after that it is not possible to say what the status was.

    There is simply not sufficient data available on the state of the northwest passage from before to state if this is unprecedented or not.

    I will put something together on the Arctic temperatures. The winter average temp has increased, but the summer temps have been stable according to the satellite data. I will have it up by the end of the week, probably Friday.

    John
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  21. TIS,
    There is a huge amount of data on the North West passage, you have just not looked for it. There are people who LIVE in the NW passage who actually write down each year what the ice is like. They have lived there for over 100 years so the record goes back a long way. Ships have a long tradition of writing down the ice concentrations they meet and that takes the record back into the 1700's, although not as complete the further back you go. Arctic explorers spent decades trying to get through the North West passage, starting with Cook in 1776, of course they kept records.

    Arctic temperatures over ice have stayed the same since the melting ice controls the temperature. The sign of AGW is more melting. NSIDC uses a chart of temperature at 1000 meters to see actual temperature rise. WUWT has a trick graph of surface temperature north of 80 degrees they use to fool people who don't pay attention.
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  22. RSVP: "No one can deny Artic ice thinning or the opening of "northwest" passages. (...and I assume these still close up in winter.)"

    You mean, you don't really know that? And you couldn't bother doing the extremely basic fact-check before piping a comment? What is the point of commenting on a subject of which you spontaneously confess that you are so ill-informed?

    This: "land" and "water", quotations marks yours. Why the quotation marks? Are you trying to suggest that they are not really water or land?

    And this: "the Artic has a built in predisposition to melting anyway due to its lower elevations." The Arctic is an ocean. Lower elevations? I don't know what you're trying to say there.
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  23. #20: "winter average temp has increased, but the summer temps have been stable according to the satellite data."
    TIS,
    Prior discussion here may save you some effort. See this prior thread and this one as well. A search will bring up others; this subject gets a lot of attention (as well it should).



    Minimum (September) ice extent anomalies are increasing in magnitude more rapidly than maximum (March) anomalies. The melt season is also getting longer. Prior discussion noted that 'new ice' melts faster than 'old ice' and that ice thickness continues to decrease. The combination of longer melt season, rising temperatures and a higher percentage of new ice to old ice makes increasingly rapid melt inevitable, with or without AMO.
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  24. Doug, good post. However, some humble suggestions. Maybe more focus needs to be placed on a) Polyak and b) Polar amplification.

    The following conclusion by Polyak et al., is in my opinion very striking:

    "The current reduction in Arctic ice cover started in the late 19th century,consistent with the rapidly warming climate,and became very pronounced over the last three decades.This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities."

    Using cycles (internal climate variability) to explain long- term trends in Arctic ice does not work, unless one can demonstrate that the cycles themselves have become locked in a particular phase, or if one particular phase of the cycle has become favoured. But then, how does one then know for sure that the change in the cycle's behaviour is purely natural of affected by changes in the circulation brought about by AGW?

    The events unfolding in the Arctic are consistent with those predicted to occur in association with AGW by Hansen (1981) and Manabe et al. (1992).

    You might be interested in a new paper out by Miller et al. (2010, Quaternary Sci. Rev., same issue as the Polyak et al. paper) which finds that Arctic amplification on Quaternary time scales consistently exceeds the N. Hemisphere average by a factor of 3-4. Right now that factor is about 2.

    By forcing the biosphere into a net positive energy imbalance, we humans have set in motion a sequence of events in the Arctic which has led to the manifestation of polar amplification. Going by the work of Miller et al. (2010), the warming (and attendant reductions in ice) in the Arctic will likely continue to accelerate in coming decades on account of polar amplification.
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  25. Albatross, you probably won't believe it but I actually had that Miller paper listed along w/Polyak, dropped it because I thought it insufficiently ice-specific. It's a deliciously rich review of proxies, an education in itself and I suppose in retrospect should have left it in as a resource for readers; next time I'll listen better to my intuition.

    Temperature and precipitation history of the Arctic (full text, pdf)

    Looking at Polyak, I agree I've probably understated the conclusions. I suppose I've become too sensitive to skeptic susceptibility to going hysterical over strongly worded hints that things are going pear-shaped.
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  26. Hi Doug,

    I do believe you re Miller et al. :o) I understand that writing these posts is probably significantly more difficult and time consuming than people expect, and that some difficult decisions need to me made along the way.

    It seems that some posters here are not comprehending the content of your post. All this talk about "natural cycles" when your last sentence reads:

    "In sum, although natural factors have always influenced the state of Arctic sea ice, research strongly suggests that today's decline is driven by the novel influence of anthropogenic C02 we've added to the atmosphere and thus is unique in Earth's history."


    "Skeptics" need to understand that sometimes in science the evidence is so comprehensive, so compelling, so robust that strong words are warranted/justified. Also, it seems things are indeed "going pear-shaped", so sticking our heads in the sand (or trying to convince ourselves that the ice loss is mostly "natural") is not going to help address or avoid dealing with the situation. Moreover, such actions are neither constructive nor responsible.
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  27. michael sweet at 18:47 PM on 13 October, 2010 said
    "For every year since 2007 unreinforced yachts have made the North West passage in less than a month..... This summer two yachts went entirely around the arctic ice, passing through both the North West and the North East passages. No icebreakers went with them."

    Do you have any links to info on this ?

    I was unaware of the yachts making it through the NW passage every year since 2007. I have seen some reports of yachts that attempted it and had to be rescued by icebreakers.
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  28. Charlie,
    This cruising world article describes the 2009 year. In the article they said 11 yachts made it through (all the yachts that attempted that year). The yacht in the article went through early and later it was more open. No-one was described as needing assistance, although I would not be very surprised if someone did need assistance. Cruising World likes to be cutting edge on sailing so this fits their style. The ice was gone for so long this year that everyone would have made it for sure. The NSIDC summer summary has links to the two circumnavagations at the bottom.
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  29. Wikipedia is a good place to start for anyone wanting to know about passages through the Arctic.
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  30. #27: "unaware of the yachts making it through"

    Try searching here for shipping news.

    This year’s retreat from a winter maximum of about 15 million square kilometres to a September coverage area of just five million square kilometres also means that the four greatest melts since satellite measurements began in the late 1970s have occurred in the past four years.
    ...
    Canada and the four other Arctic Ocean coastal nations — Russia, the U.S., Denmark and Norway — have pledged to co-operate in creating new search-and-rescue and environmental protection regimes to manage increased shipping, tourism and economic development in the melting Arctic.
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  31. michael sweet at 04:28 AM on 14 October, 2010: "The NSIDC summer summary has links to the two circumnavagations at the bottom."

    Thanks! I've added those two to my arctic bookmarks.
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  32. Philippe @ 22:

    I think you're being a little hard on RSVP ("No one can deny Arctic ice thinning or the opening of "northwest" passages. (...and I assume these still close up in winter)... You mean, you don't really know that?

    While I don't possess mind reading powers, I suspect RSVP was being ironical.

    Whether his irony was misplaced is another issue.
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  33. Philippe Chantreau #22
    "I don't know what you're trying to say there."

    Comparing the Artic with Antartica, I was saying that the Artic ice is mainly at sea level, and that Antartica ice is mostly mounted on land. Not sure if you ever noticed, but it gets colder as altitude increases, so without doing any reasearch, I made the not so unreasonable speculative comment that the Artic is more predisposed to what is actually being observed than Antartica for this reason.

    As for your question about my use of quotes around "water" and "land"... these refer to the substrate, whereas the surface is actually ice.
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  34. RSVP
    You're not distinguishing between sea ice and land ice. The big difference betwee the Arctic and the Antarctic is that sea ice just does not build up around the Antarctic, each year melts away during summer. In the Arctic, the archipelagos and the general conformation of the surrounding land mean that ice can survive the summers and multiyear ice can build up to considerable thickness.

    What's melting away these last few years is the volume - melting out from underneath the surface ice because of warmer waters. Arctic sea ice is now at its lowest ever recorded volume. The only reason we don't know exactly how bad it is is that the satellite for measuring the volume more precisely is not giving us the numbers yet.
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  35. adelady #34
    "You're not distinguishing between sea ice and land ice."

    If you compare the geographies, the poles are almost perfectly inverted. As per links (below), the area contained within the northern 70 degree parallel is ocean, coinciding with the Antartic continent which is also roughly contained with the southern 70 degree parallel. In the one case the pole is at sea level (and encapsulated by land), and in the other, the region is mountainous, surrounded by water.

    I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result.

    http://geology.com/world/arctic-ocean-map.shtml

    http://www.lib.utexas.edu/maps/islands_oceans_poles/antarctic_region_pol_2005.pdf
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  36. RSVP,

    Regarding,
    "If the problem were only due to CO2 the effects would be symetrical, and they are not. "

    I don't believe you'll find any claim that the variability of sea ice is only due to CO2. Weather patterns, changes in salinity, oscillations of current and upwelling flow, albedo feedbacks, etc. all interweave to produce the variability. Wind patterns are driven by differences in energy content, which is also effected by the radiative properties of the atmosphere (CO2 influenced). It's like a multi-body problem in Newtonian physics. If you move one body, the forces acting on the other bodies change; so, they move, which changes the forces acting on the original body, and so on. There is some evidence that the increase in sea ice around Antarctica is driven by some combination of increased snowfall (If you warm the ocean, it gives off more moisture. If it is still below freezing, that moisture will precipitate as snow, which changes the albedo of the surface water, etc.), lowered salinity, and increased outflow of the land ice.
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  37. Regarding,
    "I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result. "

    Does the ice melting in a glass of water cause the water to get cooler? No, it only prevents it from getting warmer. It does not stop the glass from absorbing energy from its surroundings; it just stops the temperature of the glass from rising until the latent energy required to melt the ice is matched by the energy absorbed by the surroundings.
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  38. ach, from* the surroundings
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  39. RSVP: "I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result."

    Read post 22 again. If you have no understanding of the most basic science concerning what you are talking about you do not make a good impression. Warm ocean waters coming from both the Atlantic and the Pacific are part of the problem with melting Arctic ice. The warm ocean is the primary concern with Greenland. If you do not know what the issues are you cannot make informed comments about those issues. The meridional overturning circulation in the North Atlantic moves enormous amounts of energy and changes in it cause concern for the future. By contrast, references to waste heat just remind us that you do not understand energy transfer either.
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  40. RSVP "I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result."

    What waters would be cooling? The waters from the Pacific do flow into the Arctic and they can be very warm from an el Nino a year or so earlier. And the strength of an el Nino is related to CO2 heating the atmosphere and the oceans at large. The more warm water there is, and the higher its temperature, the more melting of sea ice from below.
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  41. Chris G #36
    "I don't believe you'll find any claim that the variability of sea ice is only due to CO2."

    Please scroll upward and read the last paragraph of the original article. As for your comment about ice in a glass: since I am on the blue pill, the drink does seem cooler to me.

    ...and as for the rest...
    "When ice melts or water evaporates, energy must be taken from the environment in order for the ice or liquid to move to a less ordered state"

    http://www.theweatherprediction.com/habyhints/19/
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  42. RSVP, I think your semantic climate sensitivity is too high. Perhaps you'd feel better if I added a calming word such as "substantially" in order to make more obvious the qualifier "...although natural factors have always influenced the state of Arctic sea ice..."

    How about this:

    In sum, although natural factors have always influenced the state of Arctic sea ice, research strongly suggests that today's decline is substantially driven by the novel influence of anthropogenic C02 we've added to the atmosphere and thus is unique in Earth's history.

    Come to think of it, that actually reflects research findings better, though it hardens the language in favor of anthropogenic factors. How about "significantly?" Oops, same deal.

    Word-smithing won't really change the fundamental meaning of the sentence, unless we're so highly tuned that we consider "is driven by" to imply "excludes all other possible factors."
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  43. doug_bostrom #42
    The article is well written, and should serve as a vehicle for further discussion. The last paragraph is an invitation for anyone who is'nt fully convinced that everything would go back to normal if the atmosphere's CO2 concentrations returned to their pre-industrial levels, or that this is what mainly caused this situation in the first place.

    On the other hand, if the link between CO2 and Artic melting is so conclusive and significant, why is this tossed in at the last minute?
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  44. Thanks for the compliment, RSVP.

    The reason for the conclusion is the same as the requirement for the article; skeptics struggle to explain the demise of Arctic sea ice as a natural phenomenon. After a look at the latest research on the topic including Polyak's massive meta-analysis it appears quite clear that today's loss of ice is novel and related to anthropogenic CO2. The final paragraph is a brief summary of a brief article.

    There's no other way to say it, really.
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  45. To doug_bostrom:
    I would not argue at all that the pace of change in the Artic is due to the effects of unprecedented human growth. Our difference lies in the assumed mechanism, and this difference of opinion would be tolerable if humanity didnt have to make some important choices.
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  46. RSVP #45

    "Our difference lies in the assumed mechanism"

    You mean "hypothesised mechanism". And doug's hypothesis has much support, while yours has pretty much been chucked in the gutter, but being a zombie hypothesis, the so-called-climate-sceptics recycle ad infinitum in the hope that it will eat our brains!
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  47. @ RSVP at 03:52 AM on 15 October, 2010

    Please put a thermometer in a glass of ice water, stir continually, and record the temperature every minute. Plot the temperature over time. The temperature will stay right at freezing, neither cooling nor warming, until the ice is gone. I'm not sure that I'm here to teach you basic physics.

    Also, please try to understand the difference between Doug's statement, that CO2 is what is changing now that is driving the changes observed in the sea ice, and your statement, and your statement that in order for that to be true, the changes should be symmetrical. You can probably find more information under the topic on the left, 'Antarctica is gaining sea ice'. Also, feel free to use Google Scholar and search for 'antarctic sea ice'.
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  48. RSVP this CO2 affair is really not so much a matter of population dynamics as it is the unfortunate physical dynamic effects of our quite naturally seizing and using what appeared to be a eerily wonderful and even anodyne tool, one with several faces, a substitute energy source that I'll note in many places helped somewhat to arrest our breathtaking destruction of forests.

    Lately we've learned that certain physical side-effects of using this tool are incompatible with the systems over which our culture is draped. Now we need another substitute energy source. This is just part of growth, it's inevitable, really, and we should actually welcome it. The question is, will we use the ever-shrinking and increasingly hazardous lever we found in the 19th century to lift us to where we need to be in the 21st century? A topic for another thread, I think...
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  49. @RSVP: "this difference of opinion would be tolerable if humanity didnt have to make some important choices."

    Actually, humanity needs to wean itself of fossil fuels anyway.

    There is tremendous economic opportunity in renewable energy. Why do you think China is already becoming a leader in that area, while the US lags behind due to the Oil interests muddying the debate?
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  50. To understand the Arctic Sea Ice, follow the multi-year ice ( the whiter shaded areas ):

    http://seaice.apl.washington.edu/IceAge&Extent/Rigor&Wallace2004_AgeOfIce1979to2007.mpg

    Notice how the Multi-year ices is flushed out into the Arctic.

    The paper is here:

    http://seaice.apl.washington.edu/IceAge&Extent/Rigor&Wallace2004.pdf
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