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Climate Hustle

Human activity is driving retreat of Arctic sea ice

What the science says...

Select a level... Basic Intermediate

Thick arctic sea ice is undergoing a rapid retreat.

Climate Myth...

Arctic icemelt is a natural cycle
"In 2007, the Northern Hemisphere reached a record low in ice coverage and the Northwest Passage was opened. At that point, we were told melting was occurring faster than expected. What you were not told was that the data that triggered this record is only available back to the late 1970s. We know the Northwest Passage had been open before." (Matt Rogers)

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.

(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 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 caused by a new, anthropogenic mechanism ( Johannessen et al ).  

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 CO2 we've added to the atmosphere and thus is unique in Earth's history.

ABCDE

Last updated on 23 June 2013 by doug_bostrom. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Further viewing

The following animation shows how the oldest thickest sea ice has been progressively flushed from the Arctic Ocean over the last two decades. The colours are an indication of the age of the sea ice. Lighter colours are older sea ice - white is 10 years old.

Comments

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Comments 51 to 72 out of 72:

  1. OK lets correct the statement "any current trend is also natural". They state internal variability is sufficient to counteract anthropogenic forcing in the 2-20 year time frame (hence a positive trend can be observed). With that in mind I don't see how we can categorically state what is responsible for any short term trend, it will be a combination of anthropogenic and interal forcings. Those "ice loss is accelerating" claims based on short time frames need to take this into consideration.
    Response:

    [DB] "Those "ice loss is accelerating" claims based on short time frames need to take this into consideration."

    Short time frames...you mean like that covering the entire satellite record, perchance?:

    Chart 1

    Or this, hiliting that climastrological seasonal cycle?:

    Chart 2

    [Source]

    So, when we've endured 316 317 consecutive months of global temperatures above the 20th-Century average (the last cooler-than-average month was Feb 1985), and the Arctic Sea Ice trends are linearly to greater-than-linearly down (that Arctic Amplification thingy), where's the recovery for crying out loud?

    Regular readers are surely noting the zeal displayed by those that seize upon every last vestige of hope to deny the obvious:  recently the world is warming due to human activities (fossil fuel derived CO2), and the Arctic Sea Ice is in a downward spiral as a result.

    I repeat:  only Maslowski's model comes anywhere close to replicating the metric-ed trend observed in the Arctic.  And his model predicts a summer minimum with mostly-ice free Arctic Ocean by 2016, ± 3 years.

    But by all means, that's only natural...

  2. FYI: the Arctic has just hit the trifecta: extent, area, and volume minima. True, this is only according to differing agencies, but none of the agencies is in significant disagreement. The volume drop in particular is alarming, since 2010's drop was sharp enough to seem anomalous to the untrained eye (and perhaps even to a few trained eyes).
  3. Hmm, Why is there no discussion on the changing Arctic oscillation patterns as a reason for the Arctic ice melt?

    "Over most of the past century, the Arctic Oscillation alternated between its positive and negative phases. Starting in the 1970s, however, the oscillation has tended to stay in the positive phase, causing lower than normal arctic air pressure and higher than normal temperatures in much of the United States and northern Eurasia."

    http://nsidc.org/arcticmet/patterns/arctic_oscillation.html

    Could it be these changes, and not CO2 that is causing the melting ice in the Arctic?
  4. Dana69: And what do you think is responsible for this change in an ongoing oscillation?

    If this truly means this oscillation is no longer oscillating, why would the natural cycle stop on its own?
  5. But what drives 'these changes'?

    If extended periods of the positive phase of the oscillation were expected, observable or historical phenomena, we'd expect historical, archeo/paleo/anthro or geological records to show this, along with an equivalent loss of ice. They don't.

    Something is changing the oscillation and the ice melt/freeze, and we know that such changes must be driven by some physical, chemical, biological or geological impulse. There are only two such changes contemporaneous with the change in the oscillation and the associated over-a-cliff drop in Arctic ice. The biological/ecological population explosion of one particular mammal and a simultaneous injection of GHGs into the atmosphere.

    Change doesn't just happen. Something makes it happen.
  6. And, Dana69, no matter what the non-GHG explanation for the rapid downward trend, one would still need to explain why GHG-based warming isn't a factor. GHG warming is happening--must be, according to the physics of radiative transfer.
  7. Hmmm..I have been looking at this issue in more detail and there seems to be some diverse thoughts regarding this topic.

    First off, The IPCC models tend to simulate a positive phase of the Arctic Oscillation in most of the GCM simulations. Correct me if I am wrong, but don't most positive phases hold colder air in the region thereby slowing the rate of ice loss? Wouldn't this be in direct contradiction to the claim that rising CO2 increases temperature?

    Also, it seems like the Arctic Oscillation is viewed more as a weather event, and not a climate issue. Meaning, it is much more chaotic, and will not have a diverse affect on climate as a whole and vice versa.
    Response:

    [DB] The AO is what it's name says it is: an oscillation.  Thus, the long-term trend is nil.  But the reality shows that what is happening in the Arctic is indeed unlike a natural cycle and fits the understanding of the Arctic Amplification response to the ongoing warming of the world.  With the ongoing demise of the Arctic Sea Ice cap serving the role of the canary in the coal mine.

    As far as colder air forming a negative response to the amplification, see:

    BOE et.al (2009) "Current GCMs' Unrealistic Negative Feedback in the Arctic", Journal of Climate

    The vertical temperature structure of the atmosphere in the Arctic, characterized by a surface inversion during wintertime, exerts a strong control on the temperature feedback and consequently on simulated Arctic climate change. Most current climate models likely overestimate the climatological strength of the inversion, leading to excessive negative longwave feedback.
    H/T to the Artful Dodger.

  8. I'd invite Clyde to Neven's site, where such issues are the meat of daily discussion and where offering one's personal models is encouraged. The daily graphs page is a good bookmark as well. You're right, though: you'll get hammered for not addressing the carefully measured data and instead relying on a relative handful of newspaper reports, many that report from small areas of the Arctic.

    Note that Zwally said "at this rate," and if he was thinking of the drop from 2006 to 2007 that's certainly true: a drop of 1.5 million sq km in minimum extent per year would definitely have the summer free of ice by 2012. However, "at this rate" is the simplest model, and I'm sure that Zwally would never bet on it--not in 2007. As extreme as the 2007 extent was, it's been beat by 2011, and 2012, after a bizarre spring, is now racing down at a rate that may be unprecedented over the last 30 years. Volume set a record low in 2011 as well, and 2012 is tracking almost dead on top of 2011.
  9. I'm debating a Watt-bot and he's claiming that Arctic ice decline is all due to changes in wind patterns.  He's posted several articles, but the broadest claims are made here:

    Wind contributing to Arctic sea ice loss, study finds

    Anything in the article that points out this doesn't question climate change's role he describes as spin - even though the study itself only seems to attribute 30-50% of the ice loss to changing wind patterns, according to the article.

    Apparently this line is the dominant response to Arctic ice loss at WUWT other than the occasional rallying cry of "Recovery" (such as we are currently hearing).  Any thoughts on this?

  10. In reference to my own question at #59: in case anyone else encounters this argument, I dug up the answer myself.  This is from Joe Romm, and addresses that "single factor" talking point nicely:

    Study: “It is clear … that the precipitous decline in September sea ice extent in recent years is mainly due to the cumulative loss of multiyear ice.”

  11. muoncounter#46: 

    May I know the source of this graph?  Haven't been able to dig it up.

  12. PS - sorry, make that Muoncounter#49...

  13. I was reading this the other day:

    https://www.rmets.org/sites/default/files/qjcallender38.pdf

    It was published in 1938, written in 1937. In the discussion chapter I found this citation:

    "Dr. C. E. P. BROOKS said that he had no doubt that there had been a real climatic change during the past thirty or forty years. This was shown not only by the rise of temperature at land stations, but also by the decrease in the amount of ice in arctic and probably also in antarctic regions and by the rise of sea temperatures."

    And:

    "In reply to Dr. Brooks, the author agreed that the recent rise in arctic temperatures was far too large to be attributed to change of CO he thought that the latter might act as a promotor to start a series of imminent changes in the northern ice conditions. On account of their large rise he had not included the arctic stations in the world temperature curve "


    There seems to have been a large melting during possibly up to 40 years where there was a local warming of both land and sea, melting large amounts of ice. The strange thing is that there seems to have been a 10-fold increase in temperature in the polar area compared to lower latitudes.

    I thought this was a cool period and I don´t find anything in the graphs for temperature in the 19th century representing that increase which should have started 1900-1910. I´ve never seen it mentioned anywhere but in this article and old newspaper. I thought that the warming started later.

    Bu the most interesting detail is that there was such a large difference between the polar region and lower latitudes. We don´t see that now as the ice is melting.

    It indicates that we are missing something about polar ice melting. Are there any similar differences today? Are there any areas experiencing 10-fold temperature increase compared to other areas?

    I guess that there is no way of investigating the extent of melting back then, but the small bits of information i have found indicates that it was much larger than today. Even if it was smaller or the same extent, it is confusing that there was such large melting during so many years during a period where data says the global mean was low.

    Since the polar region doesn´t show a larger increase in temperature than other areas, and certainly not a 10-fold increase, maybe we don´t have that much to worry about, at least when it comes to polar ice?

  14. Seroius and I think well founded question here.

    In the source linked, http://nsidc.org/cryosphere/sotc/sea_ice.html they describe that antarctic ice has been increasing during this time period while arctic is decreasing. In terms of standard deviation from mean the arctic decrease has been twice as sharp, but:

    1. In terms of volume of ice, are we net gaining or losing ice at the poles?

    2. Since arctic ice is floating and antarctic ice is on land (pulling this from Inconvenient truth), should the antarctic ice be the main concern when it comes to rising sea levels? Or is that outweigh by the specific areas growing or shrinking  (e.g. growing areas are sea ice, shrinking are land based)?

  15. jfrantz @64, the linked source is describing sea ice for both Antarctica and the Arctic.  Antarctica has a fringe of sea ice that is preserved even in summer, though with minimal extent (about 4 million km squared).  In winter it becomes very extensive, exceeding in extent the Arctic sea ice maximum, mostly because it can extent into open ocean.  In terms of sea ice extent, the reduction in Arctic sea ice has been far greater, as shown in the graph in the section on Antarctic sea ice extent in the linked source.  That graph, however, only extends to Dec, 2012.  A more recent graph shows the Antarctic sea ice extent anomaly to have declined astonishingly over the last two years, reaching Arctic (and hence negative) levels by Dec 2016:

    (Source)

    The low extent anomaly has continued into 2017:

    (Source)

    With regard to sea ice volume, we are primarilly dependent on models, as there are insufficient depth measurements of the ice to provide a region wide, continuous time series.

    A region wide model for Antarctic sea ice volume reported in 2014, and showed sea ice volume to 2010:

    The trend of 28.7 km^3/yr compares to Arctic trends of -260 km^3/year in April, and -320 km^3/yr in September shown for the Arctic:

    Obviously the recent massive retreat in Antarctic sea ice extent will also have been reflected in a retreat in Antarctic sea ice volume, but as we do not know to what extent it has been matched by a reduction in sea ice thickness, we do not know by how much.

    Finally, if Al Gore did say that "arctic ice is floating and antarctic ice is on land", that is misleading (at least out of context).  The peak Arctic sea ice volume was about 33,000 km^3 in April (the time of maximum volume).  That is dwarfed by the 2,900,000 km^3 volume of the Greenland Ice Sheet.  Looked at differently, 14,000,000 km^2 area of the Antarctic continent, while five times the minimum Antarctic sea ice extent is about 80% of the maximum Antarctic sea ice extent.  Whether we look at either volume or extent, both polar regions are a story of land ice and sea ice.  However, Antarctica is landice surrounded by sea, while the Arctic is sea ice surrounded by land.  That makes a very large difference with regard to the rapidity of temperature responses, and the rapidity of albedo changes with warming or cooling, both being much faster in the Arctic.  With regard to sea level rise, however, both poles are a land ice story.

     

  16. To sum, the earth is losing a trillion tons of ice per year:

    - 159 Gt Antarctic land ice, McMillan el al, GRL (2014)

    + 26 Gt Antarctic sea ice, Holland et al, J Climate (2014)

    - 261 Gt Arctic sea ice, PIOMAS

    - 378 Gt Greenland, Enderlin et al, GRL (2014)

    - 259 Gt other land based glaciers, Gardner et al. Science (2013)

    Total = - 1,031 Gt

    Losses outnumber gains by a ratio of 40:1

  17. NASA's position on land-based ice sheet mass losses:

    "Data from NASA's GRACE satellites show that the land ice sheets in both Antarctica and Greenland are losing mass. The continent of Antarctica has been losing about 118 billion metric tons of ice per year since 2002, while the Greenland ice sheet has been losing an estimated 281 billion metric tons per year. (Source: GRACE satellite data through 2016)

     

    Greenland Land-based Ice Sheet Mass Losses, per GRACE:

    NASA_GRACE_Greenland

     

    Antarctica Land-based Ice Sheet Mass Losses, per GRACE:

    Antarctica Mass Losses NASA GRACE

  18. As Tom notes, both the Arctic sea ice and Antarctic sea ice are more than 2 standard deviations below the long-term average.  So that point bears repeating.

    Arctic Sea Ice (per NSIDC):

    NSIDC Arctic Sea Ice

     

    Antarctic Sea Ice (per NSIDC):

    NSIDC Antarctic Sea Ice

  19.            If the Arctic Ocean ice cover is continuing to decline the melting season, in the future Are there will have the black sheet which absorb heat causing ice to melt more.On the other hands if the ice is continuing to melting Are it will reach some point to stop melting and gaining ice instead?
                The ice movement can cause to loss of ice mass.The loss of ice mass is a key indicator for ice sheet.The major characteristic of the Arctic is the warming faster than the rest of the globe as a result especially in summer.The sea ice retreat has significant effects on high latitude ecosystems on the evolution of climate change itself.How the Arctic icemelt is a natural cycle because one of the reason because human activities?Then human activities cause to effect the climate change.And climate change of Arctic sea ice as natural phenomenon.
    If it is a natural cycle then it will not effect only on the land but how about the shortwave radiation in the atmosphere or the Arctic troposphere.Another important feature of Arctic chemistry is the involvement of bromine gas in sudden ozone depletion events in the lower troposphere during spring.However human activities not effect only climate or temperature but it effect to living organisms and their habitats.

    If it possible that polar bear immigrate to the other parts of the world because of the environment has changed.Furthermore maybe in the future there will have the technological solution to mitigate the problem that is happening.

  20. Japanese (JAXA), Danish(DMI), US (NSIDC) and US MASIE data show minimum Arctic ice extent has not decreased since 2007.

    DMI shows minimum Arctic ice volume has not decreased since 2003 when readings first began, however PIOMAS shows a decrease. One is obviously wrong.

    The first IPCC report in 1990 showed sea ice extent from the early Nimbus satellites from 1973 to 1990. (Observed Climate Variation and Change chapter 7) Ice extent grew 500,000 square kilometres from 1973 to 1979 which was probably the highest extent since about 1910.

    Ice decreased significantly in the 1920's through to the 1950's and increased until 1979. The current satellite monitoring started in 1979 but if it had started in in the 1920's, it would probably would be about the same as now.

    If you look at the Atlantic Multidecadal oscillation index, you will see that there is a close correlation with Arctic ice

     

     

  21. Bruce @70 , 

    I presume you are talking about Arctic sea ice volume.  Ice volume is distinctly more important than ice extent, in showing which way things are trending ~ particularly the summer minimum (for obvious reasons!).

    PIOMAS shows a huge decline in summer ice volume over 40 years.

    DMI shows the summer minimum volume for 2015 thru 2018 as being below the 2004-13 average.  And 2019 YTD is also below the average.

    ( Sea ice extent in the 1920's and prior, was poorly monitored, for obvious reasons!  We won't mention the war . . . or the Titanic. )

    Bruce, I must confess I don't see what point you are aiming towards.  Please go into details, if possible.   Were you leading towards a Pacific oscillation?

  22. bruce @70,

    May I add some numerical bones to the comment from Eclectic @71,

    DMI Arctic Sea Ice plots the 2016 minimum as being 1.7cukm below the average minimum 2004-13. Using PIOMAS monthly data the 2016 minimum sits 2.2cukm below th 2004-13 average, this not a great difference given the measurements being undertaken. So your assertion that one of these must be wrong requires some explanation.

    You further assert that 2007 provides the lowest annual minimum for Arctic Sea Ice Extent in JAXA, DMI, NSIDC & MASIE when all these show the minimum year as being 2012. A plot of rolling 12-month averages (as per the graph in the OP above) shows a reasonably constant reduction in Arctic Sea Ice Extent, from 12.3M sqkm in 1979 to 10.3M sq km today. The lowest annual average Arctic SIE occurred in 2016.

    You assert solely on the basis of IPCC FAR Fig 7,20a (below) that 1979 saw "probably the highest extent since about 1910."  Fig 7.20a does show a downward wobble in 1974 prior to the satellite era (as does the graph in the OP above) but this is small relative to the reduction in SIE over the satellite era. The 1974 dip, all of 0.3M sqkm, is shown in the graph in the OP above which also shows the reduction in SIE over the satellite era, something not well set out in Fig 7.20a.

     

    IPCC FAR Fig7.20a

    Finally, while values for the AMO does have reasonably uncontroversial sources, this is not the case for all sources of 20th century Arctic SIE records. Perhaps you could thus be clear as to your source of 20th century Arctic SIE data.

  23. With the absence of any further comment from commenter bruce, it might be worthwhile joining a few dots to make sense of his intervention @70.

    The insistence that Arcric SIE annual minimums have "not decreased since 2007" follows from denialist insistence that there has been an Arctic version of the 'hiatus' - Arctic Sea Ice has not been diminishing as it did in previous AGW years and the trend is now flat. Swart et ak (2015) 'Influence of internal variability on Arctic sea-ice trends' has been cited as showing evidence of this 'hiatus' operating over the 6-year period 2007-13 and which is now assertedly extended for significantly more years. Thus the "not decreased since 2007" is not interested in the 2012 minimum as the denialist assertion concerns the multi-year trend not the individual years.

    The data used for IPCC FAR Fig20 is described thus:-

    "Sea-ice conditions are now reported regularly in marine synoptic observations, as well as by special reconnaissance flights, and coastal radar. Especially importantly, satellite observations have been used to map sea-ice extent routinelysince the early 1970s.The American Navy Joint Ice Center has produced weekly charts which have been digitised by NOAA. These data are summarized in Figure 7.20 which is based on analyses carried out on a 1°latitude x 2.5° longitude grid."

    It is obviously not the best of data given it shows such a small drop in SIE 1979-1990. It may be possible to find this data within literature of the time (the likes of say Mysak & Manak (1998) also use some JIC data) but it doesn't in anyway resemble modern satellite SIE data.

    The AMO's "close correlation with Arctic ice" is probably simple nonsense. Even denialists like Connolly et al (2017) found it difficult to fabricate an Arctic SIE racord based on Arctic temperature that was much different to more respectable records using similar methods. The graphic below is from Cea-Pirón & Cano-Pasalodos presented within a Judith Curry blog-comment-thread. SIE records such as HadISST & Marsh et al (2016) developed from historical ice records show significantly higher SIE over the earlier pre-1950 years, perhaps 2M sq km higher. None of these show any AMO-like wobbles.

    Arctic SIE based on temperature

    But what Connolly et al did manage to achieve was to present a graphic to the world (below) from Alekseev et al (2016) [paywalled] (but without the actual post-1979 SIE data plotted as in Alekseev et al (2015) Fig3b) and without mentioning the finding predicting of an ice-free Arctic summers by 2030.
    Alekseev et al Fig

    If you are happy with the most basic of similarities being considered as being a "close correlation", the likes of this Alekseev et al (2016) graph may be assumed as an upside-down AMO graph but the assertion doesn't actually pass muster. Firstly the Alekseev et al graph is simply an upside-down version of a rather crude Arctic summer temperature record which are then no more than assumed as a proxy for Arctic summer SIE minimums. And even then, the upside-down AMO does have a very different shape. The 1950 AMO(us-d) was the same value as recent values with a peak inbetween in the 1970s (rather than 1960s) and a 'hiatus' since 1999. So AMO(us-d) is a long way off from being a proxy for Arctic SIE values.

  24. MA Rodger @73 & prior, 

    thank you for the depth of knowledge which you add (to this and other threads) .

    Being more than 48 hours, it is very likely that the commenter will not return to elaborate or dispute over his original comment.

    ( Each time there is a "drive-by" , I am yet again amazed at the chutzpah of a "drive-by-er" who chooses to raise his head above the parapet while possessing only a thumbnail of information/misinformation on the topic in question.   How does a large bucketful of chutzpah manage to evaporate so quickly, before the making of a second comment?   It seems the liquid chutzpah  must be a highly volatile substance.

  25. Eclectic @74,

    This particular "drive-by-er" does have a history in the SkS comment threads. As far as I can see, he doesn't stick around to discuss points he raises but there is perhaps evidence of 'lurking' in this comment as it is replying to a previous in-thread comment.

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