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Is Antarctica losing or gaining ice?

What the science says...

Select a level... Basic Intermediate

Satellites measure Antarctica is gaining sea ice but losing land ice at an accelerating rate which has implications for sea level rise.

Climate Myth...

Antarctica is gaining ice
"[Ice] is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap." (Greg Roberts, The Australian)

Skeptic arguments that Antarctica is gaining ice frequently hinge on an error of omission, namely ignoring the difference between land ice and sea ice.

In glaciology and particularly with respect to Antarctic ice, not all things are created equal. Let us consider the following differences. Antarctic land ice is the ice which has accumulated over thousands of years on the Antarctica landmass itself through snowfall. This land ice therefore is actually stored ocean water that once fell as precipitation. Sea ice in Antarctica is quite different as it is ice which forms in salt water primarily during the winter months. When land ice melts and flows into the oceans global sea levels rise on average; when sea ice melts sea levels do not change measurably.

In Antarctica, sea ice grows quite extensively during winter but nearly completely melts away during the summer (Figure 1). That is where the important difference between Antarctic and Arctic sea ice exists as much of the Arctic's sea ice lasts all the year round. During the winter months it increases and before decreasing during the summer months, but an ice cover does in fact remain in the North which includes quite a bit of ice from previous years (Figure 1). Essentially Arctic sea ice is more important for the earth's energy balance because when it increasingly melts, more sunlight is absorbed by the oceans whereas Antarctic sea ice normally melts each summer leaving the earth's energy balance largely unchanged.

Figure 1: Coverage of sea ice in both the Arctic (Top) and Antarctica (Bottom) for both summer minimums and winter maximums
Source: National Snow and Ice Data Center

One must also be careful how you interpret trends in Antarctic sea ice. Currently this ice is increasing overall and has been for years but is this the smoking gun against climate change? Not quite. Antarctic sea ice is gaining because of many different reasons but the most accepted recent explanations are listed below:

i) Ozone levels over Antarctica have dropped causing stratospheric cooling and increasing winds which lead to more areas of open water that can be frozen (Gillet 2003, Thompson 2002, Turner 2009).

and

ii) The Southern Ocean is freshening because of increased rain and snowfall as well as an increase in meltwater coming from the edges of Antarctica's land ice (Zhang 2007, Bintanga et al. 2013). Together, these change the composition of the different layers in the ocean there causing less mixing between warm and cold layers and thus less melted sea and coastal land ice.

All the sea ice talk aside, it is quite clear that really when it comes to Antarctic ice and sea levels, sea ice is not the most important thing to measure. In Antarctica, the largest and most important ice mass is the land ice of the West Antarctic and East Antarctic ice sheets.

Therefore, how is Antarctic land ice doing?

Shepherd et al. 2012
Figure 2: Estimates of total Antarctic land ice changes and approximate sea level contributions using a combination of different measurement techniques (Shepherd, 2012). Shaded areas represent the estimate uncertainty (1-sigma).

Estimates of recent changes in Antarctic land ice (Figure 2, bottom panel) show an increasing contribution to sea level with time, although not as fast a rate or acceleration as Greenland. Between 1992 and 2011, the Antarctic Ice Sheets overall lost 1350 giga-tonnes (Gt) or 1,350,000,000,000 tonnes into the oceans, at an average rate of 70 Gt per year (Gt/yr). Because a reduction in mass of 360 Gt/year represents an annual global-average sea level rise of 1 mm, these estimates equate to an increase in global-average sea levels by 0.19 mm/yr.

There is variation between regions within Antarctica (Figure 2, top panel), with the West Antarctic Ice Sheet and the Antarctic Peninsula Ice Sheet losing ice mass, and with an increasing rate. The East Antarctic Ice Sheet is growing slightly over this period but not enough to offset the other losses.  There are of course uncertainties in the estimation methods but independent data from multiple measurement techniques (explained here) all show the same thing, Antarctica is losing land ice as a whole, and these losses are accelerating quickly.

Last updated on 10 July 2013 by mattking. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Further reading

Tamino compares and analyses the long term trends in sea ice data from the Northern and Southern Hemisphere in Sea Ice, North and South, Then and Now.

Update

On 20 Jan 2012, we revised this article upon learning it referenced an incorrect quote. We apologize to Dr. Michaels and to our readers for the error.

Comments

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Comments 101 to 150 out of 211:

  1. Thank you both DB and Steve!
  2. Here's another new paper on Antarctic ice (h/t Ari).
    A multivariate analysis of Antarctic sea ice since 1979.
    The work presented here indicates that Antarctic sea ice variability is a multivariate phenomenon and that the minimum, maximum, and mean SIE may respond to a different set of climatic/geochemical parameters.
    ...
    For Antarctica, similarities were found for the minimum sea ice extent, O3 minimum, and total solar irradiance, while the mean sea ice extent was associated with the global sea surface temperature, the global air surface temperature, the CO2 concentration, and the O3 depletion area. Near similar patterns were found among the maximum sea ice extent, the SOI, and the SAM.
  3. The idea that ozone depletion is responsible for the increase in Antarctic sea ice had a cold bucket of water thrown on it. See Has the ozone hole contributed to increased Antarctic sea ice extent? Sigmond & Fyfe, 2011.
    In this study we consider the impact of stratospheric ozone depletion on Antarctic sea ice extent using a climate model forced with observed stratospheric ozone depletion from 1979 to 2005. Contrary to expectations, our model simulates a year‐round decrease in Antarctic sea ice due to stratospheric ozone depletion.

    "Circulation changes, in part due to ozone depletion, are responsible for the increase in Antarctic sea ice," would seem more correct.
  4. Given the concerns on Bishop Hill I would suggest that Sks remove comments 3, 5 and any other early comments that were replying to this post before it was updated to make a definite distinction between land and sea ice. If Sks did, for example, write the response to comment 3 after updating the post, then (-Accusations of dishonesty snipped-), when it actually seems like they were pointing out that the original incarnation of this page was unclear and certainly incomplete. I hope the Sks team sees my point.

    Our 'side' of the debate is by far the stronger, supported as it is by the weight of peer-reviewed science, and so there need be no reliance on misinformation, no matter how small a nugget of misinformation it is. Therefore all humility and reticence must be shown on sites like Sks, and things like this that have been overlooked must be corrected. Not doing so risks giving those of an anti-science persuasion an excuse to focus on something other than the science!

    Of course, the current incarnation of this page is an excellent description of the state of Antarctic ice, no problems there.
    Response:

    [DB] Accusations of dishonesty snipped.

    "Therefore all humility and reticence must be shown on sites like Sks, and things like this that have been overlooked must be corrected."

    SkS endeavors to keep its focus on the science, not on rhetoric, ideology or invective.  Hue and cry from the "skeptics" on things transparently not based in science amount to little more than tone trolling and are typically ignored.

    However, your point is made, taken and noted.

  5. DB I see that the responses to the comments in question have been updated and the whole thing makes perfect sense now.

    Tone trolling should rightly be ignored, but IMO Bishop Hill did have a point, although they vastly overstated the significance of it. That Sks is coming under fire presumably means you're doing a good job, so keep it up!
  6. A recent paper suggest that there is not sufficient evidence to conclude that ice loss from Antarctica is accelerating. The paper is open acces and can be found here: Zwally and Giovinetto, 2011

    It seems to be in conflict with the statements in this post as well as he recent paper by Rignot et al, 2011

    Does the Zwally paper hold any merits and should it be incorporated in the post?
  7. SRJ at 23:12 PM on 29 September, 2011
    The Zwally paper re-assessing the data is later than Rignot, and the science is persuasive (in my view). Although in Zwally the estimates of average mass loss have been revised and reduced over the whole continent, there is even less doubt about increasing loss of land based ice in western Antarctica. The linkage with temperature rise in this area is perhaps obvious.
  8. # 107 Peter Hogarth
    Thank you for the response.
    When you write that there is even less doubt about increasing loss of land based ice in western Antarctica, what do you then base that on? The Zwally paper?

    Another question, in Zwally the estimated overall ice loss is 31 Gt/year. Could the cause for this be an decrease in precipation over Antarctica?
  9. Is there a possibility that the earth's axis has moved marginally i.e the North Pole is now slighty closer to the sun thus warmer there but colder in the south creating more ice in the Antartic. Wouldn't this also explain the changes in the magnetic fields that some scientists have apparenty noticed? i do believe that the recent earthquakes in Japan were strong enough to move the axis of the Earth albeit a small amount.
    Response:

    [DB] If you think about this you'll be able to answer your own question.  Any astronomer in the world can tell you that there's no evidence whatsoever for it.  GPS systems would be way off.  The tides would be different.  Satellites that measure earth changes to sub-millimeter accuracy would also provide evidence against it.  There is simply no physical evidence to cause such a shift that would not also be felt the world over.

    The crustal displacement/polar wander fancies of Hapgood are just that: flights of imagination.

  10. I have come across this comment on a thread at WUWT.

    "Although the Alarmist arguments sometimes include claims about ice volume, such claims are based upon sea ice extent and subjective guesses about what they beleive a model parameterization adjustment should be to produce a desired result. Currently, there are no objectively quantitative ice volume measurements with anthing remotely close to the necessary temporal and spatial coverages. Consequently, Morano and anyone else can only make objective observations about sea ice extent."

    Is there any validity to this guys argument?
    Thanks
  11. Look at the gravity probes measurements over Antarctica. They clearly and unequivocally show a loss of mass at an accelerated rate. No models no fitting, just good old empirical unadulterated data. And if somebody thinks that the rocks have been vaporizing, then think again. Mass loss -> Ice mass loss -> Ice volume loss. No need for models to tell us that.
  12. @ peacetracker
    "Currently, there are no objectively quantitative ice volume measurements with anthing remotely close to the necessary temporal and spatial coverages. Consequently, Morano and anyone else can only make objective observations about sea ice extent."
    That is simply untrue. It is widely known that multiple physical measurements of ice thickness are taken at regular intervals. These range from ice thickness measuring buoys to US Navy submarines to aerial ice thickness measuring instrumentation packages to ships measuring the thicknesses on their recon cruises to orbiting satellites (IceSat & CryoSat2).

    Anyone who would maintain otherwise is simply talking about things about which they know nothing...or simply lying with the intent to mislead.

    http://neven1.typepad.com/blog/2011/08/polarstern-reaches-north-pole.html

    http://neven1.typepad.com/blog/2011/09/more-on-ice-thickness-from-awi.html

    http://imb.crrel.usace.army.mil/

    http://amap.no/swipa/

    http://www.osi-saf.org/index.php

    PIOMAS is a useful tool to incorporate all of these metrics into a validated model using known ocean/atmospheric/ice dynamics to compare past observations to current ones:



    and

    Response: [JH] Perhaps this comment should be transformed into a rebuttal article?
  13. Peacetracker, if you want to find out the validity of someone's argument, ask them for evidence of their claims. Ask this WUWT joker for evidence of guesswork at PIOMAS.

    Essentially, the commenter is saying that PIOMAS scientists are faking each month's data point to make sure that volume is dropping like a rock. If you don't understand how sea ice volume is measured, then ask yourself what is the more likely claim:

    A) the dozens of scientists at several scientific organizations are knowingly committing fraud to make it look like sea ice volume is dropping. They come to work every day knowing that they're doing the exact opposite of what they're trained to do, the exact opposite of what they went through 6-10 years of college to do.

    B) sea ice volume is dropping, consistent with a warming ocean and atmosphere. Volume drop is also corroborated by evidence from people who live and work around the Arctic circle.
  14. @peacetracker #110:

    A recent example of direct measurement of central Arctic sea ice volume is described in detail in “Changes in Arctic Sea Ice: Young and thin instead of old and bulky.”

    To access this informative article, click here.
  15. peacetracker#110: "based upon sea ice extent and subjective guesses"

    Can anyone seriously contemplate circumstances in which areal extent is decreasing, but volume is increasing? That's patently ridiculous.

    See the Arctic ice threads.
  16. Very useful feedback. Thanks
  17. DSL, wow that IS a bit odd.

    Antarctic sea ice is expected to eventually start declining, but this seems more likely to be some sort of short-term fluctuation. The 'growth' in Antarctic sea ice has been small enough that the current year amount still drops below the long term average semi-regularly. This contrasts with the situation in the Arctic where skeptics got excited earlier this year about the extent coming CLOSE to the long term average for the first time in years. Make sure to read this: get far cry 3. Thus, the current dip is unusual, but not unprecedented. Looks like the Southern melt season started about two weeks early for some reason.
  18. Well, obviously, Antartica is losing ice due to the fact that our planet is warming up. Just because of the floods, dosent mean thats going to make it gain ice. And even if it gains ice, it will lose that ice anyway.
    Agreements?
  19. The date of the last update at the end of the article does not match the Update date.
    Response:

    [DB] The article update date is indicative of the last update/rewrite/iteration of the main article.  The date of the "update" below that indicates the date of the specific revision mentioned (correction of the incorrect quote).

  20. On the Antarctica ice melting issue aren't there some underwater active volcanos that would melt ice?

    Being there were crops and vineyards grown in Greenland between the 9th & 12th more or less how warm would temperatures have to get for that to happen again? What caused the temperatures to rise to that point before?
  21. muttkat, have a look at the Greenland used to be green myth. I doubt there would have been any vineyards there, though.

    As for underwater volcanoes, presumably they would be very noticeable, being as how the water temperature would get warmer the deeper you go towards those volcanoes ?
    Response:

    [DB] NSIDC has a FAQ on undersea volcanoes here:

    http://nsidc.org/asina/faq.html#volcanoes

    "The heat from the volcanoes would have dispersed over an enormous volume and had little effect on ocean temperature, much as a bucket of boiling water emptied into a lake would have little effect on the lake's temperature."

  22. #120 muttkat: There's no evidence for vineyards in Greenland in the MWP, temperatures were nowhere near warm enough for that!

    The only evidence for crops are a few grains of barley found in a Viking-age midden, but that does not confirm whether they were locally-grown or imported. Local growing of barley is maybe possible in the warmest years of the Greenland MWP, but the most sensible explanation is that the Norse Greenlanders imported it, due to a combination of low temperatures and poor soils. It would be a commodity worth trading for, as the Norse were partial to beer!

    There are a few active volcanoes in Antarctica, but not enough volcanism to do much damage to a whole ice sheet (ice sheet big, volcanoes small). Iceland is a good example, where Vatnajokull survives happily despite having several active volcanoes under it, notably Grimsvotn and Bardarbunga.
  23. Lifted from The Conversation:

    "A 364-metre-long ice core record has revealed an unusual pattern of rapid warming across the Antarctic Peninsula over the past 100 years.

    An Australian National University research expedition produced findings dating back 15,000 years, resulting in the first comprehensive temperature record of the Antarctic Peninsula.

    Dr Nerilie Abram said the Antarctic Peninsula is one of the fastest warming places on Earth and the findings will allow researchers to compare recent and past temperatures in the region for the first time."

    More here.
  24. Interested in your response to this post on WUWT. Thanks.
    http://wattsupwiththat.com/2012/09/10/icesat-data-shows-mass-gains-of-the-antarctic-ice-sheet-exceed-losses/#more-70757
    Response: [DB] It is customary when linking to an outside document to first provide your understanding of it. Please proceed to do so.
  25. OK. Watts is claiming that a recent report by NASA shows that satellite measurements find that the Antarctic as a whole is gaining land ice mass rather than losing it as previously thought. He also has a side-swipe at skeptical science suggesting you update this post and he provides a link to this page.
  26. The WUWT report is about recent ICESat data that apparently show mass gain in the Antarctic ice sheet from 2003 - 2008, citing a paper (and linking a video) by lead author Jay Zwally.

    The NASA page on it is here.
  27. Apparently an internal document, not a peer-reviewed study. Maybe they have submitted/plan to submit.
  28. Yah, barry - sounds like accelerated loss in addition to accelerated gain - perfectly consistent with global warming, as the authors note: "A slow increase in snowfall with climate warming, consistent with model predictions, may be offsetting increased dynamic losses."

    Watt's the big deal?

    Ha ha ha, but more seriously, how long would you expect the mass gain to last, if indeed it is happening?
  29. I would be cautious about reading too much into these results. This is also just a conference abstract. Then again, Zwally does good work.

    It also keep in mind that they conclude that:

    "A slow increase in snowfall with climate wanning, consistent with model predictions, may be offsetting increased dynamic losses."

    If true, one has to wonder for how much longer that might hold?
  30. I would expect Zwally to have the numbers right. The interesting science question is reconciling the ICESAT data with the GRACE data.

    This abstract was done in July. The point for Watts is provide some reassurance to readers wondering about the arctic meltdown. All his readership cares about is having an excuse to do nothing. I suspect for the average US citizen, the effects of climate change are so far small, in the future, and happening elsewhere, whereas any sort of mitigation is perceived as less spending power by one means or another.
  31. Those responses seem a bit cynical. Yes, (AR4) climate models projected increasing mass balance of the Antarctic ice sheet over the 21st century. Observational analyses since then have tended to discern a mass loss, which was a surprise result - although I can't remember anyone ever mentioning that recent results were in opposition to the models (and perhaps I'm being a bit cynical here myself).

    The "big deal", to my mind, is that if the ICESat analysis is robust, there are implications for sea level projections, which of late have been much higher than AR4. I need to go back and read some of those papers, but IIRC the recent hike in sea level projections is strongly rooted in the perceived loss (acceleration?) of Antarctic ice sheet mass balance. AR4 projected a negative sea level contribution from the Antarctic ice sheet.

    I don't think SkS should wave these results away, but present them as an update with the appropriate caveats. If Zwally was up for it, a post by him here would be terrific for all sorts of reasons.
  32. Barry, please do look up those projections. I suspect you'll find them weighted more to the Northern Hemispheric contributions and to the thermal expansion component.
  33. GRACE, Icesat and models all agree on that interior of Antarctica accumulates ices while there is iceloss on the margins. However, size matters and the mass loss or gain depends of the relative magnitudes.

    Any GCM model-based estimate of sealevel rise would be based on Antarctica accumulating ice. As far as I know, these have only very primitive icesheet dynamics (if any) so sea level results from such an approach are so uncertain that the AR4 statement excluded them entirely. Vermeer and Rahmsdorf instead a semi-empirical approach. This also doesnt incorporate any icesheet dynamics so I dont think this result has any bearing on the estimate at all.
  34. Daniel, first thing I've done is to check the papers referenced in the intermediate version of the top post.

    Velicogna 2009 [PDF] discerns comparable mass loss for Greenland and Antarcica, with comparable contributions for sea level rise.

    Chen et al 2009 [PDF] conclude with a mass loss for the whole of Antarcica of 190 +/-77 Gt/yr, comparable to higher Greenland mass loss estimates of ~220 Gt/yr. Chen posits that "Using a simple linear projection for the period 2006 - 2009, Antarctic ice loss rate can be as large as -220 +/-89 Gt yr." Sea level contribution is, again, comparable to Greenland.

    Inferences on sea level rise from Antarctic mass loss mentioned here (upper bound 1.4 meters by 2100 from Antarctic ice loss). I'll have a better look for papers specifically about sea level/Antarctic ice loss.

    A quick search of SkS articles on Antarctic ice mass balance yields a range of estimates from -26Gt/yr to -300 Gt/yr, and acknowledgement that new data showing Antarctic ice loss (as wel as Greenland etc) contributes to higher sea level projections.

    The main SkS article on Antarctic ice mass balance (and mentioning sea level) is probably this one. Watts cites it in his article, and for once I find myself agreeing with him (on SkS updating), particularly in light of the final comment on that page.

    .... but multiple different types of measurement techniques (explained here) all show the same thing, Antarctica is losing land ice as a whole, and these losses are accelerating quickly.
  35. Hello Barry @131,

    "Those responses seem a bit cynical."

    I hope that you did not interpret my response that way. I'm just advocating caution, especially given the potential significance of this result. This is probably the first step towards Zwally et al. submitting a paper for publication and things can, and do, sometimes change a lot in the intervening steps. These types of data are incredibly finicky and all sorts of corrections need to be made especially for a long-term space-based monitoring platform.

    It would be nice to have Dr. Zwally post here, maybe once he has had his paper accepted for publication? If these preliminary findings hold true, this would be the first good news on the global warming front in quite some time.
  36. No worries, Albatross. Maybe the bee in my bonnet is buzzing a little loudly.

    Anyway, I was scoping google scholar for recent assessments, and found one I'd read a few months ago that probably informed my comments here (as well as remembered SkS posts).

    "Notably, the acceleration in ice sheet loss over the last 18 years was 21.9 ± 1 Gt/yr2 for Greenland and 14.5 ± 2 Gt/yr2 for Antarctica, for a combined total of 36.3 ± 2 Gt/yr2. This acceleration is 3 times larger than for mountain glaciers and ice caps (12 ± 6 Gt/yr2). If this trend continues, ice sheets will be the dominant contributor to sea level rise in the 21st century."


    Rignot, Velicogna et al 2011 [PDF]
  37. Barry, we have two different measurement systems, ICESAT and GRACE. If Zwally's results are correct, then there is a problem with the methodology, calibration or assumptions of one of them. For the moment, the published results say Antarctica is losing ice, and GRACE result indicate that it is accelerating. If it becomes clear that the ICESAT result is better, then obviously (and fortuitously), the conclusions will change.
  38. If published, with the same conclusion, it will be interesting to find out how Zwally's results compare to recent assessments using GRACE gravity satellites:

    1. Antarctic ice-mass balance 2002 to 2011:
    regional re-analysis of GRACE satellite
    gravimetry measurements with improved
    estimate of glacial-isostatic adjustment -Sasgen (2012)
    .

    2. Variability of mass changes at basin scale
    for Greenland and Antarctica - Barletta (2012)
    .

    And a forthcoming paper using satellite altimetry from (now defunct?) ENVISAT:

    Dynamic thinning of Antarctic glaciers from along-track repeat radar altimetry - Flament & Rémy (2012).

    The first two find mass losses are smaller than previous publications suggested, and Barletta (2012) finds a near-neutral mass balance trend in Antarctica between 2002-2007. It has since undergone rapid ice loss since then.
  39. scaddenp, Rob, those posts are fine briefs for an article here.

    Envisat went offline in April. Lasted 10 years, twice as long as its planned operational life. Various groups are still reprocessing the data.
  40. Tamino has another look at Antarctic sea ice based on 2012 data:

    http://tamino.wordpress.com/2012/09/20/poles-apart/
  41. NEWS ALERT: What’s happening to the Antarctic ice sheet doesn’t bode well for the future according to the latest research described in:

    Warming Oceans Will Start Massive Changes In Antarctic Ice Sheet , by Nathan, PlanetSave, Sep 20, 2012

    It will be interesting to see how the results of this new research is spun in Deniersville.
  42. John Hartz - Watts (at the hometown of denial) has already commented on this paper, dismissing it with "Oh wait, it's modeling, never mind."

    Golledge et al 2012 actually looks to be a very interesting paper - considering how fast moving peripheral glaciers in Antarctica may respond to warming oceans, with the potential to drawdown ice over very large areas. Essentially, at how speeding up these fast glaciers may "unplug" the ice stores over significant portions of Antarctica, allowing it to drain into the oceans.
  43. @KR #142:

    Proving once again that Watts hs spent wat too much tiome rattling around in the Climate Denial Spin Machine. He can no longer distinguish between up and down, right and left, forward and backward, etc. What is even sadder is that his minions automtically lap up every pile of poppycock that he deposits.
  44. Here’s yet another article hot off the press about the topic du jour.

    Does the expanding Antarctic sea ice disprove global warming? by Eric Berger, SciGuy Blog, Houston Chronicle, Sep 21, 2012

    Berger’s opening sentence: “Ice is a hot topic in the climate science community right now so let’s talk about it.”

    Berger’s concluding statement: “The bottom line is that scientists generally have predicted that the Antarctic sea ice will not begin substantially melting until the second half of this century.”

    Berger’s blog post was created in response to the recent pious pontifications about polar ice by non-scientists James Taylor and Steve Goddard.
  45. Not sure if this is helpful, but argument by analogy might be worth trying with those of a non-scientific background. The problem of arguing against global warming by using the record ice extent of the Antarctic is the basic one that there is no logical framework that says that a record Antarctic ice extent in winter cannot mean a record Arctic ice low in summer, or that this makes global warming impossible, or that this means that the planet is not going to suffer any consequences. It is simple falacious reaoning. No science is actually required to demolish this non-sequitur. Consider:

    I am a GP (and I am). A patient, a climate change contrarian, shows up in my surgery. He has a painful left leg. After some necessary investigations, he returns for the results.
    "I have some bad news", I say, "your investigations show a nasty malignant sarcoma of your left tibia. You will need an amputation to save your life"
    "Nonsense" says the contrarian, "I don't believe you, there's nothing wrong with me, look, my right leg is fine, in fact it's better than it's ever been" as he jumps up and down on his one good leg to demonstrate the unimpeachability of his logic.

    The issue is that both the Arctic and the Antarctic belong to the same natural entity, indeed if you subscribe to James Lovelock's thesis, the same organism. A healthy planet depends on the healthy functioning of all its parts. That the Antarctic ocean has so far escaped obvious global warming effects (though the Antarctic Peninsula is warming quickly) then this is neither suprising, nor does it prove anything else.
  46. I don't understand why you acknowledge that the Antarctic Sea Ice is increasing, since it seems to me that any supposed increase is statistically insignificant. Decadal averages (the linked plot is to Cryosphere Today Sea Ice Areas, which I averaged) indicate that there is no significant trend in Antarctic Sea Ice areas. The averages for the '80s, '90s, and 2000's are virtually identical. The clear and accelerating melting trend for the arctic (CT data again) is something else entirely. I'm puzzled as to why you've given the deniers even an inch on this.
  47. TimH - Because science is about looking at the full body of evidence. While 'skeptic' denial is often about looking at cherry-picked data, only the data that appears to support their points. It's quite important to not cherry-pick.

    You're quite correct, Antarctic sea ice increase is barely significant, while Arctic ice decrease is extremely significant to the point of being appalling (something the 'skeptics' appear to be hiding from, sticking fingers in ears and singing "lalalala!").

    Interestingly enough, this effect of some increase in Antarctic ice is consistent with warming due to anthropogenic greenhouse gases. Manabe 1991 Part 1 and Part 2 (a H/T to Rabett Run for the pointer) found when modeling Antarctic effects that increased precipitation from GHG warming led to fresher surface waters, suppressing convection from warmer lower waters through a steeper halocline, and thus slightly decreasing sea surface temperatures and increasing sea ice.

    Manabe's ideas weren't (at that time) widely held, as far as I can see, but he appears to have correctly predicted current observations by taking into account additional factors like halocline changes.

    Really (IMO) an interesting result. Note that this means warmer sub-surface water is not cooling as much, retaining more energy, and thus the reduced convection is a positive feedback to warming - effectively insulating, keeping the energy in the oceans. And those warmer sub-surface waters continue to melt Antarctica from beneath at the edges. Something I suspect 'skeptics' will not be pointing out.

    So - an unexpected observation leading to a better understanding? That's what science is about...
  48. FYI, a more-or-less positive press article on this:
    http://www.thestar.com/news/world/article/1275441--antarctic-sea-ice-is-increasing-is-global-warming-over
    (which might be a step forward for The Star, until recently the were still in the habit of including a random denialist quote).
  49. While not directly related to this article, it is always worth keeping in mind that the loss of Arctic sea ice is far bigger than the gain of Antarctic sea ice.
  50. Please read our latest article on the polar ice mass loss problem, it appeared today in Science: http://www.sciencemag.org/content/338/6111/1183.abstract

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