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  1. We must get better at marketing our data and corresponding interpretations to the general public. Otherwise, we will continue to loose the publicity battle despite the growning physical evidence in support of climate change.

    Comment by Randall W. Parkinson — 27 Oct 2009 @ 2:08 PM

  2. Quick comment… your first image in the post has the following typo:
    “Map of Antarctica showing number of melting days in summer 2008-2099″

    Cheers!

    [ Fixed, thanks!--eric]

    Comment by PB — 27 Oct 2009 @ 2:13 PM

  3. I don’t understand the second figure. The legend says both figures are for the same year, 1998, and it refers to left and right, and I see one above the other.

    [ Also fixed.--eric]

    Comment by Alan Robock — 27 Oct 2009 @ 2:21 PM

  4. There is a problem with the legend of the second picture.

    “Monthly averaged December-January surface temperature anomalies (K) for 1998 (left, strong negative SAM and SOI) and 1998 (right, strong positive SAM and SOI).”
    I suppose that the second “1998″ should be replaced by another year: 2008 for example

    Comment by pascal — 27 Oct 2009 @ 2:35 PM

  5. The question is: Are Antarctica’s ice sheets thinning beyond IPCC formal projections and if so is this due to or scheduled to be due to warming or increased sensitivity is this makes sense?

    [Response: There are no formal projections for thinning in existing IPCC work. Melt on the Antarctic surface has very little impact at the moment, in terms of dynamic thinning of the ice sheet anyway. Except for the Peninsula region, there hasn't been enough melt to matter (yet).--eric]

    Comment by pete best — 27 Oct 2009 @ 2:36 PM

  6. Is the figure on the right for 2008?

    Comment by Craig Cogger — 27 Oct 2009 @ 2:50 PM

  7. the recent Antarctic snowmelt minimum

    It’s nice to recognise it

    Comment by the fritz — 27 Oct 2009 @ 3:09 PM

  8. Ah, context.

    At home at RealClimate–in the denialosphere, not so much.

    Thanks for this informative post!

    Comment by Kevin McKinney — 27 Oct 2009 @ 3:44 PM

  9. The second and third figures are for 1998 and *1999* according to the auxiliary material at GRL.

    Comment by CM — 27 Oct 2009 @ 3:44 PM

  10. Re: Antarctic Glacier thinning

    A nice paper by Pritchard et al (Nature, v461, pp971 et seq.) shows how the rate of thinning has increased in both Greenland and Antarctica. As for the IPCC, I do not see any very specific predictions of future ice sheet mass balance in AR4, Section 15.3.4 or Sec. 19.3.5.2 of WG II available at
    http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg2_report_impacts_adaptation_and_vulnerability.htm

    They do say that there is “medium confidence that at least partial deglaciation of the Greenland ice sheet, and possibly the WAIS, would occur over a period of time ranging from centuries to millenia for a global average temperature rise of 1-4C”

    [Response: See also my comment above.-eric]

    Comment by sidd — 27 Oct 2009 @ 3:46 PM

  11. Curious about ozone here. When you say “ozone depletion has dominated Antarctic summer” – does that have the effect of making the summer much cooler than otherwise? Because with a healthy ozone blanket, would not the Antarctic summer be much warmer?

    Comment by Richard Pauli — 27 Oct 2009 @ 4:00 PM

  12. Of note is that we (over at World Climate Report) were one of the first places to highlight this finding, but never made any mention of how it meshed with Antarctic temperature trends.

    But, your explanation brings up a question: What is the relationship between SAM and Antarctic precipitation? If overly strong SAM is inhibiting warming, is it also inhibiting precipitation?

    Thanks,

    -Chip

    [Response: Chip, indeed you did highlight it, but in a highly misleading way. Hence this post (though I don't know that the authors were specifically responding to you). As for circulation and precip, yes one might expect what you suggest, but at least with available data, there are overall no statistically significant change in snowfall during the last 50 years (see here.--eric]

    Comment by Chip Knappenberger — 27 Oct 2009 @ 4:21 PM

  13. The deniers I’ve seen referring to your work have given it as a refutation of data from, e.g. GRACE, which show accelerating ice loss over recent years. My understanding is that your ice melt index is an approximation for ice melting at the surface of the sheet but is not a good approximation for total ice loss and it is not in contradiction with data showing accelerated ice loss. This would be a good thing for you to clear up.

    Comment by Eric L — 27 Oct 2009 @ 4:24 PM

  14. “My understanding is that your ice melt index is an approximation for ice melting at the surface of the sheet but is not a good approximation for total ice loss”

    It’s about as good (slightly more, but not massively) as sea ice extent is an approximation for total ice loss/gain. The difference being 15% coverage is counted as highly as 100% when it comes to extent, so the more broken up the ice (which is more likely in the summer and more likely still for thin ice) the worse extent is an analogue for ice volume.

    [Response: Huh? Let's not confuse things! Sea ice is floating ice 1-4 m thick. The melt we're talking about here is melt on the land ice -- the hundreds-of-m-thick glacier ice (the Antarctic ice sheet), and the floating ice shelves (also hundreds of m thick, and NOT the same thing as sea ice. The point is that melt on the surface of the ice sheet is almost all refrozen, so the ice melt index has little or nothing to do with mass loss. These are totally separate things (except when lots of melting on ice shelves leads to collapse of those shelves, as happened on the Larsen ice shelf in 2002.--eric]

    Comment by Mark — 27 Oct 2009 @ 5:07 PM

  15. “We must get better at marketing our data and corresponding interpretations to the general public. Otherwise, we will continue to loose the publicity battle despite the growning physical evidence in support of climate change.”

    Just a quick note re: the quote above. This site, and many others, are getting the evidence out there and I for one can’t thanks everyone here and to all of those contributing updates on the science.

    I’ve personally linked this site many times in the last while to counter the endless assault of skeptic arguments that tend to dominate forums. IT is working.

    Just thought you’d like to know…

    Thanks again,
    J Buote

    Comment by J Buote — 27 Oct 2009 @ 6:13 PM

  16. Thanks guys for the info. Very worthwhile site which I too send out to others for converting the doubters.
    One question I would like to ask and that is has the cumulative ice melt over the last 50 years been incorporated into the data? By this I mean that 50 years ago the ice cover would have been x % more or less than the % cover of today, or has it been pretty stable with annual increase and decrease on a seasonal basis? It would seem that from evidence that I have been given by a good friend of mine (former base leader at Port Lochroy in the mid 1950′s when they first found indications of an anomaly in the atmosphere became apparent, later called the Ozone hole.) that the ice cover is very similar today as it was way back then. This is supported by photographic evidence showing the ice sheets behind the base and little has changed. Any views on this?

    Comment by Kevin Coleman — 27 Oct 2009 @ 8:08 PM

  17. Here is a comment from the paper by Perlwitz et al that you cite
    “But just how influential a full stratospheric ozone recovery will be on Southern Hemisphere climate largely depends on the future rate of greenhouse gas emissions, according to the study. Projected increases in human-emitted greenhouse gases such as carbon dioxide will be the main driver for strengthening the positive phase of SAM.”

    Does that mean that it is a race between ozone recovery winding back SAM and allowing warmer air into the heart of the continent, and general AGW strengthening SAM and maintaining the blockage so that the centre of the continent doesn’t warm as much?

    [Response: Yup, this pretty much sums up the situtation. Of course, it is far more complicated than that, as explained e.g. in our (our paper, and a more recent one by Turner et al. about the non-SAM related variability and its relationship to sea ice changes.-eric]

    If so that is obviously a fairly complex prediction to be having to convey to the broader world. The comment earlier – “We must get better at marketing our data and corresponding interpretations to the general public. Otherwise, we will continue to loose the publicity battle despite the growning physical evidence in support of climate change.” may be particularly appropriate in this situation.

    Thanks for a very informative post guys!

    Comment by Glenn Tamblyn — 27 Oct 2009 @ 9:28 PM

  18. Stronger summer winds cause less melting? ( they might accelerate sublimation). Please also explain why increased exposure to ultraviolet rays due to ozone depletion might cause stronger west winds in Antarctica. Otherwise there will be skeptics galore about this very paradoxical result. Time to move a few hundred polar bears to this locale before they lose their arctic habitat. With larger ice mass at the south pole compared to the north, this could cause some wobble and unpredictability re the earth’s rotation and the stability of the seasons, “summer” being one of these.

    [Response: Who said this had anything to do with ultraviolet? There's a huge literature on this (start here), and one of our very first posts at RealClimate discusses it (here).--eric]

    Comment by Vern Johnson — 27 Oct 2009 @ 9:57 PM

  19. Thank you for good co0ment. I am always irritated by the arguments of deniers without correct understanding of new scientific findings. Academic communities and journalism are, I believe, responsible to providing their correct interpletation.

    Thanks again from Japan

    Comment by Mr Sh — 27 Oct 2009 @ 10:53 PM

  20. “The melt we’re talking about here is melt on the land ice ”

    OK, that wasn’t clear.

    Comment by Mark — 28 Oct 2009 @ 4:03 AM

  21. I am still not sure whether you are saying that the Antarctic ice is increasing or decreasing. If the melt is refreezing then there should be no change.

    However it would seem that the ice mass is increasing due to the Ozone hole, and so there is a negative contribution to sea level rise.

    Why can’t you come clean and say what you really think?

    Comment by Alastair McDonald — 28 Oct 2009 @ 7:05 AM

  22. May I take this opportunity to drive yet other nail into the ACC sceptics coffin. Take a look at science daily. Two links –http://www.sciencedaily.com/releases/2009/10/091023163513.htm : and this one — http://www.sciencedaily.com/releases/2009/10/091019162929.htm.
    They show highly accurate sediment data from a Greenland lake not subject to glacial erosion from the past 2 ice ages and 3 interglacial periods spanning roughly 200k years. They indicate very strongly that since about 1950 ( and I would say that date is pretty much spot on with all the reports I have read) there have been marked changes in the marine ecology specifically diatoms and algaes that have not occured ever during the past 200k years, despite ice ages and cyclical fluctuation in solar maximum’s, the earth’s tilt and associated wobbles etc. This is the first time that quatic indicators in sediment are showing the unmistakable affects of global warming. Sorry skeptics – but since these are NOT natural indicators, the only other possiblity is antropogenic! And around 1950 is when I have seen most of the worlds glaciers really begin to retreat in earnest as well and the chart of CO2 really beginning to take off like a rocket. Some feedback on this would be most welcome.

    Comment by Lawrence Coleman — 28 Oct 2009 @ 8:10 AM

  23. re: 22

    The problem is that actual thermometer readings from close to the lake you are referring to show no warming since 1950. That would seem to be conclusive proof that the changes in the marine ecology have another, non-temperature related cause.

    [Response: I haven't read the paper yet so I can't comment. I'm familiar with the location though, and I doubt very much that there is no warming since 1950 there! Can you point to some data to backup your claim?--eric]

    Comment by Cardin Drake — 28 Oct 2009 @ 9:51 AM

  24. “That would seem to be conclusive proof that the changes in the marine ecology have another, non-temperature related cause.”

    Not really.

    Somewhere nearby gets more rain because of higher water content of the air and this lake gets more runoff into it or less rain because it falls elsewhere that isn’t the catchment.

    Migrant birds now turn up earlier and stay longer because where they leave from is changing its climate. These migrants eat the fora of this lake at different times and for longer.

    Or they may move to another lake where the food is more plentiful and the larger predator species are not culled by the birds.

    That is even if the lake really hasn’t warmed since 1950…

    Comment by Mark — 28 Oct 2009 @ 10:29 AM

  25. Re #23;

    Sure, Eric, check out the temperature from nearby Clyde, N.W.T. (as represented in the GISS temperature record), as we show in our World Climate Report story.

    -Chip

    Comment by Chip Knappenberger — 28 Oct 2009 @ 10:39 AM

  26. So Antarctica is losing ice (Velicogna 2009) but it is not from snowmelt (Tedesco & Monagan 2009). So where is Antarctica losing it? May it be from ocean-driven ice shelves melting?

    Thanks for the article, it’s very helpful against the constant disinformative campaign from skeptics, specially when it comes from the authors themselves.

    Comment by PeterPan — 28 Oct 2009 @ 11:16 AM

  27. Chip.

    How come the graph you’ve got has the temperatures of 1-5C when the NASA data you link to as the original data shows temperatures -10.5C down to -14C.

    Comment by Mark — 28 Oct 2009 @ 11:33 AM

  28. Also this:
    “There is a bit of press covering a just-published paper that concludes that the current climate and ecological conditions in a remote lake along the north shore of Canada’s Baffin Island are unique”

    doesn’t really help, does it. If it’s unique, you can’t really draw any conclusions except that every other place doesn’t do that. About all you can say is “It isn’t doing this!”.

    Comment by Mark — 28 Oct 2009 @ 11:35 AM

  29. Re Comment by Lawrence Coleman — 28 October 2009 @ 8:10 AM
    Have the authors analysed the silt for chemical residues, eg DDT? This was shown to accumulate in lake silt in a Swiss study published in November’s Environmental Science & Technology.
    There is an old DEW Line station near to the the lake, so spraying against insects would be expected.

    Comment by Adam Gallon — 28 Oct 2009 @ 11:41 AM

  30. re: #26/PeterPan
    So Antarctica is losing ice (Velicogna 2009) but it is not from snowmelt (Tedesco & Monagan 2009). So where is Antarctica losing it? May it be from ocean-driven ice shelves melting?
    Exactly. Pritchard et al. 2009 (Nature)infer that grounded ice/glaciers are responding to ice shelf collapses in addition to ocean-driven melting — “a widespread phenomenon that does not require climate warming sufficient to initiate ice-shelf surface melt.”

    Comment by Luke T — 28 Oct 2009 @ 12:26 PM

  31. Mark (re:27),

    We showed summer (JJA) temperature from Clyde–which was the season most germane to the findings discussed by Axford et al.

    -Chip

    Comment by Chip Knappenberger — 28 Oct 2009 @ 12:42 PM

  32. A very cogent and credible analysis. Not inconsistent, as you say with global warming or indeed the IPCC sea level assessment but inconsistent with the more extreme forecasts of increases in sea level over say the next 30 years.

    Care needs to be taken however when we justify this sort of finding with “natural variability”.. in this case SAM, SOI and La Nina… since this begs the question of what impact does this natural variability have on temperatures. IMO, until we can build such natural variables into our GCM’s and model these impacts of natural variables on historic temperatures we will not have a truly robust basis for predicting future temperature caused by CO2and will have to live with the very unsatisfactory IPCC forecast of 1.5 to 5Deg C for a doubling CO2

    Comment by colin aldridge — 28 Oct 2009 @ 12:42 PM

  33. Re #25, #23, #22:

    First, the general trends across /Canada/ for the 50 years can be seen more clearly in:

    “Temperature and Precipitation Trends in Canada During the 20th Century” Zhang et al. (2000).

    How unusual such a steady temperature is in a global context can be seen in figure 3.9 on page 250 of Chapter 3 of the “IPCC’s Fourth Assessment Report (AR4), The Physical Science Basis”. This is for a trend of over 100 years!!! The only significant slight cooling in the whole of the Earth in the 20th century was in part of the North Atlantic. So picking a station of the North East coast of Canada is slightly cherry picking. Especially the period chosen (i.e. over the whole century).

    The IPCC also looked at 1979-present (FAQ 3.1 p253): Showing the region has warming. Compared to the data you link to, this matches:

    http://s594.photobucket.com/albums/tt25/lionfish00/?action=view&current=climate.png
    (roughly 0.17 deg C/decade)

    Papers looking at the region, such as:
    “Recent Cooling along the Southern Shore of Hudson Strait, Quebec, Canada, Documented from Permafrost Temperature Measurements” Allard (1995).
    say that the previous lack of warming is due to the Thermohaline circulation.

    http://en.wikipedia.org/wiki/Thermohaline

    In general, “no warming since 1950″ isn’t true, it’s warmed considerably over the last 30 years.

    Maybe someone else could explain or link further? :D

    Thanks,

    Mike.
    PS I study computational neuroscience, not climate science! Please correct my interpretation :D Also maybe a link to the effect of the Thermohaline circulation on such a temperature record?

    Comment by Mike Smith — 28 Oct 2009 @ 12:44 PM

  34. Chip, germane in what way?

    After all, a study into the temperature differences from 1998 to 2008 is germane to a study of how it’s cooled.

    It is only germane however in that picking the data that way is the only way to get a decade long cooling, therefore picking other data (like, say, 1988 to 1998) would not help a study of how it’s cooled.

    It comes back to the “Why the continued interest” thread: would your thesis have worked if you had used DJF instead? Or an Alaskan site. Or…

    It is also incorrect to label a point to data you used that doesn’t point to the data you used.

    Comment by Mark — 28 Oct 2009 @ 1:55 PM

  35. IS there any merit to these articles denying AGW?

    1)http://www.minimalgovernment.net/media/mg_20091021a.pdf

    2)http://www.heartland.org/custom/semod_policybot/pdf/25093.pdf

    [Response: No. Same old fudged and misleading graphs - correlations that mysteriously end in 1980, implicit climate sensitivities beyond anyone's wildest imaginations (when comparing CO2 with temperature over short terms) etc. etc. - gavin]

    Comment by Armand Chase — 28 Oct 2009 @ 2:38 PM

  36. Mark (re: #34),

    We picked Clyde, N.W.T., because it was the station closest to the lake that was being studied and thus presumably best represented local environmental conditions. We showed the summer temperature (and our graph was clearly marked as such), because that was the season that Axford et al. discussed (and produced their own reconstruction of). And I linked to the GISS data page for Clyde so if you went there you would know what you were getting (rather than linking to a page full of nothing but data without description).

    Seems reasonable to me!

    -Chip

    Comment by Chip Knappenberger — 28 Oct 2009 @ 2:54 PM

  37. #30 Luke T,

    Thanks, Luke! Now I have my three-piece jigsaw puzzle complete! ;-)

    # 33 Mike Smith,
    Baffin Island (where sediments are extracted from in Axford et al., 2009) is not covered in Zhang et al. (2000) (though the warming seems to be widespread in the southern area that they cover). I havent’t read the article, but from their press release, the attribution part seems to be that cold species survived previous warming periods (being even abundant) but not this one. (If that’s all), the reason might be the rate of the current warming, but other (surey anthropogenic) stress may share the responsibility.

    Comment by PeterPan — 28 Oct 2009 @ 3:25 PM

  38. #36: Chip thrashes about for anecdotal weather patterns that counter a specific study result and says: “Seems reasonable to me!”
    What a surprising conclusion from an off-topic uninformed denialist looking for an excuse to reject scientific evidence…

    You have no idea whatsoever as to what is scientifically “reasonable” and what isn’t, do you?

    Comment by Ben Lawson — 28 Oct 2009 @ 5:59 PM

  39. > scientifically “reasonable”

    Now, now, he’s just doing what’s required in his job, “advocacy science.”

    http://www.google.com/search?q=new+hope+advocacy+science+knappenberger

    You start with the belief, then pick the facts to support it.

    Comment by Hank Roberts — 28 Oct 2009 @ 6:39 PM

  40. Chip (#36),

    Seems that your single station data would be at odds with most other Arctic station data for that time period.

    http://data.giss.nasa.gov/cgi-bin/gistemp/do_nmap.py?year_last=2009&month_last=09&sat=4&sst=1&type=trends&mean_gen=0112&year1=1950&year2=2008&base1=1900&base2=2000&radius=1200&pol=reg

    Of course, anomalous stations that don’t show significant warming (about 0.1 C in this case) are not questioned by “skeptics”.

    Comment by MarkB — 28 Oct 2009 @ 8:05 PM

  41. How’s the ice doing on the island that has not warmed?

    Comment by JCH — 28 Oct 2009 @ 8:18 PM

  42. #36: Chip, why you picked up the summer record in the context of AGW while the guest point out “Antarctic warming has occurred mostly in winter and spring, ..”? Of course, the paper you refered talked about the arctic lake, not the antarctic, but it is quite doubtful to neglect these unless there is an evidence that the arctic warming never occurs in winter and spring.

    [Response: All I can say in response to all this back and forth regarding the Baffin paper is I guess I'd better read it and write something up. None of this speculation for or against Chip's point is likely to be enlightening. Whatever complaints one might have against Chip's take on all this, at least he has evidently read the paper! How about readers let this discussion die until I have time to put up a post on it. --eric]

    Comment by Mr Sh — 28 Oct 2009 @ 8:57 PM

  43. #31 Chip, I must disappoint I am afraid, I worked Clyde River in 1980-81 at its second station situated
    higher across the Bay the station moved with the village in the 70′s. The original station was much lower at sea level, knowing inversions Clyde’s temperature record should not to be used ! and again, in the late 80′s the station moved to the airport! Another few miles away. However did the research need be a little more thorough… Try again!!!

    Comment by Wayne Davidson — 28 Oct 2009 @ 11:58 PM

  44. Whoever did the research, of course. Clyde is a most beautiful place with mysterious Fjords just near by.

    Comment by Wayne Davidson — 29 Oct 2009 @ 12:02 AM

  45. 28: Mark. It’s unique in respect that the sediment shows an unbroken linear timeline back 200ky. Most other glacial lakes only go as far back as the last ice age 50ky when the weight of the moving ice would just scour clean the lake bed removing any old sediment in almost all cases. Mark have you read the report?

    Comment by Lawrence Coleman — 29 Oct 2009 @ 1:06 AM

  46. 24:Mark. Everything you mentioned would be cyclical at least over the last 200ky except when you mentioned migratory birds may be visiting the lake sooner (and presumably eating more midge larvae?) because the climatic conditions are changing in response to CC. There may be grain of possibility there?. Whichever way you cut it..still comes back to climate change doesn’t it!

    Comment by Lawrence Coleman — 29 Oct 2009 @ 1:27 AM

  47. Re 29: Adam Gallon. DDT would indeed affect the midge larvae more than diatoms due to bio-amplification. It seems that the more ‘silica’ in the water the faster the growth rate of diatoms due to thats what their shell is make of. I would imagine that in an enclosed lake the amount of silica in ppm would be reasonably constant.

    Comment by Lawrence Coleman — 29 Oct 2009 @ 1:45 AM

  48. Chip: “Seems reasonable to me!”

    Well, call me skeptical.

    Comment by Mark — 29 Oct 2009 @ 4:57 AM

  49. Maybe I missed it, but what has ozone got to, do one way or the other, with antarctic temperatures? Can someone point me to an answer.

    Comment by Theo Hopkins — 29 Oct 2009 @ 5:10 AM

  50. Hi Eric,

    Greetings in my first comment and thanks for the huge effort put in this site or, at least, in its huge positive role as information source for us non-scientists.

    After reading this post I keep a couple of doubts. First, why is snow melt decreasing if the ozone layer is already increasing? Shouldn’t there be a progressive trend the other way round? And second, shouldn’t we notice a similar effect in the North Pole, annular wind-wise?

    Thanks in advance and sorry for my English and lack of knowledge,

    Comment by Mangeclous — 29 Oct 2009 @ 6:33 AM

  51. “There may be grain of possibility there?. Whichever way you cut it..still comes back to climate change doesn’t it!”

    I was more concerned with the “therefore this can’t be climate change, can it” statement.

    It wasn’t supported by the statements used to proffer it as fact.

    Comment by Mark — 29 Oct 2009 @ 7:50 AM

  52. “28: Mark. It’s unique in respect that the sediment shows an unbroken linear timeline back 200ky. ”

    This didn’t appear in the paper presented.

    Comment by Mark — 29 Oct 2009 @ 7:51 AM

  53. “The original station was much lower at sea level, knowing inversions Clyde’s temperature record should not to be used ! and again, in the late 80’s the station moved to the airport!”

    Maybe surfacestations has something disavowing this station as representative.

    Chip can then pop over to WUWT to discuss it.

    Comment by Mark — 29 Oct 2009 @ 7:52 AM

  54. I do hope Eric reads the paper and makes comments. The skeptics really think they have easily debunked this paper, which, because the lakebed is unaltered deep into the geologic past, seems to be a pretty important line of evidence for the current warming not being due to natural variability.

    I mentioned this paper and the skeptic claims on another thread a week or so ago, and somebody pointed out that skeptics need to explain why DDT only killed off the cold-adapted. On ice loss on Baffin Island, they may have some ‘splainin’ to do.

    Comment by JCH — 29 Oct 2009 @ 8:14 AM

  55. Theo (#49), here’s a layman’s take — I’m happy if anyone will correct me:

    The westerly winds that circle the Antarctic are stronger in the Antarctic winter when the air over the pole is colder and there’s lower pressure aloft. The ozone hole means ultraviolet is not absorbed by ozone to heat the stratosphere as it used to in the Antarctic summer. Therefore the circumpolar winds are stronger for longer, and as this belt of wind keeps out warmer air from higher latitudes, this affects Antarctic surface temperatures.

    [Response: Pretty good. See also this post which was one of the first we ever did. - gavin]

    Note it is actually the absorption of visible and infrared, not so much ultraviolet by ozone that warms the stratosphere (and hence cools it when there is less ozone).–eric]
    [err, um, actually correction to my correction. Ozone does absorb in the visible, but not much. The relevant absorption is in the relatively low frequency UV. See e.g. here: (http://www.atmosphere.mpg.de/enid/208.html). Amazing what a quick google search gets you. Easier than going through my file drawers.--eric]

    Comment by CM — 29 Oct 2009 @ 9:23 AM

  56. > 43, Wayne Davidson, 28 October 2009 at 11:58 PM, station moved twice
    But has anyone got _pictures_ of the three different stations?

    Comment by Hank Roberts — 29 Oct 2009 @ 9:34 AM

  57. Theo Hopkins wrote in 49

    Maybe I missed it, but what has ozone got to, do one way or the other, with antarctic temperatures? Can someone point me to an answer.

    In the upper stratosphere the cooling trend is due mostly to the reduced amount of infrared radiation reaching it as the enhanced greenhouse effect renders the troposphere more opaque to infrared radiation. But in the lower part of the stratosphere the cooling trend has been more due to the depletion of ozone than to enhanced greenhouse effect. Ozone is semi-opaque to ultraviolet radiation — but like carbon dioxide and water vapor are opaque to infrared, although ultraviolet radiation is of sufficiently high energy that it will split ozone.

    The stratosphere is lower at the poles, and likewise, much of Antarctica is at a fairly high altitude. So as the ozone layer is depleted this lowers the temperature of the lower stratosphere — and by lowering the temperature of the lower stratosphere it increases the temperature differential between the surface of Antarctica (particularly towards the pole), and this increases air circulation between the stratosphere there and the troposphere, resulting in a cooling effect at the surface.

    You can see that here:

    [Antarctica: Cooling at the Center, Warming Outside the Polar Front]
    http://rst.gsfc.nasa.gov/Sect16/antarctic_temp-AVH1982-2004.jpg

    from:

    Earth Systems Science: Evidence for Global Warming
    http://rst.gsfc.nasa.gov/Sect16/Sect16_2.html

    As the ozone layer heals this will warm the ozone layer, weakening the winds that cool the polar Antarctic surface, and thus reducing the cooling effect that a weakened ozone layer has had upon Antarctica.
    *
    One more detail regarding the image of warming and cooling in Antarctica shown above…

    The polar front that encircles much of Antarctica in essence shelters it from the rest of the warming that is taking place throughout nearly all of the rest of the troposphere. This is one of the reasons why the southern pole is so sensitive to ozone depletion. However, the polar front is at roughly 67° latitude south, so its most of the West Antarctic Peninsula lies outside of polar front and therefore isn’t protected by it. Thus the West Antarctic Peninsula is already seeing the same sort of polar amplification that we are seeing in the Arctic.

    Comment by Timothy Chase — 29 Oct 2009 @ 10:16 AM

  58. CORRECTIONS to 57

    [Oh dear lord...]

    Third sentence of first paragraph:

    Ozone is semi-opaque to ultraviolet radiation — but like carbon dioxide and water vapor are opaque to infrared, although ultraviolet radiation is of sufficiently high energy that it will split ozone.

    Third sentence of last paragraph:

    This is one of the reasons why the southern pole is so sensitive to ozone depletion. However, the polar front is at roughly 67° latitude south, so its most of the West Antarctic Peninsula lies outside of polar front and therefore isn’t protected by it.

    PS

    First and last paragraphs are those that are most likely to be remembered — given the mechanics of human memory. So of course they are where you are more likely to have mistakes — in the first paragraph because you are just winding up and the last paragraph because you are already winding down.

    Comment by Timothy Chase — 29 Oct 2009 @ 10:56 AM

  59. #49 — Theo: Check out the links in Eric’s response to comment 18.

    Comment by Deamiter — 29 Oct 2009 @ 5:21 PM

  60. Re my #55 above: Yes, I should have remembered ozone was not just absorbing ultraviolet. Thanks.

    [Response: actually, you're more right than I was .. Look at my correction to me correction, above. O3 does absorb in IR of course -- and in the troposphere it acts as a greenhouse gas -- but its the absorption of sunlight (in the low-freq UV) that results in warming of the stratosphere in the presence of O3. Absorption in the visible is not very important, though non-zero.-eric]

    Also, when referring to the ozone ‘hole’ cooling the stratosphere I should have spoken of (austral) *spring*, though the effects drag on through summer.

    And, ehem, where I said “higher” latitudes, I obviously meant “lower”.
    (Well, on my map the South Pole is *down*, so everything else has to be *higher*, right? :-) )

    Comment by CM — 29 Oct 2009 @ 5:33 PM

  61. How well do models handle the interplay of the SAM, ozone depletion and Antarctic temperatures? Can anybody recommend a good review paper on the topic?

    [Response: (Cough). - gavin]

    Comment by tharanga — 29 Oct 2009 @ 10:55 PM

  62. The averaged trend of the Antarctic sea ice extent shows an increase from 1979 to 2009. The Antarctic sea ice is about 90% of the world’s ice.

    [Response: No it isn't. You are confusing the ice sheet (on land) with the sea ice (on the sea). This post is about the ice on land. - gavin]

    Comment by David Wozney — 29 Oct 2009 @ 11:30 PM

  63. # 56 Hank, Google earth Clyde River Nunavut… The near extreme West 2 small buildings next to extreme West black roof top building was the second station and garage. Across the Bay due East find the circle by the road , that was about the first station. They removed the buildings, further North a few Kilometers up road I met a huge polar bear who luckily preferred a beach whale Carcass than me. Finally, on village side of Bay follow the road much further North, the current station is there. By one of the buildings is an auto weather system and CARS community Radio operator observer installation. Before anyone quotes mysterious weather events at one location, please study hard, and eliminate
    other plausible explanations. Its warming Up Here in the Arctic! You Don’t have to take my word for it, take the satellite view:
    http://www.esrl.noaa.gov/psd/map/images/rnl/sfctmpmer_30a.rnl.gif

    Comment by Wayne Davidson — 30 Oct 2009 @ 12:07 AM

  64. Re ozone absorption spectrum, some more googling: Ozone absorbs in the visible at the 602 nm “Chappuis band”.
    http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ocean-color/ozone.shtml

    There’s a neat solar spectrum graph at GlobalWarmingArt, which compares the incoming at TOA and sea-level to give a broad-brush impression of how much energy is absorbed by what in which parts of the spectrum (averaged over the U.S. – I guess it could be pretty different over the Antarctic?).
    http://www.globalwarmingart.com/wiki/File:Solar_Spectrum_png

    Comment by CM — 30 Oct 2009 @ 4:17 AM

  65. “The Antarctic sea ice is about 90% of the world’s ice.”

    And if there’s only antartic ice left because it’s all melted elsewhere, it will have 100% of the world’s ice.

    But how does that prove it’s cooling?

    (the earlier part is forgivable: I’d not made that connection either, but that 90% is irrelevant hence needs walloping).

    Comment by Mark — 30 Oct 2009 @ 5:29 AM

  66. >62, 65, “sea ice”
    See Gavin’s inline reply correcting the gross error in 62

    Comment by Hank Roberts — 30 Oct 2009 @ 6:22 AM

  67. “Ozone (O3) is the only naturally occurring atmospheric gas that absorbs visible light appreciably. An acrid gas, ozone is blue because it absorbs orange light…. The amount of ozone in the atmosphere is tiny—about 1 part per 2 million—so if it were all brought to sea level, it would form a layer only about 3 millimeters deep, on average.

    These 3 millimeters of ozone absorb about 1.5 percent of the orange light (and none of the blue or violet light) in a sunbeam or moonbeam that reaches ground level when the sun or moon is directly overhead, but more than 25 percent of the orange light when the moon or sun is at the horizon because of the long, oblique path. Ozone absorbs enough orange light to keep the zenith sky blue at sunset and sunrise. Without ozone, the zenith sky would be almost white at sunrise and sunset! And as we are about to see, absorption of orange light by ozone can also turn the moon blue.”

    http://www.weatherwise.org/Archives/Back%20Issues/2009/Sept-Oct%202009/full-Gedzelman.html
    (A wonderful, illustrated read on sky color, aerosols and much else.)

    Comment by Hank Roberts — 30 Oct 2009 @ 6:32 AM

  68. Too good not to quote more. Mark your calendars, USAians!

    “… The next total lunar eclipse will not occur until the winter solstice, December 21, 2010, … total and visible (provided the sky is clear) anywhere in the 50 states. Furthermore the blue fringe should be deeper blue than normal because the sunlight reaching the northern part of the umbra will pass over the high northern latitudes of Earth, where ozone content is generally high.”

    http://www.weatherwise.org/Archives/Back%20Issues/2009/Sept-Oct%202009/full-Gedzelman.html

    Comment by Hank Roberts — 30 Oct 2009 @ 6:38 AM

  69. Hank @66.

    “What does 90% ice is irrelevant” have to do with whether it’s 90% of sea ice or 90% of land ice? Or, indeed, any other fraction not 90% of either?

    Comment by Mark — 30 Oct 2009 @ 7:14 AM

  70. 69 Hank! All sea and land ice is relevant! The ocean currents circulate the cool water around the sea ice packs and keep the current flowing north by thermohaline circulation..vise-versa for the arctic regions. And the land and sea ice especially at higher altitudes chills the air and keeps the world tolerably cool. That’s what I’m always saying..what happens when the arctic sea ice is gone for most of the year..what helps cools the air then let alone the sea( N.A. thermohaline conveyor)? Only the mountains in greenland, Ellesmere island and parts of northern canada..that aint enough! Missing that vital 10% will alone cause catastrophic change to the world’s climate..mark my words!

    Comment by Lawrence Coleman — 31 Oct 2009 @ 1:16 AM

  71. This comes from a non-scientist, a real estate lawyer who reads this site with great interest. Recent posts have discussed an apparent slowdown in the rate of growth of temperature readings around the world. Also discussed has been the diminishment of the arctic ice cap. Is it possible that these are connected? When we toss an ice cube into a glass of room-temperature water, the cube melts and the whole glass cools down some. Can this be happening on a global scale?
    Sorry if this is unbelievably elementary, but I just had to ask.

    [Response: Good question, but not really valid. The amount of ice loss (from arctic sea ice, and from ice sheets/mountain glaciers) is a very small number (someone care to do the maths?) is large, but the energy involved is small compared to the energy needed to heat or cool the planet. The dominant effect of ice loss would be the increase in energy fluxes into the system because of the decrease in albedo. - gavin]

    Comment by scott putnam — 2 Nov 2009 @ 12:06 PM

  72. “Climate sceptics” recently have been very active here in Norway. Two professors (Ole Humlum and Ole Henrik Ellestad) on 16. october in the newspaper “Aftenposten” (see: http://www.aftenposten.no/meninger/debatt/article3323704.ece ) said, without naming any precise sources of any kind, that 1) “The UN environmental organization” (?) now have “admitted”, that “it is wrong that temperatures in the last hundred years have been rising sharply”, and 2) “the medieval warm period was far warmer than it is now, and it was global”. Could someone help clearing up what they may be referring to?

    Ellestad and others also have some somewhat enigmatic curves in “Teknisk Ukeblad” (“Technical Weekly”) on 21. october: http://www.tu.no/natur/article226175.ece – the figures occur a bit down in the article, one claiming to show the “surface temperature of the Greenland Ice Sheet” (but no mention of exactly where!), and the other claiming to combine “observed facts” with the “IPCC calculations”. No precise sources for the figures are given. A third figure is claiming to show “antarctic snowmelt”, and is referred to Marco Tedesco, Earth and Atmospheric Sciences, City College of New York and Andrew J. Monaghan, National Center for Atmospheric Research. I sure would like some comments.

    Comment by Karsten Johansen — 2 Nov 2009 @ 1:27 PM

  73. Karsten (#72), re question (1), why don’t you write to them and ask? And report back if you get an answer, it might be fun (my best guess is they totally misread an incident with a graph in a recent UNEP compendium on climate science). Re the last question, the above article by Tedesco and Monaghan puts the graph into context.

    Comment by CM — 2 Nov 2009 @ 3:00 PM

  74. Here is what October looks like:

    October (month end averages) NSIDC (sea ice extent)

    30 yrs ago
    1980 Southern Hemisphere = 18.9 million sq km
    1980 Northern Hemisphere = 9.5 million sq km
    Total = 28.4 million sq km

    Recorded Arctic min yr.
    2007 Southern Hemisphere = 18.6 million sq km
    2007 Northern Hemisphere = 6.8 million sq km
    Total = 25.4 million sq km

    Last yr.
    2008 Southern Hemisphere = 18.1 million sq km
    2008 Northern Hemisphere = 8.4 million sq km
    Total = 26.5 million sq km

    This yr.
    2009 Southern Hemisphere = 18.5 million sq km
    2009 Northern Hemisphere = 7.5 million sq km
    Total = 26.0 million sq km

    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_198010_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_198010_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_200710_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_200710_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_200810_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_200810_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/S_200910_extn.png
    ftp://sidads.colorado.edu//DATASETS/NOAA/G02135/Oct/N_200910_extn.png

    Comment by G. Karst — 2 Nov 2009 @ 11:39 PM

  75. Yup. And you can look this stuff up, if you’re curious about what’s going on and want more than a snapshot comparison of a few handpicked instants.

    http://scholar.google.com/scholar?q=%22antarctic+sea+ice%22
    for example
    http://cat.inist.fr/?aModele=afficheN&cpsidt=2831504
    Abrupt mid-twentieth-century decline in Antarctic sea-ice extent from whaling records

    and moving to contemporary work
    http://www.sciencedaily.com/releases/2009/04/090421101629.htm
    “ScienceDaily (Apr. 22, 2009) — Increased growth in Antarctic sea ice during the past 30 years is a result of changing weather patterns caused by the ozone hole, according to new research. Reporting in the journal Geophysical Research Letters, scientists from British Antarctic Survey (BAS) and NASA say that while there has been a dramatic loss of Arctic sea ice, Antarctic sea ice has increased by a small amount as a result of the ozone hole delaying the impact of greenhouse gas increases on the climate of the continent…..”

    Comment by Hank Roberts — 3 Nov 2009 @ 1:00 AM

  76. Ice extent does not equal ice volume.

    Comment by Mark — 3 Nov 2009 @ 6:18 AM

  77. PS even by your figures, we’ve lost 500,000 square kilometers of ice extent.

    At that rate, there will be no ice at either pole in 52 years.

    How does this prove there is no global warming?

    Comment by Mark — 3 Nov 2009 @ 7:34 AM

  78. Hank Roberts and Mark:

    I don’t post my ice report to prove or disprove anything. It is posted for information purposes only.

    Another blogger asked me if I thought this year’s seasonal ice recovery (extent 1st month ice growth) appears sluggish or lagging? I thought the following might help answer the question:

    1980 Northern Hemisphere (Oct.) = 9.5 million sq km
    1980 Northern Hemisphere (Sept) = 7.8 million sq km
    Delta Sept\Oct Extent = +1.7

    2007 Northern Hemisphere (Oct.) = 6.8 million sq km
    2007 Northern Hemisphere (Sept) = 4.3 million sq km
    Delta Sept\oct Extent = +2.5

    2008 Northern Hemisphere (Oct.) = 8.4 million sq km
    2008 Northern Hemisphere (Sept) = 4.7 million sq km
    Delta Sept\Oct Extent = +3.7

    2009 Northern Hemisphere (Oct.) = 7.5 million sq km
    2009 Northern Hemisphere (Sept) = 5.4 million sq km
    Delta Sept\Oct Extent = +2.1

    1979-2000 mean (Oct.) = 9.3 million sq km
    1979-2000 mean (Sept) = 7.0 million sq km
    Mean Delta Sept\Oct Extent = +2.3

    So in the Arctic, the first month freeze-up ice growth (+2.1) is comparable to the mean first month growth (+2.3). Beyond this… we just have to wait and see. GK

    [Response: GK, thanks. Useful and interesting. Still, I feel compelled to remind readers that this post was not about sea ice!--eric ]

    Comment by G. Karst — 3 Nov 2009 @ 10:21 AM

  79. Karsten,

    Here are some studies that say it was NOT warmer during the Medieval Warm Period than it is now:

    Bradley, R.S., Hughes, M.K., and H.F. Diaz 2003. “Climate Change in Medieval Time.” Science 302, 404-405.

    Goosse H., Arzel O., Luterbacher J., Mann M.E., Renssen H., Riedwyl N., Timmermann A., Xoplaki E., Wanner H. 2006. “The Origin of the European ‘Medieval Warm Period’.” Clim. Past, 2, 99–113.

    Osborn, Timothy J. and Keith R. Briffa 2006. “The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years.” Science 311, 841-844.

    Comment by Barton Paul Levenson — 3 Nov 2009 @ 11:45 AM

  80. putting it in context might include the fact that the northern hemisphere ice area, according to Cryosphere Today anomaly plot, hasn’t been on the positive side after 2003 spring. let’s see if this winter makes an exception.

    Comment by jyyh — 4 Nov 2009 @ 11:35 AM

  81. OK, the artice is not about ice extent. However, ice extent measurement is the best proxy to test AGW hypothesis against. There is no missing data subject to “creative” methodologies, temperature “reconstruction”, etc. The ice cover data is pure and relatively untampered indicator of global temperature, (expecially considerting that according to AGW hypothesis it is the poles that are expected to warm the most).

    [Response:Actually any losses (or gains) in Antarctic sea ice there have to do with the winds, not the temperature. Temperature is almost irrelevant for Antarctic sea ice. For the Arctic, it's much more important. But in general if you want temperature, use a thermometer.--eric]

    Now getting back few posts (#74), we have roughly 2.4 (=28.4-26) ice loss, or about 10% for the 30 year time period. How can #77 assert with straight face that the poles would be ice free in 52 years?

    [Response: Neither of you is making very sensible statements. The ARCTIC may be ice free IN SUMMER in a few decades or less. The Antarctic will continue to have substantial ice in summer for some time to come, I am sure. Both regions will continue to have substantial sea ice in winter indefinitely.--eric]

    Comment by Tegiri Nenashi — 4 Nov 2009 @ 2:03 PM

  82. Tegiri, from the looks of your weblog, it might be better for people to answer you over there, rather than try to sort out and cite all the assumptions you seem to make. Ahem.

    Comment by Hank Roberts — 4 Nov 2009 @ 2:26 PM

  83. “Now getting back few posts (#74), we have roughly 2.4 (=28.4-26) ice loss, or about 10% for the 30 year time period. How can #77 assert with straight face that the poles would be ice free in 52 years?”

    By showing that 26million sq km left and 0.5 million sq km having gone in the past year, the ice COULD be free AT BOTH POLES by 2060.

    And most of that ice is in the South, so the North Pole should disappear earlier.

    NOTE: This is as rigorous a mathematical treatment of the data as you have done, so should be equally valid.

    Comment by Mark — 4 Nov 2009 @ 3:20 PM

  84. “The amount of ice loss (from arctic sea ice, and from ice sheets/mountain glaciers) is a very small number (someone care to do the maths?)” -gavin

    9.162969e+12 m^3 melt total 2009 , (assuming 1 meter thickness)
    307195000 J/m^3 to melt ice
    2.814818262e+21 Joules total to melt Arctic sea ice
    1.66 w/m^2 forcing from anthropogenic CO2 cdiac.ornl.gov/pns/current_ghg.html
    5.10072e+14 m^2 area of earth wikipedia
    2.6702146783e+22 watt-second, or Joules/year forcing
    10.541542914 percent of forcing required to melt total arctic sea ice loss in 2009 , not just the increase in loss(calculated to a ridiculous number of significant figures – even when I set the number of places to zero in Appleworks, they reappear when cut and pasted). Prior to ~ 1950, the annual melt was about 5e+12 m^3 (assuming 1m thickness), so the amount absorbed by the INCREASE in ice melt would be even less. http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg
    Most of the ice that melts is first year ice(ice that formed since the last summer minimum), and most of the first year ice is around 1-2 meters thick, but winds change the area and thickness of sea ice, resulting in large uncertainties in calculating the volume of sea ice melt from the extent (but not enough to make up an order of magnitude).
    We also have to remember that the freezing in the fall gives back most of that heat absorbed by melting the previous spring & summer, or to put it another way, some of the Joules put into the system as visible radiation are stored in melting ice for a while, before being returned by the heat of fusion from re-forming the ice and ultimately radiated away as thermal infrared radiation. The joules of energy that the change in melt of ~4e12 m^3 of ice(give or take a factor of 3?) represents have taken from about 1959 to accumulate.

    One years worth of the current anthropogenic CO2 forcing would result in 4.9e-4 deg C rise if distributed throughout the 1.3e+19 m^3 of the ocean.

    5.23e+11 m^3 Greenland ice melt
    (www.interscience.wiley.com) DOI: 10.1002/hyp.7354
    ‘Greenland Ice Sheet surface mass-balance modelling
    and freshwater flux for 2007, and in a 1995–2007
    perspective” Mernild et al

    1.0 e+11 m^3 glacial melt
    http://www.eoearth.org/article/Observed_Impacts_of_Climate_Changes

    so they are another order of magnitude away from having a measurable impact.

    [Response: Just to be clear here, you are calculating the amount of cooling effect on the ocean from dumping cold ice into it, right? That was Gavin's question but it wasn't worded clearly. Note that your figure of 0.0004 for the entire ocean would be about 0.02 for the mixed layer only (the upper ~75 of the ocean). That would actually seem significant except that as you point out it is a seasonal, not a mean annual value, and has no bearing on the trend.--eric]

    Comment by Brian Dodge — 5 Nov 2009 @ 2:56 AM

  85. Brian Dodge #84:

    I don’t see a calculation for sensible heat that is required to raise ice from (-30?) to the melting point or did I misunderstand?

    Comment by G. Karst — 6 Nov 2009 @ 11:12 AM

  86. On a tangentially related topic, according to the IJIS sea ice extent data, November 5, 2009, had the lowest extent for that date ever. Or, to put it another way, the sea ice extent trace for 2009 crossed below the record-low 2007 values, as it’s been threatening to do for about two weeks.

    I wouldn’t make too much of it–sea ice extent is volatile and variable, and there’s an excellent chance that 2009 won’t stay the lowest for long, as 2006 had exceptionally low values for early December. But if someone starts spouting off about “recovery,” there’s a rather sharp rejoinder available at the moment!

    Comment by Kevin McKinney — 6 Nov 2009 @ 5:26 PM

  87. @ G. Karst 6 November 2009 11:12 AM
    Since the question was about how much heat was absorbed by melting, I ignored the additional amount for thermal capacity. ice heat capacity ~2 J/g-degC, heat of fusion ~335J/g, so the additional heat from -30 to 0 would be less than an additional 20%. Also, the top surface of the sea ice may be -30C, but the bottom will be ~-2C.

    according to Appl Environ Microbiol. 2004 January; 70(1): 550–557. doi: 10.1128/AEM.70.1.550-557.2004
    Bacterial Activity at −2 to −20°C in Arctic Wintertime Sea Ice, Junge et al
    “Arctic wintertime sea-ice cores, characterized by a temperature gradient of −2 to −20°C, were investigated…” so we’re probably talking about an average ice minimum temperature of around -11C.

    @ Kevin McKinney — 6 November 2009 5:26 PM The “recovery” this year was still below the long term OLS trend – see http://www.arctic.noaa.gov/reportcard/figures/seaice2009fig2-sml.jpg. Note the 90-92 recovery – at least it ended above the trend.

    Comment by Brian Dodge — 6 Nov 2009 @ 9:05 PM

  88. Brian, you don’t have to tell me!

    But I can’t guarantee that there won’t be someone on a newsblog out there somewhere who’s foolish enough to claim otherwise.

    Comment by Kevin McKinney — 6 Nov 2009 @ 9:37 PM

  89. The probability to hit the low mark this late in the year in such a dataset is about 1 to 18, if the ice extent was a totally random number. So, this is not a very remarkable year in this respect. However, some previous years are, and they’re located on the latter half of the dataset, so I’d say there is a trend in the ice extent, and it is down, as the cumulative ice extent anomaly, since the beginning of the dataset, appears to be negative. But what happened before this, is another matter as far as this dataset is concerned. (I’m assuming the IJIS dataset is robust and well-documented, up to the spectrographic instruments, in the stable orbit, that are being used to obtain this data.) But of course this is trivial.

    Comment by jyyh — 7 Nov 2009 @ 1:31 AM

  90. And one might want to calculate the correct value before posting a reply to the prev post.

    Comment by jyyh — 7 Nov 2009 @ 2:44 AM

  91. Ice loss in the Antarctic is not only from melting in situ. If you do a Google Scholar search on antarctic ice sheet ice stream velocity you get some interesting results.

    Here’s one of interest that for once is not paywalled:
    Bell et al. Large subglacial lakes in East Antarctica at the onset
    of fast-flowing ice streams
    , Nature 445, 904-907 (22 February 2007).

    [Response: Indeed! Ice loss from Antarctic is virtually not at all from melting! I don't recall the numbers off hand but is is probably > 90% from calving.--eric]

    Comment by Philip Machanick — 7 Nov 2009 @ 7:07 PM

  92. Eric, do you have any idea if outburst floods could occur from under an ice stream like those in Antarctica that are long enough to reach the sea and be calving? I’m thinking of events like the Channeled Scablands flood or floods, which happened from under ice very far inland, very late in deglaciation.

    I’m also wondering whether the ANDRILL work has come up with any indication of that kind of rapid event.

    Bits and pieces of vaguely related stuff found at http://climatechangepsychology.blogspot.com/2009/07/subglacial-hydrology-basal.html

    Comment by Hank Roberts — 7 Nov 2009 @ 10:35 PM

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