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Wilkins ice shelf collapse

Filed under: — gavin @ 6 April 2009

Since people are wanting to talk about the latest events on the Antarctic Peninsula, this is a post for that discussion.

The imagery from ESA (animation here) tells the recent story quite clearly – the last sliver of ice between the main Wilkins ice shelf and Charcot Island is currently collapsing in a very interesting way (from a materials science point of view). For some of the history of the collapse, see our previous post. This is the tenth major ice shelf to collapse in recent times.

Maybe we can get some updates and discussion of potential implications from the people working on this in the comments….?


613 Responses to “Wilkins ice shelf collapse”

  1. 51
    MarkB says:

    Re: #45

    Marcus (or others),

    What might explain the relatively anomalously large spike in world ocean heat content in 2001-2002? The long-term trend is quite clear but there seems to be a fair amount of short-term noise that doesn’t seem to follow the noise in the surface records.

  2. 52

    3 Jeff from Ohio: How badly extinct did you want to be? Life has been on earth for ~3.8 Billion years and 99+% of all species that ever lived are extinct. Those climate changes caused several major and many minor extinction events. After an extinction event, new species evolve to fill the empty niches. The total number of species rebounds to a sort-of “normal” after many millions of years but the extinct species are extinct forever. The Great Dying [End-Permian or Permian-Triassic event] 251 million years ago was the worst. The End-Permian was caused by CO2 from a super-volcano. The paleontoligists say that sulfur bacteria in the warm oceans made H2S, a poison gas. H2S turns into H2SO4 in your lungs and the H2SO4 causes a very painful death.
    Smaller climate changes cause the rain to suddenly fall far from its previous location. Archaeologists have documented about 2 dozen collapses of agriculture and civilization so far that were caused by climate changes of a fraction of a degree. Death by starvation isn’t my idea of fun either. 99.99% of the population die in a typical collapse. 0.01% manage to travel far enough to find food elsewhere. Read “The Long Summer” by Brian Fagan, “Collapse” by Jared Diamond and “Six Degrees” by Mark Lynas.
    You should be terrified indeed by climate change.

  3. 53
    Jarad Holmes says:

    I actually think it’s sort of neat. The other sides of the continent have plenty of ice and growing, well above average according to the NSIDC. It’s just a natural event. [edit]

  4. 54

    We can argue about whether humans are causing it until the cows swim home… Climate “deniers” aside, the globe is warming, and whether humans are causing it or not, we have a responsibility to try to slow it – or we will face a scenario something like that in my book – “Mai Shangri-La” – available at Amazon. Spread the word

    http://www.amazon.com/Mai-Shangri-Robert-J-Rubis/dp/1434861627/ref=sr_1_1?ie=UTF8&s=books&qid=1239066051&sr=8-1

  5. 55
    Ray Ladbury says:

    Dawn: “You folks know what the problem here is don’t you?”

    Scientist: “No, really. Do tell.”

    Dawn: “Too much interpreating, correcting and estimating and not enough accurate, calibrated measuring. And way too much pretending they are one in the same.”

    Scientist: “Golly. Gee willickers. And exactly how much ‘accurate, calibrated measuring have you done in your life, Dawn. Would you even recognize a real measurement if it were about to bite your little tuckus off?”

    [Silence, crickets chirping...]

    Scientist: “Dawn? Oh Dawn? Fascinating, yet another sighting of homo trollus.”

  6. 56
    Ken Fabos says:

    How many iceshelves have grown or come into existence over the past few decades? 10 ice shelves not merely shrunk but broken up sounds like a trend to me and the abundance of evidence of a warming trend – surface air temps, glacial retreats, ocean heat content rise, phenological shifts – all reasonable expectations in the presence of a warming trend and not requiring GCM modelling to predict (except to try and narrow the range of such expectations). But it might be some other cause – with a glaring absence of evidence of other causes is not a genuine argument in the presence of well documented causes. Such argument seem predicated on presuming climate scientists are blind, ignorant and don’t know anything about Earth’s climate. Of course such arguments aren’t aimed at climate scientist but at people who are blind, ignorant and don’t know anything about Earth’s climate.

  7. 57
    Hank Roberts says:

    Dawn might want to take a look at this site for long term measurement of actual mud layers.

    Of interest to anyone wanting a collection of papers of interest on ocean cores going back into deep time.

    http://www-odp.tamu.edu/publications/

    ODP Final Technical Report (PDF; 47 Mb; November 2007)
    … publications summarize the scientific and technical accomplishments of each Ocean Drilling Program cruise.

    To view Integrated Ocean Drilling Program reports and publications go to

    http://www.iodp.org/scientific-publications/.

  8. 58
    Hank Roberts says:

    MarkB writes
    > ocean heat content … 2001-2002?

    What report are you looking at, MarkB? Something from a blog, or a paper?

    One of these?
    http://scholar.google.com/scholar?hl=en&lr=&safe=off&q=+world+%22ocean+heat+content%22+%222001-2002%22&btnG=Search

    One of these?
    http://www.google.com/search?q=%22ocean+heat+content%22+%222001-2002%22

  9. 59
    Walt Bennett says:

    One man’s troll is another man’s advocate.

    Dawn is not a troll. Dawn is a misinformed advocate. As such, she presents a teaching moment.

    Dawn, I would suggest that you lose the tone that says “you’re all in on the conspiracy” and the rest of you, empty those stones out of your pockets.

    Dawn, as I’m sure you know, measuring climate is a tricky thing. If you picked the wrong points to measure, you might get the trend backward. If you don’t calibrate correctly, you might produce fictitious trends. If your sample is too small, you might not cancel out variability. If something happens once then almost sort of happens twice, is that a possible trend or simple variability?

    A contrarian can scoop up any 5 or 6 facts and mix them into, if not proof of a point, proof that the other person’s point has flaws.

    And in the end, you can accept no theory, because no theory can pass that test. Anything that we know well enough to be certain about, needs no further exploration. In other words, it’s the uncertainty that makes us explore.

    Now, if you have not read Weart’s “The Discovery Of Global Warming” then you simply must. Advocate or contrarian, you at least have to have your facts straight.

  10. 60
    A.C. says:

    I know this is way, waaaay OT, but I’m not sure where else to go to get the goods on this “scientist” cited halfway down this article….. gee, i wonder why the folks at Fox News would want to make this molehill into a mountain?

    http://www.foxnews.com/story/0,2933,512835,00.html
    –halfwayish down

    is this guy claiming to predict earthquakes with radon a fortune teller or a scientist?

    captcha: obvious

  11. 61
    Xavier says:

    I’ve just seen this posted as a comment to an article on the shelf collapse on independent.co.uk:

    “The average temperature over all Antarctica has actually fallen by one degree fahrenheit.

    According to NOAA GISS data winter temperatures in the Antarctic have actually fallen by 1 degree fahrenheit since 1957, with the coldest year being 2004 and all the while CO2 levels have been going up. Antarctic sea shelfs regularly break up this being a normal process but this fact is never reported by the media like The Independent. Also you fail to mention that the average monthly temperature in Antarctica in 1958 was -48.92C and 50 years later the average monthly temperature in Antarctica was -48.96C. Statistically identical. These temperatures were recorded at The Amundson-Scott South Pole Station.

    Antarctic Sea Ice for March
    —–Extent————Concentration
    2009 5.0 million sq km 2.9 million sq km
    1997 3.8 million sq km 2.2 million sq km
    1980 3.5 million sq km 2.0 million sq km

    The above data indicates a 43% increase in sea ice from 1980. This 43% increase of sea ice is Highly Significant for sea ice is caused by COLDER TEMPERATURES, not by increased snow fall. This newspaper has failed to report this dramatic increase in sea ice, this ice over the ocean. WHY?

    In Antarctica severe low temperatures vary with latitude, elevation, and distance from the ocean. East Antarctica is colder than West Antarctica because of its higher elevation; Antarctic Peninsula has the most moderate climate.”

    Can someone explain to me what’s going on here? Can these data be refuted at all?

  12. 62
    RT says:

    Is there a projected time where there will be enough data available to map a graph of the overall warming trend in the entire antarctic region?

  13. 63
    Nick says:

    I’ve watched this ice bridge with fascination for months, always assuming that the likely break point would develop at the narrowing segment that has been obvious for so long. Instead, the much broader section has fractured longitudinally while the narrow point persisted. Does this suggest an anchor point below the attenuation?

  14. 64
    Phil Scadden says:

    Another point on ocean warming – can anyone do a mass balance for ice loss versus sea level rise that doesnt require ocean warming for the numbers to add up? Ie. Add up water loss from land to ocean. Look at amount of sea level rise you get. I dont think you can get the measured figure without also having some thermal expansion from ocean temperature rise.

  15. 65

    #53 Jarad Holmes

    On what basis do you think this is a natural event? If I understand your point… you are missing the point.

    The growing of the ice in Antarctica is expected. All you need to do is consider the basics.

    Warmer oceans, due to AGW, increase water vapor in the atmosphere.

    What goes up must come down.

    If its warm, it comes down as rain; if its cold, it comes down as snow.

    If you increase a regional temp by say a half a degree, and the winter average temp is well below freezing, then you will get more snow.

    Antarctica is a giant 2.5 mile thick chunk of ice. Biggest freezer in the world.

    It will grow as anthropogenic global warming increases until it also hits a tipping point and then…

    You are using facts out of context and facts out of context are worthless. If you rely on facts out of context, the likelihood of you being wrong, as you are in this case, is quite high.

  16. 66
    Bogey says:

    As it appears that the problem with ice shelves breakup is that they allow the grounded ice/glaciers to increase speed, there seems to be three more positive feedback mechanisms we may need to consider in the simulations that I haven’t heard mentioned so far.
    Increased flow would lead to an increase in friction generated heat at the base.
    Increased flow would lead to pressure induced lower melting point at the base.
    These both increase lubrication at the base.
    Also increased flow leads to increased smoothing of the surface that the glacier flows along. Due to less time to elastically deform around obstacles. This again allows a speed up.
    I apologise if these are already included, but if not they may need considering.
    I hate the way every thing seems to be speeding up, apart from our response.

  17. 67
    Steve Missal says:

    I like what Walt said in #59. I’m not out to make enemies, but I am frustrated with the reliance on ‘gee whiz common sense’ and cherry-picked facts that constitute much of the skeptic debate side. I don’t know Dawn, and have no idea is she represents herself, some group, or is in fact someone posting under a pseudonym. However, she did set herself up a bit by dismissing the scientific consensus rather airily. Ultimately, there was no answer to my question about a viable alternative theory robustly supported by data. This is because it doesn’t exist.
    I’m a lifelong teacher. If my students dodge a question asked two times in a row, I conclude that they don’t know the answer. I’m almost always right. It’s like a Cops episode: the suspect is asked a question by the policeman, and to buy time, asks the question right back.

  18. 68
    Ken Miles says:

    Are there any estimates in the scientific literature as to the age of the ice shelf?

  19. 69
    Hank Roberts says:

    A.C., just paste your question into Google Scholar. You don’t need a climatologist to answer that.
    http://scholar.google.com/scholar?q=predict+earthquakes+with+radon

    Xavier, paste some chunks of that guy’s comments into Google; it will bring up a bunch of blogs making that same claim. Did you ever wonder why they’re using Fahrenheit? They might be talking about the ozone balloon measurements — that’s a situation where temperature falls, in the upper atmosphere, in the winter. They might be talking about a guy named Ross Hays whose name comes up a lot, Google for that too.

    There’s really no telling what they’re talking about if they can’t cite a source. Posting claims without cites to blog threads is an example of the pony theory of climatology — they bring the load to your door, dump it, and assure you that if you get the scientists to look at it they will find you a pony in it somewhere.

    Good luck hunting it down. ReCaptcha says:

    “Times source”
    if that’s any help

  20. 70
    Philippe Chantreau says:

    Where is that data from, Xavier?

    This paper references data and has various graphs and tables showing very different trends than yours for both temperatures and sea ice:

    http://psc.apl.washington.edu/zhang/Pubs/Zhang_Antarctic_20-11-2515.pdf

    This graph does not show anything like a 40% increase.
    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.area.south.jpg

    I know that NSIDC does not show anything like this either. Where is your data from?

    Did you stop a second to think that IF there was anything like this actually happening, the “skeptic” blogs would spread nothing short of an epidemic of apoplexy over the internet? Since it’s not happening, perhaps your data is questionable.

    Captcha Esquire steps

  21. 71
    Hank Roberts says:

    MattT back in 38 wondered aloud if anyone had ever ….
    Here, Matt, “albedo” is the word you needed to do a useful search:
    http://www.google.com/search?hl=en&q=albedo+warming+white+black+roofing+shingles+houses

  22. 72
    Steve Ramone says:

    In response to Xavier-#61. As far as the Antarctic cooling, I found in a matter of seconds on this web site, three articles discussing the warming of the Antarctic. Have a nice day!

  23. 73
    ccpo says:

    “# Walt Bennett Says:
    6 April 2009 at 8:45 PM

    One man’s troll is another man’s advocate.

    Dawn is not a troll. Dawn is a misinformed advocate. As such, she presents a teaching moment.”

    If you read the thread you must come to the conclusion you are incorrect, Walt. Many teaching attempts were made and none were responded to in a way that indicates Dawn wishes to learn. She makes excuses, yes. Obfuscates, yes. Etc. What she doesn’t do is say, “Ah! That’s interesting!”

    Uninformed:
    Informer: What is 2+2, Dawn?
    Dawn: Don’t know.

    Misinformed:
    Informer: 2+2=5, Dawn.
    Dawn: Cool!

    2nd informer: Uh, no, 2+2=4. Here, use these blocks to check it.
    Dawn: Cool! That makes much more sense!

    Denialist:
    Informer: 2+2=4, Dawn.
    Dawn: No, it doesn’t. I read it in a blog.

    Informer: Here’s the real data.
    Dawn: No, this isolated quote proves the overall conclusion is wrong!

    Informer: Here’s more data that supports the previous data. Lots of it.

    Dawn: Science isn’t good enough to do that. You can’t do that. You can’t claim it means what you say it means.

    Informer: Have you any evidence to support your claim?

    Dawn: Why? I said your data is wrong. You’re wrong. What do I need to prove?

    “Advocate or contrarian, you at least have to have your facts straight.”

    Absolutely, but Dawn shows no sign of being a true contrarian, which implies unbiased inquiry.

    I think we are well past the time when such people as Dawn, behaving as she is, are treated as if they are wondering, wandering innocents.

    Cheers

    reCAPTCHA: slope central.

    Indeed. The slope of the trend, it is. Temps up, Arctic sea ice down.

  24. 74
    Hank Roberts says:

    Oh, Xavier, maybe what they’re going on about is this:
    http://nsidc.org/data/seaice_index/
    An increase estimated at 4.7 percent,
    with an uncertainty of plus or minus 4.4 percent.

    So that number is (most likely) an increase of somewhere between 0.3 percent and 9.1 percent — that’s the uncertainty of the estimate.

    Some of that increase is area that used to be covered by ice shelves, that is now open ocean and, in winter, covered instead by annual sea ice. How much?

    Look at this though — did you hear anything from the usual crowd about the minimum back in February, when it dropped below the longterm 1979-2000 average?
    http://nsidc.org/data/seaice_index/images/daily_images/S_timeseries.png

  25. 75
    ccpo says:

    Antarctic Sea Ice for March
    —–Extent————Concentration
    2009 5.0 million sq km 2.9 million sq km
    1997 3.8 million sq km 2.2 million sq km
    1980 3.5 million sq km 2.0 million sq km

    Can I play? Look here:

    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.area.south.jpg

    Pay attention to 1980, 1990, 2009.

    Clear downward trend.

    I love cherries.

    Cheers

  26. 76
    Hank Roberts says:

    Sorry, Xavier, if you want to know what he thinks he’s relying on, you’ll have to go ask the guy WTF he’s quoting from, or wait for someone cleverer than I at finding the pony. I’ve looked.
    I can’t find anything to match the claim.

    Try this:
    http://nsidc.org/sotc/images/arc_antarc_1979_2007.gif
    “Arctic and Antarctic Sea Ice Extent, 1979-2007: Although Arctic sea ice extent underwent a strong decline from 1979 to 2007, Antarctic sea ice underwent a slight increase. The Antarctic ice extent increases were smaller in magnitude than the Arctic increases, and some regions of the Antarctic experienced strong declining trends in sea ice extent. See the Arctic Sea Ice FAQ for more information. Image provided by National Snow and Ice Data Center, University of Colorado, Boulder.”
    http://nsidc.org/sotc/sea_ice.html

  27. 77
    Craig Allen says:

    Can I make a suggestion. It would be really handy if RealClimate had a section that listed useful climate datasets and data representation available on the internet.

    [Response: In the meantime. - gavin]

  28. 78
    Hank Roberts says:

    PS, Xavier, for a sanity check, compare that guy’s claimed numbers –3 to 5 million square kilometers of ice — with the annual variation.
    March would be around the low point in the Antarctic, end of summer. Where’s the huge increase he claims happened? Dunno where he’s looking.
    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.area.south.jpg

  29. 79
    isotopious says:

    Does anybody know where to get global temperature data for the last couple of decades (plain text /table format)?
    I’ve found plenty of graphics but…..

    [Response: Here for a convenient list. - gavin]

  30. 80
    Bill DeMott says:

    Dawn:

    For those who are concerned about the inherent variability of air temperature and the possible effects of urban heat islands, we have measurements of water temperatures of lakes and oceans and, in addition to estimates of arctic sea ice, there are longterm data on the duration of ice cover on lakes. Water temperature can easily be measured to the nearest 0.1oC, although measurements old measurments may not be as accurate. Moreover, few of these estimates are impacted by localized warming due to human dwellings.

    Water temperature and its effects on ice cover are excellent integrators of temperature change. These kinds of data are measured very accurately and show very strong trends (upward temperature and shorter ice cover) in lakes around the world over the last 30 years. These results can be found in Google scholar–try typing “climate change and lake temperature” or “climate change and lake ice cover”

  31. 81
    François Marchand says:

    Re 25. I’ll second Jaydee on his assertion: ‘t must be the urban island effect which is causing it all.
    Seriously, here in the Fiji Islands, my friends from the Kiribati or Tuvalu, who ==know== how fast coral grows, well, not very fast, and how close their atolls are to being submerged, are not amused.

  32. 82

    In the main article Gavin wrote:

    The imagery from ESA (animation here) tells the recent story quite clearly – the last sliver of ice between the main Wilkins ice shelf and Charcot Island is currently collapsing in a very interesting way (from a materials science point of view).

    Neither an expert in mechanics, materials nor engineering, but…

    What really strikes me as odd about the series of images is how the ice bridge fragments longitudinally at the both the left and right edges first, not the center. Normally I would expect it to be weakest at the center due to the principle of leverage. I mean after all, if you want to break a window, you hit it at the center, not the edges.

    At the same time, I can imagine a wave coming through in a latitudinal direction with the crest aligned longitudinally. This may put stress on the edge of the ice bridge that it encounters first, and if the bridge held together temporarily would cause the the bridge to twist about its longitudinal axis, putting the greatest stress upon the left and right edges due to buoyancy on the edge being pushed down and weight on the edge being lifted up — with the center surviving longest due to it experience the least vertical motion. Repeated waves along these lines would lead to the fracturing process that we see.

    Alternatively, if warm water were eating away at the bridge, it would thin and weaken the bridge most at the edges that it encountered first — and the edges would once again be more susceptible to waves.

  33. 83

    Re Xavier 61

    Trends in temperature in the Antarctic are fairly dependent upon where you are measuring them. For example, the West Antarctic Peninsula is warming more rapidly than just about anywhere else in the world. In contrast, there has been a strong cooling near the center of the continent due to ozone depletion cooling the stratosphere and strengthening of the Antarctic Polar Vortex with the resulting temperature differential.

    They are strongly dependent upon the season during which you are measuring the trends. And they are strongly dependent upon the beginning and ending point of trend measurement.

    However, that said, it would appear that for the period from 1960 to 1998, winters have experienced a fairly strong warming across nearly the entire continent. A bit different from what you read in the Independent. Now this isn’t the trend for winter from 1950 to present, but it was the closest I could get on short notice.

    You can see it here:

    Antarctic temperature changes during the observational period
    project funded by the University Courses on Svalbard (UNIS) 2001-2005
    Ole Humlum, UNIS, Department of Geology, Svalbard, Norway
    http://www.unis.no/studies/geology/ag_204_more_info/ole/AntarcticTemperatureChanges.htm
    *
    As for trends in sea ice, yes, of course more recently sea ice has been trending up. This could be the result of the freshening of water due to loss of glaciers along much of the coastline. However, sea ice has been trending up slowly and it has by no means made up for the loss of sea ice earlier in this century from 1960 to 1978 or thereabouts.

    Please see:

    Sea Ice, North and South, Then and Now
    October 8, 2007
    http://tamino.wordpress.com/2007/10/08/sea-ice-north-and-south-then-and-now/

    Overall, based on latitude (with the strong exception being the rapidly warming West Antarctic Peninsula), we expect the most rapid warming the at the closest to the North Pole and slower warming the further south one moves, at least in the short-run. The reason is that ocean warms much more slowly than land given the thermal inertia of ocean (which is partly the result of circulation), the fact that the northern hemisphere contains far more land than the southern hemisphere, and the Arctic Sea is surrounded by land.
    *
    In the near-term, however, we expect the ozone hole to continue to heal. In the long-run, however, polar amplification is expected at both poles as various feedback mechanisms kick in — including increased poleward circulation, the effects of carbon dioxide insulating the world more or less evenly while solar insolation is stronger the closer one moves towards the equator, and of course there is the albedo effect as ice is lost at both ends.

    I hope this helps.

  34. 84

    CORRECTION to 62

    Looking at it again, the fracturing appears to be on one side, not the other, although there is a great deal of longitudinal fragmentation on the other side prior to the event. Using Google Map and locating both Charcot and Latady Islands, it appears that the side that fragment longitudinally is the side which is further from the Peninsula.

  35. 85
    Mark says:

    What’s going on there Xavier is two classic versions of the “lying by assumption”.

    Antarctica is a big place. Saying its average temperature went down is rather silly. This ice sheet is not over the entire antartic, so the state of eastern antarctic doesn’t change what this shelf of ice is seeing. They’re hoping that you’ll ASSUME that the temperature over the entire antartic is relevant. It’s only slightly more relevant than the record temperatures in Australia. Slightly.

    And the antarctic is a dessert. They’re assuming you don’t know that.

    Now, what doesn’t happen often in a dessert? Rain. Antarctica in its center doesn’t see snow because it’s too cold to hold much moisture and what little it sees falls over the coastal areas.

    But if the air warms, the amount of water it can hold increases markedly.

    But if it’s warmed 10C it doesn’t mean it’s too cold for snow: it just means that instead of -50C it’s -40C. Still plenty cold enough for snow.

    And more snow means more snow on the ground.

    And so the ***extent*** of ice can increase because it’s warming.

    That includes another lie by assumption: that the ice extent is relevant. It’s not. It’s the amount of ice.

    We could lose ice from 100% of the glaciers on the planet instantly and see no change in sea levels. As long as it’s only the top 1mm. But that’s a change over 100% of the extent of the ice on this planet! All I have to do is not tell you about the 1mm depth bit and you’re told 100% of the ice is melted. Just don’t look at the detail.

  36. 86
    Mark says:

    “Dawn is not a troll. Dawn is a misinformed advocate.”

    And if Dawn refuses to educate herself, what’s the difference between a troll and a deliberately uninformed advocate?

  37. 87
    Mark says:

    “The other sides of the continent have plenty of ice and growing, well above average according to the NSIDC. It’s just a natural event.”

    Yes it’s natural. We aren’t shooting heat-beams at the ice to melt it unnaturally.

    Of course the warming effect of CO2 is natural, which is the cause of the melting. And extra CO2 is a natural result of burning trillions of tons of Carbon over a 100 years. And so it’s all natural.

    However, by not burning so much fossil fuel, the natural result is a reduction of CO2. The natural result of that is that the atmosphere doesn’t remain so warm at the surface of the earth. And the natural result of that is that ice doesn’t melt as quickly and may build up again.

    PS I had some mashed potatoes yesterday and some gravy. Lovely. But the odd thing was it seemed to be created!!! How? Well I had a big ladle of mash and a cup of gravy. The ladle was about 3″ across and the mashed potato was the same size. But after I plopped the mash on my plate, it was AT LEAST 4″ across! I’VE CREATED MASHED POTATO! Merely by moving it on to my plate.

    The gravy likewise but to a much bigger extent. 2″ across in the cup but after pouring, it was nearly as big as the plate!!!!

    I thought only Jesus could create food from nothing, but I seemed to do it without knowing yesterday.

    Astounding, eh?

  38. 88
    Mark says:

    “The paleontoligists say that sulfur bacteria in the warm oceans made H2S, a poison gas. H2S turns into H2SO4 in your lungs and the H2SO4 causes a very painful death.”

    Just wondering, how many ppm was the H2S? Less than 380ppm?

    Maybe this would show how silly an argument by “it’s a fraction of a percent, so how can if affect the weather?” is.

  39. 89
    Mark says:

    Jeff from Ohio, get someone else to write your talk. Really. Your post didn’t make any sense on first reading and even on the fifth I don’t know what you’re asking.

    If you give a talk like that you’ll only prove to people that there’s no clear signal.

    2C is a limit below which the changes seen will not be catastrophic. As long as the methane off the coast of america remains where it is and the permafrost in russia doesn’t let go of too much of its stored methane.

    2C will see many people move from the tropical regions and maybe even many sub-tropical to the northern hemisphere, but the number of people affected would at least be theoretically manageable. Politically, maybe not.

  40. 90
    Mark says:

    “You folks know what the problem here is don’t you?
    Too much interpreating, correcting and estimating and not enough accurate, calibrated measuring.”

    Why does your thermometer need calibration? How is it done? By interpreting the volume increase of mercury as an increase in temperature.

    What happens when your thermometer is calibrated? It’s errors are corrected. Expansion of mercury is not linear, and the gas the liquid is pushing aside is pushing back.

    And how is the real temperature asserted? After all, you can’t use a thermometer to calibrate a thermometer, can you. All you’d be proving is that the second thermometer now reads the same as the first. Oh, that’s right, the effect is estimated. Maybe even modeled.

    So how is your demand to be met?

  41. 91
    Mark says:

    #18 “Is this accurate? Do we have a good understanding of the process? ”

    Yes (in the same sense as “the ground is flat” is when building a house) and yes (in the sense that if that explanation is accurate, we must necessarily be understanding the process to explain it so well).

  42. 92
    pete best says:

    LOL, this site is now filled with the deniers and incredulous types. Volcanoism under the Antartic, this is the same as the volcano under the Arctic last year when something else was sliding into the sea.

    The amount of additional energy required to be gradually chipping away at WAIS and Greenlands ice sheets plus the annual summer additional melt of the Arctic sea ice is telling us that AGW theory is quite right scientifically speaking. Nothing else is answering the question of where has this additional heat come from ?

  43. 93
    Nylo says:

    Hi Gavin,

    Just a few very simple questions. What is the life cycle of an ice platform like the Wilkins? Doesn’t it grow and grow and grow until it collapses because of the pressure the sea puts on the ice which is not resting in the continent? Don’t all the ice platforms break at some point in time? If the Earth was cooling instead of warming, or even if just the Antarctic Peninsula was cooling, wouldn’t the Wilkins be going to separate from the continent anyway? Or is there a rule that says that a platform cannot separate from the continent with a temperature just 1C lower than what it is experiencing now?

  44. 94

    #61 Xavier: this is called a cherry-pick. You can’t derive a trend for an entire continent from one weather station. If you look at all the data sets at British Antarctic Survey, you’ll see some stations are up, some down, some steady.

    Some recent science shows that the Antarctic could be warming more than previously thought: http://antarcticsun.usap.gov/science/contenthandler.cfm?id=1686

    As for the sea ice numbers, it’s more interesting to review summer minimum than the winter maximum numbers because hotter summers have a stronger feedback effect and eventually add to the warming trend. Summer minima have hardly shifted, interesting in view of the upward trend of winter maxima. This would seem to indicate hotter summers to some extent being masked by the energy absorbed by melting the extra winter ice (if I remember rightly, the latent heat of melting of ice is 80 times the energy needed to heat water by 1°C). The loss of the ice shelves is consistent with significant warming (again, remembering that energy going into melting ice is that much less energy left to increase temperatures). The only thing inconsistent with warming is the increased winter ice, and it would be interesting to get a fuller explanation.

    To me this seems a gap in the theory or observations rather than a fundamental contradiction.

    Here are some articles of interest on the Antarctic:

    http://nsidc.org/sotc/sea_ice.html
    http://nsidc.org/seaice/characteristics/difference.html
    http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1178
    http://antarcticsun.usap.gov/science/contenthandler.cfm?id=1401

  45. 95
    Jonas says:

    Hi Xavier,

    I was wondering about the increased sea ice as well. My first thought was that it must be due to decreased sea salinity but when I checked out the long term data I noticed that the sea ice has been growing for several decades. This long term trend would tend to exclude the salinity theory – unless someone else can offer a plausible explanation ?

    You can see the data nicely in the below link. NH has been decreasing at the same time the SH has been increasing.

    http://www.woodfortrees.org/plot/nsidc-seaice-s/from:1979/mean:12/normalise/plot/nsidc-seaice-n/mean:12/normalise

    My personal view is that the increased southern vortex may have contained cold air closer to the pole.
    This could explain the increased warming at the peninsula and increased sea ice elsewhere.

    Gavin, any thoughts ?

  46. 96

    Xavier,

    Instead of using nighttime temperatures and March ice extent, try average daily temperatures and annual average ice extent. Ice extent is highly variable, which is why you have to pay attention to the trend and not to spectacular outliers.

  47. 97
    Mark says:

    “Don’t all the ice platforms break at some point in time?”
    Well, yes. But there has to be a reason other than “well, it;s bound to happen SOMETIME”.

    And the reason is it’s getting warmer.

  48. 98
    Craig Allen says:

    Xavier, there is a post directly relevant to your question at the Skeptical Science website.

    John Cook explains how, counter-intuitively, rising ocean temperatures around the Antarctic can cause increased sea ice.

    [Response: Actually his bottom line is probably more apropos - Basically, the southern oceans and Antarctica are complex environments that are both poorly observed and subject to multiple different factors (affects of GHGs, ozone loss, ice dynamics etc.). - gavin]

  49. 99
    Theo Hopkins says:

    OK, so the data for cooling has been adjusted for errors in earlier readings. (Numerous posts)

    And I have briefly looked at the links suggested here that shown the adjusted figures.

    _But_ do folk relise that leaves sypathetic outsiders like me(non scientists) feeling a bit unhappy. In my local rural newspaper today there is a letter saying that the Wlkins Ice Shelf can’t be to do with global warming – sea temperatures are falling. So how do I reply? “Dear Sir, in reply to Joe Boogg’s letter today, Joe is out of date as NASA have changed its figures. Of course Joe should have checked the latest science rather than relating on something published a couple of years back which, _at the time_, was seen as gospel truth……yada, yada.” (?)

    I forget the details, they are all here somewhere on Real Climate, but when satelite temperature readings did not comply with the models,again the readings were adjusted.

    The cynic in me (sometimes) says “…and would they ever revisit the data if it came out the way expected? Like showing heating?.

    One set of errors is OK. Two sets of errors looks sloppy. third set of errors would … well, look damn stupid. Four would look like a conspiracy.

    [Response: Don't be an idiot. There are hundreds of errors/mistakes/data gaps that have been addressed by dozens (hundreds?) of scientists around the world. These fixes have had both signs of effect (i.e. correcting for UHI and accounting for bucket vs. inlet temperatures in SST both reduce long term trends). Your myopia, driven perhaps by a focus on what the propagandists consider 'news', does you no credit. As we have always said, all science is preliminary and none of it is 'gospel truth' (where has anyone said that here?). Please - leave the conspiracy theories to the wingnuts. - gavin]

  50. 100

    Gavin, last year, in August, an enormous ice shelf off northeastern Greenland broke up, and for the life of me I could not find any mention of it. Further, it was a decided buttress to a large glacier’s outflow.

    I have never been able to find a really good map of Greenland, so I will give the google coordinates.

    The shelf went from roughly: 81° 20′ N, 11° 30′ W
    down to about: 77° 10′ N, 18° 16′ W

    The end of the tongue of the glacier is currently at about:
    79° 32′ N, 19° 28′ W

    The removal of the buttress appears to have had a very large effect upstream deep into the ice sheet.

    I have been just really surprised that I haven’t seen any talk about this. Everything was all about the Petermann’s glacier at that time.

    And not to mention all the outflow going on at 72° 10′ N, 51° 20′W on the west coast. No one is talking about that either, at least not in view of the general public.

    Greenland just seems to be going to hell in a hand basket.


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