Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
Keep me logged in
New? Register here
Forgot your password?

Latest Posts

Archives

Climate Hustle

Is Antarctica losing or gaining ice?

What the science says...

Select a level... Basic Intermediate

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

Climate Myth...

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

Update Nov. 7 2015

A study published by Jay Zwally and his team on Oct. 30 (Zwally et al. 2015) has suggested that until 2008 there might have been a bigger increase in ice on East Antarctica than there is a decrease in the west, meaning that total Antarctic land ice is increasing. While their results for the Antarctic Peninsula and much of West Antarctica agree with other research, the study disagrees with many other techniques. We will update this discussion once more studies address this issue. Until then here are links to some recently published takes on the study:

A controversial NASA study says Antarctica is gaining ice. Here’s why you should be skeptical - Chris Mooney (Nov. 5)

NASA Scientist Warned Deniers Would Distort His Antarctic Ice Study — That's Exactly What They Did - Media Matters (Nov.4)

More on Antarctic Ice Melt - ClimateCrocks (Nov. 3)

Is Antarctica Gaining or Losing Ice? Hint: Losing. - Phil Plait (Nov. 3)

Q&A: Is Antarctica gaining or losing ice? - Carbon Brief (Nov. 3)

Just Because Antarctica Might Be Gaining Ice Doesn't Mean Climate Change Isn't Happening - Vice (Nov. 2)

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

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

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

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

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

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

and

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

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

Therefore, how is Antarctic land ice doing?

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

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

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

Basic rebuttal written by mattking


Update July 2015:

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial

 

Last updated on 8 November 2015 by BaerbelW . View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Further reading

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

Update

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

Comments

Prev  1  2  3  4  5  6  7  8  9  10  Next

Comments 251 to 300 out of 463:

  1. Sigh, let's have some data here. FIrstly, evidence that Antarctica is melting from erosion of base by warm water is found here. Recent estimates of geothermal flux and its role (tiny) is found here. A commentator did the maths on upper bound of geothermal flux here

    And for the role of reduced salinity in sea ice, see papers and discussion
     Why is Antarctica sea ice growing.

    Jetfuel, show me where there is any seaice in places with rapid ocean currents.

    Also Shepherd et al. (2012), which you quoted, show you exactly what the contribution of Antarctica ice melt is to sealevel. Didnt you read it? Why would assume that rates of melt will stay the same as the world warms?

  2. "but why is the increased atmospheric moisture level going to result in increased perception in the desert of Antarctica?"

    Try this paper.

  3. The Potsdam Institute for Climate Impact Research has today posted a press release titled, Antarctica could raise sea level faster than previously thought.

    The lead paragraph of the release:

    8/14/2014 - Ice discharge from Antarctica could contribute up to 37 centimeters to the global sea level rise within this century, a new study shows. For the first time, an international team of scientists provide a comprehensive estimate on the full range of Antarctica’s potential contribution to global sea level rise based on physical computer simulations. Led by the Potsdam Institute for Climate Impact Research, the study combines a whole set of state-of-the-art climate models and observational data with various ice models. The results reproduce Antarctica’s recent contribution to sea level rise as observed by satellites in the last two decades and show that the ice continent could become the largest contributor to sea level rise much sooner than previously thought.

    The OP should be updated to reflect these new findings. 

  4. Since 70 meters of SLR=All of Antarctica melting, The 20 years from 1992 thru 2011 cumulative melt of .00006 of the 70 meters of potential SKL worth of land ice on Antarctica: .00006*7000 cm = .42 cm. At that rate per 20 year period, by 2100, there would be .42 * 4.5 = 1.89 cm. There is a lot of exponential increase in the rate of melt to get to 37 cm from less than 2 cm. In the end, even 37 cm is only .005 of Antarctica melted. The moon was at perigee this week and in some local areas tides along the US eastern seaboard were 16 cm higher than normal highs. A prelude of the effect of exponentially increasing melt through 2060? 

  5. Jetfuel,

    1) Yes the rate of melting of Antarctic land ice is increasing. Simply projecting previous rates into the future is not a useful calculation.

    2) A permanent increase in sea level, even a small one, is not comparable to the temoprary increase in tides represented by the position of the moon. In a similar way, a daily variation of +/- 20 degrees F between midnight and noon is normal temperature variation, but a permanent difference of 4-6 degrees worldwide can trigger an ice age or eliminate all glaciers and ice caps.

    I think there is a thread dealing with arguments that ciimate change isn't that bad. Perhaps this would be better discussed there.

  6. Why isn't projection of the recent past into the future useful? Taking the last 20 years and extrapolating 85 years ahead gives only 1.89 cm of SLR from Antarctica melting. Lots of graphs about ice on this and other websites give a % loss per decade change listed right on the graph. Now, since the article quoted just above says that there "could" be 37 mm of SLR, you can't say that extrapolation "could" not be useful?

    Don't compare water levels with temperature. When a sea level rises 6 inches above a level seen in a year, and that represents 1000 years of SLR rate, there is no air temp comparison

  7. Jetfuel @256, if you look around there are lots of correlations, and lost of data we can project. For most such data, simple projection of trends will not successfully predict future behaviour, or will do so only for a short period.  Project daily maximum local temperaure for the last few weeks more than a few weeks and chances are you will be making ridiculous predictions.  The key to science is finding which, which regularities and which trends are reliably projectable.  Noticing a correlation between use of the word "hemline" and global means surface temperatures, for example, means nothing without providing a physical theory as to why the correlation exists, and why it will persist.

    Your projection of current trends in SLR, for example, includes no factors except sea level, and time.  Therefore the underlying physical theory is (at best) that sea level is a linear function of time.  There are many very good reasons to think a better model is that sea level is a function of global mean surface temperature.  If you project your model, and a model which says sea level is a function of GMST into a future with global warming, they will give different results.  Assuming your projection is better on the basis of "why not" amounts to assuming on no better basis that sea level is a linear function of time, or that temperature has no impact on sea level.

    Even assuming sea level is a linear function of GMST is a very simple model, and will make different (and poorer) predictions than models that project sea level rise to be a complex function of GMST (ie, has different rates of increase with temperature for different contributing factors), or ones which make rate of increase of sea level a function of temperature.

    Because there are many projectable functions for any observable variable, simply projecting a linear trend for such variables is the refusal to do science.  If you want to know what is likely to happen, you need to actually test which physical model makes reliable projections.  When you do that, you get the projections made by the IPCC.

  8. If you want example of why ice retreat is non-linear, look at what happens to rate of mountain glacier retreat if a lake forms. You can get an order of magnitude increase in rate. 

    I wouldnt expect EAIS to melt much in next 100 years but much of west Antarctica is below sealevel and when sea water can get underneath the glacier then rate of calving goes up very quickly. I cant see how you could possibly expect linear rates from albedo change either.

    If you want acceleration, then look at a suitable time interval.

    Source:

    Frankly, I would go with results from the scientists that actually study this and published their results for the world to see rather than naive trends.

  9. I did some research on smithsonian.com and found out that Antarctica is much larger than the US lower 48 in area. The Ross Ice shelf is about the size of Texas. It lies on a shallow sea and the shelf is less than a km thick. It has always been melting from underneath. The study of Ice shelf loss recently done over a long period found that 85% of all ice shelf loss was from along the penninsula. There, the sea is warmer, has more currents, and the shelves are numerous, small, and farther from the S. pole. The shelf sits on the ocean anyway and won't add much to sea level rise because it is not on land. Right now, these shelves are surrounded by possibly the most extensive sea ice ever since records started being kept. The ice shelves are mostly the thinnest ice cover thickness areas of Antarctica, sit over the ocean, and are a small fraction of Antarctica'a huge area. They also get heavy snowfall and if they were to melt significantly, there would be an abrupt end to the melt as the area that has ocean under ice would be used up, leaving the vast majority of Antarctica's land ice still totally protected from the warm water of the sea being underneath. Really nothing new here, as this water has always been underneath the ice.

  10. I fail quite to understand what point you are making here? Sealevel rise from Antarctica comes from the loss of ice sheet, not ice shelves. The main issue with the loss of ice shelves is the buttressing effect on glaciers. Where shelves have been lost, glacial calving rates have gone up. If you want to see what is the real issue, start with this paper. It is discussed in the NASA press release here.

  11. Two arguments support growth of Antarctic sea ice which hit 19.7M sq km Sept 14th. One is the loss of Arctic ice has exposed the ocean surface there to release more heat than previously. When it was covered with ice, it's ability to give off heat was less. The second argument is that the increased ice covered area at the southern polar region is reflecting more of the sun's energy than ever before. These same two arguments can be used in reverse: The Antarctic ice area is covering more sea water than ever and allowing it to retain it's heat, and at the Arctic, the less than average amount of sea ice is reducing reflectivity of the sun's energy. The overall combined total of southern and northern sea ice, is very high this year and last year, and therefore ice/water solar reflectivity is on average, near it's recorded peak. With the Arctic sea ice looking like it will not dip below 5M sq km this summer, there will be an increase again in multiyear ice there.

    The recent articles I've read downplaying this record Antarctic sea ice are using what happened in 2012 as the overriding factor. Right now, the sea ice ring around Antarctica is now an average of 750 miles in width, and is actually widest and most massive at the Ross Ice Shelf. The Ross Ice Shelf is noted in 2012 as being in danger of dissipating to unleash the West Antarctic Ice Sheet into the Ross Sea. For warm water today to flow under nearly 1000 miles of sea ice, then enter the Ross Sea, and then traverse through a thin water layer area the size of Texas, under a km thick of ice, then still be warm enough to melt the underside of a 2000 foot thick glacier's edge? I would be more inclined to believe the heat source is the Earth's core, not warm ocean water from Madagascar's beaches that has made that arduous journey described above.

  12. jetfuel...  Can you please provide sources for these?

  13. Geothermal heat and ocean heat are both things that are measured. I pointed you to papers on both here and here. You seem to be simply ignoring measurements in those comments and going argument from Personal Incredulity and rhetoric ("Madagascar's beaches").

    "The overall combined total of southern and northern sea ice, is very high this year and last year, and therefore ice/water solar reflectivity is "on average, near it's recorded peak". Can you cite your reference for this please? Albedo change is related to summer ice extent so I am having some difficulty with this claim.

  14. And here are figures showing increasing temperature of the circum-antarctic ocean and its decreasing salinity.

    Source:

    Interesting paper, co-authored by Judith Curry, also noting the increasing sea temperatures here.

  15. Oh, a final thought - sea ice and albedo is rather different between arctic and antarctica. Running the numbers can done and see here for one example.

  16. Scaddemp, In your rebuttal to my comment about 2012 conditions being used as a rebuttal to what is happening today in the Antarctic, you point to articles written in 2012 about what happened in 2011. Further removed from recent happenings.

    Meanwhile, The Antarctic ice level far surpasses the level at this time at 10, 20, and 30 years ago. Since the turn around in the Arctic has already happened so Ice area is increasing there too, while the Antarctic is well into unchartered territory in increased area covered by sea ice, I expect another very cold winter just south of the Great Lakes. The Arctic turn back up of ice area happened already and did so only 3 days later than last year.

    In combining the number of days in the year when sea ice area was increasing at both poles at the same time, this happened for 41 days in 1994 (20 years ago). So far this year, it has been happening for 36 days and surpassing the 20 years ago mark looks easy considering 6 more days will do it. All totalled, there was about 980,000 km sq more sea at these times in 1994 than today, out of 27M, that is less than 4% less. This .98M difference is falling each day, as The Antarctic just passed 20M with a half million increase just in the last week. The vaguery of "shifting wind patterns" is proposed as the reason why we are about to have more sea ice than 20 years ago even though the oceans are supposedly the warmest since 1900. All this while state legislatures fight over sea level rise extrapolation methods that amount to less change in 1000 years than an annual but rare moon caused tidal change that happened this summer.

    Sea ice data from nsidc charctic

    Response:

    [Rob P] - Perspective is important here. A back-of-the-napkin calculation by myself, using middle-of-the-road estimates, shows that the annual average rate of global ice volume loss over the last decade is around 50 times greater than the increase in Antarctic winter sea ice. So the fact that Antarctic sea ice is increasing doesn't challenge our observations that the world is warming in a largely coherent manner - which we would expect given the increasing greenhouse effect.

    Trends in Antarctic sea are very patchy though, strong losses in some areas, but overcompensated by gains in other areas. Indeed, the growth areas appear to be in the vicinity of the Weddell and Ross Sea polar gyres - where divergence at the surface pulls cold water up from the deep. This will likely weaken when the Interdecadal Pacific Oscillation (IPO) switches to its positive phase in the coming years. So it will be interesting to see how the gyres respond, and what effect this has, when this phase switch occurs.

    The image below is from Maksym et al (2012):

     

  17. jetfuel, what are you trying to dance around?  Do you have a point?

    Btw, Arctic sea ice area minimum for 2014 is less than SIA minimum for 2013 (3.554m km2 vs. 3.483m km2).  If you're going to use a one-year change to claim "recovery," then what do you do when the next one-year change reverses the sign?  The summer minimum linear for Arctic SIA from 1979-2006 (the year before the 2007 collapse) is -47,592 km2.  The same for 1979-2014 is -69,590 km2.  Between 1979 and 2013, there are 15 years where SIA exceeds the preceding year.  Most importantly for the sake of your dance, reality is about 50 years ahead of model expectations for Arctic decline.  Call me when the ten-year linear is positive.  Maybe I'll listen.

    Also, if you don't think wind patterns, wind speed, and salinity have anything to do with Antarctic sea ice growth, by all means provide the physical mechanism through which these forces are rendered powerless.

  18. jetfuel @266 says:

    "Meanwhile, The Antarctic ice level far surpasses the level at this time at 10, 20, and 30 years ago. Since the turn around in the Arctic has already happened so Ice area is increasing there too, while the Antarctic is well into unchartered territory in increased area covered by sea ice, ..."

    It is true that the Antarctic Sea Ice anomaly is greater than at any time in the last thirty years, but even my history goes back longer than that - let alone the Antarctics.  So, let's look at the charted sea ice extent from the HadISST database, as plotted by Tamino:

    Of course, that is a little out of date.  The current data (Sept 20th, 2014) is at 20 million square kilometers.  Uncharted for the satellite era, certainly - but uncharted simpliciter?  That you choose to forget history does not mean it does not exist.

    Or we might compare the August 2014 sea ice extent to a 1904 estimate of winter sea ice extent, which is shown extending as far north as South Georgia:

    So, Antarctic sea ice extent is in uncharted territory, but only if you are carefull not to look at charts that might bust your pet theory.

  19. jetfuel @266.

    It is difficult to know when you talk of "the turn around in the Arctic" whether you are proposing the reversal of the trends of the last 30 years or that the winter freeze has arrived.

    This "number of days in the year when sea ice area was increasing at both poles" you talk of - why do you pick on 1994? Indeed, why this annual statistic? A quick bash at the SIA data shows those 'numbers of days' are not very relevant to levels of SIA & SIE for those years. Why then  do you feel the statistic is worthy of the diodes recording them?

  20. Any data out there that shows Antarctic ice mass changes since Sept 2012 cannot be found by me. I understand that the -100 GT/yr number is floated around but there is no data to support this trend over the last 2 years. It is as though 2009 and 2010 data are currently on replay.

    Per TomCurtis@268, Antarctic sea ice area is on the rise for almost 40 years as a general trend. With Nasa data showing ocean salinity as average surrounding Antarctica, as opposed to low salinity at the Amazon delta or Black sea, that salt dillution argument is weak as to why sea ice is unprecedented since the early 70's.

  21. jetfuel @270, the failure to acknowledge clear errors (such as your claim that "the Antarctic is well into unchartered territory in increased area covered by sea ice") shows your purpose in debate is not understanding, but purely rhetorical.  Further, referring to data without providing a clear web address or link suggests you are hiding behind your interpretation of the data rather than relying on it.

    More directly, the question is not the level of salinity, but the change in level of salinity.  From your wording, your NASA site only shows the former.  Here is the later,  from Zhang (2006):

     As you conveniently point out, the trend in Antarctic sea ice is 40 years long.  Therefore the 1979-2004 data should provide the clue as to the cause of the increase in sea ice extent, for the sea ice extent was increasing over that period.  We therefore notice that it is not due to changes in temperature, which was increasing over that period (panel e).  Salinity, however, was decreasing over much of the Antarctic waters (panel d).  Further, NASA accepts that data, and agrees that the decline in salinity is part of the explanation of increased ice extent.

  22. Jetfuel, it remains completely unclear quite point you are trying to make.

    Is it?

    1/ Antarctica seaice is increasing, therefore Antarctic is getting colder

      - not true as you have been shown. The paradox with seaice increase it that it happens while temperatures warm. Read the provided links/papers for why. Salinity decrease is only part of the story.

    2/ Antarctic sea-ice increase "makes up" for Arctic sea ice loss.

    - Nope, as pointed out above, the increase is only 1/6 of the climatological effect from seaice loss in arctic.

    3/?? What are else?

    I would have say that it is statement of mighty hope to believe that ice sheet loss has decreased significantly since 2012. Cryosat-2 was measuring record loss rates in 2010-2013. Glacier movement rates were increasing in southern summer of 2013-2014. What do think has suddenly changed to give you that hope?

  23. Jetfuel:   

     I Googled "Antarctic ice loss" and found This link from June 2014.  It says:

    "Between 2010 and 2013, West Antarctica, East Antarctica, and the Antarctic Peninsula changed in mass by −134 ± 27, −3 ± 36, and −23 ± 18 Gt yr−1, respectively. In West Antarctica, signals of imbalance are present in areas that were poorly surveyed by past missions, contributing additional losses that bring altimeter observations closer to estimates based on other geodetic techniques. However, the average rate of ice thinning in West Antarctica has also continued to rise, and mass losses from this sector are now 31% greater than over the period 2005–2010"

    Your suggestion that ice loss in the Antarctic is not increasing is incorrect.  Perhaps if you Googled better you would be more up to date on your data.  At least it is not doubling every five years.

  24. Again,  'between 2010 and 2013' excludes the last 21 months that includes the last 2 southern winters.  Curiosity about the last 2 winters is not rhetoric.

    Curiosity just uncovered that there was a 200 Gt snow event in East Antarctica in 2009. Things can change significantly in one year.

    I acknowledge that there was more Ant. sea ice than now in the middle of the last century. I misspelled uncharted as unchartered. I don't even know what unchartered would mean in the context I used. 1966 seems about when actual winter max numbers were annually charted and that looks like about 22M sq km back then.

    Breaking 20M for the first time since the mid seventies. Being quick to propose blaming this on reduced salinity and shifting wind patterns may be rhetoric. Those excuses were ready to go on the day the record from last year was broken.

  25. Jetfuel,

    I read 2010-2013 as inclusive so that all the data up to last December is included.  You cannot expect to have peer reviewed data about this winter available yet since the winter is not yet even over.  A single snow event is weather.  We are interested in the trend.  

    Of course scientists rapidly proposed explainations for the increase in ice: it had been predicted years ago.  When events come to pass that were predicted long ago those papers are brought back and the proposed explainations look good.  Predictions are not comparable to excuses.

  26. I disagree that 2013 is included, otherwise the quotes: "Between 2010 and 2013", "We use 3 years of Cryosat-2 radar al..",

    and:

    "are now 31% greater than over the period 2005–2010".

    imply that 2010 gets counted twice, once in each dataset?

  27. Jetfuel, you seem to be implying that continuation of a predicted trend is somehow evidence for something new and different in Antarctica. Do you seriously believe that ice loss from the ice sheets has stopped? What is going to be your reaction to the next cryosat result? Do we get a retraction?

    Again, it would help if you would actually state the point you are trying to make here. Why are you so hung up on Antarctica sea ice?

  28. jetfuel @276, from McMillan et al (2014):

    "Here we use CryoSat-2 data acquired between November 2010 and September 2013 to produce the first altimeter-derived estimates of volume and mass change for the entire Antarctic ice sheet."

    CryoSat 2 was launched in April 2010, and became officially operation in October 2010.  The reason for the "overlap" in 2010 is simply that McMillan et al relied on earlier studies which extended into 2010.  It is not clear, however, that those studies extended their data up to include Nov 2010 in any event, in which case there is no overlap.

  29. Regarding recent ice loss data from Antarctica, I was surprised Figure 5 from Williams et al (2014) hasn't made its appearance on this comment thread yet. For the present on-going chatter, it doesn't advance the data beyond that mentioned by jetfuel @270 but it do allow sight of what is the actuality by way of, as jetfuel puts it @274, "Things can change significantly in one year," and perhaps may also stop the trolling on whether years are inclusive or exclusive to some time period.

    Williams et al 2014 Figure 5.

  30. Thank you Tom.

    I note that Tom actually read the cited peer reviewed article.  Jetfuel did not read the paper he was criticizing.

  31. tomcurtis@268 states: "So, Antarctic sea ice extent is in uncharted territory, but only if you are carefull not to look at charts that might bust your pet theory."

    per NBC news: "More sea ice than ever around Antarctica,"

    Whose Pet theory?

     

  32. michaelsweet@280 says:

    "Thank you Tom.

    I note that Tom actually read the cited peer reviewed article. Jetfuel did not read the paper he was criticizing."

    I wasn't criticizing it. I did read it, and the bold quote of Tom's from the paper is not visible to me in the report. When I googled his quote, I got SS as result?

    The paper does state that for the period from 2010 to 2013, the avg ice level is falling at 1.9 cm per year and that there is a 105-130 Gt per yr loss of ice mass. Considering there are 30,000,000 Gt of ice there, and a single 2009 snowfall in East Antarctica deposited 200 Gt of snow, and the report stating that the vast majority of Antarctica is stable, forgive me for thinking that this years 1960'sish sea ice levels down there could have made West Antarctic land ice more stable. How many years of -100 Gt per year until we can round 30 million down to 29.9?  10 centuries by my math.

  33. I for one would say that jetfuel's 'science by news headline" in #281 and disingenuity in #282 are a sign that jetfuel has worn out his welcome.

  34. jetfuel @282, googling a sentence is not the same as reading the article.  Nor is failing to read the article is not evidence a sentenc is not in that article.  It is only evidence that your approach is evidence free.  For your benefit, however, here is the sentence with sufficient context to easilly locate it within the article:

    "Introduction


    With a capacity to resolve detailed patterns of elevation change at the scale of glacier drainage basins [Shepherd et al., 2002; Davis and Ferguson, 2004; Pritchard et al., 2009; Remy and Parouty, 2009; Shepherd et al., 2004; Wingham et al., 2006; Zwally et al., 2005], repeat satellite altimetry has transformed our ability to study the polar ice sheets. Nevertheless, direct measurements of elevation change have been restricted by the latitudinal limits of satellite altimeter orbits (81.5° and 86.0° for conventional radar and laser systems, respectively), by the reduced performance of conventional radar altimeters over the steep terrain that is typical of ice sheet margins and by the irregular temporal sampling of satellite laser altimeter data due to the episodic nature of ICESat mission campaigns and due to the presence of clouds. These limitations have precluded, for example, comprehensive assessments of Antarctic Peninsula volume change, and altimeter data omission may also explain differences in mass balance estimates for other ice sheet regions [Shepherd et al., 2012]. CryoSat-2 was designed to overcome several of the limiting factors that previous satellite altimeters faced, with an orbital limit extending to 88° and a novel synthetic aperture radar interferometry mode providing measurements of fine spatial resolution in areas of steep terrain [Wingham et al., 2006]. Here we use CryoSat-2 data acquired between November 2010 and September 2013 to produce the first altimeter-derived estimates of volume and mass change for the entire Antarctic ice sheet.

    Data and Methods

    ..."

    (Bolding of section headings in original, bolding of relevant sentence mine.)

    Jetfuel @281, your pet theory.

    That NBC made the same error as you six days after you made it does not prove you derived your theory from them.  Nor does NBC claiming something relating to science to be fact prove it is, given the notoriously poor standard of scientific reporting by MSM.

    Further, trying to score rhetorical points of a point where you have already acknowledged your error (@274) just makes you look silly.  Are you now trying to take that back (with a complete absence of relevant evidence)?  Or are you just trying to sow as much confusion as you can?  Either way you have just ratcheted your credibility another notch lower.

  35. Composer 99 @283, I take it then, you do not subscribe to the theory that deniers making themselves look utterly stupid is not a good antidote to the disease in other readers?

  36. Jetfuel has still not actually revealed what point he is trying to make. Obviously the increasing sea ice around Antarctica is significant for him but he has failed to communicate why. The latest seems to be because the trend has continued, somehow a contributing factor (ice sheet melt) must have stopped. This is consistant with other behaviour that places enormous significance on an individual point rather but ignores the trend (eg 2009 ice fall is latest but see also the cherry picking here). Comment 282 would imply he either hasnt looked at or doesnt understand the graphs helpfully posted by MA Rodgers. Unless jetfuel actually articulates his case, I dont think there is much point continuing. We just see repetition and a complete resistance to learning anything.

  37. Tom Curtis @285: Deniers making themselves look the fool is well and good, however enough exposure to the same commenter who trots out the same shtick, over and over, eventually just wears out my patience.

    Skeptical Science does a good job of not being overrun with deniers in the comments (as compared to, say, dana1981's blog at The Guardian) but even so I am sure I am safe in assuming there will be no shortage of deniers posting here to maintain a more-or-less constant flow of foolishness (to say nothing of any foolishness posted by yours truly).

    -----

    To keep this comment on topic, I did a Google Scholar search with the terms 'antarctic sea ice history' and found a few papers that might be of interest when it comes to Antarctic sea ice and its extent (especially in light of jetfuel's claims with respect to same):

    - Gersonde and Zielinski 2000 (link), which reconstructs Antarctic sea ice during the late Quarternary 

    - Crosta et al 2004 (link), which does the same in a geographically limited area (the Southern Ocean - Indian Ocean boundary, effectively)

    - Rayner et al 2003, already referred to by Tom Curtis upthread (via Tamino - Tamino's blog post has a link to the paper).

    These papers are unfortunately behind paywalls for me, but as I said they may be of interest when thinking about the current state of Antarctic sea ice, especially any part of the G&Z and Crosta reconstructions occurring in the Holocene.

    My apologies in advance if someone else has already shared one or both papers in a previous comment on this thread. (I have performed a cursory search and believe that not to be the case, though.)

  38. Jetfuel,

    It would be nice if we could use the rate of ice loss from three years ago as the rate loss for the future.  Unfortunately, the data MA Rodgers provided at 279 shows a continually increasing loss of ice.  You must include the rate of increase of ice loss.  Then we see that it will not be so long before Miami no longer drains after heavy rains.  Your fact free ramblings are not convincing.

  39. I was intrigued by jetfuel's comment @282 concerning McMillan et al (2014):-

    "I did read it, and the bold quote of Tom's from the paper is not visible to me in the report.   ...   The paper does state that for the period from 2010 to 2013, the avg ice level is falling at 1.9 cm per year and that there is a 105-130 Gt per yr loss of ice mass."

    How to make sense of that? The quote is apparently quite promanent within the "report" (as quoted @284) and, with Antarctica being 14 million sq km, an annual 1.9cm fall in ice level would of course result annually in 7mm SLR and 2,660 Gt mass loss. Further the 105-130 Gt figure is not the finding of McMillan et al. and also is not specifically for the period "from 2010 to 2013." This comment from jetfuel is totally nonsensical, something not of this planet.
    And so it proved.
    I tracked down only one potential source and that is where you would expect to find it - the planet Wattsupia. There, back in May, they gathered all the populus at the feet of an idiot called Larry Hamlin who was greatly angered by the reporting provided by The Guardian about McMillan et al. It is Loony Larry who quotes from McMillan et al. in which he doesn't provide sight of the "bold qulte from Tom." However the 105-130 GRACE figures appear, as does the mention of "the exceptional snowfall event of 2009, which saw an additional ~200 Gt of mass deposited in East Antarctica," just as jetfuel has been banging on about down this thread. And while the "falling at 1.9cm per year" is absent, a 0.19mm SLR contribution is mentioned which presents a possible source of a grossly misquoted figure.

    And if anyone is in the slightest bit interested by Loony Larry's thesis, it can be summarised thus:- The Guardian is outrageously alarmist. There is no "doubling" of ice loss and obviously so. Does not McMillan et al. state that it' findings are "consistent" with other studies, so it can't have found a doubling. The Guardian confuse "two distinct issues." The "doubling" is not the rate of ice loss but the SLR contribution which has doubled from 0.19mm pa to 0.45mm pa. Of course Loony Larry says it better than I do. When I summarise his argument, I seem to make him sound like a congenital idiot.

  40. Composer 99 @287, the first to papers you link to study late quaternary (ie, 2.6 million years ago to present) fluctuations.  As such they mainly report differences in sea ice extent between glacials and interglacials.  Not having read more than the abstracts, I cannot comment on how accurate they are for distinguishing differences in Holocene sea ice extent.

    Perhaps more usefull are the proxy studies using MSA in ice cores, which show regional variations in Antarctic sea ice extent.  Thus we have Curran et al (2003) showing Antarctic sea ice extent of East Antarctica near Law Dome (80 to 140 degrees Longitude).

  41. I got the 1.9 cm from here in the report linked in michael sweet @273:

    "Results

    The CryoSat-2 observations confirm the continuation of existing signals of elevation change [Pritchard et al., 2009; Shepherd et al., 2002, 2012; Wingham et al., 1998; Zwally et al., 2005], identify regions which have evolved since previous surveys, and allow investigations of new terrain. Between 2010 and 2013, the average elevation of the Antarctic ice sheet fell by 1.9 ± 0.2 cm yr−1. Although most of the observed changes are smaller than expected fluctuations in snowfall (Table 1), those that are not coincide with areas of known dynamical imbalance (basins 13, 18, and 20 to 22) or with episodes of anomalous snow accumulation (basin 6) [Lenaerts et al., 2013]."

    And quoting from the discussion section, I got the 105-130 Gt numbers:

    "At the continental scale, the most recent estimates of Antarctic ice sheet mass balance are based solely on satellite gravimetry surveys [Barletta and Bordoni, 2013; Velicogna and Wahr, 2013; Williams et al., 2014]. According to these studies, the rate of ice mass loss from Antarctica has increased progressively over the past decade and, between 2010 and 2012, fell in the approximate central range 105 to 130 Gt yr−1"

    MA Rodger @279 has a graph showing only 58 Gt per year loss. I am impressed that the snow/ice layer boundary depth can be determined by a satelite, and I am assuming they are ignoring the snow. I had been pondering the 1.9 cm per year ice depth loss as not much at the point where the ice is 13,200 feet thick, but as an avg across the entire continent, is seems like a lot and now i read it is way off base. ratioing the 58 to 2660 Gt calcs above, I convert the 1.9 cm to 4 mm of ice mass loss spread across the entire continent. Of course, 4 mm is an average and the concern is at the places that are falling at 9 m per year.

    I'm sure there are easily a dozen different sources stating that this year is setting records. Me and NBC aren't the only ones getting it wrong. In this case, I'm in with a bunch of other idiots who are getting it wrong. From NOAA in August this year (2014): "This was the largest August Antarctic sea ice extent on record, surpassing the previous record set just last year"

    I compared the Nimbus 1 data from 1964 with this week's extent and there are plenty of areas that have farther reaching sea ice now than then, out off Ross Sea for instance.. Granted, it is a crude comparison, roughly scaling maps from Charctic, and there are areas of greater extent from 1964.

  42. Jetfuel - and your point is? We know the seaice is a record for recent times - if the conditions that create seaice trend continue, then upward trend will continue. So what? What do you see as the significance of this?

  43. Jetfuel - Yes, there is currently a small (barely statistically significant, IIRC) increase in Antarctic sea ice extent. 

    But this small increase, likely due to increased surface fresh water from land ice melt, increased halocline inhibiting mixing from (relatively) warmer deep water, and wind changes, is but a flyspeck on the wall compared to the observed mid-20th century 25% decline in sea ice extent (de la Mare 1997). 

    You seem to be repeatedly arguing that recent Antarctic sea ice extent is somehow contradictory to observations of a warming globe - and even leaving out the masses of evidence such as thermometers, the Arctic, growth zones, etc, focusing entirely on Antarctic sea ice extent, that's just nonsense. 

  44. Jetfuel @291, McMillan et al's own finding about the rate of mass loss from 2010-2013 is 159 +/- 48 Gtonnes per year, as detailed in table 1, and also in the sentence immediately following that which you quote, and which reports other results.  That is 65% of the mass loss expected if we assume the 1.9 cm per year is all ice.  Ergo they have included both snow and ice loss in the calculation, and difficulty distinguishing between the two accounts for the increased uncertainty in the mass figure relative to the altitude figure (30% vs 10%).

    In your post @282 you wrote:

    "The paper does state that for the period from 2010 to 2013, the avg ice level is falling at 1.9 cm per year and that there is a 105-130 Gt per yr loss of ice mass. Considering there are 30,000,000 Gt of ice there, and a single 2009 snowfall in East Antarctica deposited 200 Gt of snow, and the report stating that the vast majority of Antarctica is stable, forgive me for thinking that this years 1960'sish sea ice levels down there could have made West Antarctic land ice more stable. How many years of -100 Gt per year until we can round 30 million down to 29.9? 10 centuries by my math."

    And here is the relevant quote from the paper:

    "At the continental scale, the most recent estimates of Antarctic ice sheet mass balance are based solely on satellite gravimetry surveys [Barletta and Bordoni, 2013; Velicogna and Wahr, 2013; Williams et al., 2014]. According to these studies, the rate of ice mass loss from Antarctica has increased progressively over the past decade and, between 2010 and 2012, fell in the approximate central range 105 to 130 Gt yr−1.Our survey puts the contemporary rate of Antarctic ice sheet mass loss at 159 ± 48 Gt yr−1, a value that, although larger, is nevertheless consistent given the spread of the gravimetry-based uncertainties (16 to 80 Gt yr−1). A possible explanation for the discrepancy is the exceptional snowfall event of 2009, which saw an additional ~200 Gt of mass deposited in East Antarctica [Boening et al., 2012; Lenaerts et al., 2013; Shepherd et al., 2012] that, although absent from the CryoSat-2 record, does factor in the gravimetry-based estimates of imbalance. "

    I have italicized your quote @291, from which you also derived the total figures @282.  I have bolded the sentence which reports McMillan et al's own result.  The following sentence contains the only mention of the 200 Gt snowfall in 2009 in the paper, a snowfall you have mentioned several times including @281.  Clearly you have read the paper's report of its own result for it lies immediately between two sentences you have clearly read.  Depite that you chose to report other paper's results rather than those of the paper under discussion, and what is worse, left the impression that you were quoting this paper's results when you did so.  This looks to me like a very open and shut case of deliberate misrepresentation of the paper.  How the moderators choose to view this clear dishonesty, and act on it is up to them.

  45. Scaddenp @292, Tamino made that claim a couple of years ago, when it was true.  Since then Antarctic sea ice has continued to expand and the expansion is now statistically significant, and was in most of 2013 as well:

    Indeed, by pixel count, the Antarctic sea ice extent lies at approx 4 Standard Deviations above the mean for the satellite era.  Of course it is well below that of the pre-satellite era, and approx 10% below that of the 1960s as shown by HadISST (contrary to Jetfuel's claims above).

    Further, although is also a possibility of an error in baselining a transition between two satellite records that has been raised by Eisenmann et al (2014) and discussed by Tamino.  Even if accepted, which the NSIDC does not (I believe), that only accounts for 0.2 million square Km of the record, and the trend is still significant.  It does not place the satellite era record under threat.

  46. Sorry, Scaddenp, your mention of "significant" along with KR's discussion of statistical significance seems to have made my mind to skip a few lines and (I suspect) start teaching my grandma to suck eggs.  Just take my comment as a general comment with relevant information and ignore the fact that I addressed it to you.

  47. Of course, we all make mistakes. Indeed, I managed to trip over a decimal point myself @289 by converting 1.9cm into 19cm. The trick is to correct mistakes and not compound them.

    jetfuel @291.

    Your explanation for where you obtained your numbers is helpful but it also indicates that you are entirely inattentive to what the numbers you present here actually represent.

    @291 for instance you say that @279 I have "a graph showing only 58 Gt per year loss." This you apparently consider as "only 58 Gt pa" because you are comparing it with the preceeding quoted sentence "According to these studies, the rate of ice mass loss from Antarctica has increased progressively over the past decade and, between 2010 and 2012, fell in the approximate central range 105 to 130 Gt yr−1."

    What you fail to appreciate here is that the graph reproduced @279 is Figure 5 from Willams et al (2014). This source is made palin @279 and you will note that in the quote you present @291, one of "these studies" helpfully listed by the quote is the very same Williams et al (2014). Hey, and guess what? A quick regression of the Williams et al. data for 2010-12 yields 107 Gt/yr. You of course are quoting the average for 2003-12 which will be different if there is an acceleration involved which there obviously is.

    You are also wrong @291 suggesting the 105-130 figure came from this discussion thread. I see no sign of it prior to you introducing it @282.

    And "these studies" do not determine "the snow/ice layer boundary depth" as your comment suggests. "These studies" use GRACE gravity measurements.

    And you may take comfort that such a small proportion of Antarctica is melting away each year but the point is not to preserve Antarctica as a frozen continent. It is to prevent damaging SLR. If Antarctica were to melt to nothing (and the way humanity is acting, that is not so silly on a multi-century time scale) it wound drown 90% of present human endeavour.

    You are probably at liberty to call the NOAA "a bunch of idiots". They likely get called worse fro time to time. But it is you that is wrong in saying the NOAA is "wrong". Their quote of a record breaking August this year is helpfully accompanied by a graph illustrating the record which is thus obviously the record since 1979.

    NSIDC Southern August Sea Ice 1979-2014.

    And yes, we are all comforted that Antarctic Sea Ice is not yet showing  the slightest sign of collapse, but that does not make up for melting cryosphere everywhere else in the world. And perhaps, because Antarctic Sea Ice is not part of some grand global equasion, it is also off-topic in this comment thread.

  48. Physicist and space scientist Dr. Duncan Steel has recently discussed how well-known variations in Earth’s orbit around the Sun result in variations in the solar flux received at different latitudes and at different times of year, which are in accord with observed climate changes, independent of effects due to anthropogenic global warming. Dr. Steel finds that the most substantial variations are occurring at high latitudes across spring: in the northern hemisphere the spring insolation is increasing markedly, while in the southern hemisphere the insolation across austral spring is reducing. In itself this might be anticipated to result in what is actually observed: record melting of ice and snow cover in the Arctic, while there is year-on-year growth of Antarctic sea ice. See: http://www.duncansteel.com/archives/996. Dr. Steel seeks independent confirmation of his calculations, and welcomes comments, but only on the substantive subject of how Earth’s shifting orbit is affecting the insolation received at different latitudes and different times of year in the present epoch.

    Response:

    [PS] Fixed link

  49. karly @298, let me first note how silly I think it for people who, having observed an effect that could alter the climate, then automatically assume it is more important than the enhanced greenhouse effect without comparison.  In this case Steel concludes is essay for a hypothesis he has not presented for peer review, by saying:

    "Ockham’s razor demands that the CSI theory be accepted as the working hypothesis for observed climate change, because it is the simplest explanation and is undoubtedly valid (unless someone can demonstrate that my calculations are wrong, along with those made using Berger’s software code) although the AGW mechanism is certainly a (smaller) contributing factor."

    As it happens, he is claiming AGW is a smaller contributing factor because the difference in his calculation sprind insolation (on a particular day)  over a 1000 years is greater than the radiative forcing over the last 250 years.  The effect he calculates appears, however, to be linear over time.  From his figures, the effect of the last 250 years is 0.6 W/m^2 on that particular day, ie, less than a third of the radiative forcing over that period.  What is more, the effect is not an annual effect (as is the case with the radiative forcing from greenhouse gases).  In fact, the total effect sums to zero over the course of the year so that the net forcing from his mechanism is in fact zero.  Unless you wish to entertain a change in the laws of thermodynamics so that they only apply on the spring equinox, that alone refutes his conjecture.

    Further, his theory does not even match the evidence.  As noted, his theory predicts a near linear change over the last thousand years.  Temperatures, however, have on average declined over the first 750 of those years - something AGW "skeptics" are famed for noting.  The transition from the MWP to the LIA is a direct observational refutation of his theory.  So also is the southern hemisphere warming which he is determined to neglect but which is certainly occurring.

    That, however, may not be the worst part of his theory.  He makes a very big point of the fact that Berger (1978), from whom he draws his algorithms, uses the equinoctial method to calculate daily insolation in preparing his daily insolation tables, often used by climate scientists.  Berger, however, does not state that.  He defines a method for determining the insolation using the equinoctial method, then provides formula to calculate the calendar day method (see section 3 of Berger 1978).  That being the case, the majority of the effect Steel finds may simply be due to his using the wrong method, and therefore introducing a drift into his calendar.  That is, he may be making the same error he accuses climate scientists of.

    Regardless, his refusal to calculate a total year energy balance, inflation of the effect by using unequal comparison times, and neglecting of straightforward empirical disagreements with his theory render it an example of pseudo-science, not science.  I would not waste my time on it. 

  50. Mr Curtis, your criticisms are wasted on me. I am not a physicist, astronomer or climate scientist, nor am I associated in any way with Dr Steel. I have only a layman’s interest. If you believe his analysis is erroneous, please respect his request, and discuss the matter with him directly.

Prev  1  2  3  4  5  6  7  8  9  10  Next

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page



Get It Here or via iBooks.


The Consensus Project Website

TEXTBOOK

THE ESCALATOR

(free to republish)

THE DEBUNKING HANDBOOK

BOOK NOW AVAILABLE

The Scientific Guide to
Global Warming Skepticism

Smartphone Apps

iPhone
Android
Nokia

© Copyright 2017 John Cook
Home | Links | Translations | About Us | Contact Us