Yes, the review you’ve all been waiting for. Before I start, let me point out that this has been discussed by WE at WUWT, who has pointed out the obvious problem. It has also been mentioned by KK, though that appears to be more of a meta-discussion about the paper’s reception rather than the paper itself.

[Note: follow-up here.]

To quote KK:

But back to the show. One commenter at WUWT, noting the negative reaction to Judith, gives her a backhanded compliment when he writes: I have to applaud Judith Curry on having the guts to present her paper in the boxing ring of climate blogs where the wild and ignorant rule. but also these that think unbiased and try to address problems in creative ways. I just hope she was not counting on any mercy here. Here’s Judith’s devastating parry: I don’t want your stinkin’ mercy, I’m just lookin’ for some evidence of sentient thought.

Having read through the comments, I don’t think she got any (in the comments). Which is a good time to remind you of my comment policy, which will be strictly applied if needed. In particular, there are plenty of other venues for you to discuss motives, if you want to. This thread is to discuss the science.

Incidentally, because no-one has heard of Liu, everyone is calling this “Curry’s paper” or whatever. Which is wrong. It is Liu and Curry. I’ll call it LC in the sequel, for short.

I was ready to credit LC with the idea of explaining the recent Antarctic sea ice “increase” (it is in quotes because I haven’t myself verified that there is a (stat. sig.) increase; nor (unless I’ve missed it) does the paper present any evidence for a (stat. sig.) increase. That doesn’t matter too much: the important point is the non-decrease, which is interesting, and which is what I’ll call it from now on) but Hank points out that Bob blogged on this back in March pointing out that Manabe said much the same thing back in 1992. Hank’s attempts to get Curry to answer this are here and there but so far Curry hasn’t really read what Hank is saying so her answer is besides the point.

Looking at the paper – data

The main problem with the paper is the uncritical use of invalid data. WE conveniently provides a picture. Note that the pic is somewhat misleading: remember that we only care about 1950 onwards. But it isobvious from that picture there is a clear discontinuity in 1978/9, when the satellite record starts: before then, there is little variablity. This is true at the very least south of 60S. And arguably you can see it south of 50S. There is nothing new in this – everyone in the field knows there are very few obs before the satellite era. Curry knows it very well. But all the paper says is:

We confine the analysis to the period 1950-1999 due to large uncertainty associated with sparse in situ SST samplings in the Southern Hemisphere for the first half of the 20th century.

This is unacceptable. This should get a review of “major revisions” just for this problem. I’m open to correction on this point but I don’t think PNAS is strongly page-limited (unlike, say, Nature of GRL) so there is no reason why they haven’t got room to investigate their data set and see how suitable it is (err, other than the obvious: if you do the investigation (which they must have) you rapidly discover that it *isn’t* suitable). There is no excuse at all for doing what LC have done: which is to say, just picking up a dataset and using it with no attempt at verification (Curry comments on that but WE doesn’t buy it and just for once I’m with him).

So, all the obs stuff they have done S of 60S, or more likely S of 50S, is meaningless. But it gets worse (I think) because EOF is a field process: the inevitable corruption they’ve mixed in doesn’t stay S, but invalidates the entire EOF. So none of the obs EOFs can be trusted, anywhere. The same applies to the analysis of P-E. It uses ERA from 1958 onwards, but again: there are precious few obs to tie the analysis before the satellite ERA. Maybe you can use the data – but you need to use care, and you need to either do some validation or cite some papers that do it for you. LC do neither.

Which brings in another problem: why are they using EOFs anyway? Had they used simple temperature trends point-by-point, at least the fields where there was vallid data would remain valid (curiously they *do* provide this, or equivalent, in fig 4 – but only for the models.Argh). There is no justification in the paper for using EOFs. Also, they only show the first EOF and they only tell us how much var is in the first EOF. Quite often the trainling EOFs have far less var – but not always. And ~30% is hardly overwhelming. There is clearly more info in the unreported EOFs. Oh, and they don’t say if the EOFs are area-weighted. This begins to look like one of those papers where people pull off an off-the-shelf dataset, and some off-the-shelf stat software, and run them through to see what happens. The results are not usually happy.

Indeed, it gets worse: they only use obs from 1950-1999. This means they are gratuitously throwing away an entire decade of hard-won observations (1999-2009 or thereabouts). Why? Because they want to use the C20C (climate of the 20th century) integrations to compare to the obs. But… this is just laziness. Those integrations continue into the 21st century. It is possible to patch the runs together. But LC couldn’t be bothered. This, too, would be grounds for “major revision” before publication.

All of which means that what I take to be the major interest of the paper, viz:

Over the course of the second half of the 20th century, strong warming in the middle latitudes of the Southern Ocean with weak cooling in the high latitudes is hypothesized here to lead to an enhanced hydrological cycle in the Southern Ocean, whereby evaporation is enhanced and the moisture content of the lower troposphere increases in the middle latitudes of the Southern Ocean. This additional moisture is transported poleward by the meridional circulation (Ferrel Cell), resulting in an increased precipitation, and a freshening of surface water in the high latitudes of the Southern Ocean.

remains an interesting hypothesis, but the observational testing done in the paper is badly flawed, probably to the point of uselessness. Disclaimer: it is more than two years since I last played with these datasets. I’ve probably forgotten much.

[Update - oh yes, the other thing to think about might be the De la Mare whale-catch data, though the interpretation of that was always controversial. And see-also the TAR fig 2.16 which (if you believe it) would call into doubt LC. However, marrying ESMR into SSMI/R isn't well accepted]

Looking at the paper – models

As to the modelling, I’m dubious about:

To increase confidence in the interpretation of simulated SST variability, we restrict our analysis to models that perform well in simulating the Southern Ocean climate: 1) the NCAR Community Climate System Model 3.0 (CCSM3), since the observed Antarctic Oscillation and sea ice variability is well represented in CCSM3 (10, 11), and 2) the Geophysical Fluid Dynamics Laboratory Coupled Climate Model (GFDL-CM2.1), which has peak winds close to the observed latitude and a reasonable wind stress over the Southern Ocean, fed with the right amount and properties of the North Atlantic Deep Water, resulting in near-observed ACC transport.

I think they’ve just picked a couple of their favourite models. See-also An Antarctic assessment of IPCC AR4 coupled models for a more objective assessment (by me, of course).

Having just read through the paper, I was looking for what they would then actually do with the modelling results. With the 21stC runs, they don’t do much more than say “it got warmer”, which isn’t news. What they do with the C20C runs sort of slipped by me. Looking back, there doesn’t seem to be much there. What they *could* have done, since with the model you really do have all the info, would be a careful analysis of the hydrological cycle, P-E, and the ocean salinity, and the ocean vertical heat transport. OTOH, there is a big problem with doing that, because (as they admit) none of their models show EOFs that look anything like the obs; so by examining the models, whilst you could look at the mechanisms that affect the ocean vertical heat transport, you wouldn’t overall be looking at what had happened in the real world.

Looking at the comments – Dumb America (again)

OK, that is enough about the paper for now at least. Time for some fun.

Since I ref’d WUWT, I should point out that there is a true classic of the Dumb America problem. At first it was just funny, but then someone managed a second layer of ignorance on top of the first that made it delicious. And that all of this is in the context of the poor septics unsure whether to bury Curry or to praise her makes it all the better.

So, the problem. The paper includes

This increased precipitation, mostly in the form of snow, stabilized the upper ocean and insulated it from the ocean heat below. This insulating effect reduced the amount of melting occurring below the sea ice. In addition, snow has a tendency to reflect atmospheric heat away from the sea ice, which reduced melting from above

So, all reasonable enough, to anyone who knows about this stuff: this is a scientific paper after all, we don’t need to draw with crayons. Snow falls on the ocean (and melts – this was so obvious that the paper didn’t say this, but alas it has confused many – see later) and therefore reduces the salinity of the upper layers. Less saline water is less dense, and therefore the tendency of the upper layer to turbulent motion, leading to heat gain from the relatively warmer lower layers, is reduced. Indeed, this is explicitly spelt out in the paper:

The increased freshwater input in the high latitudes of the Southern Ocean would decrease the upper ocean salinity (density), leading to a more stable thermohaline stratification and weakened convective overturning. This reduces the upward ocean heat flux available to melt sea ice.

But, maybe you don’t know this stuff – that isn’t unreasonable either. I’m sure there are papers about QM or GR that I don’t understand. But the difference is that with the septics, anything not understood must be wrong, and must be mocked. So we have:

So I read it; ten times actually; and it forms a picture in my brain. In this picture I have the Southern Ocean which is a favorite place for round the world sailors; and it consists of salty water and other stuff. So there are clouds above this salty water; and if it is cold at times it snows over the Southern Ocean and the snow falls in the salty water; and being fresh water the snow floats on the salty water. Funny thing is I have never heard of any round the world sailor who ever mentioned finding snow on the water while down there in the Southern Ocean; but I’ll Take Dr Curry’s word for it if she says there is snow on the water.

and there is more (someone provides the right answer here). But even that doesn’t cover all the misunderstanding, because someone then manages:

I can understand the effect of snow on the albedo of ice, but that is not the issue. It is the effect of warmer water sea ice is floating on. I have looked up the thermal conductivity of pure water (0.561 W/mK) and of seawater (0.563 W/mK). This small difference in no way makes fresh water an “insulator” from sea water or makes it easier to cool, in fact it appears to be the opposite.

The error there being the assumption that thermal conductivity matters much, when the heat is actually transported by bulk motion, which is what is being suppressed by the less-saline surface water. Err, as the paper itself says (Curry explains that, but perhaps not as clearly as they need; rt explains it more clearly; but not clearly enough it seems).

Additional reading

* More context on Curry – relevant, because the way she behaves on blogs has strong similarities to the way the paper is written.
* The Glossary
* What I used to do in my spare time

Comments

  1. #1 D. C. Sessions
    2010/08/23

    I confess to being a fan of the IEEE publication standards which call for defining an acronym the first time it’s used in a paper. I think I puzzled out most of the unfamiliar acronyms, but at times it was pretty thick getting enough context to triangulate.

  2. #2 JBL
    2010/08/23

    “EOF” is mysterious to me, although (1) I assume if I had read anything else about this I would know what it meant, and (2) knowing what it stands for is unlikely to increase my understanding in any case.

    [There are a lot of people confused by EOFs. It is somewhat like Fourier analysis - in that you decompose a signal into components that are "orthogonal" (in a fairly trivial generalisation of the usual sense of the word) but instead of using pre-defined "basis functions" (in Fourier analysis, sine and cosine functions of varying frequencies) you allow the dataset to select its own most appropriate basis - hence the word "Empirical", meaning what-the-data-wants, not what-you-impose.

    So, just like Fourier analysis, a (full) EOF decomposition contains exactly the information present in the original dataset, but in a different representation. And just like (most common uses of) Fourier analysis, it provides a way of ordering the various components so that you can throw away the "least important" and find a representation that is much simpler, and yet retains most of the original signal, or at least its most important aspects.

    What the (first) EOF captures is the mode of variability of the signal that contains the "most variance". Subsequent EOFs also contain the "most variance" but subject to the constraint that they have to be orthogonal to higher EOFs. The variance captured is the percentage figure given in the various pix of LC.

    It is fairly commonplace to throw away all but the first EOF, and assert that the first EOF describes all the variance you are interested in, or somesuch. However, that needs to be done with some caution - if you have two EOFs with similar-ish degrees of variance (the eigenvalue of the matrix decomposition is this same degree of variance) then the physical patterns in the theoretically distinct eignevectors (which are the EOFs) get mixed up. There is no hint in the paper that LC are even aware of this problem, let alone having checked for it (sorry, I was supposed to be explaining EOFs not complaining about the paper any more. Is that enough?) -W]

  3. #4 pough
    2010/08/23

    I thought it meant End Of File and stopped reading. :-p

  4. #5 tupid
    2010/08/23

    when the heat is actually transported by bulk motion, which is what is being suppressed by the less-saline surface water….
    but that is the real problem
    incomplete study of all factors in the equation
    for instance the recent superblooms of algae
    ascension of cold (und rich in nutrients) turbiditic oceanic currents ?

  5. #6 Michael Hauber
    2010/08/23

    The observed increase in Antarctic Sea ice is from 1980ish. So a temperature trend from 1950 is not overly relevant. A trend map from GISS between 1980 and 2009 seems to show more cooling than warming in the southern ocean adjacent to the sea ice region, so I personally am happy just to say – Antarctic sea ice has increased due to cooling in that region. Arctic sea increased due to warming in that region. And if you put together the temperature trends for the entire globe you get a warming trend at roughly the same rate predicted by scientists several decades ago.

    Am I missing something?

    [I don't have any objections to that view, though I would add: the Arctic warming / ice retreat is clearly significant, in the statistical and more commonplace terms. Is the Antarctic trend significant? I used to know: from what I recall, it hovered at the verge of 95% sig a few years ago -W]

  6. #7 Andy
    2010/08/24

    Buh Buh Buhhh/ Buh Buh Ba Buh/ Buh Buh Buh Buh Buh Buhhhhhhh
    Snow on the water……(Dumb American Humor)

  7. #8 JBL
    2010/08/24

    That was quite excellent, thank you! (I wasn’t expecting a response as I was just piling on to D. C. Sessions’ complaining, but that was both clear and enlightening.)

  8. #9 Judith Curry
    2010/08/24

    The paper is about a hypothesis, which is then evaluated with available data and model simulations. The paper is not based on inductive reasoning that starts with data or models. It starts with our understanding of the thermodynamics of sea ice, and then a hypothesis is posed to explain the slight increase of antarctic sea ice in a warming climate.

    To sort out natural variability (e.g. the AAO) for forced anthropogenic warming, you need decades of data. The data are incomplete, and the models inadequate. However, a physically consistent explanation emerges from the analysis in the paper, which is an illustration of piecing together basic physical understanding, incomplete observations, and inadequate models to increase our understanding of how something works.

    I am prepared to spend some time on this thread if people want to discuss the science of the paper, but i am tied up until late afternoon.

    [I think the major question you need to address is the probable corruption (or some other more neutral word) of your results by invalid data. Secondary issues off taht are the lack of assessment of the data in the paper, and the failure to use 1999-2009 data, which would have extended the useable rcord by ~50%, no small gain -W]

  9. #10 caerbannog
    2010/08/24


    Buh Buh Buhhh/ Buh Buh Ba Buh/ Buh Buh Buh Buh Buh Buhhhhhhh
    Snow on the water……(Dumb American Humor)

    I know that spelling flames are in bad form, but this *screams* for a correction.

    The *proper* American spelling is:


    Duh Duh Duhhh/ Duh Duh Da Duh/ Duh Duh Duh Duh Duh Duhhhhhhh…

    HTH ;)

  10. #11 Hank Roberts
    2010/08/24

    > Is the Antarctic trend significant?

    Bob Grumbine wrote:
    “The trend in Antarctic ice cover managed to be statistically significant by about 1997, as documented in
    [Cavalieri et al.]” in his discussion linked above.

    [That does appear to be what he says, and the TAR backs this up (http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/062.htm). But that doesn’t fit with my memory. AR4 tells a very different story (http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch4s4-4-2-2.html) rather more in accord with what I thought: a trend of 5.6 ± 9.2 × 103 km2 yr–1, ie not sig (There is a significant decreasing trend in arctic sea ice extent of –33 ± 7.4 × 103 km2 yr–1 (equivalent to –2.7 ± 0.6% per decade), whereas the antarctic results show a small positive trend of 5.6 ± 9.2 × 103 km2 yr–1 (0.47 ± 0.8% per decade), which is not statistically significant.)

  11. #12 Hank Roberts
    2010/08/24

    Argh. 187 papers citing the original Cavallieri paper Bob Grumbine refers to. Let’s see what Cavallieri has written more recently. Hmmmm.

    http://www.atmos.umd.edu/~kostya/Pdf/Seaice.30yrs.GRL.pdf
    GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 18, 1970, doi:10.1029/2003GL018031, 2003
    30-Year satellite record reveals contrasting Arctic and Antarctic decadal sea ice variability

    “… not inconsistent with some GCM simulations in which CO2 concentrations were increased gradually [Manabe et al., 1992; Cavalieri et al., 1997]”

    [In
    contrast, the Antarctic sea ice extent decreased dramatically over the period 1973–1977, then gradually increased. Over the full 30-year period, the Antarctic ice extent decreased by 0.15 ± 0.08 106 km2/10 yr.
    - the problem here is that Cavalieri is one of the few people who believe that the ESMR record can be meaningfully merged into the SSMI/R record (you'll notice that HadISST doesn't believe it). So we have to ignore those numbers, and lookat table 1 instead, where he provides 1979-2002 numbers. There you'll see that at least annual and summer (feb) is non-sig -W]

  12. #13 Hank Roberts
    2010/08/24

    The last 2 paragraphs in Cavallieri (2003) seem cautionary about using less than all available information.

  13. #14 Hank Roberts
    2010/08/24

    William, thanks, this sort of thing isn’t obvious to me as an ordinary reader and adds very helpful perspective:

    > Cavalieri is one of the few people who believe
    > that the ESMR record can be meaningfully merged ….
    > So we have to ignore those numbers ….

    I realize journals conserving paper limit space given to authors for both text and references, and much may be ignored in print that might be said here.

    More please! To those in the field such detail may be unnecessary, but to us outside readers it’s very helpful.

    [Basically ESMR isn't as good. To be honest I've never really known exactly why, I've just known this factoid. Pushed, I've now upgraded [[Electrically Scanning Microwave Radiometer]] with what may be an explanation.

    You can also see it form the figure in that Cavalieri paper – the declie in ice during the ESMR period is too steep to be plausible. You could also try Bob, who still works in the area -W]

  14. #15 D. C. Sessions
    2010/08/24

    Not really complaining, or trying not to. However, since this blog occasionally attempts to engage those of us who aren’t actually professionally engaged with the climate science it seems like a useful practice.

    And thanks for the far-more-detailed-than-we-had-any-reason-to-expect explanation.

    As for “snow on the water,” I’m afraid I keep thinking Deep Purple (which also seems appropriate) and want to follow up with “gasses in the sky.”

  15. #16 Hank Roberts
    2010/08/24

    William, thanks, this sort of thing isn’t obvious to me as an ordinary reader and adds very helpful perspective:

    > Cavalieri is one of the few people who believe
    > that the ESMR record can be meaningfully merged ….
    > So we have to ignore those numbers ….

    I realize journals conserving paper limit space given to authors for both text and references, and much may be ignored in print that might be said here.

    More please! To those in the field such detail may be unnecessary, but to us outside readers it’s very helpful.

  16. #17 Tony Sidaway
    2010/08/24

    Yes, you’re back doing the initialisms thing again. I had to go to Watts Up With That to see who “WE” was (fortunately for once it was worth the trip, and for those who don’t know WE, he’s Willis Eschenbach, who seems to be a regular on Climate Audit).

    KK I can guess is the freelance environmental journalist Keith Kloor, who I know for his recent interviews with Judith Curry and a rather nasty feud with Joseph Romm of the Climate Progress blog.

    There are also references to “Bob” (Robert Grumbine) and Hank, who I assume is Hank Roberts.

    How much time is saved by typing initials and familiar names, and how much time is wasted by readers guddling about trying to work out who you’re referring to?

    [Oh dear sorry - I barely notice I'm doing it. I'll update and link the glossary. And now I find you're a tweeter -W]

  17. #18 Eli Rabett
    2010/08/24

    One of the problems with all of these discussions is the tyranny of 2 sigma. For a lot of life 1 sigma is more than enough, and certainly, anyone who fusses over the difference between 95 and 90% must be either a pre-med, an analist or a statistician, but Eli repeats himself. Variability can easily move one over or under the line in short data records. 2 sigma is a very arbitrary line, and here as in many other places a distracting one.

    [I'm not sure how else you solve the problem of picking out a small signal from noisy data. You can just declare that if it isn't obvious you don't notice it, but that is an even higher threshold -W]

  18. #19 Chip Knappenberger
    2010/08/24

    There is a lot left wanting in the AR4 version of Antarctic sea ice trends.

    I touched on some of the issues here.

    Basically, everyone *but* the IPCC thinks the sea ice increase is significant in the SH since 1979.

    -Chip

    [Thanks for the link. You damage your credibility by referring to the ridiculous NIPCC text. As for the rest: I wouldn't ref a 1996 paper for recent trends. You criticise IPCC for not adding J in, at his own request; I don't see why they would. Using Comiso updated seems reasonable to me (I see that when I last did anything real with this stuff I used both Team and Bootstrap but marginally preferred Bootstrap: http://www.antarctica.ac.uk/met/wmc/papers/ULS-grl-2005.pdf). Yes the Team and Bootstrap people don't agree with each other. Your discussion of the monthly/annual trend significance is wrong. Using extent not area is standard, and for good reasons. The pic at the end is nice, and indeed interesting, but wasn't available to AR4 -W]

  19. #20 Michael Hauber
    2010/08/24

    On statistical significance, I’ve read enough Tamino to know that if I tried to apply a statistical significance test on this data, that it would be wrong….

    Eyeballs say that between 1979 and 2006 the data does an excellent impression of flat + noise, and that there is a jump up since 2007.

    It strikes me as odd that we had an exceptionally low Arctic sea ice in 2007, an unusually strong cooling response in early 2008 to the La Nina, and possibly a step up in Antarctic Sea ice area, that seems to mostly apply during the growing half of the annual cycle, and not the shrinking half.

    Coincid

  20. #21 Michael Hauber
    2010/08/24

    Coincidence or connection?

  21. #22 Robert Grumbine
    2010/08/24

    The satellite story for sea ice embraces, so far, ESMR, SMMR, SSMI, SSMI-S, and AMSR. (Electrically Scanning Microwave Radiometer, Satellite Multichannel Microwave Radiometer, Special Sensor Microwave Imager, Special Sensor Microwave Imager-Scanner, Advanced Microwave Scanning Radiometer — more or less, none of this will be on the test.)

    The last 4 all have multiple microwave channels, around (give or take), including 18, 22, 37, 85 GHz, usually with both vertical and horizontal polarization being observed. All 4 are used without much compunction as to trend effects, though probably (imho) more concern should be given the SMMR to SSMI transition, and the recent SSMI to SSMI-S/AMSR transition(s). Not to mention a gap period between instruments (memory fails, perhaps SMMR to SSMI F8).

    ESMR was the first to fly, and had only a single channel, about 19 GHz (total power). Resolution, about 30 km, was comparable to the standard gridding of the SMMR/SSMI (25), but superior to the low frequency channel of those instruments (actually 50 km, grid however fine you want, the footprint wasn’t/isn’t that fine again until AMSR).

    For the Arctic, a single channel is not very informative about area — it isn’t too bad for extent, but area is only within some tens of percent. The reason is that you can have either a moderate amount of first year ice, lot of multiyear ice, and a bit of water, or, for the same observed intensity a lot of first year ice and a lot of water, with no multiyear ice.

    In the Antarctic, on the other hand, most of the ice (80% at winter maximum) is first year. A single channel does quite well (some eyeball experiments of my own) at representing, particularly, Antarctic ice extent. It isn’t even too bad (same eyeballs) at the summer minimum, at least for extent. So, as far as this sort of consideration goes, I’m mostly with Don (n.b.: I’ve worked with Don).

    Where I think some (many? most?) of the community part company with Don (and me) is the fact that the ESMR detected a massive Weddell Polynya* most winters that it flew (1973-1976). There’s something more than a little disturbing at the thought that the only years something happened were the same years that the first satellite capable of detecting it were flying. So some reluctance to accept ESMR from the meteorological community, and the non-polar oceanographic communities.

    *Polynya = large area of open water in the sea ice pack. This as opposed to a ‘lead’ which is open water, but a fairly linear area.

    In the polar oceanography community, I think the polynya, thence ESMR, is better-accepted. There were ocean surveys in years following the polynya which showed its effects in the water column. At least that’s part of why I’m inclined to think that ESMR was seeing something real.

    I haven’t seen a curve for the decline in ice cover for the ESMR period in a long, long time. I would be entirely unsurprised, though, if it were exceptionally steep. The conditions that seemed to be required to generate the massive Weddell Polynya in that period would have included strong winds expanding the ice pack away from the polynya’s center — more than compensating for the loss of extent from the polynya itself.

    [Thanks for that - very helpful. Now if only someone could write it up into a paper and get it past both Comiso and Cavalieri as referees. The TAR has a nice pic of ESMR:

    I'm pretty sure that I - and everyone else at, say, BAS - took the sharp decline in ESMR as evidence of its non-reality -W]

  22. #23 Chip Knappenberger
    2010/08/24

    William,

    OK. Well, regardless of how it was reported, and who knew what when, it seems like *now* it is pretty well establihed that there has been a statistically significant trend in Antarctic sea ice extent since 1979. This, of course, may be subject to change in the future. :^)

    -Chip

    [I'm not at all sure that is true. I'd like to see a proper analysis of it - there must be a fairly up to date paper on Antarctic sea ice trends, I'd have thought. In the meantime,

    * ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/S_09_plot.png
    * ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Mar/S_03_plot.png

    don't show significant trends (though they do show positive trends). This is based on NASA team, says the doc, and that also looks to include some useful discussion -W]

  23. #24 chris
    2010/08/25

    re your comment:

    “Incidentally, because no-one has heard of Liu, everyone is calling this “Curry’s paper” or whatever. Which is wrong. It is Liu and Curry. I’ll call it LC in the sequel, for short.”

    yes, it would be a shame not to fully credit Jiping Liu (J.L.) since it essentially J.L.’s paper. e.g. PNAS requires a statement of author contributions which in this case is:

    Author contributions: J.L. designed research, J.L. performed research, J.L. analyzed data,
    and J.L. and J.C. wrote the paper.

    [Yeees... how this works might be a matter of convention. Who-did-what is something of a recent change; when I were a lad none of that was there. I wouldn't rely on it to be accurate -W]

  24. #25 MItch
    2010/08/25

    Liu’s disappearance even though he is first author and apparently did most of the work is a classic example of the ‘Matthew effect’ (http://en.wikipedia.org/wiki/Matthew_effect)where the better known author gets the credit for the work. Graduate students and post-docs beware…

  25. #26 Hank Roberts
    2010/08/25

    Robert, when
    > ESMR detected a massive Weddell Polynya …

    do you mean there was no independent verification (say, from the surface or aircraft or submarine observation) of a polynya during those years)? I’m not quite clear what people found dubious about the ESMR data.

    I found, well, a lot I haven’t read yet, that seems to describe Weddell polynyas as a real climate event. Was it the size, existence, or ???

    An image search shows both satellite and aircraft photography

    http://www.google.com/search?q=Weddell+Polynya

    First two hits:

    “A sea-ice-ocean computer model simulation vividly demonstrates how this mechanism fully accounts for the characteristics that mark Weddell Polynya events….”
    http://www.scienceonline.org/cgi/content/short/292/5522/1697

    “A recent major climatic event was the occurrence of a very large region, 350000 km2, of open water or polynya. within the ice-covered Weddell Sea …
    http://www.atmosp.physics.utoronto.ca/ANTARCTIC/weddell_polynya.html

    Thank you.

  26. #27 Hank Roberts
    2010/08/25

    Paleo work: “… results document the presence of a seasonal or perennial polynya in the NW Weddell Sea …”
    http://dx.doi.org/10.1016/j.epsl.2010.05.008

  27. #28 Hank Roberts
    2010/08/25

    perhaps lost in the spam filter, query to Robert–is the existence of the polynya questioned? ground truth or air photos? Not quite sure why the early satellite info is doubted; found lots about that polynya appearing to assume it’s a real and recurring phenomenon.

    [Sorry; rescued -W]

  28. #29 MapleLeaf
    2010/08/25

    Why did LC not cite and discuss Manabe et al. 1992 (J. Climate)? Read the para on page 113 which starts with “The geographical distribution of sea ice thickness……” in Manabe et al.

  29. #30 Judith Curry
    2010/08/25

    Checking in, don’t see much to respond to, if anyone has a specific question for me pls post. I agree with everyone that I wish we had more and better data. The paper represents primarily Liu’s effort; I contributed say 10-15%, primarily in terms of developing the arguments and writing. The idea and general approach was Liu’s (personally I am not a fan of EOFs). My inclusion as coauthor on this reflects my fractional effort and intellectual contribution to the paper, and perhaps more significantly, my willingness to defend the paper and be involved in outreach activities involved in the paper (e.g. press release, blogging). The paper has gotten associated with me in the blogosphere owing to my blogospheric notoriety, whereas Liu fielded nearly all of the MSM questions.

    [I find it hard to believe that you've read the whole post and can find nothing to argue against. OK, let me summarise a few:

    1) you use data from 1950-1978 that is clearly meaningless.
    2) this data contaminates the entire (obs) analysis.
    3) the hypothesis that you put forward is not novel.
    4) you could have used an extra decades worth of obs data.
    5) there is no justification for the EOF analysis.

    If you have no answers to any of those questions, then perhaps you could ask Liu to respond? -W]

    The papers for which I have earned blogospheric notoriety are in the area of climate dynamics (e.g. this one and the hurricane paper), and are not representative of my “oeuvre” and an unlikely topic for me to first-author a paper on. I find the reliability of large scale datasets and climate model simulations to be a rather frustrating and depressing issue. My comfort zone is theoretical analysis and process modeling, which relies more on laboratory and local field data. Of relevance to sea ice processes and the exchange of heat at the upper and lower sea ice boundaries, see these two papers on Arctic sea ice, which address issues related to snow and ocean/ice exchanges of heat that are also of relevance to the Antarctic sea ice.
    http://curry.eas.gatech.edu/currydoc/Schramm_JGR102.pdf
    http://curry.eas.gatech.edu/currydoc/Holland_JGR102.pdf

    [I disagree with your implication, here. You blogospheric notability doesn't come from the science -W]

  30. #31 Eli Rabett
    2010/08/25

    Well, Dr. Curry and JL could start by discussing her and JL’s view on whether there is a statistically significant trend in in Antarctic sea ice extent since 1979 and which, if any, satellite measurements, or models one should trust

  31. #32 Judith Curry
    2010/08/25

    As per NSIDC plots, there is an apparent increase in average Antarctic sea ice extent since 1979 of about 2% but this increase is not statistically significant at a high confidence level. Different satellite data sets and retrieval techniques provide slightly different answers, which gives a sense of the uncertainty in the data. One of my big gripes for almost two decades now is the the plethora of different sea ice datasets that reside on the NASA DAACS. Can Comiso, Cavalieri or whoever please put together one “best” data set with some error bars on it. I have been on NRC panels that have made this recommendation, I am now on the NASA Science Advisory Subcommittee, continuing to make this recommendation to no avail. I guess we need some sort of ice-gate scandal or something to get some movement on this issue.

    [I'm confident that if you offered funding for this work rather than just recommendations, people would do it -W]

  32. #33 Hank Roberts
    2010/08/26

    Can anyone help rephrase my question so that Dr. Curry recognizes it? I’ve tried and failed several times to ask it in a useful way.

    [Do you mean on the Polynya? You want Bob for that. Go on, ask him to do a whole post on it, he likely will, and I'd be interested too -W]

  33. #34 Judith Curry
    2010/08/26

    Hank, I could not identify a question from you, perhaps something related to the Weddell Polynya? If you google Weddell Polynya, you will find much information on it. Bob Grumbine is a much better person than myself to discuss this.

  34. #35 Eli Rabett
    2010/08/26

    This appears to put us somewhat in the position of Shindell, who about a decade ago gave a series of talks on whether one should believe observations or models of climate in the 19th century. His reply was neither but that while the models were slightly better, the combination of the two is to be preferred. Much the same comes from other fields where observations are, shall Eli say, doubtful.

    Still, in discussing such a situation, one must be absolutely clear. Eli believes that Wm is not seeing the needed clarity in Liu and Curry

    [If you're asking for clarity, Eli believes that Wm is not seeing the needed clarity in Liu and Curry isn't at all clear. Do you mean, I think that LC lacks clarity? Or that it has clarity, that I'm missing? My position is taht LC is clear enough but is badly flawed -W]

  35. #36 Robert Grumbine
    2010/08/26

    Judy:
    I think the question Hank meant for you is not the Weddell Polynya; that’s for me. Rather, for you to provide perspective on what your paper with Liu adds to the Manabe 1992 paper.

    Hank:
    The issue on the Weddell Polynya is the matter of the giant one ESMR found in the early 1970s vs. the much (5-10x) smaller ones of more recent years. There’s a nontrivial contingent which is inclined to think the giant one is the figment of ESMR’s imagination. The BAS objection that William mentions is closely related.

    William:
    I probably will take up the Weddell Polynya at my place. It’s responsible for me being in polar oceanography (or at least having been so) and having selected the graduate school I did.

  36. #37 Eli Rabett
    2010/08/26

    Wm, if you read JC above, she agrees that the data sucks. She is a bit less clear about why they used it without noting that the data sucks. That is one of your questions, correct, as in

    1) you use data from 1950-1978 that is clearly meaningless.
    2) this data contaminates the entire (obs) analysis.

    So you got an answer to 1. The data sucks. Her agreeing to 2 or not now becomes the key point up for discussion.
    You’re both welcome.

    This has been another episode of EliExplainsItAll.

    [OK, agreed (mostly) and thanks: the key point is 2 (though that folds in another point I made in the main text: there is no "data exploration" in the paper) -W]

  37. #38 Hank Roberts
    2010/08/26

    Dr. Curry, William mentioned my question, and linked to my earlier attempts to ask it, above in this thread:
    “Hank’s attempts to get Curry to answer this are here and there

  38. #39 Hank Roberts
    2010/08/26

    spamfiltered again; 2 links is too many?

  39. #40 James Annan
    2010/08/27

    Hank,

    If it’s any consolation I thought your question was pertinent and clearly expressed, and Curry’s repeated refusal to even see it tells a pretty clear story (entirely in character with her performance over recent months, unfortunately).

  40. #41 Chris Ho-Stuart
    2010/08/27

    Hank’s question to Dr Curry and/or I presume to Dr Liu is:

    Can you clarify how your paper differs from, adds to, or disagrees with Manabe (1992), Cavalieri et al. (1997), and Markus et al. (2006)?

    Refs:

    Manabe, S., M. J. Spelman, R. J. Stouffer, 1992: Transient Responses of a Coupled Ocean-Atmosphere Model to Gradual Changes of Atmospheric CO2. Part II: Seasonal Response. J. Climate, 5, 105-126

    D. Cavalieri, P. Gloersen, C. L. Parkinson, J. C. Comiso, H. J. Zwally, “Observed Hemispheric Asymmetry in Global Sea ice Changes”, Science, 278, pp 1104-1106, 1997.

    Markus, T., and Cavalieri, D. J., “Interannual and regional variability of Southern Ocean snow on sea ice”, Annals of Glaciology, 44, pp 53-57, 2006

    Brief discussion, including these papers, at WUWT trumpets result supporting climate modelling, in “More Grumbine Science” blog March 12 2010.

    I am only posting this to see if it helps, as requested, identify the question which has been asked several times already. I am also genuinely interested in the answer, simply because I had been looking at this topic myself a year or so ago with yet another paper: Zhang, Jinlun (2007) Increasing Antarctic sea ice under warming atmospheric and oceanic conditions in J. Clim. Vol 20, pp 2515–2529.

    Hope this helps. It seems pretty straightforward. Dr Liu, as first author of Liu and Curry 2010, is probably the one most able to answer quickly.

  41. #42 Judith Curry
    2010/08/27

    Hank and William et al., your questions are on my to do list, but i am swamped, things have piled up as a result of spending too much time on the blogs last week. Anyone who feels like i am not “seeing” their question, pls send me an email, too many threads and comments for me to keep up with.

  42. #43 Judith Curry
    2010/08/28

    William, all of these issues were discussed ad nauseum over at WUWT, on three threads. These are certainly valid questions, but not particularly interesting ones IMO, which is why I was not motivated to answer them until repeatedly queried (including email) about them. Here goes.

    1) you use data from 1950-1978 that is clearly meaningless.

    Reread the 2nd para of the introduction. The problem with the data is acknowledged. The data from 1950-1978 is not meaningless. There is data in the region during these periods. Missing data in the two SST data sets is filled in by an EOF analysis. The two different SST analyses give reasonable agreement in the period post 1950 (they diverge sharply prior to 1950). Our analysis of the trend is broadly consistent with other assessments of the temperature trend that are cited in the introduction.

    2) this data contaminates the entire (obs) analysis.
    The obs analysis is a minor part of the paper, intended to compare with the model simulations that were the main source of data used in the analysis. The whole issue of filling in missing ocean obs using an EOS analysis is definitely troublesome, particularly prior to 1950. In fact it makes me really queasy about the “unequivocal” confidence of the IPCC. William, let me know if you are prepared to throw out both the baby and the bath water on this one.

    3) the hypothesis that you put forward is not novel.
    We cite the Zhang 2007 paper that describes a different mechanism that is not inconsistent with ours, but does not include the atmospheric hydrological cycle. I probably read the Manabe et al. paper back in the 1990’s, but didn’t recall it as we were writing this paper. Did any of you (other than Grumbine) actually read the Manabe paper? There is one statement in the Manabe paper that is relevant: “ the reduction in surface salinity resulting from the increase of freshwater supply at the oceanic surface is mainly responsible for the weaker convective activity in the G integration.” This statement is made in a paragraph discussing the deep ocean convection in the Southern Ocean. Manabe doesn’t discuss the increasing sea ice extent in this context. Grumbine connected the dots in the Manabe et al. paper and came up with generally the same idea we did (we came up with the idea via a different route), and describes it in a half sentence. So, our hypothesis is not put forward per se in the Manabe et al. paper. I occasionally check in at Grumbine’s site, didn’t spot his post on the Antarctic sea ice. Note, the Zhang paper did not cite the Manabe paper either; it just doesn’t say much about the Antarctic sea ice.

    [Lazar demolishes this -W]

    4) you could have used an extra decades worth of obs data.

    The purpose of the obs data was to demonstrate the consistency of the 20th century climate model simulations with the observations. Data from 2000-2010 would not have helped here, since the AR4 climate model simulations do not extend past 2000.

    5) there is no justification for the EOF analysis.
    EOF analysis is basically a filtering technique. You can conduct an analysis with the original data, or with filtered data. The latter can clarify the signal. In this particular paper, the EOF analysis didn’t filter all that much. If the study had been conducted with the original data, it would have been more easily understood by a broader audience. The use of EOFs arguably complicated the analysis, but did not in any way compromise the analysis. Jiping Liu prefers to use EOF analysis; I do not. I think I’ve convinced him not to use the EOFs in future papers unless there is a clear advantage that outweighs the addition of the complexity.

    Hank, see answer to question #3 re the Manabe paper. Why was a press release issued on this? Georgia Tech (along with nearly every other university) encourages researchers to publicize any results that they think are of broad interest. Pretty much anything that gets published in a journal with a press embargo policy (e.g. Science, Nature, PNAS) is in this category.

    [See Round in circles with Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice? for replies -W]

  43. #44 Hank Roberts
    2010/08/28

    > Why was a press release issued on this?

    No, that wasn’t my question. I understand press releases are routine.

    I asked why the language of the press release suggests the idea is new, because it was familiar to me as a casual reader, e.g. Zwalley et al. 2002 mention:
    “… [Manabe et al., 1992], gives the counter-intuitive result that the sea ice cover would actually increase with global climate warming …”

  44. #45 Judith Curry
    2010/08/28

    Hank, the paper was reviewed by 3 reviewers at Science and 3 reviewers at PNAS. None of the reviewers mentioned that this was unoriginal (or said we should cite Manabe or Zwalley). Your previous post mentioned the Manabe et al. 1992 paper. I read the paper, see message 43 point 3. They mention increasing snowfall in the context of oceanic deep convection but not in the context of sea ice. As far as I can tell, this is the first time a Zwalley paper has been mentioned in the context of our paper. If you give me the citation or better yet a link, i will go read the paper (I’m pretty sure I have not read this paper). Are you referring to the Cavalieri et al. paper cited by Grumbine? They state that the behavior is expected. As I stated in the interview with Eric Berger, scientists have known about the increase of antarctic sea ice and it is consistent with what the models produce, so people haven’t worried about it, and it somehow is consistent with global warming. What we did was actually provide a physical hypothesis for this that connects the warming, hydrological cycle and sea ice and examine test the hypothesis using climate model data. Is it the text in the press release “the researchers provide an explanation” that suggests to you that the idea is new? The statement in the press release is a pretty modest statement.

  45. #46 Hank Roberts
    2010/08/28

    OK, cite below for what I quoted a bit from.

    You’ve given a good enough answer, for press release purposes — that the authors and the reviewers either knew about that work and didn’t think it relevant, or didn’t know about it. The press release just sounded funny to me, from what I happened to know.

    I found a bit more, after reading what Robert Grumbine posted, by doing this search (of course search results differ for each person each time, but it’s what I have):

    http://scholar.google.com/scholar?q=manabe+antarctic+%22sea+ice%22

    The quote I gave is from what I got as the third result, this one:

    [PDF] Variability of Antarctic sea ice 1979–1998
    … HJ Zwally, JC Comiso, CL Parkinson, DJ … – J. Geophys. …, 2002 ….
    … atmosphere interactions [Manabe et al., 1992], gives the counter-intuitive result that the sea ice
    cover would actually increase with global climate warming. … [3] Clearly, if changes in the distribution
    of Antarctic sea ice are expected to be indicative of global climate change, a …
    Cited by 123

  46. #47 Hank Roberts
    2010/08/28

    Oops. The ‘cited by’ list for Zwalley et al. (2002) is:
    http://scholar.google.com/scholar?cites=2438491923589866582&as_sdt=2005&sciodt=2000&hl=en

  47. #48 Eli Rabett
    2010/08/28

    Not to put a fine point on it, but one of those cites is to a paper by a J. Liu and J. A Curry and Douglas G. Martinson Interpretation of recent Antarctic sea ice variability

    Now some, not Eli he hastens to add, might have expected anyone who cites an article to have at least read the abstract, which reads in part

    The observed increase in Antarctic sea ice cover is counter to the observed decreases in the Arctic. It is also qualitatively consistent with the counter-intuitive prediction of a global atmospheric-ocean model of increasing sea ice around Antarctica with climate warming due to the stabilizing effects of increased snowfall on the Southern Ocean.

    [Manabe et al., 1992], gives the counterintuitive result that the sea ice cover would actually increase with global climate warming. The physical processes in the model that cause the predicted sea ice increase are increased precipitation with a warmer atmosphere in polar regions, more snowfall on sea ice, lower salinity in the near-surface ocean layers, more stable mixed layer and reduced heat flux to the surface, and consequently, more sea ice.

    At this point the auditors go nuts. Must be a tribal thing.

  48. #49 Hank Roberts
    2010/08/29

    Citation: Zwally, H. J., J. C. Comiso, C. L. Parkinson, D. J. Cavalieri, and P. Gloersen (2002), Variability of Antarctic sea ice 1979–1998, J. Geophys. Res., 107(C5), 3041, doi:10.1029/2000JC000733.

    Direct link (paywalled):
    http://www.agu.org/pubs/crossref/2002/2000JC000733.shtml
    The abstract available there ends:
    “… The observed increase in Antarctic sea ice cover is counter to the observed decreases in the Arctic. It is also qualitatively consistent with the counterintuitive prediction of a global atmospheric-ocean model of increasing sea ice around Antarctica with climate warming due to the stabilizing effects of increased snowfall on the Southern Ocean.”

    Full text as a PDF:
    http://lgmacweb.env.uea.ac.uk/ajw/Sea_ice/zwally_et_al_2002.pdf

  49. #50 Hank Roberts
    2010/08/29

    Direct PDF link for Zwally et al. 2002:
    http://lgmacweb.env.uea.ac.uk/ajw/Sea_ice/zwally_et_al_2002.pdf

    Longer reply with more links maybe in the bit bucket; got a Movable Type error message.

    [Remember, to defeat the zealous spam filters you can only use one link. I've approved that comment now, since I'm back from a brief break -W]

  50. #51 cce
    2010/08/29

    The Antarctic EMSR data is included in this series.

    http://polynya.gsfc.nasa.gov/datasets/sh_daily_observed_or_interpolated_sie_1973_2002.txt

    All of Cavalieri et al’s datasets are here:
    http://polynya.gsfc.nasa.gov/seaice_datasets.html

  51. #52 David Jones
    2010/08/31

    Links to glossary (the one at the tail of the article, and in the navi-bar on the top-left) are 404ing out.

    [Thanks for pointing that out. It turns out to be because wordpress includes the year/month in the URL, and I'd bumped it up to keep it "current". So I've un-bumped it -W]

    Is EOF on it?

    [It is now :-) -W]

  52. #53 Recycle
    2010/09/15

    Thank you for writing about this! What an important issue. It reminds me of the kind of stuff I often see at http://www.youtube.com/greenopolistv and it’s always great to be educated and kept up to date on what’s going on!

  53. #54 seo company
    2011/10/14

    “Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice

    The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models’ internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.

  54. #55 ringtone maker
    2012/05/02

    This problem is obvious and I’m glad that people started talking about it! Finally! Some paper work and proofs are exactly what I wanted to see. Thanks for the post.

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