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State of Antarctica: red or blue?

Filed under: — eric @ 21 January 2009 - (Italian)

A couple of us (Eric and Mike) are co-authors on a paper coming out in Nature this week (Jan. 22, 09). We have already seen misleading interpretations of our results in the popular press and the blogosphere, and so we thought we would nip such speculation in the bud.

The paper shows that Antarctica has been warming for the last 50 years, and that it has been warming especially in West Antarctica (see the figure). The results are based on a statistical blending of satellite data and temperature data from weather stations. The results don’t depend on the statistics alone. They are backed up by independent data from automatic weather stations, as shown in our paper as well as in updated work by Bromwich, Monaghan and others (see their AGU abstract, here), whose earlier work in JGR was taken as contradicting ours. There is also a paper in press in Climate Dynamics (Goosse et al.) that uses a GCM with data assimilation (and without the satellite data we use) and gets the same result. Furthermore, speculation that our results somehow simply reflect changes in the near-surface inversion is ruled out by completely independent results showing that significant warming in West Antarctica extends well into the troposphere. And finally, our results have already been validated by borehole thermometery — a completely independent method — at at least one site in West Antarctica (Barrett et al. report the same rate of warming as we do, but going back to 1930 rather than 1957; see the paper in press in GRL).


Here are some important things the paper does NOT show:

1) Our results do not contradict earlier studies suggesting that some regions of Antarctica have cooled. Why? Because those studies were based on shorter records (20-30 years, not 50 years) and because the cooling is limited to the East Antarctic. Our results show this too, as is readily apparent by comparing our results for the full 50 years (1957-2006) with those for 1969-2000 (the dates used in various previous studies), below.

2) Our results do not necessarily contradict the generally-accepted interpretation of recent East Antarctic cooling put forth by David Thompson (Colorado State) and Susan Solomon (NOAA Aeronomy Lab). In an important paper in Science, they presented evidence that this cooling trend is linked to an increasing trend in the strength of the circumpolar westerlies, and that this can be traced to changes in the stratosphere, mostly due to photochemical ozone losses. Substantial ozone losses did not occur until the late 1970s, and it is only after this period that significant cooling begins in East Antarctica.

3) Our paper — by itself — does not address whether Antarctica’s recent warming is part of a longer term trend. There is separate evidence from ice cores that Antarctica has been warming for most of the 20th century, but this is complicated by the strong influence of El Niño events in West Antarctica. In our own published work to date (Schneider and Steig, PNAS), we find that the 1940s [edit for clarity: the 1935-1945 decade] were the warmest decade of the 20th century in West Antarctica, due to an exceptionally large warming of the tropical Pacific at that time.

So what do our results show? Essentially, that the big picture of Antarctic climate change in the latter part of the 20th century has been largely overlooked. It is well known that it has been warming on the Antarctic Peninsula, probably for the last 100 years (measurements begin at the sub-Antarctic Island of Orcadas in 1901 and show a nearly monotonic warming trend). And yes, East Antarctica cooled over the 1980s and 1990s (though not, in our results, at a statistically significant rate). But West Antarctica, which no one really has paid much attention to (as far as temperature changes are concerned), has been warming rapidly for at least the last 50 years.

Why West Antarctica is warming is just beginning to be explored, but in our paper we argue that it basically has to do enhanced meridional flow — there is more warm air reaching West Antarctica from farther north (that is, from warmer, lower latitudes). In the parlance of statistical climatology, the “zonal wave 3 pattern” has increased (see Raphael, GRL 2004). Something that goes along with this change in atmospheric circulation is reduced sea ice in the region (while sea ice in Antarctica has been increasing on average, there have been significant declines off the West Antarctic coast for the last 25 years, and probably longer). And in fact this is self reinforcing (less sea ice, warmer water, rising air, lower pressure, enhanced storminess).

The obvious question, of course, is whether those changes in circulation are themselves simply “natural variability” or whether they are forced — that is, resulting from changes in greenhouse gases. There will no doubt be a flurry of papers that follow ours, to address that very question. A recent paper in Nature Geosciences by Gillet et al. examined trends in temperatures in the both Antarctic and the Arctic, and concluded that “temperature changes in both … regions can be attributed to human activity.” Unfortunately our results weren’t available in time to be made use of in that paper. But we suspect it will be straightforward to do an update of that work that does incorporate our results, and we look forward to seeing that happen.


Postscript
Some comment is warranted on whether our results have bearing on the various model projections of future climate change. As we discuss in the paper, fully-coupled ocean-atmosphere models don’t tend to agree with one another very well in the Antarctic. They all show an overall warming trend, but they differ significantly in the spatial structure. As nicely summarized in a paper by Connolley and Bracegirdle in GRL, the models also vary greatly in their sea ice distributions, and this is clearly related to the temperature distributions. These differences aren’t necessarily because there is anything wrong with the model physics (though schemes for handling sea ice do vary quite a bit model to model, and certainly are better in some models than in others), but rather because small differences in the wind fields between models results in quite large differences in the sea ice and air temperature patterns. That means that a sensible projection of future Antarctic temperature change — at anything smaller than the continental scale — can only be based on looking at the mean and variation of ensemble runs, and/or the averages of many models. As it happens, the average of the 19 models in AR4 is similar to our results — showing significant warming in West Antarctica over the last several decades (see Connolley and Bracegirdle’s Figure 1).


128 Responses to “State of Antarctica: red or blue?”

  1. 51
    dave p says:

    Have noticed that the Ross Ice Shelf seems to have nearly disappeared. Is this normal? If not why hasn’t there been more publicity about it?

    [Response: Huh? Where do you get your information? The Ross Ice Shelf is still very much present. - gavin]

  2. 52
    Calum says:

    Anyone like to comment on this article?

    http://www.realclimate.org/index.php/archives/2008/02/antarctica-is-cold/

    [Response: Sure. That article is talking about relative cooling of Antarctica compared to the rest of world and the impact of adding dynamic oceans to the models in the 1990s. Spencer's historical point was very well made - as models got more realistic, the increased ocean thermal inertia simulated meant that the expected trends in Antarctica were much weaker than elsewhere. With weaker expected trends, short term variability will obviously be more important on shorter timescales. This new paper is quantifies that over the 50 year time scale - the trends are positive, but still much smaller than elsewhere. - gavin]

    [Response: Small correction to Gavin's comment above. Actually not "much smaller than elsewhere" depending on what one is talking about. The mean Antarctic warming over this time period is about the same as the global mean warming. But it is concentrated largely over West Antarctica. East Antarctica is warming considerably less than most other areas. -mike]

  3. 53
    Eric Swanson says:

    RE: #15, Chip Knappenberger,

    You wrote: “3) Why do you need reconstructions of the period of record when you have full satellite coverage?”

    But, what satellite data record do you propose to compare with? I suppose you are referring to either the TLT produced by Christy and Spencer at UAH or the similar product from Mears and Wentz at RSS. The TLT from UAH is seriously flawed over the Antarctic, as I demonstrated in a GRL paper some 5 years ago (doi:10.1029/2003GL017938). Here’s a graph of the annual cycle, which is much like that from my paper. Compare that with a similar graph produced from the UAH TMT data. Notice that the TLT has a steep drop in brightness temperature during the early months of the year, a drop not seen in the TMT data. But, the TLT is derived from the the MSU Channel 2, which is also the source of the TMT data. The difference is very curious and was the reason I wrote my paper. In my paper, I also pointed out that data from radiosonds did not exhibit this curious annual cycle. I suggested that the cause of the difference was surface influence, including that from sea-ice.

    Oh, perhaps you want to use the RSS data? But, the folks at RSS understand the problem and do not include any information poleward of 70S. They do this because the MSU channel 2 includes a strong influence from high altitude land areas. RSS also excludes areas over high mountains, such as the Himalayas. One might conclude that there is no other valid “satellite temperature data” available over the Antarctic, so no comparison is possible. But, I’m sure that your side of the “debate” will attempt to do so anyway.

  4. 54
    Adam Gallon says:

    How do these findings square with http://icecap.us/images/uploads/ANTARCTIC_SP.jpg?
    (Sorry, never learnt these Aitch-Tee-Em-El things!)

    [If you look at the figures, you'll see that we don't find significant warming at South Pole. This location is not representative of the continent as a whole. Nor is Vostok (where it has been warming, at the same rate South Pole has been cooling). You can't rely on just one or two sites like this.]

    Seems to show a steady fall of the temperature at the South Pole over a comparable time period.
    And isn’t sea-ice around Antarctica 20% above average? http://nsidc.org/data/seaice_index/images/daily_images/S_timeseries.png

    [If you look at the paper, you'll see that we know sea ice is increasing on average, but it has decreased in the Amundsen/Bellinghausen (Pacific) sector where we find the greatest warming]

    Also, why pick 1957 as a start point? Is it simply to select a 50 year period?

    [There are some data but very few before 1957. 1957 was the International Geophysical Year, when most of the weather stations were put in.--eric]

    Is there any good data to extend the study’s period, since man’s been trudging around the pole since the early 1900s?
    I must say, that comment #12 needs answering, if there’s been cooling between 1969 & 2000, (Why has that cut off been set at 2000, why not 2006 as in the study?) but overal a warming between 1957 & 2006, what’s caused it and is the warming been since 2000?
    My PC monitor isn’t good enough to resolve the trend scale, is the maximum about .2 Degrees per decade? If that’s all, then what’s the worry folks? Surely this means it goes from exdeptionally cold, to almost exceptionally cold?

  5. 55
    pascal says:

    mike

    you say “East Antarctica is warming considerably less than most other areas. -mike]”

    in the paper I read:

    west antarctica: 0.17°C/dec

    east antarctica : 0.10°C/dec

    global antarctica : 0.12°C/dec

    I add: land SH anomaly for the same period (1957-2006) = 0.116°C/dec

    So, If I well understood, the warming trend of east antarctica is a little smaller than elsewhere but not “considerably” smaller.

    [Response: thanks, yes I accept this correction of my correction of Gavin ;) -mike]

  6. 56
    Hank Roberts says:

    “dave p”– Gavin asked where you got the picture making you think the Ross ice shelf had almost disappeared. Are you confusing the sea ice with the ice shelf?

    If so this may help, from

    http://www.antarctica.org.nz/03-environment/index.html

    ——excerpt follows——–
    The Ross Ice Shelf

    The Ross Ice Shelf varies in thickness from over 1000 m where it is fed by glacial ice from the ice sheet to less than 100 m at the ice front. On its seaward side it calves icebergs at a rate of about 150 km3 per year, and it also loses volume by bottom melting at a rate of about 2.5 m per year. One of the largest icebergs recorded from the Ross Ice shelf in modern times appeared in the spring of 1987 and measured about 154 km long x 35 km wide.

    Sea Ice

    The sea around the ice shelves is often frozen to form 2m thick sea ice which can extend from 4 x 106 km2 in late summer (February) to 22 x 106 km2 before the thaw begins (September). …

    ——end excerpt——

    Note the sea ice comes and goes:
    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.365.south.jpg

  7. 57

    Re 53:

    Er, Eric, I was referring to the satellite data used by Steig et al. I was interested in the comparison between their reconstruction and their raw data for the period of overlap (~25 years).

    -Chip

  8. 58

    Erik,

    Quick question regarding the sensitivity of the trend to the starting year: would the trend from 1935-1945 to present still be positive given the large ENSO event in West Antarctica (data permitting, of course)? Did/will you guys release an estimate of average and regional reconstructed Antarctic temperature by month or year that we can play around with?

    Overall, it seems like quite an interesting and important study, especially the results for the West Antarctic region. I’ll withhold complete judgment till I can get through the Nature paywall and read the entire paper, of course!

    On an unrelated note, it looks like the usual suspects in the blogosphere haven’t been entirely dissuaded by this post. Their explanation for West Antarctic warming? Well, apparently it has more volcanoes, and thus must be warming faster independent of any actual trend in vulcanism!

  9. 59
    dave p says:

    I thought the ice shelf was the bit which extended in to the sea. According to the UICC the sea ice has almost gone except for an outer ring. I thought the sea ice at the south of the sea was permanent. Can’t find any comparison maps.

    [Response: There is very little permanent sea ice cover around Antarctica (though there is always some ice to be found). The ice shelf is land ice that has flowed into the ocean and is now floating (and usually hundreds of meters thick). Sea ice forms 'in situ' in the ocean is rarely more than a couple of meters thick in the south. - gavin ]

  10. 60
    Phil. Felton says:

    Eric & Mike I found the paper very interesting, one thing I found distracting though was the references to the seasons. Sometimes the season name was used sometimes it was prefaced by ‘austral’ with result that I was unsure which season was being referred to.

  11. 61

    Mike et al., re: 52 temperature trends

    At the beginning of your paper, you all write “Although the Antarctic Peninsula is one of the most rapidly warming locations on Earth…”—repeating an often used factoid. But later in the paper you all report the warming of the Peninsula as being 0.11+/-0.04ºC/dec, which is just slightly less than the Antarctic average of the same period (0.12+/-0.07ºC/dec), and which you describe (in comment 52) as “The mean Antarctic warming over this time period is about the same as the global mean warming.”

    Thus, it seems that it is not the case that the Antarctic Peninsula is one of the most rapidly warming places on earth (heck, it is warming less than average).

    Perhaps this throwaway line should be thrown away?

    -Chip

    [Response: In our paper we make it clear that we likely underestimate trends, particularly on the Antarctic Peninsula. The weather stations locations on the Antarctic Peninsula definitely do show trends far exceeding those just about anywhere else -- as much as 0.5 C/decade (though with large error bars). So, no I don't think that this line needs to be thrown away. Having said that, it is not clear how representative the weather stations really are of the Peninsula as a whole. Those high numbers come from the coast, where huge declines in sea ice definitely contribute to the warming; but those really high rates warming may not extend very far inland, or very far south.--eric]

  12. 62
    Chris Colose says:

    Alan (47),

    I don’t quite like the whole “skeptical argument refuted” twist on that news article. Pretending that there was a problem before, but now there’s no discrepancies after this new paper provides a misleading perspective.

    The Antarctic trends (with or without the recent Nature paper) were never a contradiction to GW (or the ‘A’ component in GW); certain models (e.g. Shindell and Schmidt 2004) reproduce the observations relatively well as a function of GHG+O3 depletion. Dr. Mann’s comment to #45 is right on-target…you cannot simply lump together all forcings and expect every spot on Earth to warm.

    You are correct about water vapor being a feedback. It’s a feedback because it condenses at Earth-like temperatures and pressures. Similarily, CO2 condenses on Mars, and methane condenses on Titan. The saturation vapor pressure (loosely ‘how much the air holds’) increases almost exponentially with temperature, so if the condensing substance is a greenhouse gas, you can build more up before it rains out.

  13. 63
    Gary Plyler says:

    Hank,

    Thank you for the link. I have read the thread on validation. Sorry, but I still don’t see how the GCMs validation process works with accepted scientific method. It would seem to be trying to validate to many hypotheses simultaneously.
    V/R
    gary

  14. 64
    Hank Roberts says:

    dave p, thanks for explaining the source of the confusion.

    The thickness difference between ‘ice shelf’ and ‘sea ice’ is because the ice shelf is glacial (frozen snow) ice, after it’s pushed out to where it floats (beyond the grounding point). The sea ice is what starts to freeze late in February.

  15. 65
    Marion Delgado says:

    What about the last part? How likely is it that if we’re seeing a minimum of sunspots that we’ll get acyclical, lower solar radiation in general?

    http://www.globalwarmingart.com/wiki/Image:Solar_Activity_Proxies_png

    http://www.globalwarmingart.com/wiki/Image:Solar_Cycle_Variations_png

    http://www.globalwarmingart.com/images/2/28/Sunspot_Numbers.png

    Just a couple of things about this. If we’re entering a period of significantly decreased solar activity:

    1) It will be a great way to test climate sensitivity as determined by climate models.

    2) It might buy us some time before we get into some real dangerous climate change.

    Posted by: Miguelito

  16. 66
    Curious says:

    Comparing both pictures it would look to me as if there was a recent (overall) cooling (1969-2000) and the (overall) warming would have taken place before (1957-1969) Do I get the picture wrong? (thanks in advance)

    *The warming on that period would seem consistent with the sea ice drop (HadISST):
    http://tamino.files.wordpress.com/2007/10/shfin.JPG
    http://hadobs.metoffice.com/hadisst/data/download.html

    *You already advised here at RC 4 years ago: “the widely-cited “Antarctic cooling” appears, from the limited data available, to be restricted only to the last two decades, and that averaged over the last 40 years, there has been a slight warming (e.g. Bertler et al. 2004. [...]“. :)
    http://www.realclimate.org/index.php?p=18

    Thank you very much for sharing your knowledge and devoting your time to us.

  17. 67
    Maya says:

    For the Wilkins Ice Shelf bet, I’ll take March 15th, the Ides of March.

  18. 68
    Joe Hunkins says:

    With the Antarctic temperatures so low I don’t follow why there appears to be so much concern (from others – not by you in this study) about how warming will lead to loss of ice volume or SLR changes. At a degree per century aren’t we looking at a system that is likely very stable in terms of melting?

    [Response: a) Past performance is no guarantee of future returns.... and b) significant ice loss on WAIS is already occurring - though there is an important ocean component to that. - gavin]

  19. 69
    Maya says:

    Curious, I think you need to include warming in the 2000-2006 period as well as 1957-1969.

  20. 70
    Steve Bloom says:

    Re #58: See #42, Zeke.

  21. 71
    Hank Roberts says:

    While the article is paywalled at Nature, they usually make the Supplementary Information available. It’s here as a PDF
    http://www.nature.com/nature/journal/v457/n7228/extref/nature07669-s1.pdf

    A chart from the Nature piece appears linked here:
    http://lawprofessors.typepad.com/environmental_law/2009/01/antarctic-warmi.html

    http://www.nature.com/nature/journal/v457/n7228/images/nature07669-f2.2.jpg
    along with the caption, which I’ll copy and paste:

    a, East Antarctica; b, West Antarctica. Solid black lines show results from reconstruction using infrared satellite data, averaged over all grid points for each region. Dashed lines show the average of reconstructed AWS data in each region. Straight red lines show average trends of the TIR reconstruction. Verification results for the continental mean of the TIR reconstruction are RE = 0.34, CE = 0.31 and r = 0.73. Grey shading, 95% confidence limits.

  22. 72
    Ray Ladbury says:

    Gary Plyler,
    In complicated systems with lots of feedbacks it simply is not feasible or informative to separate everything into nice, neat little boxes. Rather, what is done is construct a dynamical model with the best physics (each piece in itself validated) and observe how it does on the trends observed in the real system. This is standard practice for everything from semiconductors to supernovae. I think it is you who needs to update your understanding of the scientific method.

  23. 73
    Ron Taylor says:

    Gary Plyler, in addition to Ray’s good explanation above, I would add that you are misusing scientific terminology, which may be a reason for your confusion. What is in the GCMs are not hypotheses, but well established laws of physics. The form of verification you are suggesting would bring all attempts to model physical systems to a halt, including such things as launching a rocket. As Ray says, you build the model using sound principles of physics, then see if the result matches what actually happens. The model is never perfect, so you see where you may need to tweak the model, using more sophisticated analysis to better match the real world.

  24. 74

    Mike,

    In Spencer Weart’s prior RealClimate article discussing Antarctic cooling, he mentioned a Schneider and Thompson model from 1981 and a Bryan and Manabe model from 1988 that predicted “no warming at the sea surface, and even a slight cooling over the 50-year duration of the experiment”. Both of these came out well before the Thompson and Solomon article on the cooling effect of stratospheric ozone depletion. Weart also stated that “computer models have improved by orders of magnitude, but they continue to show that Antarctica cannot be expected to warm up very significantly until long after the rest of the world’s climate is radically changed”, and implied that this was primarily due to the deep mixing in the Southern Ocean.

    Was Weart only referring to East Antarctica here? If not, how do we reconcile this with your results (that Antarctica as a while is actually warming slightly faster than the southern hemispheric average)? Does this have any implications for the modeled heat transfer rate from ocean mixing in the Southern Ocean, or is that extrapolating things a tad far?

    I understand that there is a lot of nuance here, given all the different forcings and sources of variability at work (GHGs, negative forcing from stratospheric ozone depletion, ENSOs, etc), but I’m genuinely curious what this study implies for past modeling efforts. Were there any models produced post-2002 that included the ozone forcing that closely matched the temperature reconstruction in your article?

    [Response: Zeke. Your query probably deserves a longer answer but a very short answer is that you really should look at the Connolley and Bracegirdle paper summarizing AR4 model results. Some (most?) of those models include ozone. As you'll see, some of the models match our results rather well. Some don't.--eric]

  25. 75
    Mark says:

    Chris, 62.

    You’re forgetting a BIG elephant in the room.

    The size of the earth and its systems compared to the energy coming in.

    If it takes 10 years to raise the temperature of the earth 1 degree so that it really IS hotter rather than just a warm surface then a week of over-present GHG before it rains out is practically irrelevant.

    How long it will take could be worked out by figuring out the total mass of earth to, say 10m (so deep that it will stay around long enough even if it’s a clear cold night for months and therefore keep the surface temperature warm enough to matter). Multiply by the specific heat capacity of, say, sandstone.

    Now do a similar thing for the sea (but you have to do probably 100m, or several 10′s of m because light does penetrate ~10m, so you can get “light” *out* from that depth quickly) and multiply by the SHC of water (saline if you like, but we’re going to do a back of the envelope figure here, so why bother).

    Add these together.

    Makes a number X.

    Now how much energy would we get from the sun each day, if 100% were kept in and none radiated?

    Call that number Y.

    Divide X by Y and that gives you how long it would take to warm it up 1 degree in days.

    I don’t know, but I would be suprised if it’s only decades. That’s a LOT of mass to warm up…

    And it’s not going to be 100% capture, is it.

  26. 76
    colin Aldridge says:

    I don’t get this 50 year warming but 30 year cooling trend supporting AGW. Surely this must indicate warming in the 50′s and 60′s and cooling therafter which sounds to me like a local effect since it does not correlate with the rapid rise in CO2 since 1970 and has negative correlation with the Northern Hemispheric trends.AmI being stupid.

    [Response: Read the article. Yes, much of this is local. No, you are not being stupid in thinking that it is more complicated that a simple "yes or no" on the question of the relationship with the global picture.--eric]

  27. 77
    John Lang says:

    Any idea when the base data will be made available?

    And regarding the Wilkins ice shelf break-up: it looks like it has already broken off. The latest satellite pic shows the end of the thin ribbon has already been separated from the island as of December 31, 2008. Newer pics show there is new snowfall over the region so it can’t be determined what has happened since the end of the year.
    ftp://sidads.colorado.edu/pub/DATASETS/ICESHELVES/wilkins/wilk_2008363_1400_modis_ch02.png

  28. 78
    Colin A says:

    I am somewhat confused by the philosophy behind this method of analysis. I very much appreciate your point that prior analyses which show cooling in Antarctica do not cover a long enough time span to be of much interest to AGW science. 20 years of cooling is nothing to be worried about. This gives scientists a prima facie reason to investigate Antarctic temperature trends via other methods. In particular, your method allows us to see temperature trends over 50 years–which looks like an improvement. However, it strikes me that your analysis still hinges on climate trends from the original ~20 years of data.

    We know that the relationship between temperature and time over the past 20 years does not necessarily reflect a relationship that holds over a longer period of time (nor is the 20 year relationship as important as the longer-term relationship: thus, 20 years of global cooling would not disprove AGW).

    Now, why should a 20 year spatial relationship between Satellite and Surface temperatures hold over a longer period of time? Which in turn implies the question: why should a statistical analysis based on this 20 year relationship allow us to estimate longer-term trends? In order for this analysis to improve upon our understanding of Antarctic cooling/warming, we have to assume that spatial relationships between temperatures in Antarctica are much more reliable over time than are temporal relationships (i.e. are relationships between coastal and interior temperatures, or satellite and surface temperature, more highly correlated over time than are relationships between avg. temperature in year x and avg. temperature in year x+1?–something we can only investigate in the 20 year time span for which we have actual measurements of all relevant data). To make this assumption without rigorous support would implicitly beg the question in favor of both the conclusion in your paper and AGW.

    I understand that the statistical analysis still suggests a statistically relevant 50 year trend, statistical results sometimes overlook the philosophy with which they were put together.

    [Response: You are not thinking about the problem correctly. The shorter dataset is simply being used to provide a means of spatially interpolating the long-term dataset in a 'smart' way. The long-term trend is coming from the long-term data. Rather than using parameteric basis functions to perform the spatial interpolation, you are instead using non-parametric basis functions which are eigenfunctions of the covariance matrix of the data. There is a rich literature on this, and you would be well served by reading the paper and the references in the paper that are provided for the underlying statistical methodology, including the various tests that have been done to validate the methodology in the literature. -mike]

  29. 79
    Colin A says:

    Mike – Thank you [edit] I did not immediately see reference to the rich literature on the algorithm used in the paper (other than what appeared at first glance to be other papers on climatology–which though likely very rich, did not immediately suggest that they would contain substantial validation of the method–which tied to my view above, would require a forray beyond just climatology). But it sounds interesting, so I thank you for the opportunity to investigate further.

    [Response: Sometimes you actually have to look at the references cited. If you read the Mann et al '07 and Schneider '01 papers cited, you will see that they reference a substantial statistics literature (Tikhonov, Golub, Dempster, Fierro, Little and Rubin, etc.) behind the method used (a regularized version of the classical Expectation-Maximization algorithm). As for validation, there is no such as thing as a generic validation of a method, because the performance of a method is, of course, related to whether or not the assumptions of the method are fulfilled in the context of the type of data being analyzed (are the data essentially Gaussian distributed? Poisson Distributed? Are they discrete, or quasi-continuous? Are they stationary or not? Is the noise 'white' or 'red' or 'blue'?). A statistical method that works well for analyzing digital cell phone signals will not necessarily work well in analyzing gappy atmospheric or oceanographic data, and vice versa. In this case, it is climate data that are being analyzed, and the relevant question is, how does the method perform in tests using synthetic data that have the characteristics typically encountered in atmospheric and/or climate data. You will find this addressed not just in the Mann et al '07 and Schneider '01 papers, but in many others that are referenced by them. Happy reading! -mike]

  30. 80
    Steve Bloom says:

    Eric, over at the cold weather and astrology blog is a letter to you (text pasted below) from a meteorologist who objects to the paper. His complaints seem to be pretty much either anecdotal evidence or arguments from personal incredulity, with the exception of the final one where he says you allowed the Peninsula weather station readings to contaminate your results for West Anarctica. My impression is otherwise, and indeed it seems a little offensive to accuse a scientist of such a gross error without a specific reference, but your thoughts would be appreciated.

    [Response: Yes, this guy wrote to me. Yet, it is offensive because it is a thinly-veiled accusation of scientific fraud. I've spent many seasons in Antarctica over the last 18 years. My personal anecdotal observations don't bear on the science, and nor should Ross Hays's. (For the record, last time I was there, it was much warmer than the first time I went, but that's because I was at lower elevation!)--eric]

    ———————-

    Eric,

    Let me first say that this is my own opinion and does not represent the agency I work for. I feel your study is absolutely wrong.

    There are very few stations in Antarctica to begin with and only a hand full with 50 years of data. Satellite data is just approaching thirty years of available information. In my experience as a day to day forecaster that has to travel and do field work in Antarctica the summer seasons have been getting colder. In the late 1980s helicopters were used to take our personnel to Williams Field from McMurdo Station due to the annual receding of the Ross Ice Shelf, but in the past few years the thaw has been limited and vehicles can continue to make the transition and drive on the ice. One climate note to pass along is December 2006 was the coldest December ever for McMurdo Station. In a synoptic perspective the cooler sea surface temperatures have kept the maritime storms farther offshore in the summer season and the colder more dense air has rolled from the South Pole to the ice shelf.

    There was a paper presented at the AMS Conference in New Orleans last year noting over 70% of the continent was cooling due to the ozone hole. We launch balloons into the stratosphere and the anticyclone that develops over the South Pole has been displaced and slow to establish itself over the past five seasons. The pattern in the troposphere has reflected this trend with more maritime (warmer) air around the Antarctic Peninsula which is also where most of the automated weather stations are located for West Antarctica which will give you the average warmer readings and skew the data for all of West Antarctica.

    With statistics you can make numbers go to almost any conclusion you want. It saddens me to see members of the scientific community do this for media coverage.

    Sincerely,

    Ross Hays

    [Response: Non-rigorous, muddled rantings from a member of the climate change-denying "Inhofe 400". - mike]

  31. 81

    John Lang wrote in 77:

    And regarding the Wilkins ice shelf break-up: it looks like it has already broken off. The latest satellite pic shows the end of the thin ribbon has already been separated from the island as of December 31, 2008. Newer pics show there is new snowfall over the region so it can’t be determined what has happened since the end of the year.
    ftp://sidads.colorado.edu/pub/DATASETS/ICESHELVES/wilkins/wilk_2008363_1400_modis_ch02.png

    You may be right about it having broken off. However, ESA images suggest to my untrained eyes at least that it is still there and in roughly the same condition it was this fall.

    Please see:

    Webcam’ from Space
    Image archive
    http://www.esa.int/esaEO/SEMYBBSTGOF_index_0.html

    In the upper right hand corner you will see “‘Webcam’ from Space: Wilkins Ice Shelf” with a rough hourglass image of the shelf in white, and in the photos for January 19 through January 5 descending you will see the essentially the same image only with the ice shelf in black.

    In any case, this is definitely something to watch. The earlier Larsen B collapsed five degrees to the north at 65 degrees seven years ago in 2002. Five degrees to the south is the end of the West Antarctic Peninsula and the beginning of the mainland.

    *

    Captcha: Reckoning sort

  32. 82
    Steve Bloom says:

    Re #42: Oops, I erred regarding availability of the full text. It’s not on the GISS site yet, but if they follow their usual practice it will be within a few days.

  33. 83
    EL says:

    You guys did a very good job on that report.

    5. I agree with you that there should be more discussion on Thermohaline Circulation. A complete collapse of that would be a nightmare.

  34. 84
    Adam Gallon says:

    I’m following this paper both here and, (Dare one mention them?) wattsupwiththat.
    In view of the statement on watts..

    “In a 2007 press release on Antarctica, NASA’s describes their measurement error at 2-3 degrees, making Steig’s conclusion of .25 degrees Celsius over 25 years statistically meaningless.

    “Instead, the team checked the satellite records against ground-based weather station data to inter-calibrate them and make the 26-year satellite record. The scientists estimate the level of uncertainty in the measurements is between 2-3 degrees Celsius.”

    That is from this 2007 NASA press release, third paragraph.

    http://earthobservatory.nasa.gov/IOTD/view.php?id=8239

    Saying you have a .25 deviation over 25 years (based on one-tenth of a degree Celsius per decade per Steig) with a previously established measurement uncertainty of 2-3 degrees means that the “deduced” value Steig obtained is not greater than the error bands previously cited on 2007, which would render it statistically meaningless.”
    http://wattsupwiththat.com/2009/01/21/antarctica-warming-an-evolution-of-viewpoint/

    Are the findings of this paper statistically significant?

    [Response: The 2-3 deg C uncertainty is an absolute error, it isn't the same as the uncertainty in the trend (i.e. you can often tell that something has warmed much more accurately than you can tell it's absolute temperature). The WAIS temperature trend is estimated to be 0.17+/-0.06 deg C/dec (95% confidence) - so yes the changes are statistically significant. - gavin]

  35. 85
    Nick O. says:

    The ‘Watts up …’

    (http://wattsupwiththat.com/2009/01/21/antarctica-warming-an-evolution-of-viewpoint/)

    site has already commented that this latest ‘warming’ is highly suspect, probably down to observational error, or volcanoes under the ice, or misunderstanding the effects of the Ozone Hole, or scientists being too keen to get out a ‘hot’ story, etc. etc. etc., and certainly ABSOLUTELY NOTHING (of course!) to do with CO2 or Man’s activities.

    Just thought I’d let people know …

  36. 86
    Alan Neale says:

    Re #62, the media and science are poles apart (no pun intended)when it come to the nature of AGW. I am just pointing out that every UK broadsheet newspaper(The Times, Daily Telegraph, Guardian and Independent) covered this report and seemingly fairly. Real climate had the DT down as second favourite in their list of supporting deniers (which is in actual fact fairly accurate). Its just that some reports on climate science cannot be twisted although I am sure it will not be long before some people attempt to do so. I will take a look on the web for people attempting to contradict this report and surely it will happen.

    This site was setup to both educate the interested and refute the deniers I guess. Sometimes it does both very well. The contributors names are literally pasted all over the deniers sites and other places so it must be having a great effect.

  37. 87
    dhogaza says:

    site has already commented that this latest ‘warming’ is highly suspect, probably down to observational error, or volcanoes under the ice, or misunderstanding the effects of the Ozone Hole, or scientists being too keen to get out a ‘hot’ story, etc. etc. etc., and certainly ABSOLUTELY NOTHING (of course!) to do with CO2 or Man’s activities.

    I’ll pay attention when Watts personally dives and takes macro photos of those subsea volcanoes in action …

    After all, his mantra is that a photo is worth 1000 research papers.

  38. 88
  39. 89

    dhogaza, do you think that dive will be before or after he looks into the history of paved parking lots at NOAA?

  40. 90
    Mark says:

    The paved paradise, put up a parking lot.

  41. 91

    Re:61,

    Eric, this then brings me back to one of my initial questions, that is, how do the trends from the long-term weather stations compare to your reconstructed trends for the same locations? That is why I thought that perhaps a map with the observed trends superimposed on the reconstructed trends may have been useful.

    Given your response in 61, I take it that you are suggesting that the reconstruction is useful when taken as a whole (as an average), but that for smaller spatial scales (like over the Peninsula or at the South Pole, for example), the reconstructed trends may differ (somewhat sizably in some instances) from the actual trends.

    So, I guess the bottom line is, that your conclusions are that while the reconstruction is not better than the long-term observations at any specific location, that taken as a whole (including many areas with no local, long-term observations) the reconstructed trend better represents what has occurred than do other methods of averaging the long-term records.

    The problem is, from a user’s standpoint, is over what spatial scale (and which locations) is the reconstruction preferable?

    When I suggested that it was preferable over the Peninsula, you suggested I was wrong. But, based on your paper, I presume that you think it *is* preferable over the continent, and I guess even over subcontinental East and West Antarctica. What about smaller scales still? (I am not sure if I am supposed to be able to figure this out from your Figure 1 or not).

    Thanks for your time and guidance.

    -Chip Knappenberger

    [Response:The point of the paper was to get a large-scale averages. Indeed, we essentially ignore local information; any variations that are not correlated on a fairly large spatial scale are treated as noise in the principle component analysis. We would have done a rather different analysis if the point was to get a the very local scale. There are already comparisons in the blogosphere between our results and the South Pole weather station record, and the claim is made that they are "in conflict" (the South Pole record shows cooling over the last 50 years, whereas our record shows no significant trend. [As our paper Figure 3 shows, Vostok, the only long term record in the interior other than South Pole, shows warming; of course, they don't tell you that on the contrarian web sites]. This kind of comparison is just silly and entirely misses the point. You cannot get at the local scale without local information, which we don’t have (except where we have weather stations of course) prior to 1982. You can of course use the satellite data for post 1982 local information. There is a very nice study that did this — Shuman and Stearns, 2001, in Journal of Climate — in West Antarctica, and demonstrate greater rates of warming that we show (but with larger uncertainties too, and only for a 20-year stretch); they used, incidentally, an independent satellite data set, using microwave rather than infrared frequencies. See Figure 3a in our paper, which shows the locations of their study. The microwave data have a different set of potential biases from the infrared data, so this is very independent support of our results for West Antarctica. Similar local studies such as theirs ought to be done at more locations.
    I hope those comments help you better understand the uses (and potential abuses) of our work.–eric]

  42. 92
    Simon Evans says:

    FAO Eric Steig

    Hi Eric (my first post here),

    I note that you have been sent an email critical of your paper by one Ross Hays which has been reproduced on ‘Watts Up With That?’, in which he references his experience of Antarctic summers as follows:

    “In my experience as a day to day forecaster that has to travel and do field work in Antarctica the summer seasons have been getting colder.”

    http://preview.tinyurl.com/awyrjv

    In case this should be of any relevance, may I draw your attention to the following blog entry of his, in which he makes clear that he has only experienced one summer visit to Antarctica:

    http://darynkagan.ning.com/profiles/blogs/new-career

    I realise that this may seem trivial and that, doubtless, you get many emails of such a kind, but given the prominence given to his letter at the “Best Science Blog” I trust that my observation here does not seem inappropriate.

  43. 93
    John Lederer says:

    Apparently there already is video of one Antarctic submarine volcano:

    http://www.cbsnews.com/stories/2004/05/20/tech/main618807.shtml

    ….The research team led by Eugene Domack of Hamilton College in Clinton, N.Y., used a bottom-scanning video recorder, rock dredges and temperature probes to survey the sides and crest of the submarine peak.

    While large areas were colonized by submarine life, none was found on dark rock around the volcano itself, indicating that lava had flowed fairly recently.

    In addition, dredges recovered abundant fresh basalt, a volcanic rock. It normally would be rapidly acted upon and transformed by seawater.

    Highly sensitive temperature probes moving continuously across the bottom of the volcano showed signs of geothermal heating of seawater, according to the agency.

    Domack said the volcano stands 2,300 feet above the seafloor and extends to within roughly 900 feet of the ocean surface.

    The volcano is in an area known as Antarctic Sound, at the northernmost tip of Antarctica. There is no previous scientific record of active volcanoes in the region where the new peak was discovered. The volcano is located on the continental shelf, in the vicinity of a deep trough carved out by glaciers passing across the seafloor….

    [Response: I don't think anyone is taking exception to the existence of undersea volcanoes or hydrothermal vents. It is more that the idea that they are releasing enough increasing amounts of energy to warm the whole continent of Antarctica is ridiculous. There is first no evidence that their activity has increased over the last 50 years, and more to the point, the energy they release is completely trivial compared to what is required to warm a continent that is thousands of miles across. - gavin]
    [I'll add another note: There are under-the-ice-sheet volcanoes too of course. But the heat from the volcanoes goes almost entirely into melting ice at the base of ice sheet, a good two miles below the surface. Averaged over the ice sheet are mere milliwatts per meter squared of heat coming up from the ground (even including the volcanoes). That's 1/1000th of a 60 W light bulb folks...--eric]

  44. 94
    Sekerob says:

    dhogaza Says:
    23 January 2009 at 8:59 AM

    Is that 50mm, fisheye or 500mm telelense for optimal image compression ;?

    He just started part 2, maybe because part 1 has some molto dubbioso in there.

    Momentarily, Antarctic SIA actual is playing fast catch up with 79-00 mean. Would it hit that low this year?

    http://nsidc.org/data/seaice_index/images/daily_images/S_timeseries_thumb.png

  45. 95
    dhogaza says:

    Is that 50mm

    Oh, I was thinking 50mm, I want him as close to the bubbling vent as possible. And if he falls inside, well, at least he did so proving science wrong, eh?

  46. 96
    Tom Dayton says:

    Eric Steig (author of this post) is going to be on NPR’s Science Friday today (2009/1/22) in the second hour: 3:00-4:00 U.S. Eastern Time. It’s a call-in show, but you don’t have to use a phone; you can Twitter, e-mail, or visit in Second Life. See the Science Friday site for instructions.

    If you miss it live, you’ll be able to listen to it via the Science Friday web site (or download it as a podcast) by about a day later. ScienceFriday.com.

  47. 97
    John Philip says:

    Volcanos notwithstanding, the problems with Mr Watts’ coverage start with the title. ‘ An evolution of viewpoint’, the journalistic hook he has chosen is the ‘shift in scientific opinion’ represented by these results.

    He has two mocked up satellite images of the continent from NASA one showing a predominantly cooling Antarctic from captioned ‘NASA Viewpoint 2004′, another from this year showing an Antarctic dominated by West Antarctic warming, captioned ‘NASA Viewpoint 2009′. the text has … Let’s take a look at how the imagery has changed in 5 years…. the combined effect strongly implying that the new work contradicts the earlier viewpoint and has brought about a shift of opinion from a cooling to a warming Antarctic..

    Incomprehensively the ‘Science Blog of the Year’ fails to mention that: the two images cover different periods, the 2004 picture is of the period 1982-2004 and was lifted from here http://earthobservatory.nasa.gov/IOTD/view.php?id=6502

    the second is of the 5 decades to present day covered by Steig et al, and included in the NASA press release. Here’s the larger scale version, rather beautiful: http://www.giss.nasa.gov/research/news/20090121/305938main_A….

    So the two images do not illustrate an ‘evolution’ of view about the same thing at all, and the captions inviting direct comparison of the two images are, shall we say, misleading. If only Mr Watts had consulted the author: Our results do not contradict earlier studies suggesting that some regions of Antarctica have cooled. Why? Because those studies were based on shorter records (20-30 years, not 50 years) and because the cooling is limited to the East Antarctic.

    Wouldn’t it be droll if Mr Watts was criticising a paper he has not actually read?

  48. 98
    Hank Roberts says:

    Agh. One of the most disappointing SciFri bits I remember. Blew the intro, corrected it. Ira asked one good question, then cut Eric off in the middle of his answer saying there wasn’t time for it. This was unprepared, no help from whoever they have as the SciFri staff. Not even enough time to do what seemed the plan — have Ira state some old ideas then give Eric time for a few words to say ‘no that’s not right’ or something about what’s new. I think he gave Eric maybe five minutes on the clock, and far less speaking time.

    Dang. I know it’s always disappointing to see what a newspaper does with any story one knows anything about, but SciFri usually seems to do better than this.

    [Response: Hank. Yeah, Ira wasn't quite on his game today, it seemed. The only really good short answer to "is Antarctica cooling or warming?" is "YES".--eric]

  49. 99
    Hank Roberts says:

    And SciFri is doing much better with the half hour given to Andy Revkin, going on now.

  50. 100
    Hank Roberts says:

    Note for next time — find out in advance from the staff how many actual seconds of airtime the scientist gets to speak during a typical segment of the planned length. Is there a science fair candidate reading? You could listen to some typical segments of that length with a stopwatch. I’d guess five minutes total on the clock allows maybe 180 seconds to explain the subject. Ow.


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