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How to cherry pick your way to Antarctic land ice gain

Posted on 25 April 2009 by John Cook

I've been reflecting on the recent poll that found a record 41% of people now think global warming is exaggerated. Meanwhile, 86% of climate scientists think we won't restrict warming to under 2°C. Why the discrepancy between qualified climate scientists and the general public? I would suggest that scientists are not always completely effective at communicating their science to the average person. Global warming skeptics, on the other hand, have a wide range of rhetorical techniques that are quite successful in sowing doubt.

One of the most common techniques is cherry picking selected pieces of data while ignoring the big picture. A perfect example is the argument that human CO2 emissions is tiny compared to natural CO2 emissions. After all, humans only emit 26 gigatonnes of CO2 per year. Nature, on the other hand, emits a whopping 770 gigatonnes per year, via the ocean, animals and vegetation. Put that way, how could we possibly say mankind is having that much of an impact compared to nature?

But that argument ignores the fact that while nature emits 770 gigatonnes, it also absorbs roughly the same amount through the ocean and land plants. So the net amount that nature contributes to atmospheric CO2 is practically nothing. In fact, it's slightly negative as nature absorbs a fair chunk of the CO2 we emit.

So there you have it - cherry pick a few incriminating factoids, neglect to give the whole picture and bingo, you've constructed a perfectly functional skeptic argument that while thoroughly debunked, continues to make the rounds to this day. Within the last few weeks, I've had the human CO2 is tiny argument told to me twice by two different family members (gotta love those family get-togethers).

An argument that has found new life in recent weeks is Antarctica gaining ice. It even shot its way into the top ten (at least until the next fad pushes it out). This is largely attributable to an article in The Australian, Antarctic ice is growing, not melting away. The article makes its argument simply and effectively in a single sentence:

"East Antarctica is four times the size of west Antarctica and parts of it are cooling."

Both statements are true. However, what the article fails to mention is that while parts of the East Antarctic interior are gaining ice, it's also losing ice around the edges and overall, is in approximate mass balance. So with West Antarctica losing ice and East Antarctica in balance, Antarctica is overall losing ice. But all The Australian does is cite the size of East Antarctica, mention that parts of it are cooling and the inference is East Antarctic ice gain must outweigh West Antarctic ice melt. It's clever persuasion but very misleading.

The article then transitions into a discussion of sea ice so smoothly, you barely even notice they're no longer talking about land ice. Many discussions of Antarctic ice melt fail to distinguish between land ice and sea ice which are two separate phenomenon. Antarctic land ice is falling. Antarctic sea ice, on the other hand, is increasing. This is partly due to less ocean heat rising to melt sea ice and partly due to cyclonic winds caused by the ozone hole (more on this in an upcoming post). It's important to note that sea ice is increasing despite the Southern Ocean showing pronounced warming.

So to properly understand what's happening with climate, you need the full picture, not a selection of conveniently cherry picked factoids. But how do you communicate complex climate issues in a soundbyte? How do scientists give a user-friendly version of climatology science without over-simplifying? It's an issue I wrestle with a lot lately and welcome any discussion on the topic.

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Comments 1 to 15:

  1. April 25 posting? Could you please include tomorrows winning lottery numbers? (I understand why but it startled me) Current "Ice anomaly" in the antarctic is at about +1Million km2 this is more than 3 times the negative anomaly in the north and makes the worlds sea ice anomaly a positive as it has been quite a bit lately. I have seen contradictory papers on land ice as well, I think I know what you are reading,but I think most are still finding tha Antarctic land bound ice is not decreasing and that near the pole (the larger portion of the continent) it is increasing in thickness. It isn't just warming and cooling being different in different areas. There was one paper recently that claimed the antarctic was warming. (Steig) But, that looks to me to have been well refuted and is likely a figment of the data on a poor data set with a lot of holes. The original theory that warming would occur first near the poles and most at night is certainly now refuted as well, unless the time lag is MUCH bigger than thought. How indeed do we make people understand that the issue is wildly complex when we have so many vested interests that are telling us that we "know" far more than we do.
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  2. "86% of climate scientists think we won't restrict warming to under 2°C." Caution this survey was of true believers attending a conference to push for more changes. Labeling them as a group "climatologists" as the Guardian did...
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  3. The skeptic arguement also has the distinct advantage of being the arguement that people want to believe. It's no coincidence that as the economy gets worse, more people don't believe in global warming( or just don't care as much). Just one less thing to worry about.
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  4. So, it isn't true that Antarctica is gaining ice? Well, concidering the last article posted on this site, ya'all were fooled to. I like this site.
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    Response: Did you read the full post above? Where it says people "fail to distinguish between land ice and sea ice which are two separate phenomenon". Sea ice is increasing. Land ice is falling. The Australian article confuses the two to mislead people into thinking land ice is increasing.
  5. WA: So far, the Steig paper has been "refuted" only on "skeptic" blogs, not in the litterature. Since you doubt the guardian's labeling, why don't you try to find for us what the immense majority of scientists who study climate all the time really "believe"? And sorry, no, Heartland Institute lists do not count. "Contradictory papers on land ice?" How about some links? This source does not appear too ambigous. Accelerated loss at the margins is not incompatible with increased accumulation at the pole. If there is increased accumulation at the pole, it is hard to imagine how that could happen other than by increased moisture. That would happen to be what the models show. Your characterization of sea ice is, well, a characterization. It's best to look at the data: Tells a different story. You have lots of assertions but no references.
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  6. Re Steig(2009) This may be denialist in your book, and I suppose it is as it allows anyone to join in and unlike RC does not immediately delete any intelligent descent. But if you think Steig is significant you better read up on it here or you will be surprised later on. My first response on reading Steig was that the method looked shaky and the trend was dependant on the dates chosen and a mighty weird way of filling in missing spots that tended very strongly to amplify what was happening in some of the worst stations in one small area and using it to represent a much larger area. You are always going to run the risk of this when the data is limited. I know that my colleagues are having a lot more trouble with thickening ice than thinning but that may be bias because thickening means more work. However they do not agree with the premise that the land bound ice is shrinking. I agree that increasing ice thickness at the pole may not mean cooling, in fact I would think that may indicate warming in the surrounding sea. It took me a long time to look up the global ice anomaly links and than when I hit submit I get an error message and it's all gone. But, you can find it at cryospere and various places including NSIDC it is at about +850,000 square km this week due to the antarctic being at about +1 million and the arctic being very near normal. I don't know what you want, the data, including the data you refer to shows global ice anomaly positive and has for much of the last 2 years. So the land bound ice may be thickening and the sea ice is above normal, and the Steig paper though flawed suggests warming the last 50 years but cooling for the last 30. Where am I supposed to get sudden dramatic warming from this?
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  7. Hi Philippe Chantreau, If artic ice keeps on regaining mass and aproaching to median 70-00value will you begin to cast doubt on AGW theory? if not, what would? thank you for your time.
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  8. WA, We must not be looking at the same graph. The global anomaly (red line bottom part of graph) shows several excursions and even long periods around -2 with troughs down to -3. The periods of positive anomalies are not only fewer and far between but none reaches even +2 in the recent past, which seems to be what you consider. The very way your sentence is worded is strange and could mean many things. Anomaly positive now and for "much" of the past 2 years. How much? Is it more than the time spent in negative anomalies? What is the direction of the largest anomales? How large have the positive anomalies been, compared to the negative ones? I don't really care who your colleagues are but references once again would be helpful. Are you saying that Grace has it wrong? What ice are we talking about? Land based, shelf, sea ice, coastal, continental? I don't know much about the Steig paper except that skeptic blogs seem to have made it a target. I know that this statement of yours: "suggests warming the last 50 years but cooling for the last 30" does not make sense at first glance. O.M.: A reversal of the trend over the next 20 years would not a priori comply with the consensus model. But then again the speed of the recent negative trend is far beyond what the model suggested so it does not comply either.
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  9. Re #1 WA You make a number of unsupported assertions that don't seem to accord with the scientific evidence:
    The original theory that warming would occur first near the poles and most at night is certainly now refuted as well, unless the time lag is MUCH bigger than thought.
    (i) night/day warming: There has been considerably more warming at night compared to daytime warming. The most recent analysis is: Vose, R.S. et al. (2005) Maximum and minimum temperature trends for the globe: An update through 2004. Geophys. Res. Lett., 32, L23822. and the data can be accessed from the IPCC report (AR4) (see page 244): During the period 1950 - 2004, night-time (minimum) warming considerably exceeds daytime (maximum) warming. Night-time warming is around 1.15 oC during this time (over land) whereas daytime warming is around 0.75 oC. The details are complicated by other factors. For example the aerosol load has suppressed daytime warming somewhat in the early period of the analysis and the last 15-20 years has seen some cutback of aerosol load over total land surface which has seen daytime temperatures rebound somewhat in the more recent period. But overall night time warming has significantly exceeded daytime warming. (ii) warming at poles: Modelling since the early 1980's predicted that enhanced greenhouse-induced warming would be focussed in the Northern polar regions leaving the Antarctic regions relatively unaffected for considerable periods. For example a recent review of early modelling of the ocean response to global warming described predictions from early modelling: S. Manabe and R. J. Stouffer (2007) Role of Ocean in Global Warming J. Meterolog. Soc. Jpn. 85B 385-403 quoting from this article in the sections describing the predicted hemispheric asymmetry (much greater N. hemispheric polar warming and delayed Southern polar warming): Discussing the early models of Schneider and Thompson (1981) to evaluate the delay in the response of the sea surface temperature to gradual increase in CO2, Manabe and Stouffer say:
    [“Their study shows that the time-dependent response of zonal mean surface temperature differs significantly from its equilibrium response particularly in those latitude belts, where the fraction of ocean-covered area is relatively large. Based upon the study, they conjectured that the response in the Southern Hemisphere should be delayed as compared to that in the Northern Hemisphere because of the inter-hemisphere difference in the fraction of the area covered by the oceans.”]
    In a later model Bryan et al (1988) made the same sort of analysis, investigating the role of the oceans in modulating the response of surface warming to enhanced greenhouse gases.
    [“They found that the increase in surface temperature is very small in the Circumpolar Ocean of the Southern Hemisphere in contrast to high latitudes of the Northern Hemisphere where the increase is relatively large.”]
    It’s not just the oceans per se of course. It’s also ocean and air currents, and particularly the mechanisms governing the efficiency of surface heat transfer into the deeper oceans. If this is efficient, the deep oceans will absorb heat and there might be little measured surface warming, at least for a while. So (speaking of Bryan et al (1988)) again:
    [“However, the detailed analysis of the numerical experiment reveals that the absence of substantial surface warming in the Circumpolar Ocean is attributable not only to the large fraction of the area covered by the oceans but also to the deep penetration of positive temperature anomaly into the oceans.”]
    Later models predict the same hemispherical asymmetry that is seen in the real world. e.g. discussing the simulations of Manabe et al (1992):
    [“Figure 3 also reveals that there is a large asymmetry in surface warming between the two hemispheres. In the Northern Hemisphere, the surface warming increases with increasing latitude, and is particularly large in the Arctic Ocean. This is in sharp contrast to the Southern Hemisphere, where warming is relatively large in low latitudes and decreases with increasing latitudes. It becomes small in the Circumpolar Ocean of the Southern Hemisphere, particularly in the immediate vicinity of Antarctic Continent.”]
    Why is this, one might ask?! Here’s what Manabe and Stouffer say:
    [“One can ask: why the polar amplification of warming does not occur in the Southern Hemisphere, despite the existence of extensive sea ice which has a positive albedo feedback? As discussed in the following section, the absence of significant warming in the Circumpolar Ocean of the Southern hemisphere is attributable mainly to the large thermal inertia of the ocean, which results from very effective mixing between the surface layer and the deeper layers of ocean in this region. This is in sharp contrast to the Arctic Ocean, where very stable layer of halocline prevents mixing between the surface layer and the deeper layer of the ocean.”] [“In view of the absence of significant surface warming, it is not surprising that the area coverage of sea ice hardly changes in the Circumpolar Ocean despite the CO2-doubling.”] (n.b. remember this is a prediction from a model; we’re nowhere near CO2 doubling yet!). However that's what we're seeing in the real world.
    So the delayed warming in the deep Southern oceans and Antarctic is consistent with models/predictions from more than 20 years ago. and so on….
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  10. Re #1 WA This doesn't seem right either in the light of the scientific data. Why not cite the sources of your assertions?
    WA: "....but I think most are still finding tha Antarctic land bound ice is not decreasing and that near the pole (the larger portion of the continent) it is increasing in thickness."
    There are continuous analyses of polar (Arctic and Antarctic) land ice, using either the GRACE gravity calculating satellites or satellite altimetry, and these show that Antarctic land ice is decreasing. Some of the most recent data can be found here: Chen JL et al. (2008) Antarctic regional ice loss rates from GRACE Earth and Planetary Science Lett. 266, 140-148 and here: Moore P and King MA (2008) Antarctic ice mass balance estimates from GRACE: Tidal aliasing effects J. Geophys. Res. 113 art # F02005 which show Antarctic polar ice mass loss of around 164 +/- 80 km(3) per year in the period April 2002 - Jan 2006. As John Cook has shown in his top post it's very easy for the unscrupulous to misrepresent the science in this area. So statements like "near the pole (the larger portion of the continent) it is increasing in thickness", are misrepresentations of the important question (of whether Antarctica is in net mass balance or is growing or shrinking) since no one expects that in the high altitude polar interior the ice cap won't increase in thickness somewhat as snow is deposied there. The question is whether melting at the edges of the ice cap (we're not talking about sea ice) is greater than the accumulation of snow/ice in the interior. The science indicates that the net mass balance is negative. It's not a huge amount of mass loss in the grand scheme of things, but no-one expects a very significant mass loss in Antarctica, at least for a while; Greenland melt is a much greater concern. However we may as well address the science rather than base our "understanding" on unsupported assertions!
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  11. Well as of yesterday the anomaly was down some, to +675,000 km2. Thats Still mighty positive and as I characterized it is a small negative in the arctic and a large poistive anomaly in the antarctic. The problem I have with this is it doesn't seem to fit my idea that thickening of the ice in the continental interior and fairly high snow fall are caused by warming of the surrounding sea. It isn't definitive and I didn't say it was. I just don't see how someone draws the conclusion that it fits warming either. I don't know what you're looking at either. I think I am looking at same data as cryosphere today data I am getting it originally through U of Illinois linked site similar address. Odd in that my unsupported assertions are coming from your sources. I told you I have colleagues they are having more trouble with thickening that thinning and that is land based. I also told you that I did not think thickening proved anything. As I have told you before on this, though you may not remember, I will not risk an important piece of research becoming a witch hunt target because some fanatic reader fears their data may damage his pet cause. It is not their intent to enter this debate on either side. They just aren't noting the ice getting thinner, they are having some trouble because thickening has been greater than expected. Chris I will investigate your references if I get a bit of time it would be interesting to know. How does it match up with the permafrost studies?
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  12. Looking at the data for global sea ice on Cryosphere Today, considering the bottom red line, daily anomaly. How much of the past 2 years has been spent with a positive anomaly? eyeballing, about a month in late 07-early 08 and about 3 to 4 months in 08. That's 5 months out of 24, or 21% of the time. The rest, 79%, was spent in negative anomaly. What is the direction of the largest anomalies? Negative, as we see late 07 and late 08 reaching or flirting with -3. How large have the positive anomalies been? You have to go back to 1987 to find one that exceeds +1.5; 96, 01 and 08 barely exceed +1. It means that the largest recent positive anomaly does not reach 35% of the largest recent negative anomaly. I'll add that, without the short tiny spike in late 06, you would have 3 straight years of negative anomaly. Do you see something different on that graph? This:"Our analysis, using this specific method of data handling and adjustment, from this set of specific data gathered in this specific way seems to suggest" Is not the same as "the science says". Actually, it is exactly the same thing. IMO you were mistaken if you ever perceived science to mean something else. There is no such a thing as certitude.
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  13. I'd like to comment in the first paragraph: "I would suggest that scientists are not always completely effective at communicating their science to the average person. Global warming skeptics, on the other hand, have a wide range of rhetorical techniques that are quite successful in sowing doubt." Whilst I'm still without an opinion on anthropogenic climate change (through lack of knowledge on this complex subject), this opener certainly rings alarm bells with me. Chiefly: 1. Having 'scientists' on the one hand and 'global warming skeptics' on the other. This suggests that skeptics aren't scientists and proponents are. This is no more accurate than the reverse: that most proponents are layman and skeptics are scientists. Consider the hoards of ill informed protesters... 2. The assertion that global warming skeptics are adept at rhetoric whilst proponents struggle in this area. The wealth of scientific papers supporting anthropogenic climate change, plus the unrelenting media support, contradicts this. As the authors personal views are so obvious, I immediately worry there will be a bias in the text. And, in a complex subject area where bias and misinformation is rife, its not something I as a confused layman can afford! And aside from anything else, it makes someone still considering a skeptical point of view feel alienated and patronized - hardly the point of this website. Its a good article, but the absolute need for objectivity shouldn't be forgotten, no matter what gets publicized elsewhere.
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  14. Tree, your argument is flawed on several counts. First there is the fact that the overwhelming majority of climate scientists do not dispute at all the reality of AGW. Second is the fact that the overwhelming majority of "skeptics" are not scientists. Most of the ones who are come from different areas of practice. The true dissenting climate scientist are a very small minority. Their ideas, when they have any alternative to propose, have not been ignored. You're equating a "wealth of scientific papers" with rethoric. That does not make any sense. The problem stated in the post you refer to is exactly that what is contained in a wealth of scientific papers can not be so easily communicated as good rethoric, no matter how empty. WA earlier had a great example of rethoric by calling 21% of the past 2 years "much." Anyone reading that and not bothering to actually look at the data could easily interpret it as "most of the time" although it is quite far from it. By using this one little word, WA can convey the message (without actually saying so) that most of the past 2 years saw positive anomaly, although the data shows exactly the opposite.
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  15. "The article then transitions into a discussion of sea ice so smoothly, you barely even notice they're no longer talking about land ice." Yep. This confusion seems deliberate by the author. And it's land ice that has the implication for sea level rise. Also, here's more interesting spin from the Australian article: "Last week, federal Environment Minister Peter Garrett said experts predicted sea level rises of up to 6m from Antarctic melting by 2100, but the worst case scenario foreshadowed by the SCAR report was a 1.25m rise." A potential contribution of 1.25 m of sea level rise by 2100 from just Antarctic ice sheets is big news, yet the author here is downplaying it by comparing it to quotes (or misquotes in this case) by a politician. An excellent debunking of this trashy piece from the mainstream media can be found here: Fran Kelly: Today, some positive news. Rather than melting, the science shows that ice is expanding in much of Antarctica and that in parts is getting thicker. ... Ian Allison: We have now new evidence that confirms that on average we are losing ice from both Greenland and Antarctica which is contributing to sea level ... Kelly: ... but you found something that suggests its perhaps not as rapid a melt as we once thought. Can you tell us about what you've found, the difference in the East and West in Antarctica. Allison: ... In East Antarctica there might be a slight increase due to increased snowfall. ... on average West Antarctica is losing more ice that the East is gaining
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