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How blogs convey and distort scientific information about polar bears and Arctic sea ice

Posted on 22 December 2017 by Bart Verheggen

This is a re-post from My view on climate change

Our article on sea ice and polar bears proved to be a hot-button issue in the blogosphere. This was not entirely unexpected, of course. What is striking though, is that amidst all the criticism nobody has challenged our core finding: blogs on which man-made climate change and its impacts are downplayed are far removed from the scientific literature, at least regarding the topic of shrinking Arctic sea ice and the resulting future threat to polar bears.

Even more so, alternative figures that have been prepared by some critics basically underscore this same message (see examples below). That’s not so strange of course, since the signal is so clear: there is hardly any overlap between contrarian blogs and the scientific literature on this topic. Take a look at the pie-charts below for the three statements on sea ice and those on polar bears, for the two different groups of blogs (termed denier and science-based blogs, respectively), and the peer-reviewed scientific articles that investigate both polar bears and Arctic sea ice. This is basically an extension of figure 1 in the paper, in which only the two blog categories were shown. Most scientific articles as well as science-based blogs assess Arctic sea ice extent to be shrinking and polar bears to be threatened as a result, and most denier blogs take a contrary view on both sea ice and polar bears. They are poles apart.

You may argue that it was overkill to use an elaborate statistical analysis such as PCA on this dataset. It was used mainly to visualize our results in one figure. All the criticism on the PCA and the details of how data were analyzed misses the forest for the trees: there is a clear distinction between blogs, where the group that accepts AGW appears to base their claims on peer-reviewed science, and the group that doesn’t accept AGW does not. The latter group appear to base their claims to a large extent on blogs written by one particular biologist, Susan Crockford, whose views run counter to the relevant ecological literature.

Our paper is first and foremost a characterization of the blogosphere, and how it compares to the scientific literature. We restricted our literature search to scientific articles that investigate both polar bears and sea ice, and that shed light on polar bear ecology and how it may or may not depend on the presence of sea ice. An article such as “Evolutionary roots of iodine and thyroid hormones in cell signaling” does not fit that bill, to name just one example of Crockford’s scientific articles that has been pointed out as evidence of her having published on polar bear ecology. She has not.

Even though it is not the main scope of our paper, we described the scientific context of polar bear ecology and explained how and why polar bears depend on their sea ice habitat (summarized in my previous blog post). As such, we argued that the scientific understanding of arctic sea ice decline and polar bear ecology is more credible than the viewpoints put forward on contrarian blogs. However, providing new ecological evidence was not the point of this paper. The point was to investigate how our current ecological understanding is conveyed and distorted in the blogosphere.

If some people think that our conclusion is wildly wrong, then they could at least show some evidence to prove their point, right? They probably realize that our conclusion is robust, so instead they try to nitpick on details and make it appear as if that undermines our conclusion. It does not.


Appendix: A collection of PCA graphs depicting our results, all basically underscoring the main conclusion that one group of blogs correctly conveys our current scientific understanding, while another group of blogs distort this understanding and promotes a very different viewpoint regarding sea ice and polar bears.

From top to bottom the following PCA figures are shown:

  • As published in the Bioscience paper, in which missing values are replaced by zero after scaling the data
  • List-wise deletion of all records with missing values, considerably reducing overall sample size
  • Using multiple imputation with logistic regression (5 rounds of 40 iterations each)
  • PCA figure of the same data as produced by Richard Tol, where sample size of each location in the graphs is depicted by symbol size
  • PCA figure of the same data as produced by RomanM at ClimateAudit, without information on sample size

As mentioned in the supplemental information with our paper, jittering was applied to our PCA figure to gently offset data with the exact same entries from each other for graphical purposes. Tol uses an alternative method to provide information on sample size for specific data entries, namely via the size of the symbol used in the figure. Whatever your preference, the conclusion drawn from these figures is the same: there is a clear gap between the consensus in the scientific literature and science-based blogs on the one hand, and contrarian blogs on the other hand. We thank Roman Mureika and Richard Tol for underscoring the validity of our conclusion.

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Comments 51 to 64 out of 64:

  1. Or ImaginaryNumber could provide a brief summary of what he thinks is convincing in Crockford's writings, or why the many links he's been given do not provide him with any information about the lack of credibility of Crockford's wiritings.

    Until then, he's just hand-waving. I've read enough about Crockford's work to make up my mind, and chasing rainbows for ImaginaryNumber is not on my list of priorities.

    "I am, however, playing Devil's Advocate"

    It's not working. You are looking more and more like a troll. A Devil's Advocate would actually present a case, not send people chasing squirrels.

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  2. Thank you all for your patience. I'm away from home, and have to fit in this extra-curricular activity whenever I can.

    First of all, I haven't read a lot of what Crockford has written about polar bears. And I haven't read much of what her critics say about what she has said about polar bears. I'm hoping you won't mind just sticking, as much as possible, to the Pagano paper, and those Crockford papers that deal most directly with the Pagano paper. Thanks :)

    Now back to the Pagano paper --

    As I understood it, the study by Pagano, et al, was primarily designed to determine the how much energy polar bears expended during the yearly time period (late spring and early summer) when they typically put on the most fat. Nine female bears were caught and monitored for between 8 and 11 days, each year, in April of 2014, 2015, and 2016. During the study period, four bears gained 5% to 15% of their initial weight, four bears lost at least 10% of their initial weight, and one bear lost a very slight amount of weight. Pagano notes that--

    "Bears that successfully killed and ate adult or subadult ringed seals either gained or maintained body mass, whereas bears that only scavenged or showed no evidence of eating lost mass."

    From my reading of the Pagano paper, the major conclusion of the study was that polar bears expend about 1.6 times the amount of energy, during late spring/early summer, as had been previously estimated. Thus, to put on the fat needed to fast through the summer/autumn months, when they are land-bound and fasting, they need to be able to capture and eat more seals than other researchers had previously estimated. Clearly, not all of Pagano's polar bears were able to capture enough seals to meet their energy needs, at least during the observation period. This later point is important, because Pagano also noted that --

    "previous researchers reported that 42% of adult female polar bears in the Beaufort Sea during the spring from 2000 to 2016 had not eaten for ≥ 7 days before capture."

    — suggesting that historically polar bears are not always able to find food when they want it. Pagano then goes on to say that --

    "This rate of fasting was 12% greater than measurements from 1983 to 1999, suggesting that spring ice conditions are affecting prey availability for polar bears even before the summer open water period."

    Pagano concludes by saying that --

    "These studies suggest that an increasing proportion of bears are unable to meet their energy demands. Our results indicate that further increases in activity and movement resulting from declining and increasingly fragmented sea ice are likely to increase the demand side of the energy balance ratio."


    Now to Susan Crockford's critique.

    Her primary concern with Pagano's paper was a lack of explaination for why the Beaufort polar bears were having trouble catching seals? Crockford claims that in the spring of the year ringed seals have their birthing lairs on the ice, and that in good years they should be relatively easy for bears to raid. But Pagano's paper only mentioned eating adult or subadult ringed seals (for the healthy bears), or carcasses (for the unhealthy bears) — but no pups.

    Crockford provides a link to another paper she wrote  in which she discusses the snow conditions under which ringed seal births are either successful or unsuccessful. She cites various research papers which show, for example, that when snow cover over the sea ice is deep, seal lairs are well-protected, bear predation is low, and bears became malnourished. Conversely, when snow cover is light, or when there is rain, seal lairs are easy to locate and break into, and bears are better fed. In that same paper Crockford also cites research which shows that when sea ice is very thick polar bears also have trouble finding enough to eat.

    Now back to Crockford's more recent paper. She notes that Pagano makes no mention of ringed seal lairs or sea ice conditions in their paper. This seems to me to possibly be a critical omission.

    Crockford then posts US Navy sea ice thickness maps for the Southern Beaufort Sea, for April 2014, 2015, and 2016. In all those years, but especially for 2014, there was a band of very thick (up to 5m) sea ice along the coast of Alaska. She suggests that this thick band of sea ice may have been critical to the study polar bears not finding sufficient nourishment.

    Crockford also quotes from another paper (by Stirling) --

    "Polar bears prey mainly upon ringed seals and, to a lesser degree, on bearded seals. Polar bears appear to be more abundant in polynya areas and along shoreleads, probably because the densities of seals are greater and they are more assessable. For example, between March and June in the Beaufort Sea from 1971 through 1975, 87% of the sightings of polar bears were made adjacent to floe edges or in unstable areas of 9/10 or 10/10 ice cover with intermittent patches of young ice.”

    Stirling also says in the same paper:

    "the influence of rapidly changing ice conditions on the availability of open water, and consequently on populations of seals and polar bears, has been observed in the western Arctic. Apparently in response to severe ice conditions in the Beaufort Sea during winter 1973-74, and to a lesser degree in winter 1974-75, numbers of ringed and bearded seals dropped by about 50% and productivity by about 90%. Concomitantly, numbers and productivity of polar bears declined markedly because of the reduction in the abundance of their prey species. … If the shoreleads of the western Arctic or Hudson Bay ceased opening during winter and spring, the effect on marine mammals would be devastating."

    This suggests that polar bear foraging is best when there is a reasonable number of open leads, which is less likely when there is very thick sea ice. Again, is seems that Pagano was remiss in not including more information about sea ice conditions, and seal lair conditions.


    My thoughts and questions:

    Now that I've read Pagano's complete paper, and not just the abstract; and now that I've read two relevant papers by Crockford, it seems to me that Crockford is raising valid questions as to why some, but not all, of Pagano's polar bears were malnourished? Maximim sea ice extent occurs in mid-March, and maximum sea ice volume typically occurs in the later part of April. So lack of sea ice is certainly not the problem.

    Did Pagano provide an answer in their paper that I (and Crockford) missed, or was their analysis of polar bear dietary habits and processes less than complete?

    Likewise, has Crockford misunderstood seal breeding cycles, or misinterpreted the polar bear research that she cites?

    As I understand it, if Pagano (and the news media which reported Pagano's findings) has just stuck with saying that their research showed that polar bears expend 1.6 times more energy than previously thought, Crockford might not have found anything to criticise. As it was, many concluded that because half the bears in Pagano's study were malnourished (at least during the 8-11 day study window, which apprently happens quite a lot — sort of a feast or famine situation for bears), that it must be true that all polar bear populations, at all times of the year, were also not finding enough to eat. While that concievably may be true, it appears to me that you can't infer that from Pagano's study, as Pagano didn't include a number of relevant factors in their study (e.g. sea ice thickness; snow thickness; number of open leads; relative abundance of seals, etc).

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    Moderator Response:

    [JH] You have stated your case and expressed your concerns multiple times. You are now skating on the thin ice of excessive reptition which is prohibited by the SkS Comments Policy

  3. ImaginaryNumber @52 , firstly: the polar bear occupies a limited niche in the arctic environment.   It is a highly-specialized apex predator.   It relies upon its build-up of fat reserves, to get it through the annual cycle of feeding & breeding  — and it leads a hazardous existence because of the prolonged & irregular fasting periods between kills of prey.   It cannot benefit from the broad environmental band which is available to its cousins, the various species of "brown" bears (which are omnivorous).

    Essentially the polar bear is in a rather precarious position, and its survival (as a species) depends on a complex interaction of sea-ice conditions suitable to itself, and sea-ice conditions suitable to its prey, the seals.

    Secondly , the study by Pagano et al 2018, does little more than indicate that the situation [of polar bear energy requirement] is even worse than previously thought.  And it points out that the arctic warming is producing conditions requiring even greater travel/energy-requirement.   Thus an even more precarious existence for the polar bear. 

    None of this provides any real support for Dr Crockford's contention that "all is well" for the polar bear & the polar bear future as a species.  In essence, Crockford takes a short-term [not "big-picture"] view of the situation.   Short-term and unsupported [= anti-scientific] . . . and quite reprehensible "Fake News" propaganda.

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  4. Imaginary Number,

    I noticed that you incorrectly linked to a "paper" by Crockford and compared it to a peer reviewed paper by Pagano.  The piece by Pagana was a carefully written paper reviewed by experts to determine that there were few or no errors in it.  By contrast, Crockford's "paper" was only a blog post that has not been reviewed for errors.  It is not more authorative than a high school term paper.

    Crockfords work is simply the paid shilling of a non-expert.  You cannot compare a peer reviewed paper in a scientific journal to a blog post by a paid shill who is not an expert.  It has been well documented that Crockford is paid to write her nonsense.

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  5. Reading your summary of Pagano's paper I did not see any mention of the fact that polar bears are white because of evolution.  There is also no mention that the polar bears and the ice they stand on are made of atoms.  It appears to be incomplete. 

    Peer reviewed papers are written for experts to read.  They leave out information that everyone who is expert knows.  There is not enough space to rewrite the history of science in every paper.  Crockford's suggestion that they have left out necessary information is only relevant to people who are not experts (like Crockford).   Subadult seals include pups, experts know this and it does not need to be explained.  Experts know about snow conditions and leads, Crockfords comments are irrelevant. 

    Pagano's paper shows that polar bears are expending more energy to survive.  That suggests that that reproduction is threatened.  

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  6. @ImaginaryNumber

    You haven't given a few links to some of the thousands of posts you have made about the climate. Why not? As you are so industrious and assiduous on this subject you must think what you have to say is worthwhile and informative. 

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  7. Moderator(s):

    I am dismayed by the instructions you have given me. In my first post (#35) I simply asked for help in understanding two articles, and gave the links for each. I thought that anyone who read the two links would then be able to understand the nature of my questions, and possibly give me assistance.

    By post 39 it was becoming clear to me that few, if any, were actually reading Pagano and Crockford, so I posted a more extensive synopsis of what they had said.

    At the end of post 49 you said

    Moderator Response:
    [DB] Yes, it's time for an evidence-based based approach for your position, grounded in the reputable literature and using citations.

    By this point I was getting really frustrated. Both Pagano's and Crockford's articles provided a number of citations from reputable sources. I did not understand why you wanted even more information, but I attempted to comply with your request by spending four hours creating post 52. A huge waste of my time, as far as I was concerned, as I figured if folks would simply read Pagano and Crockford they would understand the arguments far better than anything I could write down.

    And now I am being told:

    Moderator Response:
    [JH] You have stated your case and expressed your concerns multiple times. You are now skating on the thin ice of excessive reptition which is prohibited by the SkS Comments Policy.

    It appears I'm damned it I do, and damned if I don't. I came to SKS wishing to learn, and had high expectations of my questions being taken courteously and seriously (and they were by some — thank you), but for others it was clear that they had not read either article, yet they seemed to enjoy piling on.

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    Moderator Response:

    [JH] Moderation complaints snipped. 

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  8. michael sweet said:
    I noticed that you incorrectly linked to a "paper" by Crockford and compared it to a peer reviewed paper by Pagano...

    Thank you for correcting my improper use of the word "paper".

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  9. michael sweet said:

    Peer reviewed papers are written for experts to read. They leave out information that everyone who is expert knows. There is not enough space to rewrite the history of science in every paper. Crockford's suggestion that they have left out necessary information is only relevant to people who are not experts (like Crockford). Subadult seals include pups, experts know this and it does not need to be explained. Experts know about snow conditions and leads, Crockfords comments are irrelevant.

    As evidenced by your own faulty knowledge, you are not a polar bear expert and therefore shouldn't be reading Pagano's paper. I'll not comment on your other questionable comments for fear of the moderators censoring my remarks as being argumentative.

    According to this paper seal pups are different than seal subadults.

    pup < 1 years old

    subadult1–4 years

    old adult ≥ 5 years old

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    Moderator Response:

    [DB] Inflammatory and moderation complaints snipped.

  10. JohnSeers said:

    Why don't you give some links to just a few of your thousands of posts on climate change issues? That should be sufficient to allay any doubts.

    JohnSeers said:

    You haven't given a few links to some of the thousands of posts you have made about the climate. Why not? As you are so industrious and assiduous on this subject you must think what you have to say is worthwhile and informative.

    This seems to be very important to you, though somehow I doubt providing the requested information will greatly improve my standing in this forum.

    Here are two few threads I've started (screen name SailOar, and screen name ImaginaryNumber). I've posted many thousands of posts in other threads.

    Northwest Passage - 2018

    Ocean News

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  11. I'd like to make another comment regarding my experience in asking questions on this forum. Many of you seemed to think that the interests of science were best served, not by working to understand my point of view to better answer my questions, but rather to blast Crockford without even reading the particular posts I had questions about, and by leveling all sorts of criticisms against me for using the word "paper" when I should have used the word "article", and for criticizing me for either not explaining my point of view well enough, or my saying too much, or my not listing the correct number of scientifically-approved citations.

    While the gods of scientific correctness are undoubtably smiling on your heroic posts, your winning a few battles obscures the fact that you/we are losing the war. By that I mean that it really doesn't matter if you totally prove to the scientific community that a climate disaster of epic proportions is about to swamp the Earth. What matters is if you can convince the voting public to put into office people who take climate change seriously. I thought we in the U.S. had plumbed the depths of stupidity we we elected G W Bush president. But no, we doubled down to elect Trump. What an awful choice we've made.

    Those many thousands of posts that I referenced were made in an attempt to change the minds of the voting public. I came to this forum asking for help with a question that had me stumped. I feel that collectively you did a very poor job in furthering what I think would be a mutual goal to better explain and persuade the non-scientific community of what the world is facing.

    I hope the next non-scientific fool who comes to this forum to ask a question has a better experience than I've had.

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    Moderator Response:

    [DB] Multiple JAQing off and inflammatory snipped.

    I suggest that a venue such as this one, one based in science and credible evidence...and one that is a moderated forum that enforces the Comments Policy on all participants equally, is not to your liking.

  12. ImaginaryNumber @61 , it is fair enough for you to raise your point of criticism — but your criticism is misplaced.

    SkepticalScience [SkS] website is primarily about the science of climate (and especially the modern AGW).   It is not a website about politics — if you wish to discuss that aspect, then please go to another venue.   True, the politics of what best to do about about our AGW climate problem . . . is an aspect which cannot entirely be avoided — but SkS exists for scientific education, rather than for "persuasion of the voting masses".

    Yes, there have been occasional articles on the psychology of (rational) persuasion.  But that aspect is largely pursued elsewhere.  Indeed, I gather John Cook, one of the founders of the volunteer website SkS, has moved to George Mason University, Virginia, for that purpose.

    People come to SkS to be educated through the articles (which also give links to the scientific research).   Attached to the articles are comment columns, which attract certain subgroups of people :-

    ( A ) Those who wish to engage in genuine discussion of certain aspects e.g. in giving, gaining, or exchanging information

    ( B ) Those who disingenuously troll the topics

    ( C ) Those who truculently come to rant, sloganize or otherwise vent their denialism.

    ImaginaryNumber, when you log on to post in the comment columns, you ought first to make a clear decision in your mind — whether you wish to participate per A , B , or C .    And you should clearly express yourself in a manner in accordance with A or B or C .    Do not try to straddle 2 or 3 of these categories.   Nor be so careless or clumsy in execution, as to give the reasonable reader the impression of straddling.

    If you are clearly in category A , then you will be treated politely.

    On the matter of Dr Crockford, she is well-known for her unscientific attitude regarding polar bears and global warming.   You encroach on categories B and C , by asserting that the other posters here are not familiar with her or have not read her comments nor understood her.

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  13. @ImaginaryNumber

    "... somehow I doubt providing the requested information will greatly improve my standing in this forum."

    Exactly. That is my point. 

    It is telling that out of your "thousands" of posts about climate change you can only offer something about your hobby. 

    Many people here have long experience of dealing with climate contrarians and can recognise the style and techniques that are used. In short they can detect insincerity from a mile away. One of those techniques used is pretending not to be a contrarian. This is often backed up by the unwillingness to properly engage, to answer questions and a rather shifty, reluctant demeanor, often reinforced by aggression and criticism of the people responding.

    You have shown all these traits so it is not surprising people are not taking you very seriously. If you want a real discussion you have to engage properly and openly.

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  14. ImaginaryNumber @52 finally posts some specific claims that can be examined. I have downloaded Pagano et al (along with the supplementary material for the paper). I have not followed links to Crockford's blog posts - I will start from a position of assuming that ImaginaryNumber has provided an accurate summary of Crockford's arguments.

    Let's look at the first claim:

    "Crockford claims that in the spring of the year ringed seals have their birthing lairs on the ice, and that in good years they should be relatively easy for bears to raid. But Pagano's paper only mentioned eating adult or subadult ringed seals (for the healthy bears), or carcasses (for the unhealthy bears) — but no pups.[emphasis mine]

    On the first page of Pagano et al, the paper says "...a solitary female bear on the spring sea ice would on average need to eat either one adult ringed seal, three subadult ringed seals, pr 19 newborn ringed seal pups every 10 to 12 days..." [emphasis mine]

    On page 4, figure 4 shows feeding demands for polar bears. In fgure 4a, the first bar is labeled "Pups". In figure 4D, the second legend entry is labeled "Pup ringed seal".

    In the supplemenatary material:

    On page 3, we find " Nutritional demands were determined from the caloric value and digestibility of ringed seals in polar bears (55, 56) as ringed seals are the primary prey of female polar bears in the Beaufort Sea in the spring (57–59). Ringed seal pups were mean total (fat + protein) caloric values from pups < 1 month old, carcasses were mean caloric values of protein from subadult and adult ringed seals, and subadults and adult ringed seals were mean caloric values of fat. "

    On page 6, in the caption for figure S1, we find " Figures show locations where bears were captured (green squares), recaptured (white squares), resting (red circles), walking (blue circles), exhibiting mixed behaviors (black circles), kill sites of seals (yellow asterisk), kill sites of seal pups (white crosses), scavenging sites of seal carcasses (green pluses), or scavenging sites of whale carcasses (yellow pluses)."

    On page 7, in the caption for figure S2, we find " ...kills sites of seal pups (white crosses)..."

    At this point, I think the claim that Pagano et al did not mention bears eating seal pups is, shall we diplomatically say, less than fully accurate. They considered them as an energy source, and they observed bears eating them.

    Now, it may be that ImaginaryyNmber has not accurately summarized Crockford, or is reading into it something that is not there. I don't care which it is, and I don't care to pursue the rest of the so-called "criticisms". The first criticism is so egregiously wrong (to be less diplomatic) that I can only conclude one (or both) of two things:

    1. ImaginaryNumber is not a trustworthy source of critisicm of Pagano et al.
    2. Crockford is not a trustworthy source of critisicm of Pagano et al.

    In either case, ImaginaryNumber is no longer worth listening to on this subject. No, this is not ad hominem. I am not saying "ImaginaryNumber is wrong because he can't be trusted", I am saying "ImaginaryNumber can't be trusted [on this subject] because he is wrong".

    In comment 43, I linked to another SkS post. That post included a link to this paper on denialism. A quote from this paper is:

    "The third characteristic is selectivity, drawing on isolated papers that challenge the dominant consensus or highlighting the flaws in the weakest papers among those that support it as a means of discrediting the entire field.

    In ImaginaryNumber's case, he is drawing not on an isolated paper, but a blog criticism of one single paper.

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