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Climate Hustle

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

Comments 1 to 34:

  1. The climate denialism pie charts are very one sided or extreme, because if they admit any uncertainty in their own views, the whole denialist edifice collapses. The deniaist edifice can only survive if it takes an extreme position of conceding nothing, because it cannot withstand open discussion and application of logic.

    The denialists also fail to look below the surface in terms of data. For example, the denialists claim numbers of polar bears are growing. However this is only in some areas, and is due to less hunting, etc. In areas where numbers of polar bears are falling, research has highlighted specific causative factors lined to climate change, so this is a better indication of what future trends are likely to look like for the arctic as a whole. So the denialists fail to look at the complete picture.

    Anyway the denialists claim polar bears and seals will "adapt". They might adapt to some level of shrinking sea ice, but it will certainly reach a tipping point where it becomes much more difficult to adapt.

    Someone said on some denialaist blog polar bears will just eat other foods like birds eggs. I doubt a few eggs will provide much nutrition, and other predators will be very well adapted to targeting those birds eggs. Yet the denialists seem immune to such obvious things.

    1 2
  2. I am interested in whether polar bears are declining. This is an opinion poll and not scientific fact. Could we have an article regarding the polar bear counts etc and the relative merits of the various arguments? At the moment I seem to be inclined to think that polar bears will always need ice, but how much do they actually need? The deniers seem to point out that during other times the bears survived through warmer times with less snow. Could we have a comparisom of the data?

    The dig at Susan C again was not merited. Someone coming in fresh to a subject does not invalidate their work. I seem to recall reading in his biography thatNiels Bohr moved from Cambridge as his ideas were not well recieved by Thomson and moved to Manchester, that was at the time regarded as an upstart university and became part of a group that made history. 

    Criticise her work and results but not her pedegree. 

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  3. Alchemyst @2

    "Could we have an article regarding the polar bear counts etc"

    As you can see from this study some populations of polar bears are currently declining, and a couple are increasing, and for many we don't have good data. The decline of polar bears is associated with climate change, particularly due to  declining food resources like declining seal populations.

    Projections are that all populations of polar bears will eventually decline.

    "The deniers seem to point out that during other times the bears survived through warmer times with less snow"

    The bears survived through warm temperatures after the end of the last ice age. We are heading to much higher temperatures, and less sea ice than this, by 2100.

    Susan Crockford hasn't published any science on polar bears related to climate change, and very little research on any aspect of polar bears. Perhaps you should bear that in mind when you read research and opinion. Who has more basic credibility, the expert or non expert? 

    Of course people like Crockford might be onto something, but given she is a non expert I suggest look at every single thing she says carefully and double check it against what the research and what others are saying. Check her source dara carefully, to see if its reliable and properly relevent and not cherry picked. Her various claims do not stand up to even the most superficial scrutiny IMO.

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  4. Alchemyst @2 , please note that there is no meaningful comparison between the ordinariness of Susan Crockford and the outstandingness of Neils Bohr.   It is a logical non-sequitur to suggest that Bohr's brilliance somehow adds lustre to Crockford.   Nor is she a Galileo !!

    Please look at the faulty/unscientific nature of her assertions — assertions which are also strongly outlier to the views held by the generality of polar bear experts.

    Although the white polar bears are specialized in diet and are of fairly recent evolutionary divergence from the "colored" bears, yet they managed to survive through the recent (Eemian) interglacial period — a period which was distinctly warmer than the present Holocene interglacial.   How so?   It seems that the Arctic region during the Eemian had disproportionately cooler temperatures, owing to "a reduced intensity of Atlantic Ocean heat transfer to the Arctic" [ Bauch et al., 2012 ]

    The big picture presently is that: (A) despite wishful thinking, we have a very incomplete idea of polar bear numbers & population dynamics,

    ... and (B) the polar bears [as mega-fauna carnivores with a highly-specialized diet/lifestyle ] are facing almost 100% loss of their habitat during the next century or two.   Crockford as well as anyone, should know that habitat loss is the biggest threat to endangered species.   Yet she still makes soothing noises to the denialists.

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  5. Alchemyst, you're getting this backward. S.C.'s "pedigree" was misrepresented in the first place by pseudo-skeptics, who then used the misrepresentation as the basis of an argument from authority. Although that argument is a logical fallacy in its own right, it was also useful to examine the claim on the pedigree itself, which, as it turns out, is not all that impressive. Nonetheless, arguments from authority are still wrong. If Niels Bohr had started ranting nonsense, he would have been called on it, regardless of his previous achievements. Said achievements did not contitute a 100% guarantee on anything coming afterwards.

    S.C. does not have a large body of orginal research work on polar bears. That does not invalidate by itself any claim she would make, but certainly withdraws from her being presented as an authority. I don't see anyone here "attacking" her pedigree. That's kind of impossible to do anyway. That's like attacking the sky. Her pedigree, the sum of her publications and contributions, is really a matter of public record; it is what it is. What contributors have done was to attack the idea that said pedigree granted her status as such an authoritative figure that what she said should be regarded with more respect than what any/all others say, and constitute the end all/be all on the subject. It was shown that there was no factual basis for it, and it is a logical fallacy.

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  6. Thanks, nigel, Eclectic and Philippe. 

    You are still going back to authority. It should not be used to support an argument. 

    With regards to niels Bohr, he came to Cambridge to study with Thomson the discoverer of the electron. Now Bohr had gained his PhD in Copenhagen on the theoretical studies of the electron in metals. He had done little practical experimentation. The university did not have a physics lab!   From the accounts he was not regarded highly by Thomson and his ideas on the electon were not taken up. As a consequence he dropped out of Cambridge and his work to the scietific community was lost for a decade. Yet the ideas of electrons in metals that were worked out by Bohr in his PhD thesis are our current understanding.  Yet it was decade later that they were being begining to be accepted in physics. Bohr dropped out Cambridge and went to the then poorly regarded University of Manchester where again his genius was allowed to flourish.  Thomson the then great authority (he even had a nobel prize in the topic) on the electron had got Bohr, a man who had to a great extent taught himself physics and spoke poor English, wrong. 

    I am a profesional scientist and I hear all the arguments about global warming and they all hold less weight than that the winter snow cover on the mountans that I remember as a child is nowerdays much less.

    There is too much on personalites and projections used as fait accomplis and not enough on well etablished facts.

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    Moderator Response:

    [JH] Off-topic and sloganeering 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.

  7. Alchemyst @6, I will clarify:

    1) The denialist community presents Susan Crockford as an expert in polar bear science, when she clearly isn't. So this is a missrepresentation. (If anyone is using the "argument from authority" the climate denialist community is.)

    2)Of course she has a science degree and is entitled to present her theories and they should be judged on their merits. She is not automatically wrong because she lacks expertise. However as a non expert she requires some extra scrutiny of some aspects of her work. This is commonsense.

    And when she voices little more than an opinion, without much of anything in the way of supporting data or a specific mechanism, then the specialist expert has more credibility. And some of what  Crockford says is little more than opinion.

    3) There are many voices screaming for attention and only so much time. We should always firstly consider the views of the real experts. They must always at least take priority.

    4) When we do look at susan Crockfords views and conclusions, they just fail to be convincing for a whole range of reasons all based in evidence. The well established facts you talk about do not support Susan Crockfords conclusions. 

    Right now in regard to personalities and mud slinging, Michael Mann  for example has had death threats, been called every name imaginable, to pick just one example. Most of the mud slinging is coming from the climate denialists from what I have seen, and its serious mud slinging.

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  8. Interesting discussion of Susan J. Crockford's work on polar bears.  I wonder if you could offer your professional assessment of her "Polar Bear Science" website, in particular her claim that polar bear populations have been stable or increasing since the 1970s.  I ask because I'm reviewing the climate change denialist Gregory Wrightstone's book, "Inconvenient Facts," and on pp. 98-99 he identifies what he calls "Inconvenient Fact 52 ("The population of polar bears is growing") and "Inconvenient Fact 53 ("There are more polar bears now than we've had for 50 years.").  The chart in the book showing increasing polar bear populations cites SJ Crockford (2015), "Polar Bear Population Estimates, 1970-2017).  wp.me/p2CaNn-gP2" (the URL takes you to her Polar Bear Science website).

    A related question:  is the "IUCN/SCC Polar Bear Specialist Group" website reliable and authoritative, in your view?  It certainly seems to be.  Or, a better question:  What are the most reliable sources on polar bears & anthropogenic climate change, in your view?  Thanks in advance for any help you might offer.

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  9. Dear moerator

    not once have I supported Susan C's views only her right to express them. I have asked you or arguments to bring it down. The only one that I hear is that she is not an expert.  please could you please be specific as to why I am censored.

    I believe that personalities should be left out of the arguments because I think it is counter productive

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    Moderator Response:

    [JH] Moderation complaint snipped.

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

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive or off-topic posts. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site. 
     
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    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.

  10. Michael Schroeder,

    The IUCN/SCC Polar Bear Specialist Group is a group of polar bear experts.

    Susan Crockford has never studied polar bears in the wild.  She has published on dog genetics and some polar archaeology.

    Regarding polar bears over the last 50 years, around 1970 the USA, Canada and several European countries passed laws restricting the hunting of polar bears.  Before that they were overhunted and the numbers were low.  Unsurprisingly, when overhunting stopped the population of polar bears increased.  This is urelated to global warming.  Not everything is related to AGW.

    Crockford and Wrightstone pick 50 years to get the full increase in population from the stoppage of hunting.  Somehow they have left off the eplaination of the increase.

    Experts are concerned about the future of polar bears.

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  11. Alchemyst @9, you ask for "arguments" about why Susan Crockford is wrong. Ok, one of the main things she claims is polar bears will simply adapt to less sea ice. The following two articles explain why this is unlikely, with reference to comments and research by polar bear experts.

    www.desmog.ca/2017/11/30/polar-bears-chosen-bizarre-symbol-deny-climate-change-scientists-say 

    motherboard.vice.com/en_us/article/aepnpz/climate-change-deniers-think-polar-bears-are-thriving-in-a-melting-arctic

    They cover only the main points, but straight away it's possible to see how weak Susan Crockfords views are. If you want the detail use google to find relevant research papers.

    As stated by MS above, numbers have increased due to hunting, not climate issues. If Crockford was open and transparent she would have acknowledged this.

    However according to the experts, numbers are only increasing in some places, and where they have decreased it appears to be lack of seals due to lack of sea ice as discussed below:

    www.worldwildlife.org/stories/polar-bear-population-decline-a-wake-up-call-for-climate-change-action#

    To me this is a good indication of what is most probable long term as sea ice declines.

    Clearly the increase in numbers in some sub populations from some moratorium on hunting is essentially a "one off" event that has hidden the effects of climate change, so far.

    This polar bear issue is difficult currently in terms of exact numbers, because of measuring difficulties, and many factors influencing their populations, and I think its of more use to ask what is most probable looking ahead. On this issue Susan Crockfords conclusions are implausible.

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  12. Michael Sweet, thank you for your concise, clear & understated response, which confirms my own evaluation of these sources.

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  13. I most certaintly did not "underscor[e] the validity of [y]our conclusion." Quite the opposite, in fact. I argue that your analysis is poor and your data is worse. Your conclusion is therefore invalid.

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  14. Richardtol @13 , would you (without going to extremes of effort) please give some detail of your objection.

    Do you feel that the Verheggen basic data are worse (the selection of the 45 + 45 blogs; or perhaps the selection of the blog contents/articles)?

    Or do you object to the content analysis in terms of the six categories of the sea-ice/polar-bear nexus?  Or some more general aspects of analysis?

    Presumably you do not object to the qualitative or statistical division of the 90 blogs, with respect to their being science-based or "science-denier".   Here seems to be one of those fortunate situations where the division is so black-or-white, as to need no actual mathematical analysis.

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  15. TPohlman

    "Her (Susan Crockfords) thesis is that sea ice conditions expected in those papers by 2050 has already occurred, but expected population declines have not."

    She doesn't have enough information to reach that conclusion. The following are the estimates of population trends in the sub populations according to the polar bear experts here

    3 Are Declining
    6 Are Stable
    1is Increasing
    9 Are Data Deficient

    So overall numbers do appear to actually be declining slightly, but despite this with so many data deficient areas, I don't think we can be sure of overall trends in numbers with any degree of real certainty, so its not possible right now to draw conclusions, or say any predictions have been proven wrong.

    You also need to understand there has been a reduction in hunting polar bears due to changes in the law, and this could have had more effect than realised on numbers further confusing the picture. 

    I'm no expert in polar bears or biology, but it only takes a minute to find the critical information underpinning this issue. You should be able to do this yourself, and apply some healthy scepticism to Crockfords views.

    It should literally be  self evident a decline in ice affects their basic habitat, so at some stage will pose problems. Habitat loss has been a prime factor in the decline of many species. Polar bears are not as resourceful and adaptable as humans, and the trouble is we tend to see things through our own eyes.

    I'm always open to alternative opinions, but Crockford is unconvincing.

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  16. NigelI,

    thanks for responding to my post, which apparently has been moved back to moderation for some reason. Note that per your count, 7 populations are stable or increasing, and 3 are declining. several of the 9 listed as ‘data deficient’ (mostly on the Russian side of the Arctic) have never been accurately measured, due to well-known issues, and aren’t typically considered in Red List assessments. Given the existing measured relatively stable population, the primary rationale for Polar Bear listing status as ‘Vulnerable’ is modeled projections of impact of sea ice loss, based on IPCC models.

    Given the data on actual sea ice loss vs. actual polar bear population trends, Dr. Crockford has disputed this theory, and as far as I can tell, has not had any serious challenge to her paper. Her thesis (shared by some others) is that excessive sea ice in the spring feeding window is far more dangerous to polar bear survival than reduced ice in the summer fasting period, as evidenced by 2007. If there is science to reject that theory, it would be good to see a discussion of that as well.

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    Moderator Response:

    [JH] While deleting a series of spam posts, I inadvertently deleted your post. I apologize for doing so. Here is the text of your deleted post:

    TPohlman at 12:44 PM on 28 December 2017 

    i would have been a bit more sympathetic to your point of view if you or any of your 13 coauthors had taken the time to refute Dr. Crockford’s recent paper that uses published, peer-reviewed papers on the projected relationship between sea ice decline and polar bear populations to show that the theory advanced in those papers appears to be disproven. Her thesis is that sea ice conditions expected in those papers by 2050 has already occurred, but expected population declines have not. If you wanted to refute that, you should do so. Admittedly, a number of the coauthors don’t have the expertise that Dr. Crockford has in Arctic biology,  but several of you do. You could have spent the time wasted on this paper challenging her published science, if you wanted to build credibility in what you call the denial blogosphere. Instead, you have played into their hands with this hastily constructed hit piece.

  17. I note with some interest the comments by nigelj and Michael Sweet about the growth of the polar bear population since the 70’s (in the face of declining sea ice) being due to the cessation of hunting. While that is entirely reasonable in concept, it would be good to see some papers on the topic cited, since it seems to an underpinning of the argument.

    i mention this because of an alternative (more likely joint) hypothesis. That theory was that polar bear recovery was due in part to the fact that the 70s were a period of extremely high sea ice and cold conditions which made for poor seal harvesting conditions in winter and spring. Warming and the retreat of sea ice in the 80s and 90s would have removed those constraints. I don’t know how valid that is, but it is certainly consistent with sea ice trends since satellite records were kept.

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  18. TPohlman @16 and 17.

    No it was not my count. It was information stated on the website I linked to.

    The table of data  also didn't say "7 populations were stable or increasing" it said 6 are stable and 1 is increasing.

    "Dr. Crockford has disputed this theory,"

    To repeat yet again, the data is too pooor to draw much conclusion either way.

    "Her thesis (shared by some others) is that excessive sea ice in the spring feeding window is far more dangerous to polar bear survival than reduced ice in the summer fasting period, as evidenced by 2007.

    What others apart from armchair bloggers? What recognised polar bear experts agree with it?

    To me all this is somewhat beside the point. Arctic ice is projected to decline further. At some point this will include all ice spring and summer posing a challenge for the bears. 

    You go on to say "I note with some interest the comments by nigelj and Michael Sweet about the growth of the polar bear population since the 70’s (in the face of declining sea ice) being due to the cessation of hunting. While that is entirely reasonable in concept, it would be good to see some papers on the topic cited, since it seems to an underpinning of the argument."

    Well I suggest you do a google search, if thats not too much trouble. To me its obvious less hunting would be a factor in increase in polar bear numbers. Some things are just obvious.

    "i mention this because of an alternative (more likely joint) hypothesis. That theory was that polar bear recovery was due in part to the fact that the 70s were a period of extremely high sea ice and cold conditions which made for poor seal harvesting conditions in winter and spring. Warming and the retreat of sea ice in the 80s and 90s would have removed those constraints. I don’t know how valid that is, but it is certainly consistent with sea ice trends since satellite records were kept."

    It's possible the cold period followed by warmer conditions caused a temporary bounce back in numbers, but this is a short term thing that could explain the pattern over a decade. You cannot conclude this process would continue for decades, and also forever unabated. There is going to be a point where warming and lack of sea ice starts to cause problems. Warming reduces areas of sea ice and this can affect breeding of seals. I posted some research above relating to this problem in more recent decades.

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  19. @eclectic

    Details are in the link provided by Bart. Just click on my name.

    To summarize, it appears that a single coder was used; 4/182 data entries are nonsense. Dimensionality was artificially inflated before being reduced by PCA. The second PC is dominated by imputed data. The PCA reveals that sources split in one dimension, not two. Nuanced positions were forced into binary codes. The jitter applied hides the previous two points from the casual reader. As the data release is incomplete, we cannot know whether the observed separation is real or an artefact of the database construction.

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  20. Thank you Dr Tol @19.  Yes I have read your own site's 20th December post (including the note on redundancy, and the brutal simplicity of basic positions taken by blogs — rather than the six variables mentioned).

    A more detailed examination of the denier blogs might well discover nuanced positions — but mundane experience of climate science denialism indicates that [their] nuanced positions, when they exist, are mutually contradictory and generally lacking in scientific worth.  The arctic-ice/polar-bear nexus seems to fit the pattern.  And Dr Verheggen's depictions are prima facie "binary", very much so (though probably not more than would be expected, given the mindset of the average denialist).

    You are a busy man, and I do not wish to importune you to provide close analysis of the blog contents themselves.   I agree with you that the positions expressed (by the anti-science bloggers) are likely to be quite predictable and "anything but AGW".

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  21. Tpohlman,

    The Wikipedia article I linked upthread contains many peer reviewed citations that cover your questions.  In any case, it is common knowledge that hunting reduced polar bear numbers.

    Adult polar bears have high survival even in bad conditions.  Current sea ice conditions threaten cub survival.  It will take years for the effects of sea ice decrease to be measured in polar bear counts.

    I noticed that you do not provide any references for your wild claim that the 1970's had high sea ice amounts.  Unfortunately, Cryosphere Today is not online, but this page has several ice graphs that do not show any increase in sea ice that could have had the result you claim. Satalite data show little decrease in sea ice beore 1996.

    It is typical for deniers to insist that scientists produce peer reviewed references while they spew false, unsupported claims without a shred of evidence.  My claims are those supported by experts.  Your claims are unsupported.  Please provide citations to support your wild claim that sea ice conditions affected polar bears in the 70's.  

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  22. Michael Sweet,

    For a look at sea ice conditions (actual vs. modeled) in the late 20th century that clearly shows high conditions in the 70s and then the decline, I think you will find this paper useful, particularly see figures 2 and 7 in the PDF version.

    http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00201.1

    It‘s more difficult to find references to the low points during the first half of that century, due to lack of data,  but I will look for you.

    As for the conjecture that recovery from excessive sea ice could have helped polar bear recovery along with the hunting ban, I will see what I can find. As I was clear, I “don’t know how valid that is”,  but reasonable conjecture sometimes leads to fruitful lines of research, as I’m sure you know.

    in that regard, I’m somewhat surprised at your in referenced assertion that ‘adult polar bears have high survival in bad conditions“. I suggest you look at what happened in periods of high Spring ice in 2004-2006, as well as in previous episodes in the 20th century and well documented in the literature. For more on that try these (Amstrup et al. 2006; Cherry et al. 2009; Pilfold et al. 2012; Stirling 2002; Stirling and Lunn 1997; Stirling et al. 1980; Stirling et al. 1993; Stirling et al. 2008).

    Finally, you and another responder have referred to me as a ‘denier’, a perjorative that is apparently within the Code on this site. I’d be curious as to what you think I’m denying. Or is it that you just assume that any deviation from orthodoxy must imply a uniform ‘denialist‘ worldview? You have no idea what my views are on AGW, sea ice trends, greenhouse gasses, etc. because I haven’t expressed any. Therefore, be more cautious with such a powerful term: spread thinly like peanut butter over everything, it is meaningless, and frankly, somewhat tasteless.

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  23. Michael,

    just to make this easier, here’s the “money quote” from Stirling, et al 2008:

    “The 1960s, 1970s, and 1980s each experienced a two- to three-year decline in seal productivity in the eastern Beaufort Sea and Amundsen Gulf, associated with heavy ice conditions, around mid-decade. Each was followed by a decline in polar bear reproduction and condition, after which both seal and bear populations recovered (Smith, 1987; Harwood et al., 2000; Stirling, 2002). The beginning of each of those three periods was associated with heavy ice conditions through the winter before the reproductive decline of the seals, followed by a late spring breakup.”

    In summary, first seals, then bears, recovered from a decline caused by excessive sea ice and late spring breakup. More ice does not always imply ‘good for bears‘ any more than less ice always implies ‘bad for bears’, no matter how many times the mantra is repeated.

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  24. Tpohlman @ 22,

    From your reference

    ice graph

    I see no evidence of increased sea ice around 1970 or before. This paper does not metion polar bears or the effect of sea ice on bear polulations.

    From your quote "Each was followed by a decline in polar bear reproduction and condition,"  This is consistant with my claim "Adult polar bears have high survival even in bad conditions. Current sea ice conditions threaten cub survival. It will take years for the effects of sea ice decrease to be measured in polar bear counts."  Bad conditions cause failure of reproduction but the adult bears survive in poor condition.  Your quote does not say that polar bear numers decreased, only that reproduction failed.  Because polar bears live so long it takes a long time for bad conditions to be reflected in polar bear numbers.

    These yearly fluctuations have nothing to do with my claim that polar bear numers increased after the control of overhunting.  The control of overhunting would result in long term (decadal) increase in the population while yearly variation in sea ice would only afffect yearly variation.  

    I do not think your data supports your claim that sea ice fluctuations affected long term increases in polar bear populations.  The data do not address the claim that control of overhunting resulted in increase in polar bear populations.

    From Wikipedia

    "Due to warming air temperatures, ice-floe breakup in western Hudson Bay is currently occurring three weeks earlier than it did 30 years ago, reducing the duration of the polar bear feeding season.[163] The body condition of polar bears has declined during this period; the average weight of lone (and likely pregnant) female polar bears was approximately 290 kg (640 lb) in 1980 and 230 kg (510 lb) in 2004.[163] Between 1987 and 2004, the Western Hudson Bay population declined by 22%,[185] although the population is currently listed as "stable".[8]" (my emphasis)

    A decline of 22% of one of the best studied populations of polar bears is considered "stable".  The decrease in female weight portends a failure of reproduction.  This is caused by a decadal decrease in sea ice, not a single bad year.

    From Dr. Derocher, a polar bear researcher in Canada:

    "After the signing of the International Agreement on Polar Bears in the 1970s, harvests were controlled and the numbers increased. There is no argument from anyone on this point. Some populations recovered very slowly (e.g., Barents Sea took almost 30 years) but some recovered faster. Some likely never were depressed by hunting that much, but the harvest levels remained too high and the populations subsequently declined. M'Clintock Channel is a good example. The population is currently down by over 60% of historic levels due only to overharvesting. Some populations recovered as harvests were controlled, but have since declined due to climate-related effects (e.g., Western Hudson Bay). In Western Hudson Bay, previously sustainable harvests cannot be maintained as the reproductive and survival rates have declined due to changes in the sea ice."

    He states that all numbers from the 50's and 60's are guesses and cannot be trusted.

    I withdraw my suggestion that you would not produce data.  In the past those who challenge the scientific consensus have not replied to me with data.

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  25. TPohlman @22 and 23, I have not referred to you as a "denier". Just wanted to clarify  this.  To me its just interesting discussion on polar bears, and thank's for the links you posted.

    You say "More ice does not always imply ‘good for bears‘ any more than less ice always implies ‘bad for bears’, no matter how many times the mantra is repeated."

    So are you seriously saying that no sea ice, or very small extent of sea ice, would have no effect on polar bear numbers? Come on it has to have an effect.

    Look at the picture very long term. According to research by Noaa linked below, summer ice will decline drastically and  spring ice during the feeding season you mentioned will also decline. Even winter ice will eventually be down to 10 - 15 %. I simply suggest this has to effect seals and polar bears.

    www.theverge.com/2013/4/12/4217786/arctic-ice-free-summer-2050-noaa-study

    According to NSIDC website:

    "Combined with record low summertime extent, Arctic sea ice exhibited a new pattern of poor winter recovery. In the past, a low-ice year would be followed by a rebound to near-normal conditions, but 2002 was followed by two more low-ice years, both of which almost matched the 2002 record (see Arctic Sea Ice Decline Continues). Although wintertime recovery of Arctic sea ice improved somewhat after 2006, wintertime extents remained below the long-term average. In 2015, the wintertime extent set a new record low: 14.54 million square kilometers (5.612 million square miles). The next year reached a statistical tie: 14.52 million square kilometers (5.607 million square miles)."

    nsidc.org/cryosphere/sotc/sea_ice.html

    Sea ice is all going one way, down, down, down...

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  26. Sea Ice Extent is currently well within normal variability. It started to freeze early this year and has a lot of very cold air temperature to force a deeper freeze (more multi-year ice).

    HadSST3 data shows an overall GLOBAL ocean warming trend of 0.05C per decade over the past 167 years.

    Polar bears mostly feed on other ocean mammals and fish. I would think that they would prefer the lack of sea ice in order to hunt something other than themselves (They are cannibalistic).

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  27. Zippi62 @26

    "Polar bears mostly feed on other ocean mammals and fish"

    Actually they dont eat fish, or only rarely, as follows. 

     "Polar bears feed mainly on ringed and bearded seals. Depending upon their location, they also eat harp and hooded seals and scavenge on carcasses of beluga whales, walruses, narwhals, and bowhead whales. On occasion, polar bears kill beluga whales and young walruses."

    seaworld.org/animal-info/animal-infobooks/polar-bears/diet-and-eating-habits

    They also scavenge on land sometimes but with difficulty as follows.

    en.wikipedia.org/wiki/Polar_bear#Hunting_and_diet

    Polar bears aren't adapted to eating fish. Land based bears eat salmon in some places, but you can easily see why they are able to do this. Capturing fish from the sea is much more difficult for bears.

    The problem for polar bears is shrinking sea ice threatens the habitats of polar bears, and also their prey, such as seals. Seals need sea ice to breed etc. So shrinking ice is basically affecting the whole food chain / pyramid.

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  28. Polar bears eat fish. - Bing Image Search

    60% of polar bears live in Canada, which is NOT part of the Arctic Ice terrain. - " ... They are found in Canada (home to roughly 60% of the world's polar bears), the U.S. (Alaska), Greenland, Russia, and Norway (the Svalbard archipelago).
    The polar bear Range States have identified 19 populations of polar bears living in four different sea ice regions across the Arctic. ... " - https://en.wikipedia.org/wiki/Polar_bear

    I'm surprised that you didn't read your own article thoroughly.

    The death of polar bears in the wild is poorly understood. They live longer in captivity (according to WIKI.

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    Moderator Response:

    [BW] Properly embedded links. Please use the "Insert" tab of the comments box to do this yourself. Thanks!

  29. Zippi@62, fair enough, polar bears do sometimes eat fish when they get lucky. I didnt say they never ate fish. But I doubt they would capture enough in the arctic region to be of much use. Remember it's the arctic bears we are all talking about.

    I don't know why death of polar bears would be poorly understood. Old age, disease, hunting surely? There is some research suggesting it has been due to lack of seals related to climate change in one sub population. 

    Habitat loss and changes in food sources have been important  causes in the extinction or decline of many species. I haven't seen any convincing reasons why polar bears are going to be immune to this, as the climate continues to warm and reduce sea ice extent.

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  30. "To the north, Arctic sea ice reached a record low wintertime maximum (this year) extent as, incredibly, temperature instruments in Alaska malfunctioned due to the surging warmth."

    www.theguardian.com/environment/2017/dec/28/climate-change-2017-warmest-year-extreme-weather

    But no, Susan Crockford says nothing going on here, and it can't possibly affect bisophere and polar bears. There just comes a point where people are clearly in denial, and simply loose all credibility.

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  31. This is precious. TPohlman mocks the use of the word denier as "a pejorative within the Code on this site."

    Zippi62: "Sea ice extent is currently well within normal variability."

    NSIDC: "Arctic sea ice extent for November 2017 averaged 9.46 million square kilometers (3.65 million square miles), the third lowest in the 1979 to 2017 satellite record." Examination of the graph shows that it is well below both interquartile range and interdecile range for November. How far can we be from "well within normal variability"?

    Zippi62:"It started to freeze early this year and has a lot of very cold air to force a deeper freeze (more multi year ice."

    NSIDC: "November air temperatures at 925 hPa (about 3,000 feet above sea level) were above average over essentially all of the Arctic Ocean, with prominent warm spots (more than 6 degrees Celsius, or 11 degrees Fahrenheit above the 1981 to 2010 average) over the Chukchi Sea and north of Svalbard." 

    Perhaps TPohlman can propose a different word to include within the "Code" for this kind of contributors. As for myself, I'm a big advocate of concise and simple language so I think denier is appropriate.

    And lastly, when  this pattern manifests over and over and over again, patience for it runs even thinner than peanut butter...

    As for Polar bear diet, no article I have found to date suggests that fish is an important part of their diet. It is not exactly easy for polar bears to catch fish. However, all isotope based studies I have found so far show they almost exclusively find their sustenance from the marine food web. The variations in organic contaminants according to the trophic level of their main food soure is especially interesting. They have only recently started to learn to extract food from land based sources and they are mostly opportunistic about it but also not very smart. One study showed no significant intake of readily available fruit, something that other bears would not pass. Perhaps hundreds of thousands of years of maritime meat eating can't be easily erased.

    TPohlman seems to trust Stirling. Interestingly, Stirling has been the subject of extensive persional attacks from a certain part of the blogosphere, perhaps after refuting a very poor piece involving the infamous trio Soon-Baliunas-Legates.

    Nonetheless, Stirling and Iverson certainly have more of a claim to polar bear expertise than Crockford. The study referenced below shows that ringed seals and harp seals are the main staples, the abstract does not mention fish. It has a interesting list of references.

    onlinelibrary.wiley.com/doi/10.1890/07-1050.1/abstract

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  32. 2 parts of the Arctic are above normal. Alaska and NE North Atlantic sea basin. Residual El Nino ocean warming is the most probable cause.

    60%of the Polar Bears of the Arctic Region live in Canada and Canada has been very cold since November.

    I sincerely doubt the polar bears are currently in any danger of losing Arctic Sea Ice any time soon. The current "record" of Sea Ice Extent only goes back to 1974. Sea Ice Extent was at its peak in 1979. Chapter 7, page 224 of the 1990 UN IPCC Report shows the graph.

    https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapter_07.pdf

    The 1930s and 1940s were also a rough time for polar bears, but there is barely any REAL record of Sea Ice Extent. Getting caught up in the Arctic Ice Melt misinformation trail isn't moving any understanding of the Arctic Region forward. Arctic Sea Ice Extent seems to be pretty safe for now.

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  33. I note that Zippi62 conveniently fails to address the blatant flasehoods already pointed and instead attempts to distract by changing the subject. Fine, let's talk.

    How far above aveage the sea ice extent is plainly visible on the NSIDC map and does not serve your argument at all. It does, however, show the depth of your denial.

    Your IPCC source, which is over 20 years old, does not show anything remotely similar to a "peak" in 1979. It shows a positive anomaly barely reaching 200,000 sq. km. A cursory examination of the record shows that such an anomaly does qualify as "well within normal variability." The graph shows that the current interdecile range is wider than such a variation. Look more closely at your sources. The numbers on the axis do have some meaning.

    In depth research has been conducted on historical levels of sea ice. One of the most comprehensive studies is that of Leonid Polyak and his team from Ohio State University, who concluded that the ice loss we are currently witnessing was unmatched for the time duration they could explore (several thousand years).

    www.sciencedaily.com/releases/2010/06/100602193423.htm

    The current data shows a steep downward trend for every month. The trend is most pronounced for the summer months, when sea ice is at its lowest. Reality does not care one bit about the sincerity of your doubt. Arctic sea ice is nowhere near safe.

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  34. About Canadian temperatures: that would qualify as weather rather than climate, but deserves sonme substantiation anyway. Parts of Canada experienced negative anomalies, but, since we are talking about sea ice and polar bear, the entire Arctic Ocean coast of Canada saw positive anomalies:

    www.ncdc.noaa.gov/sotc/global/201711

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