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Some curious things about Svensmark et al. reference list

Posted on 25 December 2017 by Ari Jokimäki

The hypothesis of significant effect of cosmic-rays to climate has been shown wrong many times. This is a pet hypothesis of Henrik Svensmark, who continues to push papers on the subject to scientific journals. A few days ago, the journal Nature Communications published a paper of Svensmark (& co-workers). I checked out its reference list because I think that some indicators of the quality of a paper can be found simply by checking the reference list, and how references are used.

S17 reference list - first impressions

I immediately noticed a few things about S17 reference list. I made some tweets (@AGWobserver) where I mention them:

The Kulmala et al. paper I mention there is this one: "Atmospheric data over a solar cycle: no connection between galactic cosmic rays and new particle formation". It shows results against Svensmark's hypothesis, but it is not cited by S17. The mentioned paper list in my tweets is this one from my blog AGW Observer: "Papers on the non-significant role of cosmic rays in climate".

(Note added December 28, 2017: This paragraph is incorrect – S17 cites two Laakso et al. papers and I somehow got them mixed.) One Kulmala team paper S17 cites is "Detecting charging state of ultra-fine particles: instrumental development and ambient measurements" (Laakso et al. 2007). S17 uses it in this context: "Cosmic rays are the main producers of ions in Earth’s lower atmosphere21." (21 is the S17 reference list number for the Laakso et al. paper.) This is strange because Laakso et al. don't say anything about cosmic rays. Cosmic rays are mentioned only in their reference list in the title of Eichkorn et al. (2002) paper, and Laakso et al. refer to it in this context: "Ion mass spectrometers have been used successfully in the studies of new particle formation in the upper atmosphere (Eichkorn et al., 2002)." Furthermore, as Svensmark's cosmic ray hypothesis relies on ion induced nucleation, it is noteworthy that one of Laakso et al. conclusions is this: "During a large fraction of days considered here, the contribution of ion-induced nucleation to the total nucleation rate was either negligible or relatively small." To me it seems that either S17 is citing a wrong paper here, or then the cosmic ray ion production thing is implicitly in Laakso et al. results and I just don't see it.

Svensmark et al. paper was also discussed in …and Then There's Physics. In the comments there, one commenter ("dikranmarsupial") noted an issue that relates to the reference list issues I'm discussing here:

It is hard to see how this made it through peer review when it cites early work on the CLOUD project, but not it’s negative (for the argument of the paper) outcome. Surely reviewers competent to review the paper would be aware that the CLOUD project doesn’t support Svensmark’s hypothesis?

S17 reference list - comparison with other paper

I decided to look S17 reference list further. I chose a comparison paper, Gordon et al. (2017, "G17"), which is a research paper on the same issue than S17. Both papers have been published and submitted to their journals during 2017, S17 in May 10 and G17 in March 24, so S17 is a bit newer in that sense. S17 was published in December 19 and G17 in August 24, so also in that sense S17 is newer. I emphasize newer here because it suggests that references in S17 reference list should be as new or newer as references in G17 reference list.

The reference list of S17 contains 39 entries while the reference list of G17 contains 85 entries. As the papers are on the same subject, it seems that S17 reference list is a little short. However, scope of G17 seems to be somewhat broader, so reference list length doesn't necessarily tell anything.

I also compared the temporal distributions of papers in the reference lists of these two papers. Result can be seen in this graph:

It is quite clear from the graph that S17 reference list focuses on older papers than G17 reference list. highest peak of temporal distribution of S17 is 2005-2009, while corresponding highest peak of G17 is 2010-2014. Also, G17 distribution is rather sharply concentrated on the more recent times, while S17 distribution is more spread out in time, and it almost seems as if the most resent research is being avoided in S17 reference list (the share of 2015-2017 papers is very low in S17 compared to G17).

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Comments 1 to 10:

  1. It's not just Svensmarks research paper that has an apparently unbalanced or unusual list of source material. The telegraph in the UK has similar issues, and so do other similar media. It ran an article on this latest Svensmark 'research' as below.

    Notice how the article presents the research in a way that says 'scientists' have made a strong connection between comsmic rays and global temperatures. This leaves the impression this is breakthrough proven research, when this is just not the case.

    At no point in the article do the journalists say Svensamarks ideas have already been refuted by most climate scientists. At no point do they give an alternative view to Svensmark, or quote other research papers. They may eventually do an article critical of Svensmarks research, but my experience is it doesn't happen often or is so much later nobody reads both or connects them.

    This is partly how climate denialism spreads. People read this material and gain a clear impression cosmic rays are absolutely proven to be a huge factor in climate, when they aren't. The general media create these unbalanced impressions repeatedly. IMO It's just pure journalistc incompetence, bias, laziness, and attention seeking hubris.

    In addition, cosmic rays have been at record levels over approximately the last decade, and so should have been causing a cooling effect. Instead warming has been especially strong, so if cosmic rays have an effect it looks very weak. Again nothing on this from the media.

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  2. Q. How do cosmic rays cool the stratosphere?

    A. It's cosmic.  You wouldn't understand.

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  3. Nigelj - I have worked on radio as a news writter & news reader.  I have found that most journalist have a profound lack of knowledge of even the basics of science.  I got accused of being sexist when I mentioned that only female mosquitoes bite.

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  4. Richard Alley pretty much killed the cosmic rays hypothesis here.
    At 42:00 he mentioned the Laschamp event about 40,000 years ago, when the Earth's magnetic field was weakened by 75-95% and the flux of cosmic rays into the atmosphere greatly increased. According to Svensmarks idea this should have had a huge impact on the global climate, but it didn't.

    In Alley's own words:
    "We had a big cosmic ray signal, and the climate ignores it. And it is just about that simple! These cosmic rays didn’t do enough that you can see it, so it’s a fine-tuning knob at best."

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  5. #3 Funkypants:
    You are not the first to notice that!
    This is a citation from this article by George Monbiot (second § from bottom):

    "Newsrooms tend to be largely peopled by humanities graduates. Over the years, I have found myself explaining to other journalists how to calculate percentages, that two orders of magnitude greater does not mean double, that animals and mammals are not synonyms, and that CO2 stands for carbon dioxide. There is a lack of contact not only with most of the population, but also with the material world and its physical parameters."

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  6. I guess it doesn't really matter what you do or don't think as Nature Communications, first published in 2010, is a peer-reviewed open access journal with an impact factor of 12.2 .  This puts in the top 1.7%  of the 12,016 journals tracked by Journal Citaton Reports.  In view of its pedigree it is a reasonable assumption that Nature Communications publishes only those papers that meet fairly stringent criteria.  That this paper by Hensmark has been published in a high quality journal indicates the reviewers had a different opinion from you regarding  the validity of the findings and conclusions drawn and  the relevance of the papers cited.  

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    Moderator Response:

    [JH] "Hensmark"?

  7. My apologies "This puts in the top 1.7%"  should read "This puts it in the top 1.7%"

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  8. #6. Haze, A research paper that fails to recognize recent research related its subject of investigation, rather than challenging it, building on it, or at least indicating that it raises no difficulty with the paper's conclusions, strongly suggests that it should not be published in a reputable, peer-reviewed journal. That it also includes a sentence inaccurately referenced only increases the belief that, at the minimum, it should have been returned to correct these shortcomings.

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  9. Note that in my article above the paragraph about S17 citation of Laakso et al. was incorrect. I have added a note about this and marked the paragraph for deletion.

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  10. The reviewers made a very poor  job. The fact that they never noticed that Svensmark et al. avoid mentioning recent studies with result conflicting with their own shows they were not experts on aerosols. By the way, at minimum Svensmark and colleagues should address the negative result of the CERN CLOUD project. Pretending that contradictory results never happened is not the way one is supposed to write scientific papers.

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