Eight Degrees of Separation

Steve McIntyre has been playing a fun sort of “degrees of separation” game, identifying members of climate science’s “hockey team” based on coauthorship of paleoclimate papers and using their team membership to disparage their work. I’ve not found it to be a particularly useful or persuasive argument, and Tim Lambert has pointed out the inconsistency with which McIntyre applies it.

But I’ve always been fascinated with the whole Erdös/Kevin Bacon degrees of separation thing. So for a lunchtime exercise, I thought I’d see the shortest path I could find between McIntyre and Michael Mann, the two main characters of climate science’s long-running soap opera.

There’s only one rule in my game: No use of IPCC chapter co-authorship.*

Herewith, then, are the eight degrees of separation between Steve McIntyre and Mike Mann:

  1. In 2005, Steve McIntyre and Ross McKitrick published “Hockey sticks, principal components and spurious significance” in GRL
  2. McKitrick and Pat Michaels have worked together on several projects. We’ll go here with their 2004 “A test of corrections for extraneous signals in gridded surface temperature data.”
  3. In 2003, Michaels and John Christy were among the coauthors of a “Test for harmful collinearity among predictor variables used in modeling global temperature.”
  4. Last year, Christy and Roger Pielke Sr. wrote a critique of a paper in Science by Jim Hansen.
  5. In 2004, Pielke Sr. and Craig Allen were coauthors of a really interesting PNAS paper entitled “Cross-scale interactions, nonlinearities, and forecasting catastrophic events.” (In fact, rather than wasting your time on all this hockey stick war stuff, I suggest you go read this paper.)
  6. In 1999, Allen, Tom Swetnam and Julio Betancourt wrote “Applied Historical Ecology: Using the Past to Manage for the Future” in Ecological Applications. (Julio’s not technically necessary for this list, except that a) he’s one of the most interesting scientists I’ve had the pleasure to know, and b) it’s because of him that I knew enough about these fields to find a path through the literature.)
  7. It would be remarkable to not find a Swetnam-Malcolm Hughes link. I was sitting in Tom’s office a couple of summers ago interviewing him about tree rings and drought and he asked, “Are you going to talk to Malcolm? You must talk to Malcolm,” and took me upstairs and introduced us. I guess I’ll go with Hughes/Swetnam/Diaz – “Tree Rings and Climate: Sharpening the Focus,” published in EOS in 2004.
  8. Which brings us, of course, to Mann, Bradley and Hughes, co-authors in 1998 of “Global-Scale Temperature Patterns and Climate Forcing Over the Past Six Centuries”.

* I made up this rule ex post facto, because it made it too easy. Mann and Christy were co-authors of Chapter 2 in the last IPCC report, which short-circuits a whole bunch of interesting people. What can I say? It’s my game, I get to make up the rules.

update: In the comments I detail the discovery of a five-degree chain between M and M. For the first person to beat that (without using the IPCC chapter), I’ll buy a beverage of your choice the next time we happen to be in the same city at the same time.

Bonus points for anyone who can make a chain of any length linking William Connolley and Luboš Motl .


  1. BTW, that PNAS paper’s abstract talks about emergent properties and contagion in ecosystems and cites Holling. Holling helped start the Resilience Alliance to work on these concepts and they have a very interesting blog here [if you like ecology. If not, fuhgeddaboudit]. That place is a great high-level view of anthropogenic impacts on ecosystems.

    Poor Steve Hempstead can see at that blog that they talk about differential transport in the hydrological cycle, germane in another thread huh Steve?



  2. Oh, man, I’m so lame. Mann and Roger Pielke Sr. were coauthors on a 1997 piece in Eos on a meeting of climate modelers in Sweden. So we’ve got:


    That’s five.

  3. That’s cute, but my beef wasn’t chains of coauthors. The “Hockey Team” – Mann’s term, not mine – was not just MBH, but a larger group, which reasonably includes Jones, Briffa, Ammann, Rutherford. I objected to people with active relationships with the Hockey Team precluded under NAS policies, not to 2nd degree coauthors. Otto-Bliesner is section head of the Paleoclimatology group, where Ammann is employed and recent coauthor with Bradley. Nychka is listed as currently collaborating with both Mann and Ammann. Arguably these relationships rise above bias to conflict of interest under NAS policies.

    Also I’m not objecting in some abstract sense of fair play or injustice. I objected in writing to NAS under their policies as I’m entitled to do. I’m sure that the architects of the procedure did it for a reason. They’ve advised me that they will consider the objections.

  4. M -> M -> Micheals -> Russell S. Vose -> Mann

    Michaels, P. J., R. C. Balling, Jr., R. S. Vose, and P. C. Knappenberger. 1998. Analysis of trends in the variability of daily and monthly historical temperature measurements. Climate Research 10:27-33.

    L’Heureux, M.L., Mann, M.E., Cook B.I., Gleason, B.E., Vose, R.S., Atmospheric Circulation Influences on Seasonal Precipitation Patterns in Alaska during the latter 20th Century, Journal of Geophysical Research, 109, D06106, doi:10.1029/2003JD003845, 2004.

    That’s four.

    (Incidentally Mike has an Erdos number of at minimum 4)

  5. William, it shouldn’t be too hard to link you to Lubos if both modelers and string theorists ever bring in math types as co-authors.

    Re the “Hockey Team,” Mike did resort to the term on RC. I’m not sure if he’s the one that made it up, but in any case it was just a cute way of pointing out that numerous papers had drawn broadly similar conclusions. Contrary to the cherished view of some of the Climate Audit denizens, it is not evidence for an ubiquitous International Paleodendroclimatological Conspiracy. While we’re on the subject, technically it may not be possible to tag Steve M. with responsibility for the wacky views of many (I would even say a majority) of his regulars, but I don’t seem to recall him spending any time correcting them either. To paraphrase Bill Rumsfeld, I guess Steve has to go with the fans he has.

  6. “Bonus points for anyone who can make a chain of any length linking William Connolley and Luboš Motl .”

    Piece of cake 🙂 I posted the chain in the comments on WMC’s entry about this – using mathscinet, as steve bloom implicitly suggested above.

  7. Pierremenard – You must of course let me know next time you’re in Albuquerque, and I will purchase for you the beverage of your choice (assuming, of course, that you’re of legal age :-).

  8. There has been a bug in our chain connecting us with William – a paper that was claimed to have two Nelsons on it although there was only one.

    I am able to find distance 8 from WMC – William’s Motl number is probably eight:

    William Connolley – J. S. Rollett – James Hardy Wilkinson – Richard S. Varga – Andrew M. Odlyzko – Daniel S. Freed – Edward Witten – Andrew Strominger – Luboš Motl.

    See my blog for more details.

  9. Correction: Connolley’s Motl number is 7 after all:

    William Connolley – J. S. Rollett – James Hardy Wilkinson – Richard S. Varga – Andrew M. Odlyzko – Richard S. Stanley – Alexander Postnikov – Luboš Motl.

  10. Not that a tie is worth anything, but the most recent “Paper of the Year” award from the Climate Specialty Group of the American Association of Geographers goes to the following article, which is sitting right here in fron of me:

    Frauenfeld, O.W., Davis, R.E., and M.E. Mann. 2005. A distinctly interdecadal signal of Pacific ocean-atmosphere interaction. Journal of Climate, 18: 1709-1718

    Author #2 there is Robert Davis, noted contributor to “world climate report”…


    Davis and Michaels have co-authored many papers, comments (in journals) and such. If I must track down some proof, here’s:

    Robert E. Davis, P.C. Knappenberger, W.M. Novicoff, and P.J. Michaels. “Decadal changes in summer mortality in U.S. cities.” International Journal of Biometeorology 47:166-175

    So, that’s

    M->M->Michaels->Davis->Mann. 4 again, but I think more interesting this way, with Mann co-authoring with a WCR editor.

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