Hansen Scores

If media coverage is your measure, climate Scientist James Hansen scored big today with his paper in the Proceedings of the National Academy. Earth Headed for Warmest Temps in a Million Years was the ABC news headline. I love it that they called him “the U.S. government’s top climatologist.” And you’ve got to love a PNAS paper going out of its way to trash Michael Crichton, a trashing Crichton richly deserves. He’s been misrepresenting Hansen’s work, and there’s a bit of exquisite justice seeing him taken down in the peer-reviewed literature.

But the most interesting bit for me is the part of the paper that doesn’t seem to be getting much play – its discussion of El Niño.

El Niño matters because of its significant effect on climatological variability worldwide – droughts in Australia, wet across the southern U.S., etc. And in terms of climatological impact on humans, it’s variability that bites you.

In a previous draft of the paper circulated for comment, Hansen made a tentative forecast of a “Super El Niño” this year. That was pretty far out of the mainstream, for which Hansen was criticized by me and others. That is gone from the paper’s final version. But Hansen does lay out his belief that global warming increases the likelihood of stronger El Niños – “Super El Niños”, as occurred in 1983 and 1998.

I’m not qualified to substantively evaluate Hansen’s argument. The models are all over the map on this, and there’s a body of literature that seems to point in the opposite direction: a link between a warmer planet and more La Niña – the opposite of El Niño, with opposite regional climate effects. Maybe that’s why it’s reasonable not to give this part of the paper too much media play. But I think it’s the most important bit, because understanding the effect of global warming on El Niño, and therefore on issues affecting regional variability, is critical. So I applaud Hansen for sticking his neck out on this.


  1. Could you briefly discuss or point us to “the body of literature” that lays out a link between a warmer planet and more La Nina? I looked at your previous post on this topic but couldn’t follow the argument. Thanks.

  2. Kit –

    Mike Mann, Ed Cook and Mark Cane are the ones who have laid out this argument. Cook makes it in a paper in Science in November 2004:


    It was based on an empirical relationship between warm periods and the extent of drought in the western U.S. Cook et al. cite a paper by Mann, who worked with Mark Cane modelling the relationship between global temperature and ENSO:


    I wrote about this here:


    fFreddy –

    You’re kidding, right?

    Hank –

    I was among those who ballyhooed it when Hansen suggested we were in for a super El Nino this year. Now that he’s backed off of that claim, it’s not surprising that it’s a bit dustier, given the much more modest nature of the claim in the new paper.

  3. Uh, you’re kidding, right?

    Hansen circulated a draft paper–last spring–to people on his mailing list for comment; the PNAS article appears to me to be the first actual publication of a final text.

    He didn’t say what you say he said — ‘a super El Nino this year’ –either in the draft as quoted that I saw, or in PNAS yesterday.

    The only version of the draft text I’ve seen published is at that link at Peilke’s weblog, Peilke says … well, read it there, or somewhere. If Peilke misstated the prediction and you are describing it correctly, can you give a cite to your source for this?

    One of the nastier games I see all the time is overstating, understating, conflating bits of or flatly lying about what someone supposedly wrote or said, then claiming their work was wrong, their prediction failed, or their comments were, deceptive or mistaken.

    I see that done a lot with Hansen’s work, and people pick up the mistakes and repeat them. So –please, a cite for what you say he said? Who told you that, why do you believe your source?

  4. John, no offense intended, I’m a nitpicker — the only draft I’ve seen is the PDF file that’s still available at Peilke Jr.’s web page (link above in my earlier comment).

    Would you check whether that text is different than the version you remember? Both are from April sometime, but certainly may be different predictions. I realize that “likely” and “good chance” aren’t defined, but surely there’s a distinction made there.

    Peilke’s quote (I have not rechecked it against the original PDF today, but I think I recall it was indeed a direct quote) was:

    “I’m not really sure what to make of this, other than there is a dark line being drawn in the sand by NASA’s Jim Hansen and colleagues (PDF):

    We suggest that an El Nino is likely to originate in 2006 and that there is a good chance it will be a “super El Nino”, rivaling the 1983 and 1997-1998 El Ninos, which were successively labeled the “El Nino of the century” as they were of unprecedented strength in the previous 100 years.

    So what I’m chasing is drafts other than what I saw at Peilke’s page, in which Hansen predicted
    —- as likely: an El Nino originating in 2006
    —- as ‘a good chance’: becoming ‘super’ in 2007

    You may have seen a stronger prediction elsewhere?

  5. Hank –

    That’s the same one I wrote about back in April. That’s why I called it a “tentative forecast” (“tentative forecast” being sorta like “good chance”) in my post above, and just quoted his words directly in the newspaper story. “Prediction” (your word) is too strong. Roger, in his post, did the same thing I did in the newspaper story, which was to just quote Hansen rather than characterize his words.

  6. Ah, the light dawns.

    You wrote:

    “Hansen made a tentative forecast of a “Super El Niño” this year.”

    You meant:
    this year he made a forecast
    of an El Niño beginning this year
    growing to Super intensity early next year.


    Wordy I would have written:

    “Hansen, _this_ year, tentatively forecast an El Nino beginning later _this_ year, and growing early _next_ year to “Super El Niño” intensity.”

    By my count, so far, Hansen’s proven right about El Niño — we have one in 2006 — and, by mid-2007, we’ll know if he’s right about it then growing to “Super” intensity.

    More words, true. Newspapers hate that. The short form to me read as:
    Hansen forecast a Super El Nino would, this year, occur.

    I didn’t have a problem with Peilke’s using “Prediction” to mean a likelihood — rather than a certainty — but I trust your judgment about what readers likely think the word means.

    Peilke seems to be saying a forecast should be done only by the weather agency.

  7. Yeah, you’re right, “this year” is terribly imprecise. What I *meant* was the ENSO year, which spans fall-winter-spring seasons. But that wasn’t what I said (thought I *did* explain it that way in the newspaper story.)

  8. I thank you too. I hadn’t seen anyone else use the term “ENSO year” and had forgotten it.

    Do you think Peilke Jr. was correct that Hansen bet his credibility — and won more — by having predicted an El Nino starting in 2006 correctly?

    The Science review article I linked to on Peilke’s thread continues to interest me in this regard — discussing the difficult question of how much confidence an experimenter gains from testing a successful hypothesis based on theory, compared to an equally successful test of a hypothesis based on fitting previously observed facts.

    And I’m not at all clear what Hansen’s “empirical” basis for predicting the El Nino was. Have you any idea beyond his early paper whether he’s got model info, or a notion that with warmer oceans it’s just less of a stretch to reach a critical temperature to change the Walker circulation, or …. ???

  9. Hank –

    I sorta made up “ENSO year”. It’s just how I think about it. It’s analogous to the “water year” that water planners use – Oct. – Sept., so you capture the whole northern hemisphere winter precip season.

  10. Hank, as I recall he said the WPAC was already primed for an El Nino, based on some specific observations I cannot now recall (but I think mainly the obvious presence of the necessary large warm pool), but noted that the trigger event(s) (something to do with Rossby waves, I think) were basically random given present knowledge.

    Did anyone else notice that Hansen pointedly omitted RP Jr.’s name from the list of thanked commenters?

  11. *I* care, although I’m afraid I’m not up to the same technical standard as you, Hank. That said, the patented RP Jr. cloud o’ ink that was emitted in response to Almuth Ernsting made it very clear that the discussion wasn’t going to continue on Prometheus. It would have been you and me vs. Jim Clarke and Paul Biggs, and where’s the fun in that?

    BTW, thanks for your excellent connection of the dots between Hansen’s El Nino forecast and the hurricane forecast failure. One can imagine that Bill Gray would have very prone to wanting to ignore anything Hansen said.

  12. Speaking of nitpicking (grin):
    NOAA’s final prediction for the year, in mid-November:

    El Niño Southern Oscillation (ENSO)
    El Niño conditions have developed across the Tropical Pacific during the past few months and are predicted to be the dominant factor affecting this winter’s climate.

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