3% chance of +10 oC by 2100?!?

Posted by William M. Connolley on October 17, 2007
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[Ooh err. DC points out that she may mean 10 oF. Being American, this is possible. Being a scientist, it shouldn't be (but were she being a scientist there should be a unit symbol, so this is probably the newspaper, so this may well be oF). 3% chance of 10 oF is probably plausible, though I'd still be curious as to where she gets it from. The realisation that this is oF not oC makes this post just about pointless, but I'll leave it up anyway :-) -W]

Thats what Judith Curry says the IPCC says (she is trying to counter Lomborg; thanks to CC for pointing out the article). It doesn’t look compatible with SPM-6, errrm, and since when I last looked there were no probablilities on any of the SRES scenarios I can’t see it could possibly exist.

There is a prize of the copyright to a naughty photo to anyone who can tell me where she gets her number from.

Oh dear. I’ve just read on: “The rationale for reducing emissions of carbon dioxide is to reduce the risk of the possibility of catastrophic outcomes”. Is it? Suppose you believe that a catastrophic outcome is totally implausible – a quite defensible viewpoint. Should you then argue against *any* CO2 reduction? Of course not. Nor does Curry believe her own words, since the very next para defends a cost-benefit analysis.

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  1. #1 Douglas Coker
    2007/10/17

    You say 10 degrees C she says 10 degrees … ! C or F we need to know!

    Douglas Coker

  2. #2 Ambitwistor
    2007/10/17

    Eh, I wouldn’t be too hard on her for that last sentence you quoted. I’ve said similar things myself when trying to explain the concept of mitigation as insurance. It’s an oversimplification, but the main point is that the risk is likely dominated by the lower probability, higher impact events – regardless of what you choose to label “catastrophic”.

  3. #3 Hank Roberts
    2007/10/17

    The USA is in the middle of an ugly and muddy education about risk. The current mess was in large part caused by taking the approach of smoke and mirrors, chopping and dicing “financial instruments” and selling bits and pieces of transactions, with the intention of spreading out the _overall_average_appearance_ of risk while carefully ignoring the individual, local, instances.

    Today’s WSJ, PAGE ONE
    Behind Subprime Woes, A Cascade of Bad Bets:

    “Much of the mortgage lending of the past several years, as well as investments in mortgage-backed securities, was based on assumptions that left little room for error. As a result, even slight deviations from a perfect world … pose risks …. Lending standards were more lax than most people imagined ….. ‘a case study on the way that greed convinced everyone there wasn’t risk,’….”

    Hmmmm. The previous IPCC report is discussed here:
    http://news.nationalgeographic.com/news/2006/07/060711-glaciers-alps.html

    “… by 2100, given a nine-degree-Fahrenheit (five-degree-Celsius) rise in summer air temperature … within the range forecast by the Intergovernmental Panel on Climate Change (IPCC)….”

  4. #4 James Annan
    2007/10/17

    I saw that article, and thought it was rather reasonable and well-written compared to most of what gets printed in newspapers (on both sides of the “debate”). It’s obviously 10F (and before you blame her for being unclear, consider that the newspaper would do that much editing), which is only the 6C that forms the upper bound (95%ish? I think they are vague about that) of the high scenarios. If you think that is exaggerated your argument is with the IPCC!

    [If its 10 oF (and you're right, it almost undoubtedly is) then I'm not complaining anymore about 3%, just curious as to where it comes from exactly -W]

  5. #5 Hank Roberts
    2007/10/17

    So, having confirmed your headline was a case of over-rating the intelligence of the WaPo editor or copy editor, and “what Judith Curry said” did _not_ have the “Celsius” abbreviation in it at all — would you fix the headline?

    Just to save her the trouble of denying she said it for the next few decades?

    [The headline doesn't have Curry in it, so it should be OK -W]

    It’d be a kindness.

    Heck, invite her over, maybe she’ll confirm what’s most likely, that the newspaper dropped one or two other bits.
    They do that.

    Meanwhile the closest I’ve found with my naive poking about is here:

    “a 1-in-40 chance (5 percent) that the increase will exceed 4.9°C. ” http://cbo.gov/ftpdoc.cfm?index=6061&type=0&sequence=6
    http://cbo.gov/docimages/60xx/doc6061/606102.gif

    “Source: Congressional Budget Office adapted from Figure 1(B) in Mort Webster and others, “Uncertainty Analysis of Climate Change and Policy Response,” Climatic Change, vol. 61, no. 3 (December 2003), p. 310.
    Note: The specific policy illustrated in this figure is to stabilize carbon dioxide concentrations in the atmosphere at 550 parts per million.”

    550? So what’s the likelihood of _that_?

    I assume we’re talking American parts, not British parts, and American millions, not British millions, there.

  6. #6 James Annan
    2007/10/17

    I can’t be bothered looking it up but 3% could be a rounding of 2.5% based on a “very likely” (95%) range of 2-6C (for a specific scenario?), or something like that. Whatever, I don’t think it is an unreasonable summary of “the IPCC”, as it seems quite a reasonable summary of the literature even if they didn’t say it exactly.

  7. #7 bob koepp
    2007/10/17

    I’ve never been able to make head or tails of the reported probabilities associated with various climate change scenarios. On occasion I’ve even wondered if these are pseudo-bayesian priors; i.e., hunches or “gut feelings.”

  8. #8 JamesG
    2007/10/18

    So are the “projections” now predictions again? Humpty dumpty strikes again. Just like predicting the next years weather, getting it dead wrong and then saying it wasn’t wrong because “climate isn’t weather” and of course wet & cold is just as likely as hot & dry because it’s “climate change” not “global warming”.

  9. #9 Andrew Dodds
    2007/10/18

    Hank -

    Given the way that world CO2 emissions are currently skyrocketing, and the projections (which assume a slowing in the growth rate), we are currently looking at perhaps 450ppm by ~2030, 500ppm by ~2045, and 550ppm by perhaps 2055-60. This is driven by several factors:

    (a) Massive build out of coal fired plants; these typically have an operating life of 50 odd years, which means the above extrapolation has some backing.

    (b) Shortages of conventional crude oil; most immediate replacements (Heavy oils, tar sands, GTL or heaven forbid ‘oil shales’) have much increased emissions per unit end use.

    (c) Shortages of (loacal) Natural gas; at best we’ll have a global LNG market, boosting emissions by ~30% per unit end use.

    I cannot see how these trends could be turned around within less than 20 years even with an all-out effort.

    This all assumes that CO2 sinks all work as before and Nature dosen’t decide to add to the party by burning down Brazil, melting Siberia or somesuch.

    So stabilisation at 550 ppm dosen’t seem very likely.. and 5K by 2100 does seem a lot more likely then 3%. What is climate sensitivity to tripled CO2, anyway?

  10. #10 Hank Roberts
    2007/10/18

    > [The headline doesn't have Curry in it, so it
    > should be OK -W]

    Nope. Scienceblogs quotes the first line of the item, and so does Google. That’s observed fact.

    [Ah, OK. Try now -W]

    Both the error in units in the headline and Judith Curry’s name showed up together in those reprints/pointers, as of yesterday.

    You can’t control what others display, but you can fix the mistake so the robots that grab text don’t get wrong info here.

    Please? I’m a nitpicker. Make me happy …

  11. #11 Judith Curry
    2007/10/18

    Should have been 10 degrees Fahrenheit. WP did some editing, and I didn’t catch this when I approved it.

  12. #12 Dave Eaton
    2007/10/21

    I cannot see how these trends could be turned around within less than 20 years even with an all-out effort.

    Short of the take over of the whole world by some Eco-Stalin, I don’t either.

    Thinking about where to put scientific efforts, I think (were I in this field rather than chemistry) I would focus on how to live in a warmer world.

    Considering the politics and economics of getting human beings to concentrate past a couple of months or years, the time horizon for climatological consequences is too long, and the size and rapidity of the allegedly necessary changes to prevent it too large, for climate change to be stopped by political means short of eco-totalitarianism. Which isn’t going to happen, at least until things get much, much worse.

  13. #13 uBeR
    2007/10/22

    I think the 3% figure comes from Wigley and Raper (2001) who asses the TAR warming range in probabilistic terms.

    [Possible but unlikely, in that I would expect JC to be using AR4 by now -W]