Betting on climate change?

Posted by William M. Connolley on July 11, 2006
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The betting on climate change thing seems to have gone rather quiet. This post is prompted by a comment posted to an old entry on my old blog Probably not betting on climate with Lubos Motl (that post is still worth reading, I think, for the attempt to calculate what are “fair odds”. In some email discussion afterwards, I think I discovered that there isn’t really a good answer to that question). But if you haven’t seen the circuit before, look at James A’s stuff and Brian Schmidt’s. That last post offers a list of bets that GS is prepared to take.

My anonymus commenter said:

I have been making a regular, annual bet with my environmental science and biologist friends… every year from 1998 we would look at the earth average temp, if it was [down] from the previous year, I pay, if it were [up], they pay, I have not lost yet, 2005 was a push. Are you a betting man? No odds, just a simple bet that climate is not simple at all nor is it being driven directly by human CO2.

Well, I’m happy to accept that climate is not simple. “Directly” driven by CO2 would depend on the meaning of directly – clearly, the spike in 1998 was mostly an El Nino. Anyway, as I recall 2005 was about equal to 1998 – different datasets gave different answers. I’m not sure what “no odds” can mean – presumably, 1:1. Unless it means no stake, when it becomes less interesting.

At base, this is stuff thats been gone over before, in a different guise. Taking 1998 as a base year is cherry-picking. 1998 was exceptionally warm: its no surprise that the next few years were cooler. After 1973, the years until 1981 were cooler (see graph on old blog), so this is hardly unprecedented. If anyone had started anons bet in 1974, and continued to today, those betting on cooler would have lost heavily.

And so the answer is… betting on any given pair of years is a noisy statistic and won’t tell you much about climate. Doing it starting from a high year isn’t a good bet. Betting on 10 year trends is a better idea. Based on the HADCRU data, the trend from 1998 to 2005 (or 2003, or 4) is positive (albeit small), and I’d be prepared to bet on that staying true, given suitable odds.

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  1. #1 anon
    2006/07/11

    Good answer to my bet, but my biologist and enviro-sceince friends still think that CO2 and temps are directly related, and since CO2 is going nowhere but up for many years to come (since no one will do anything drastic about it anyway), they think they will beat me, I know better, so I keep taking their money. Oh and if you think 1998 was unusually warm, perhaps you should have a chat with Ralph Cicerone or Al Gore, both of which said 1998 was tied to AGW and increased CO2, glad you are smarter.

    [Its perfectly clear that CO2 and T are not in lock step - a glance at the record shows that. There are more influences than jus CO2 - this is obvious. But its also true that increasing CO2 is mostly responsible for recent increasing T. I'm not sure what Gore has said re 1998 - probably that there is some evidence for CO2 affecting the mean ENSO state. Which is also true -W]

  2. #2 Mark Hadfield
    2006/07/11

    I’d like to hear from your biologist and enviro-sceince friends, anon. I’d like them to explain why they took the bet.It’s not one I’d be willing to take.

  3. #3 James Annan
    2006/07/11

    The bet as stated seems to be based on consecutive years, and there has not been a monotonic decline sine 1998, so I don’t understand the “not lost yet”. Year-to-year changes should be close to 50-50, with a modest bias (over the longer term) in favour of higher temps.

    If, OTOH, the comparison is always made with 1998 then all that proves is there are some on the warming side who don’t understand the science very well!

  4. #4 James Annan
    2006/07/11

    Oh I just checked the old blog and it’s the latter…

  5. #5 Mark Hadfield
    2006/07/12

    Oh I just checked the old blog and it’s the latter…”

    Thanks for the clarification, though I don’t see how that can be reconciled with the quote from William:

    …every year from 1998 we would look at the earth average temp, if it was [down] from the previous year, I pay, if it were [up], they pay.

    Still, anon’s friends are smarter than I thought. After a few years paying out they are going to have a steady source of income! Let us know how it’s going in a couple of decades, anon.

  6. #6 Adam
    2006/07/12

    It also depends on the dataset. GISS had 2005 warmer than 1998, whereas HADCRU had it slightly cooler (if I read them rightly). You could have made it a spread bet if you were really adventurous (on tenths or hundredths of a degree up or down).

  7. #7 crandles
    2006/07/12

    Anon,

    Are you going to wimp out in a few years time or does the bet after you loose one or two get changed to comparing the current year to the previous highest year?

    Are you willing to make further bets where you are locked into comparing each year from 2007 to 2016 with 2006?

  8. #8 Mikel Mariñelarena
    2006/07/13

    Hi William,

    I think that you’re not being very adventurous at all in your bet offer, are you?

    For you to postulate that the decadal temperature trend is going to continue being positive is a little bit like me suggesting that the per capita income of Venezuela will continue being behind that of the USA in the coming decade.

    When it comes to global temperature forecasts, I assume that you must broadly agree with your Real Climate colleagues Gavin or Raypierre. The former argues that we are committed to a 0.5 C temperature increase that will be realized in the coming 2-3 decades, just because of the energy imbalance provoked by the GHGs emissions. To that one should obviously add the additional forcing produced by current and future emissions. The latter is convinced that a catastrophic scenario is likely by 2050.

    Any of these forecasts clearly requires not only the continuation of a positive trend but a frank increase over the current ~0.17 C decadal one.

    I don’t quite understand why, being sure as you must be, that we face an impending and dangerous global warming all you offer is a bet on a non-negative trend (given suitable odds!). If someone offered me a bet I could afford on Venezuela or Bolivia surpassing the US per capita income in the coming decades I’d gladly take it, even at say 1:500 odds.

    [Certainly I agree with G/R re the T trends. But I'm not trying to bet against them, but against the skeptics. The skeptics say CO2 has a negligible effect, and so they have no reason to expect future warming. Its hard to translate that into your income example... I suppose you would have to say, that the skeptics are people who believe that next years income bears no relation to this years or the previous - W]

  9. #9 Mikel Mariñelarena
    2006/07/14

    I’m not familiar with that skeptic argument you’ve formulated. Just because CO2 has a negligible effect it doesn’t follow that there will be no more warming. Who says that?

    I think that most AGW-sceptics would favour a natural/unknown cause for most of the warming observed lately. With that being the case, the warming could well continue for some time. In fact, prominent sceptics like Michaels accept the -indeed small- contribution of AGHGs to global warming and, as far as I know, all of them acknowledge that, all being equal, CO2 rises should lead to a bit more warming. I don’t think you’ll find many takers for your bet.

    [But if the warming is caused by some natural, unknown, cause - why should it continue? Why do you expect this unknown thing to be the same next year? -W]

    I used the future national incomes example merely to illustrate what a bet based on a strong believe may typically look like. If you strongly believe that GW is an important problem that is going to intensify in the coming decades your bet is not reflecting such a believe, in my view.

    [I agree - and JA has argued too - that simply betting on warming/cooling doesn't reflect the true balance of odds. Which is why I was prepared to offer 7:3. There would be some level of trend - I don't know what it is - that would also be fair -W]

  10. #10 per
    2006/07/14

    FYI:
    http://energycommerce.house.gov/108/home/07142006_Wegman_fact_sheet.pdf

    [Thanks for that. Weird or what. Worth a post - W]

  11. #11 Martin Lewitt
    2006/07/15

    The leading skeptic theories for natural GW, would not be “unknown cause”, but would either be solar forcing, perhaps with unknown factors which increase climate sensitivity to solar, such as modulation of cosmic ray flux, or aerosol or upper atmosphere effects, or alternatively, just internal climate variability, e.g., multi-decadal oscillations, etc.

    In the solar case, the conveyor theory has the next solar cycle being particularly active, and then the following cycle finally a significant reduction in activity. So there would be a continued warming trend for a couple decades, with the decadal trend turning or significantly moderating in the 2025-2035 range. That is a long way off for a bet.

    Perhaps the models though will be a leading indicator, and will be able to credibly predict the cooling before then. By the next IPCC round after the FAR, the models should already be attributing more of the recent warming to solar forcing, as they will have corrected their positive albedo biases and adjusted their climate sensitivities. The observation of an active solar cycle along with solar model improvement, may allow greater confidence in solar prediction.

    Perhaps the bet could be whether there will be climate models by 2012-2014 that in peer reviewed publications, project moderation or cooling by 2030 using plausible solar activity and GHG emissions scenerios.

  12. #12 Mikel Mariñelarena
    2006/07/16

    Just fascinating, the different reactions to the Wegman report. Unfortunately, not carrying any alarmist message in it, the media are totally unconcerned by the report so I’m having to hop from weblog to weblog to see how the players react. Looks like we’ll have fun for a while. I think that the obvious move now would be to arrange some report from another group of statisticians in defence of the HS…

    Anyway, going back to my last post, a simple prolongation of the current warming trend (~0.17 C/d) would only get us to something like a meagre 0.75 C warming by the year 2050. It’s very hard to see how this would bring about any catastrophic scenario à la Raypierre. Gavin’s explicit forecasts would also fail to materialize, as we’re obviously going to continue emitting additional GHGs.

    William, are you not willing to offer a bet on an increase of the current trend in support of your RC colleagues?

    (I also think that a plain continuation of the current trend would be totally at odds with the IPCC climate sensitivity range but I don’t want to get entangled in a sulphate-masking-effect, thermal-lag, etc sort of discussion).

    [Im only willing to bet on something that would make money. My base position is the same as the IPCCs. What exactly are you proposing? -W]

  13. #13 Mikel Mariñelarena
    2006/07/16

    I propose that you offer a bet on an increase of the current warming trend during the next decade.

  14. #14 James Annan
    2006/07/17

    I propose you read the relevant sections of the IPCC TAR and related research, all of which makes it abundantly clear that scientists expect the current trend to be (roughly) maintained (in the absence of large volcanic eruptions or similar) for the next 2-3 decades, with subsequent acceleration or deceleration of the warming depending on future emissions.

  15. #15 Brian S.
    2006/07/17

    Hello anon – can I be your friend?

    A series of annual bets, increasing from smaller to larger amounts, could help solve the problem of the winner not trusting that he or she will collect from the loser.

    Anon, I’d be very happy to set up a series of annual bets right now comparing this year and future year temps to 1998, on the 1:1 odds you’ve accepted. Come over to my blog if you like – my email address is on the left hand side, and we can work details out by email.

  16. #16 Mikel Marinelarena
    2006/07/18

    Strange. If the TAR makes it abundantly clear that the current warming will not accelerate in the next 20-30 years (even though we’re inevitably going to add to the GHG forcing during this period) why would Gavin Schmidt think otherwise?

    So then I understand that you’re not willing to bet on an increase of the current warming trend, William. Is this correct?

    [Um. I suggest you quote Gavin exactly rather than vague paraphrase. As to betting on increase... its not on the table at the moment. What time frame do you have in mind, what do you mean by "current", etc etc. Also See JA's answer -W]

  17. #17 Mikel Mariñelarena
    2006/07/18

    I am a bit disappointed, I must say. I do appreciate that the idea of this post is to get some skeptic to accept some scientifically unsound bet (in the year x it will be colder than now) or, even better, to show how dishonest they are by refusing to back their positions with their money, as you often claim. But I don’t see you showing much commitment yourself.

    [Well of course its scientifically unsound, given that GW is sound. Thats the entire point -W]

    A skeptic (like me) is by definition someone who at a given moment is not convinced about something he’s being told. By contrast a believer (like you) should be totally convinced and thus be much more willing to bet on that something being true. But in effect, all you’re willing to bet is on a positive warming trend for the future (given suitable odds). An increase of the current GW is too risky for you to bet on, even though assuming the current trend to be 0.17 C/decade, it will not get us any warmer than +0.3 C by the year 2025, or +0.75 C by 2050. Hardly a scenario to feel very scared about.

    [As ever, you types misuse the word skeptic for your own ends. I'm willing to accept the std.IPCC position as the most-likely-thing-to-occur. If you think that there is probably less warming due, then we have the grounds for a bet. If you want me to bet on *more* than IPCC predicts - no thanks. As to betting to 2050 - thats a long way off, and not very attractive, so I haven't bothered to work out what odds might be interested -W]

    As for Gavin’s quotes: “Even in the extremely unlikely event that there is no further growth in emissions…there is around 0.5 C extra warming already in the pipeline that will be realised over the next 20 to 30 years. Any growth of emissions above that will lead to more warming.”…” Any conceivable growth rate (even a constant 1.5ppm/yr) will add by 2050, another ~1W/m2 to the climate forcing. Add in the current radiation imbalance of ~1 W/m2, you have at least 1.5 deg C surface warming to come”.
    > Comments in http://www.realclimate.org/index.php?p=74

    And Raypierre: “Believe me, by 2050, the trend will be all too obvious even at the regional scale — and then you’ll be wishing it weren’t!”
    > http://www.realclimate.org/index.php?p=269#comment-9607

    [0.5 in 30y is entirely compatible with 0.17 oC (though its probably more than 0.17 by now). But if you're betting over a 10 y timeframe then you need to take natural variability into account. And the point that I think you are missing it that I want a bet where the odds are in my favour - whats the point betting on something at 50:50? -W]

  18. #18 Mikel Mariñelarena
    2006/07/19

    As ever, you types misuse the word skeptic for your own ends.

    I hope you’re not saying that you know what my real believes (and final ends) are better than myself :-) How have I misused the word skeptic?

    I’m willing to accept the std.IPCC position as the most-likely-thing-to-occur.

    According to Annan, the IPCC makes it abundantly clear that the current trend will be maintained for 20-30 years. Wikipedia says this trend to be 0.17 C/decade on the surface since 1979, so it should warm about 0.4 C in the coming 25 years. According to Gavin, we would only get a 0.5 C warming in the coming ~25 years if we stopped our GHGs emissions altogether (see quotes above). Which side are you on?

    the point that I think you are missing it that I want a bet where the odds are in my favour

    Fair enough, but the choice of bets and odds I see you accepting does not reflect a strong believe in GW being a very big issue any time soon.

  19. #19 Hank Roberts
    2006/09/23

    Did anybody make an actual bet on an El Nin~o happening this year?
    Peilke Jr. says Hansen went out on a limb about it:

    http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/000771out_on_a_limb_with_a.html