# Sea ice, part 2

Or perhaps part 3. I've lost track. Sea ice - and now for something just a tiny bit different refers, as does the earlier This year's sea ice. Yes, it looks like being part 3.

The above is the IJIS sea ice. Nothing very exciting at the moment (NSIDC have some nice pix. April 2011 was bang-on trend). As you recall, we're trying to agree a bet or bets. I want to bet on monthly extent and some of the others want daily. After too much equivocation, I've decided to stick to my guns: monthly it is, and if you don't like that, you'll need to find someone else to bet with. Or, you can apply a handy adjustment. Rob reckons (based on IJIS) that the difference between monthly and daily is 0.17 (see this comment so you can adjust your expectation based on that, if you like.

Here is the pic I'm basing stuff on:

Green line is trend-to-year-using-all-data; so the 2011 point is the first extrapolated, and so on. Blue-dash is the trend, using last-10-years. And purple-dash is the same, but excluding 2007 (on the 2007-was-weird-theory; I'm not actually using that line). Red is the LS/Crandles exponential fit. What I find interesting is that every year since 1997 (except 2001) has been below the long-term trend "prediction" for that year. So I'm coming round to the view that things have changed. That means that for the pocket-money type bets, I don't mind sticking to my pet theory (green line, so to speak) but for the serious money I'm afraid I'll shift to the last-10-years theory (blue-dash). Where is the line dividing pocket from serious money? I don't know, but \$100 is P and \$10k is S.

So to re-visit some earlier stuff: I said the chance of something beating 2007 and setting a new record low within the next 3 years (including 2011) seems quite good. So I'm not betting on that in response to Neven's offer. But if I switch to the not-so-safe green line I think that just about fits the error bounds, so I'm now happy to take that on for the proposed E50. I'm basing that on the monthly values, of course. If you want to take up the offer based on daily values, then OK as long as we have a "buffer": if the daily and monthly disagree about whether there is a record or not, the bet is void. Covering "the next 3 years" ie 2011, 12 and 13.

Another multi-year bet was Peter Ellis who says Allowing myself a reasonably wide fluff margin, like you're doing, I'm prepared to bet Â£50 that the September monthly average will go below 2 million some time between now and the end of 2016. Bet voided if there's one or more Pinatubo-scale eruptions between now and then. That looks OK; accepted.

Crandles offers 3 separate bets on the average of [2012, 2013 and 2014] (to be above/below 4.294, I take the high side), of [2013, 2014 and 2015] (4.119, ditto) and of [2014, 2015 and 2016] (3.94, ditto) for Â£67 each. That seems reasonable and is accepted.

That leaves me trying to satisfy Rob, which I think will be harder, since he wants to bet Real Money (\$10k), so I'm going by the pale-blue-dashed-line. I think we might best off going for a bet on the single year where we disagree most, which (within an interesting timeframe) is probably 2016. So taking the 2016 point and subtracting my cowardly 0.5, I offer above/below 3.1, with me taking the high side. The data I'm using there is NSIDC (I'm fairly sure :-) monthly average extent. Having just checked, the IJIS seems to agree closely, as I'd expect (but I can't find the monthly averages for that pre-made, so I checked 2007/09, which was within 0.1 of NSIDC). I suggest again that we buffer it: if the 2016 value for NSIDC or IJIS differs enough to affect the result, the bet could be void. To sweeten this not-very-good deal, I also offer Rob (but not me) the option to back out once the 2011 minimum data is in.

I think there are other people who have suggested they believe Maslowski's "near total ice loss by 2016" stuff, and if you believe that, then I'd hope you'll be happy with 3.1.

Did I forget anyone?

Tags

### More like this

##### Betting on sea ice with Crandles
Crandles kindly reminded me that I had three £100 bets with him; they're formalised here (an earlier version at £67 each is here), as: Crandles offers 3 separate bets on the average of [2012, 2013 and 2014] (to be above/below 4.294, I take the high side), of [2013, 2014 and 2015] (4.119, ditto) and…
##### Sea ice: the triumph of the William
This year's sea ice was unexciting. NOAA goes for "2015 Arctic sea ice fourth lowest on record" which is doubtless true. Tamino has some helpful plots, so I've nicked one. I'm pleased that my 2014 comment "Hopefully that too [i.e., 2012] will look like an outlier in years to come" now looks quite…
##### Sea ice - and now for something just a tiny bit different
[Update: see comments. We're having some dispute about whether to bet on the monthly averages (the scientifically respectable thing to do) or daily min (the wildly exciting popular choice). I need to bother work out the numbers. Until then, you'll have to be patient (2011/3/31; I've adjusted the…
##### Sea ice betting report
And not before time, you might say. Sea ice this year reached a new record minimum in the Arctic (though not in the Antarctic, which begins to look wind-driven. And before you think the two trends might be opposite-and-nearly equal, look at Tamino's convenient analysis which I can never find).…

Nothing like serious money to prompt checking the data ... fits ... assumptions ...

[Agreed. It does make one look at the data more carefully. Whether it helps predict the future is another matter -W]

Well, FWIW you did forget to note that Maslowski's projection had a +/- three years on it.

Eyeballing, the red line looks as if it would be around 1.5 in 2019; if so is that a win for Maslowski?

[I'm not really sure exactly what M's prediction was. Something along the lines o "essentially no ice" but I'm not sure he ever formalised it -W]

Just to note also that the difference between blue-dash and red would seem to be, climatoligically speaking, essentially nil (not, BTW, that this would constitute a basis for accusing anyone of retrenchment). But betting is fun!

[By 2016 it has become significant. Fortunately, I only need red and green to be distinct, which they are -W]

By Steve Bloom (not verified) on 11 May 2011 #permalink

William, thanks for getting back to this and thanks for reconsidering my bet proposal (or was it yours?).

So to re-visit some earlier stuff: I said the chance of something beating 2007 and setting a new record low within the next 3 years (including 2011) seems quite good. So I'm not betting on that in response to Neven's offer. But if I switch to the not-so-safe green line I think that just about fits the error bounds, so I'm now happy to take that on for the proposed E50. I'm basing that on the monthly values, of course. If you want to take up the offer based on daily values, then OK as long as we have a "buffer": if the daily and monthly disagree about whether there is a record or not, the bet is void. Covering "the next 3 years" ie 2011, 12 and 13.

So if I've understood correctly we are betting â¬50 that either 2011, 2012 or 2013 will beat the minimum extent record of 2007, based on daily IJIS SIE numbers (which makes it more fun), but the record has to be confirmed by the monthly NSIDC extent number (which is a great idea, because if the daily minimum extent record is broken, we'll have extra fun waiting for the final NSIDC number to roll in).

If this is the case, then I say we're on for a great bet.

[Yes, that is right (well, you can regard it as daily, and I'll regard it as monthly, but we're both safe because if they differ as to a record the bet is null) -W]

Hi William,
Considering the vast amount of other interesting things happening in the world of climate science, I appreciate your commitment to resolve Arctic Sea Ice bets.

In regard the bet, let me first make some notes on your proposal, and then propose an alternative.

First, here are NSIDC's monthly average extent numbers :
Is that the table you want to use as the reference ?

[Yes -W]

Second, let me note that you choose to put the 3.1M km^2 bet offer right on the exponential drop-off line that I am expecting, while you expect ("pet theory") the (green) long term trend line that is much closer to the IPCC projections.

So with all due respect, there seems to be a whopping 1.7 million km^2 (3.34 standard-deviations) difference between where your 'money' and where your 'mouth' is. What is that about ?

Overall, if your theory (green line) is the best reflection of reality, then you have a 99.9997 % chance of winning this bet (calculations similar to my previous ones).

[I don't think you've read the post carefully enough; admittedly, there is quite a lot of it. The green line is the pocket money bets line. For Real Money, I'm using the blue-dashed line. That covers me. As to "your side" - is the exponential drop-off the line you're expecting? That line was supposed to be the one that Crandles liked. The only "theory" I know that you like is the Maslowski total-wipeout theory, or at least that is what I thought you thought... hold on, going back, you were initially OK with "Ice extent, as reported by IJIS (IARC-JAXA), will dip below 3 million km^2 in 2011, 2012 or 2013". Moving to 2016 makes things better for you -W]

Needless to say, I would be nuts to accept 1/1 bets for 3.1M km^2 NSDIC monthly ave in 2016.

So I suggest the following adjustments :

(1) Make it a multi-year bet 2011 through 2016.
That is much more fun, and since it would imply going (far) below even exponential drop-off, there is virtually no chance of that happening, so it hardly changes probabilities.

[What do you mean by multi-year? If you mean, "if it ever goes below 3.1 in any of those years, then Rob wins" then we're back in the needing-more-margin territory, because of the averaging effects, as previously explained. That becomes complicated. I don't object to splitting the bet into independent sub-bets for each year - but I can't see that as being good for you. Your best hope is for 2016 -W]

(2) Make it a 1/10 bet : If you win, I pay you \$1000, If I win, you pay me \$10,000.

That's around 99.999 % chance of winning \$1000 for you, and a 0.001 % chance of loosing \$10,000.

Deal ?

[No, sorry, 1/10 is uninteresting for me: I get to win an amount small enough not to care about, versus losing enough that I would care. Some of your deal is (I think) based on a misunderstanding of my (current) position; could you have another check? -W]

By Rob Dekker (not verified) on 17 May 2011 #permalink

Another reason to make it a multi-year bet : if I win, the Arctic is in imminent deep trouble, so I will donate the money to a charity that helps Arctic wildlife (or whatever is left of it once the ice disappears) immediately.

By Rob Dekker (not verified) on 17 May 2011 #permalink

Thank you for accepting my bet.

Your green line for pocket money but blue dash for serious money seems a large difference to me. There is nothing really wrong with requiring a much larger safety margin for serious money. However in refusing some bets and what you have written I think it is clear that you don't really believe the green line.

[Yes, that is true. I thought I'd said that in the post, though not quite unambiguously -W]

I suggested that 0.4M below green line is more like your belief and we reached a deal so I have no reason to change what I believe is your belief.

>"Red is the LS/Crandles exponential fit."
Is LS a typo for LH = Larry Hamilton?

[Very likely my fallible memory, yes -W]

>"So with all due respect, there seems to be a whopping 1.7 million km^2 (3.34 standard-deviations) difference between where your 'money' and where your 'mouth' is. What is that about ?

Even the gap between green-.4 and blue dash seems to me to grow sharply. So, money vs mouth difference seems tempting to argue especially when you can pick quotes like "But it is what I'm basing my "predictions" on, and why I still expect there to be summer ice n 2050". However, as I am not willing to bet serious money, it is hard for me to criticise W for requiring a large safety margin for doing so.

It appears to me that Rob could try a couple of things:

One is to try and agree say \$500 on each of my three bets (and Neven's bet) terms. (Then...)

Another would be to try to persuade W that his green-.4M less blue dash safety margin grows much more sharply than Rob's safety margin. I suspect Rob's beliefs are a little more aggressive than mine but maybe not by all that much so it could well be that W safety margin grows more rapidly than Rob's.

I think you should try and get a sure thing by offering a couple of bets over at Watts place. The comments on this thread are a riot!

[[I was going to throw in a comment, but (disregarding the rhetoric) the actual bets are fairly plausible, not to say dull. There were a few at or above 5.8 (which is what I'd take) but none of them looked at all serious -W]

By Rattus Norvegicus (not verified) on 19 May 2011 #permalink

Crandles, thanks for your advice and you perspective.

William, I am sorry that you declined my latest offer. I still think that the 1/10 bet is a good one for you, since the odds of crossing the red line when the blue line is reality are still less than 10 % (calclations as usual, using detrended standard deviation).

I understand your conservative stand with 'Real Money' at stake. After all, we all want to win money and not loose it, especially when it's a lot. However, by making your projected sea ice extent dependent on the amount at stake you make it difficult to come to a resolution.

I thought a great deal about your and my position and opinion and expectations, and I think that I found a compromise that suits both of us. Let me just tell you that this will be my last proposal, since I do not want to drag this discussion on forever. Life is busy, and there are other challenges to address.

So here is the basic idea :

If by 2016, sea ice extent is above the green line, you win \$10,000. If it is below the red line, I win \$10,000.
If it is in between, the bet is null and void.

The rationale for this structure of bet is simple : You (and IPCC projections) hold the opinion that sea ice extent will recover from 2007-like fluke minima, based on modeling of ice extent (Tsietche et al and your own publications). I hold the opinion that sea ice extent will reduce exponentially based on observations, albedo effect and ice volume reductions.
If the truth is in the middle, we call it even, but if either you or me is explicitly correct, we win big time.

What do you think ? Is this a framework that you can agree too ?

[OK, I agree, it is about time we stopped fencing and came to and agreement, or not. I'm happy with the terms you offer, provided only that by "If by 2016" you mean "If in 2016", so it reads: "If in 2016, sea ice extent is above the green line, WMC wins \$10,000. If it is below the red line, RD wins \$10,000. If it is in between, the bet is null and void." I think we have to interpret it like that to make sense; otherwise, some years could be above green and others below red.

My interpretation is that I think the ice is likely to be somewhat under the green, though not by any great margin; so I believe the chances of me winning are less than 50%, but let us say greater than 25%. I regard the chances of the ice being below the red line (3.1 in 2016) as "very unlikely" (less than 10%, let us say) so the bet is reasonable, from my viewpoint. I regard the most likely outcome to be void -W]

By Rob Dekker (not verified) on 20 May 2011 #permalink

Congratulations William, we have a deal !

For any difference of opinion, there is always a win-win solution which makes both parties feel they have the advantage, and I am glad that we have found the right formula in our case.

Let me attempt to formalize the basic agreement here in bold :

If both NSIDC and IARC-JAXA September 2016 monthly average sea ice extent report are above 4.80 million km^2, RD pays WMC US\$ 10,000. If both are below 3.10 million km^2, WMC pays RD US\$ 10,000. In all other cases the bet is null and void.

This statement includes your suggestion "if the 2016 value for NSIDC or IJIS differs enough to affect the result, the bet could be void", which I think is a sensible inclusion to avoid disputes.

If you also agree on the bold text, then that will be our agreement.

I hope to shake your hand on this in person somewhere in the next 5 years, but for now, the textual confirmation here will have to do as a solidification of this agreement.

I think the 2016 date is well chosen, since the most aggressive Arctic decline models (Maslovski) start to predict instable or possibly catastrophic decine within that timeframe. So in a sense, this bet is a test of the most agressive models against the more conservative ones used by the IPCC today.

By Rob Dekker (not verified) on 21 May 2011 #permalink

Sorry to bother you William.
But just to be sure, are you OK with the bold text above being our agreement ?

This bet will take more than 5 years before we know the outcome, and thus it is better if we are sure exactly what the conditions and parameters are, don't you think ?

P.S. You do not have any link from your main page to this thread. Did you do that intentionally ? If so, why ? Just curious.

[Hi, sorry, I should have replied, life has been a bit busy. I'm planning to do a full post announcing the bet, since it will be of interest to others too.

Yes, I accept -W]

By Rob Dekker (not verified) on 25 May 2011 #permalink

I am still trying to decide whether I am or should be jealous of the terms Neven got so I thought I would ask if I can take a bet on Neven's terms (per comment 3) for another Â£67. (If I get a larger bet then I needn't be jealous.)

Guess at some point I should point out that I want to be able to refuse if William accepts after more information comes out. With SEARCH report due out tomorrow, I guess now is as good a time as any to say this.

Alternately maybe W didn't notice or forgot about my last post.

[Sorry, I was too busy worrying about the Big Money. Yes, you're on. You can even have the option to back out after tomorrow :-) -W]

Thats ok, I'll accept now and give up my option to back out tomorrow. (Found it was published yesterday, oops. Maybe that is why you offered the back-out tomorrow option :-) )

http://www.arcus.org/search/seaiceoutlook/2011/june

[I hadn't realised. OK, we both agree its on. I looked at the IJIS ice.. hmm... -W]