It’s a Sure Bet - by Josh Willis


My wife likes to gamble. She’s no high roller or anything, but give her a hundred dollars, a spare weekend and a room full of slot machines and she’s happy.

Not me, though. Somewhere along the way, I guess I took one too many math classes and betting against the house just isn’t much fun anymore.

But I understand why she likes it. It’s the ups and downs of gambling that are fun. You lose, lose, lose and then every once in a while you win a great big jackpot. Maybe you even win enough to make up for the last 30 or 40 bets you lost. But like any game in the casino, the odds are stacked against you. If you play long enough, you will eventually lose.

Global warming and climate change work in much the same way. Wait long enough and odds are, the Earth will be warmer. But will tomorrow be warmer than today? Who knows! There are plenty of things about the atmosphere and ocean that can’t be predicted. Over a period of days or weeks, we call these unpredictable changes “the weather.”

No one can predict the weather more than a few days in advance, any more than they can predict which slot the roulette ball will land in before the croupier spins it. Weather, like roulette, is essentially random.

But a little randomness doesn’t stop casino owners from taking your bet at the roulette table. They know the odds, and they know if enough bets are laid they will eventually come out ahead. Climate scientists know that, too.

Random events happen in the atmosphere and oceans all the time. Not just the weather, but things like El Nino, La Nina and huge volcanic eruptions can make the planet warm up or cool down for years at time. There could even be a few others that we haven’t discovered yet.

Still, for all its short-term ups and downs Earth’s average temperature has risen dramatically over the last one hundred years. That’s no accident. Like the house edge at the roulette table, human-made greenhouse gasses have tilted the odds in favor of a warming planet.

This graph shows Earth’s global temperature has been in an upward swing overall for more than 100 years. Image credit: Goddard Institue for Space Studies

Sometimes it’s easy to forget that fact when new science results come out. Like the recreational gambler, we often find it more fun to focus on the ups and downs: a short-term cooling period, a warm year during a big El Nino.

But for climate change and casino owners, it’s important to remember the big picture. The roulette player might win three or four bets in a row, but that doesn’t change the odds. Eventually the casino will win. Likewise, as long as humans continue to add carbon dioxide to the atmosphere, the planet will continue to warm.

So whenever people ask me about the latest warming or cooling in the climate record, I’m always reminded of my wife and her slot machines. By the end of the weekend her hundred dollars is almost always gone, but the thrill of the ups and downs kept her entertained for the entire time. “Did you win?” people ask. She always flashes her sly smile and says, “Sometimes!”

    15 Responses to “It’s a Sure Bet - by Josh Willis”

  1. johnny Says:
    August 13th, 2008 at 12:20 pm

    seems like a short time range on the geological scale, but nice graph.

  2. Derek Says:
    August 13th, 2008 at 10:32 pm

    Hey, maybe we should launch the GoreSat, ah hem I mean Triana, ah hem I mean the Deep Space Climate Observatory. On a serious note, I think we do spend about $1 million a year just storing the thing. Let’s launch it already, it’s already built. Silly politicians, Triana is for grown-ups.

  3. malcolm shykles Says:
    August 14th, 2008 at 12:52 pm

    On global warming, public policy is where the science was in 1998. Due to new evidence, science has since moved off in a different direction.
    The UN science body on this matter, the IPCC, is a political body composed mainly of bureaucrats. So far it has resisted acknowledging the new evidence. But as Lord Keynes famously asked, “When the facts change, I change my mind. What do you do, sir?”
    CO2 in the Northern hemisphere reached a peak of 400ppm in 1942 - when does the warming start?

    Willis says:

    Actually, atmospheric CO2 was closer to 300 ppm in 1942. See the first figure in the Summary for Policymakers of the recent Intergovernmental Panel on Climate Change (IPCC) report:
    The IPCC report was written by hundreds of the world’s top climate scientists, and it summarizes scientific understanding of global warming. The IPCC shared the 2007 Nobel Peace Prize for its comprehensive and carefully researched reports.

  4. Roger A, Pielke Sr Says:
    August 14th, 2008 at 1:23 pm


    I am puzzled by your weblog, and have weblogged on it. You are ignoring the value of heat in Joules (not surface temperature) as the primary global warming metric, despite your pioneering research using heat content change in Joules in the upper ocean to diagnose the radiative imbalance of the climate system.

    Best Regards


    Willis says:

    Roger, thank you for the comment and the cross-link to my blog. I’m glad you enjoyed the gambling analogy, but I’m not gambling on the models or ignoring the Joules in the Great Ocean Heat Bank. I’m just looking at the bigger picture. Like the casino owners.

    True, ocean heat content is the better metric for global warming, and the past few years of no warming are interesting. But tacked on to the 50-year-record of ocean warming before that, the last four years pretty much ARE just a wiggle. And yes, the estimates of global surface temperature do have errors and uncertainties. But the record of sea surface temperature also shows about 1 degree C of warming over the last 100 years. Remember, the oceans are 2/3 of the Earth’s surface and that record has fewer problems than the temperature data over land. Between the long-term records of ocean heat content, land and ocean surface warming, global sea level rise (about 20 cm over the last 100 years) and the increase in atmospheric CO2, you get a pretty simple, consistent picture of man-made warming. No models required.

    Of course, the data are not perfect. Our understanding and our climate models are missing important pieces of the puzzle. But let’s not miss the forest for the trees. You don’t have to count every tree around before you realize you’re in the woods, just like a casino doesn’t have to win every bet to turn a profit.

    Despite all the uncertainties, I think it is pretty clear that humans have already warmed the planet. And if we continue to add more CO2 to the atmosphere, we will warm it even further.

  5. Spence_UK Says:
    August 15th, 2008 at 6:04 am

    Like all analogies, this can be stretched a little. Let’s see how it holds together.

    It is possible (albeit difficult) to beat the house at gambling. But you need to be very clever indeed. A classic example is blackjack. The house assumes, at the start of a hand, equal probabilities of cards coming up, and on this basis, the house wins. But then a card counter comes along. The card counter uses a better statistical model than the house; the card counter accounts which cards were played in previous hands, and uses this a priori knowledge in their statistical model. In this way, the card counter can change the bets based on this knowledge and beat the house. The house tries to modify things, of course, by using multiple decks to make the card counting more difficult, but there are still are handful capable of beating the house by application of a better statistical model than the house uses.

    How does this apply to climate? Well, some clever bods have what they think is a better statistical model of climate. People like Cohn and Lins, Koutsoyiannis and Montanari, argue that the climate science “house” statistical model is inadequate. Under their more complex statistical model, the same conclusions cannot be drawn as under the “house” statistical model.

    Back to the analogy - how do the casinos deal with this situation? Well, the casinos aren’t public places, so they can take photos of the few who are capable of beating the house, distribute these to the bouncers, and make sure that the people with the best statistical models can’t get in to play.

    It will be interesting to see how climate science deals with this situation. I really hope your analogy doesn’t stretch to the last paragraph (all analogies break down eventually). But if you really believe the house can’t be beaten, you have a lot to learn about statistics.

    (PS. Roulette can be beaten also, but the best known models are still too complex for a human to process in real time)

    Willis says:

    Fortunately, we don’t have to rely on complicated stastical models to understand global warming because, like the casino owners, we understand the basics of how the game works. If card counting happens in your casino, there’s no need to send in the bouncers. You could just play with several decks at once, or shuffle the cards more often to make counting virtually impossible. Likewise, with roulette, you could simply stop taking bets before the croupier spins the ball. The truth is, casinos win in the long run because they understand how the game works, not because they control it and not because they chase away players with good statistical models.

    In climate science, the basic physics of global warming are also understood. The rise in atmospheric CO2 over the last 100 years has trapped extra heat in the climate system. We observe this extra heat in the 50-year record of ocean warming and the 100-year record of sea level rise. Because of the extra heat in the oceans, the planet’s surface temperature has increased by about 1 degree C. Fancy statistics aren’t necessary to explain this, just simple physics.

  6. George Crews Says:
    August 15th, 2008 at 12:03 pm

    Hi Josh,

    The problem with your analogy is your assumption that the house has an advantage, and that this advantage is significant and increasing.

    But let’s say we assume the opposite. The house advantage is small or the house is only giving us an advantage temporarily, say, 100 years. Then your analogy is turned on its head and works against you as the warming over the last century is just a “lucky streak”.

    So your analogy does not address the basic controversy, which is more to the nature of the house advantage, rather than short sequences of outcomes.


  7. johnny Says:
    August 15th, 2008 at 8:17 pm

    its more or less based on what time zone one looks at. the longer trend is the dominant trend, the shorter trend will correct to the dominant trend or longer term trend. all trends end at a sum of zero.

  8. MeltyMan Says:
    August 16th, 2008 at 7:26 am

    George (#6): We know that the house has an advantage b/c we understand the radiative effects of trace gases and can estimate the magnitude of the +ve feedbacks (with some level of uncertainty).

  9. Mike O'Reilly Says:
    August 17th, 2008 at 2:13 am

    When the dinosaurs roamed and ruled the planet there were no polar ice caps, as recently as 10,000 years ago we were in an ice age and much of the temperate zones were covered with glaciers. My theory is that the planet has been warming ever since the last ice age and that is why the glaciers are disappearing and we are not breaking new ground on warmth as Al Gore would have you believe. Wait another 30,000 years and we may be covered in ice again. Be patient.

    Willis says:

    10,000 years ago, the Earth was coming out of the most recent glacial period when ice sheets covered much of North America. But unlike the more recent warming, that change was caused by natural cycles, not human-generated CO2. In fact, humans have raised the level of CO2 in the atmosphere to its highest level in at least 600,000 years.

    Of course, no single graph tells the whole story of human-caused global warming. It is the cumulative weight of many kinds of data and a basic understanding of how the climate works that makes the story so complete and so certain.

  10. Bonnie Says:
    August 17th, 2008 at 1:44 pm

    So there is 100 year warming trend. Such trends occurred 10,000 years ago, when there were no industrialized nations. Your graph proves neither that the earth is truly warming in the sense of a cataclysmic event, nor that it was caused by humans.

    Willis says:

    Actually, temperature reconstructions show that the Earth has not warmed steadily since the end of the last glacial period twelve thousand years ago, but instead has experienced periods of warming and cooling since then. Nevertheless, data show that the amount of warming in the 20th century was much bigger than any time in the last 1000 years or more.

  11. Climate Science: Roger Pielke Sr. Research Group News » Josh Willis Reply To My Weblog Of August 14 2008 Says:
    August 19th, 2008 at 8:33 am

    [...] Josh Willis graciously replied to the Climate Science weblog of August 14 2008 entitled “An Odd Weblog By Josh Willis” on the JPL weblog site [...]

  12. Roger A, Pielke Sr Says:
    August 19th, 2008 at 8:34 am

    Josh- I have posted a reply on my weblog. Thank you for always being willing to engage in scientific discussion.

  13. Spence_UK Says:
    August 19th, 2008 at 1:30 pm

    Dr Willis, thanks for the reply, and before I respond, I wanted to take the opportunity to say that I have tremendous respect for the good work you and your colleagues are doing on the ocean heat content, which I think will be a valuable resource to help us understand a bit more about the complexities of the planet on which we live.

    Having got that off my chest, after reading your response, I still think your analogy is flawed, and your response shows a great naivety with respect to how casinos are run, and in the relationships between physics and statistics.

    On casinos, your response simply underlines my point. The house thinks it knows the games, but has to constantly change the rules as people figure out how to beat it. You concede this point in your reply, but this supports my position, not yours. If the house really knew the game, and got its model right in the first place, it wouldn’t have to keep changing the rules. (Of course, changing the laws of physics can’t be done. So the best statistical model in science becomes the “house model” anyway)

    As to your opinion that casinos don’t black list legal card counters, you are very wide of the mark here as well. One example: try googling: griffin investigations card counting. And this is just one organisation that was a little too public, less than ethical and got caught out. There are many others still operating. That people get black listed from casinos for entirely legal card counting is well known, and I’m amazed you question it.

    The simple physics explanation is also unconvincing in my opinion. If by “simple physics” we’re referring to (for example) EBMs, then we have a problem - EBMs don’t predict 4 years of cooling atmospheric temperatures and insignificant changes to ocean heat content and sea level, like we have just had. A typical defence to this would probably be that it is just weather noise. But this defence invokes statistics. You need a model to determine what can be considered noise and what is not. Simple physics (e.g. EBMs) cannot characterise these stochastic elements. So the separation of “simple physics” and statistics in your response makes no sense.

    Of course, GCMs can (in theory) include some “weather noise”. But GCMs are hardly “simple physics”, and they are chock full of statistics in terms of the parameterisations - so even they cannot be truly separated from statistics. And how good are GCMs anyway? They don’t perfectly predict climate (which has an initial value component), so their “skill” has to be described statistically. In a system as complex as climate, you can’t get away from the statistical model. It is fundamental, and underpins the science.

    So whether you are a gambler or a mathematical modeller, the statistical model is critical to success. I’m not going to speculate any further on which statistical model is the better one. Time will tell.

    Willis says:
    Spence_UK, thank you very much for the comments and for the compliments on my work.

    I think we agree about the casinos. I wasn’t suggesting that casinos don’t blacklist people. Only that they shouldn’t really need to.

    By “simple physics,” I meant that the 50-year record of ocean heat content proves that on average, the planet has been out of energy balance-absorbing more energy than it emits-for at least the last 50 years. And, the 100-year records of sea surface temperature and sea level rise suggest that the imbalance goes back even further. It’s true that the relative importance of other climate forcing, apart from carbon dioxide, should be better understood. But how can you explain 50 to 100 years of the planet gaining excess energy without at least some impact from humans increasing the amount of carbon in the atmosphere by the 35 percent over the last hundred years?

  14. Rick Says:
    August 21st, 2008 at 7:01 pm

    My issue is with the immature science being applied to point to the effects of man as the sole cause of global warming. I think the science and study is of value, but it seems immature.

    There’s four terrestrial planets, all with signs of global warming. There’s long-term 100K+ year cycles that show global warming and cooling. There’s way too much of what we don’t know and too much imperfect science to use it to frame public policy.

    That said, I think a common-sense, moderate approach is more appropriate. Our planet’s resources and capability to recover are limited. Population control, through better education, makes sense: The better educated a population, the less likely over population. Population and the desire for resources drives our impact on the planet.

    We need to be good stewards of our planet. To what degree and how that is accomplished is the real debate, whether global warming is caused by man or not. And public debate and the resulting policy are likely to be imperfect. We should be looking for progress, not perfection.

    Also, don’t expect something for nothing. If a hydrogen economy were to replace a carbon one, we would likely have greater cloud cover and possibly global cooling. Again, the real debate should be how we act as good stewards of the only place we have to live.

    Willis says:
    You bring up a good point about human population. In fact, the rise of population and atmospheric carbon track each other very well over the last 1000 years. And the debate over how to sensibly manage our consumption of resources and our impact on the environment will be one of the great challenges of this century.

    However, I would disagree about the maturity of climate science. Svante Arrhenius wrote about the possible climate impacts of increasing carbon in the atmosphere back in 1876. And he wasn’t the first. It is true that projections of future warming have uncertainty, and aspects of climate science still need improvement. But efforts like those of the Intergovernmental Panel on Climate Change (IPCC) prove that a great deal is understood about climate change and that policy makers have plenty of opportunity to be informed by science if they choose to.

  15. johnny Says:
    August 23rd, 2008 at 11:43 pm

    carbon cover is not good, then we would be toast, either way we be toast or a popcicle, lets be happy where we are, and a little bit of extremes is not too bad, as long as it doesnt get outta control.