Climate change explained through probability and risk: It doesn’t matter if it exists, we should act anyway


Craven has created a series of fun, educating videos that should be watched by all.Science teacher Greg Craven posted a video entitled ‘The Scariest Video you’ll ever see’ on Youtube in June 2007. The ten minute video garnered over 7000 replies including many criticisms from global warming sceptics. Craven decided to rebut these criticisms. He spent four months of his spare time researching data on the debate, ticking off each criticism that had been made. He then released “How It All Ends”, another ten minute video but this time with an ‘expansion pack’ of videos going into each of his arguments in exhaustive detail.


Interestingly, much of the content of the six-hour, 44 part series is not devoted to proving whether global warming is happening or not, or whether man is causing it or not. He looks instead at the four main outcomes: global warming exists and we do something, it exists and we don’t do something, it doesn’t exist and we do nothing or it doesn’t exist and we do something. He concluded the costs of doing nothing far outweigh the cost of doing something, so it makes sense to take action even if we don’t know whether global warming is happening or not.

A site has also started up devoted to the videos, where the forum members critique and find responses to each new criticism as it comes through on Youtube. The efforts of these people to encourage reasoned debate is heartening. Many of the arguments against combating climate change revolve around the fact that science doesn’t agree 100% with the precise outcome. Well, science never will agree, not totally, especially with oil industry-paid advocates in the mix. But even without more and more evidence leaning towards the ‘we need to do something camp’, the logical thing to do is to take action, even if it turns out we didn’t need to. There’s also a great interview with Kim Stanley Robinson at BLDGBLOG about this.

8 thoughts on “Climate change explained through probability and risk: It doesn’t matter if it exists, we should act anyway”

  1. He emphasizes the outcomes, but ignores the probabilities. Consider this:

    Two Options:
    1) Play the Lottery Numbers: 1,2,3,4,5,6,
    2) Don’t Play the Lottery Numbers 1,2,3,4,5,6.

    Two Outcomes:
    A) The Winning Numbers are 1,2,3,4,5,6
    B) The Winning Number are NOT 1,2,3,4,5,6

    Decision Tree:

    Option 1, Outcome A: WIN millions of dollars!!!!!
    Option 1, Outcome B: Lose $1.
    Option 2, Outcome A: No Change
    Option 2, Outcome B: No Change

    I have a 25% chance at winning millions, and the worst that happens is I lose $1! I would be a fool not to play the lottery numbers 1,2,3,4,5,6!

    The reason this is foolish reasoning is because it implies similar probabilities for each outcome.

    When probabilities are included the lottery becomes a bad bet even with its amazingly lucrative winning outcomes because the probability of winning is so very low.

    I am not saying anything about global warming… I am saying that the argument used here to advocate action is even less scientific than the models used to predict global warming.

    Use a real argument. This kindergarten crap is beneath us all.

  2. I think you will find that within the six hours of appendix videos there is a momentous number of arguments surrounding what the probabilities are. This was a well-reasoned argument and presented in an enjoyable way.

    If you watch the video, it never suggests there are similar probabilities for each outcome. There are entire series of videos in the set addressing this very issue. If you look at science, the vast number of evidence weighs the probabilities in favour of global warming existing. But by the time we’re sure, it will be too late. This was a carefully considered attempt to take an objective view of the subject and calling it ‘kindergarten crap’ for not having arguments that it does in fact contain is neither helping or furthering debate. He uses your very lottery example against you, for instance. Explore the additional videos, especially the 7-part ‘Risk Management’ series.

    this is a very detailed summary of how probability and the nature of science work. Just because it’s presented in a fun, accessible way is not saying it isn’t accurate. Science works from a probability way much more than you’d realise. (I am studying for my master’s in Particle Physics and almost every result in my research project is presented as a statistical probability of results being correct, just like the IPCC.)

    Almost every aspect of science collates scientific results into a probability of for and against arguments that result in scientific consensus on a given topic. You may not like the result of this probability but to say it’s not science is naive. The fact that someone has taken the time to explain this in layman’s terms deserves respect.

  3. This isn’t science and it isn’t math, and you know it.

    Since when did science become a “forget about whether the argument is right or wrong, just act the way I tell you to becasue you don’t have enough time to decide…” scare tactic debating technique?

    This argument wouldn’t get past the critical eye of a 12th grade statistics class.

    You can believe in global warming and advocate change, but if you are doing so because of this presentation, please take my word for it… the lottery is NOT a good way to get rich!

    ps. i have a masters in econometrics and math stat, so i understand the flaws in his presentation just fine, and I don’t think he deserves respect becasue anyone who calls himself a science teacher shouldn’t be passing off this bunk as science.

  4. Probability is math. If you actually watch more than the first few minutes and the backup material, you’ll find the guy picking apart your criticisms utterly.

    Your lottery example is a bit misleading because in a lottery all outcomes have the same likelihood. There are also usually far more combinations (speaking generally there are nine main combinations of climate change based on permutations of the three factors: a) it exists/does not exist, b) it is/is not caused by us (or we can do something to stop it, conversely) and c) we do/don’t do something about it. Of course these factors all vary by degrees but by modelling it like that you get a reasonably acceptable simplified model for possible futures)

    However, of these permutations, it is an error to suggest that each has the same likelihood of occuring. Because we are in the system we are trying to study, we cannot say for certain what the exact probabilities of the outcomes are – but we can certainly look at evidence to see which is More Likely and weight our decision based upon this. This is simple decision making.

    I wouldn’t play the lottery – 1 chance in 20000000 or whatever is not good odds. If this model resembled the pure chance statistics of a lottery, I’d agree with you. But we’re not talking about random chance here. The example is far more like predicting the path of a billiard ball – there are lots of factors but if you understand some of them you can make a pretty good estimate of how the ball will behave, at least for the first few bounces. If you collect more information on the probability of each factor, your understanding of which outcome is most likely helps you make the decision.

    The IPCC reports suggesting 90% probability of some amount of climate change existing is such a collection of analysis of factors effecting climate change. Now, they don’t say for certain it’s happening – and they never will, for that is the nature of science, some factors will always give errors, or simply factors working in the other direction and a lower magnitude than the whole.

    We can never say for certain that global warming doesn’t exist until a long way further down the line. But when the factors are studied, the chance of this outcome changes. At the moment that chance is greatly diminished by evidence, making the size of probability of the outcome ‘global warming doesn’t exist’ less.

    In time science may change its mind and some evidence will skew the evidence the other way, making global warming less likely than its nonexistence. In that case I would be making the same argument, based on the probability, for inaction. However, currently we do not see this and the outcomes and their probabilities are skewed in such a direction that doing something makes sense.

    That in essence is what this man is attempting to explain to the layman. Although his model starts out with four equal possibilities (essentially a lottery with 1 ball drawn from four numbers), he quickly goes on to say that we can weight these four (admittedly simplified, but that’s how a model works) from the evidence we see around us.

    A given scientific paper may have a definite opinion on a matter. But summed over large numbers of scientists and studies the nature and degree of these opinions vary widely. Only by taking a summation of these opinions and applying them to this way of doing probability can we give ourselves the chance of making the correct decision. This is essentially how betting works, for example, when it is not entirely chance based (like horse racing). With a math stat masters, I would hope you would understand that outcomes are not all weighted with the same probability.

    The videos are not saying ‘forget about whether the argument is right or wrong’. They are saying ‘we don’t know whether the argument is right or wrong and we never will for certain. However we do know that certain people with experience in the fields important to the decision are giving us evidence pointing us towards a closer probability to right than wrong, so as they have more experience with the fine details we should use this probability to influence our decision.’

    PS I agree with you about Pascal’s Wager. However, that doesn’t work not because the method is flawed but because there’s no way of skewing the argument – the matrix remains 4 outcomes which we don’t know the probability of. Here, we can clearly pick up evidence that changes the size of each cell in the matrix, making this method a very useful way to making a decision. And the more experiments and studies that are done, the clearer those outcomes become.

  5. We could apply this child like reasoning to any imaginary hypothetical situation and come to the same conclusions about action that he did for global warming.

    Let’s make up one. Car tires exploding on the highway are the number one cause of accidents. Sometimes people die when they explode. Therefore you should stop your car every 50 feet and check your tires so that you won’t die from exploding tires.

    Now if we make his ridiculously over simplified chart, I can argue that you should at least stop your car every 20 ft and check because you could die, and if your wrong you will die.

    Simply put it does not matter what you are arguing about the result is always the same, whether the reasoning is sane or not.

  6. How science works: gather data, make a model, make a prediction from it, and watch to see if that prediction occurs. The more unlikely the prediction, the bigger credibility you give the theory if it occurs.

    So for general relativity, it predicted a different rate of advance of the planet Mercury’s perihelion from that of the Newtonian theory. Eddington went to the Gambia for a solar eclipse and got a measurement for Mercury in accordance with the prediction of general relativity. And from that single experimenal result basis the theory of general relativity became established as one of the two building blocks of modern physics.

    By comparison, the theory of global warming has been making many predictions – and getting many confirmations.

    More than twenty years ago, the models were predicting for the north and west of Scotland a pattern that would be warmer, windier and wetter. That is exactly what we have got.

    Now of course it may be that over a longer period some other factors may somehow cut in and the situation reverts to the staus quo. But the question is: is it worth taking that gamble? If a series of surveyors look at your house and tell you that its foundations are cracking because it’s built over old mine workings, do you ignore them on the basis that it’s just possible that they might be wrong?

    In the case of climate change, if we act on it now, we not only cover ourselves against the climate predictions, we also tackle two other crises. One of these is the problem of declining supplies of oil, which mean that we have to get away from our dependence on it. And the second is the current global financial crisis, where we need to stimulate economic recovery by kickstarting new industries.

    If the economies of the world had been investing more in new carbon-reduction R&D and less in financial services, we might all be better off in practical economic development terms now.

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