William M. Briggs

Statistician to the Stars!

Stream: Attack Of The Black Swans From Outer Space!

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Today’s post is at The Stream: “Attack Of The Black Swans From Outer Space: Nassim Nicholas Taleb and his co-authors fail to show their precautionary principle provides any guidance in climate policy.

Aliens from outer space utterly hostile to humanity might attack! They’ll know we’re here because of our electronic emissions, which continuously bathe the earth in a soft glow. If these aliens discover us and manage to get here, it’s obvious that mankind is kaput. As in wiped out. À la mort.

Solution? Hide! Cease immediately all use of anything and everything powered by electricity. Sure, this necessary action will cause some inconveniences such as the ruination of the world’s economy and maybe the odd mass starvation since food will become scarce. But, hey, we’re talking about the survival of the human race. Don’t you care what happens to people? You brute.

What’s the likelihood of an alien attack? It’s complicated, but all the best scientists say it’s not impossible. Anyway, what’s the difference? As long as the chance is non-zero and the costs of failing to act are near infinite, shutting down the world is the only sane move.

What’s that you say? The burden of proof is on me? There’s no evidence of a forthcoming invasion?

What are you, some kind of denier? …

Go there to read the rest.

I was asked on Twitter about the “falsification” of climate models. Models are falsified when they say, conditional on their innards, “The probability of X is 0” and X happens. Since the output of the global average temperature from any given model is a point, or anyway that’s what we see, then unless the actual temperature matches that point, the model is formally falsified.

The way around this is either to add some uncertainty to the point or to use an ensemble of models and interpret them probabilistically. The latter approach is more usual. But it isn’t done well. If the “envelope” of the ensemble doesn’t contain the reality, again the models are falsified. Unless a statistical model is fit to the ensemble, as is done sometimes in weather forecasting, it’s very easy to falsify the models.

Mental “fuzz” is usually added to deterministic models so that, in the minds of their creators, the models aren’t falsifed. And this isn’t crazy because it’s rare in physics experiments to expect the reality to perfectly match the predictions. But unless this is done formally, there can be disagreements.

This is why skill is often used to verify. Skill is a measured improvement over some simplified model, like persistence. Persistence says next year will be just like this year. Climate models can’t beat persistence, thus they don’t have predictive skill. I speak loosely here, and even more loosely in the Stream piece, but it’s obvious that the models are busted.

Whether they have hindcasting skill is irrelevant. Hindcast skill is the ability to fit past data, which is no great feat.

25 Comments

  1. I was really sad to see that Taleb said those things. I really enjoyed Black Swan, and thought that he had a good handle on predictability and risk.

    But comparing uncertain, falsely predicted future scenarios to certainly bad economic crippling and coming down on the side of the former makes no sense. In his books he talks about all kinds of fallacies and biases, and I think we’re seeing him succumb to one.

    I hope it isn’t the Fallacy of the Desired Solution, but it might be the more relevant Fallacy of Trying to Stay Relevant.

  2. I like the comparing Pascal’s Wager to the Precautionary Principle. It really does fit. Also illustrates the metaphysical nature of the Precautionary Principle.

    “They didn’t, so we cannot claim to know what the effects of carbon dioxide additions or deletions would be (within the limits of possible human actions).” Yes. It is not that the theory is disproven, it’s that it’s NOT proven.

    It does become difficult to explain how probabilistic models are falsified. People don’t understand error margins, etc. They unfortunately fall for the “mental fuzz”. In medicine, they hire a lawyer and sue for “mental fuzz”. I suppose skeptics could take up malpractice climate science lawsuits like the “failure to act on climate change” ones teachers have taken to prostituting their students out for, but skeptics don’t usually think that way. Next time a personal injury lawyer claims drug X did bad things, perhaps we should hit him with the rhetoric of climate change and prove he’s a science denier!

  3. Sheri, there are major fallacies underlying Pascal’s Wager and, correspondingly, the Precautionary Principle (if it operates on the notion that infinitesimally small probability times infinite amount of loss or gain gives a finite expectation value of loss or gain).
    See my post, and references contained therein, particularly the “St. Petersburg Paradox”
    http://wmbriggs.com/post/8821/
    Always like to blow my own horn!

  4. Saw it, read it and commented on it, Bob.

  5. The St. Petersburg Paradox was solved by Daniel Bernoulli by the introduction of utility. People who use the precautionary principle rarely supply a utility function. It’s not even clear if one exists for AGW response.

  6. Pascal’s wager doesn’t work, a devout catholic may end up in muslim hell.

  7. A ridiculous analogy, and then more parsing around with models… Never mind the piles of other visible evidence – it’s all aliens and computer models!

    JMJ

  8. Briggs

    July 21, 2015 at 11:59 am

    JMJ,

    Wait. You’re going with the alien theory?

    That may explain mayor de Blasio.

  9. Read a useful blog on failed climate predictions by Paul Matthews: ‘The skillful predictions of climate science.’ https://ipccreport.wordpress.com/2013/11/20/the-skillful-predictions-of-climate-science/

  10. Dav, I did use a Decision Analysis approach for Pascal’s wage, a mini-max “regret” principle, and I suppose the same could be applied to a Precautionary Principle problem.

  11. Why is it that the invokers of the Precautionary Principle never apply it to the invocation of the PP itself? Certainly, if it’s valid then it must submit to its own standards or be considered worthless.

    As for aliens, anecdotal evidence suggests they’ve been here at least since the Roswell incident and from what I can see our government has done more damage to life, liberty, and the pursuit of happiness than any undocumenteds from beyond the ionosphere. If they’re so dangerous they sure haven’t proved it yet. In fact, they’ve been a multi-billion dollar benefit to the entertainment industry. I’m eagerly awaiting the X-Files reboot, aren’t you?

    Pascal’s Wager includes the false premise that mere belief in God is sufficient for reward. As Someone once said, “even the demons believe.”

  12. Pascal’s wager fails because the problem is not binary (i.e. True -False). Likewise is climate not a binary issue.

  13. Bob,
    I saw that but, in general, you can’t find an optimum “value” if the utility function is not convex. In both Pascal’s Wager and the Precautionary Principle the “value” increases to one side or the other and there is no optimum solution.

  14. Sander van der Wal

    July 21, 2015 at 2:48 pm

    there have been lots of Climate Changes in the past, but visits from Aliens, not so much. Therefore, *investigating* Climate Change is a good idea.

    Believing your own models hardly ever is a good idea, given that almost most scientific theories are falsified.

    So, the Precautionary Principle tells you to investigate Climate Change, but not Aliens, and not to believe the resulting Climate Change models.

  15. Thanks for a great post about the PP! I enjoy Taleb’s books but he seems to have this belief that “randomness” is a cause for things. Which I learnt here is just silliness.

  16. Sander van der Wal: “Ancient Aliens” begs to differ with you. There have been many possible visitations in the past. Since the show is on the History channel and people with what appear to be university degrees are discussing this, it must be true. (/sarc)

  17. Briggs:

    L Ron Hubbard has already reported on the infiltration of Aliens

    He’ll help you get rid of them if you’ll just believe

  18. Mayor de Blasio?

    http://www.nytimes.com/2015/07/16/nyregion/mayor-de-blasio-in-italy-next-week-will-address-a-vatican-conference.html?_r=0

    How can ANYONE continue to deny that the Pope’s Encyclical was rubbish and a lever into the hearts and minds of hundreds of millions of people in the name of GAIA

  19. “there have been lots of Climate Changes in the past, but visits from Aliens, not so much. Therefore, *investigating* Climate Change is a good idea.”

    The fear or concern is not Climate Changes in the past, but Climate Changes Caused by Human Emissions of CO2. This has never occurred in the past. Hence the criticism of the analogy used by Dr Briggs is invalid.

    (Analogies are powerful tools, but many people tend to get confused by them as they cannot separate what is important in an analogy, and what is cosmetic.)

  20. Will Nitschke said: “there have been lots of Climate Changes in the past”

    Will, climate change was: human invented how to make fire artificially -> from few acres of deserts, they created big deserts; produced dry heat there is effecting on great distances negatively on many different ways. All made by rubbing two sticks together. Now human has bulldozers and cement mixers – to save storm-water and improve the climate!!! Nobody is talking about ”improving the climate” B] is it perfect climate now, to stop it from changing?!

    #2: you people are confusing / substituting your ”phony global warming” with climatic changes; because you are ashamed to admit that is no warming! please, stop wetting the bed from fear of something that doesn’t exist – read my post, where is ”proven beyond any reasonable doubt” that: not enough extra heat will be in 100y accumulated on the whole planet, as much as one Al Gore’s fart: https://globalwarmingdenier.wordpress.com/2014/07/12/cooling-earth/

  21. I’m quoting someone else, not agreeing with the quote. The point I was making is that people tend to nit pick analogies in ways irrelevant to the argument being made. But it’s even worse than that. The Hominidae family has been around for 15-20 million years. Past climate changes have had plenty of opportunity to kill off humans. But of course it’s all so vague as to what alarmists are worried about. Maybe it’s not about killing off humans, but shortening our life spans in some way. It’s a sort of vague feeling that bad things will happen, buttressed by pointing to a group of speculative papers collected by the IPCC, that none of them have read.

  22. Will Nitschke @ JULY 21, 2015 AT 6:55 PM
    “The fear or concern is not Climate Changes in the past, but Climate Changes Caused by Human Emissions of CO2. This has never occurred in the past. Hence the criticism of the analogy used by Dr Briggs is invalid.”

    The source of CO2 is immaterial there is no significant difference, chemical or physical, from a human source, a volcanic source, or an extraterrestrial source. The Deccan traps, not to mention many other volcanoes, produced more CO2 than any sum of human sources.

  23. LOL! Ya’ know, this alien black swan thing would work even better as an analogy for religion!

    JMJ

  24. Mysterian,

    As I noted earlier, you’re getting yourself confused by interpreting the analogy in an irrelevant way. The concern is not over rising or declining levels of CO2. CO2 has always increased or decreased throughout history. The only thing it is not, is stable though time. The claim is that what humans have done, has upset the ‘natural balance’. What nature does naturally, is not what worries alarmists. (Or if it does, it is considered fait accompli and not fussed over).

    But if you really want to focus on the trivial, and be a like a dog too stubbon to give up your bone, then swap ‘alien invasion’ for ‘extinction level asteroid event’. That way the analogy is ‘fixed’ for the anally retentive.

  25. JMJ: Yes, it does fit. And you are always telling us why religion should not be used as a method of governing. So, it follows that climate change should not be used as part of governing, since it’s little more than religion painted with a faux science sign.
    Religion has always been “black swans” and it does not deny this. That’s why it’s about faith. You know, like belief in the liberal play book or class envy or any number of fantasies people indulge in.

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