Climate Computer Models

April 8, 2010

The Washington Post has an article pointing out how the climate contrarian community has now focused heavily on the unreliability of computer models (as if this weren’t already the case).

It’s true, as they say, that climate models are only educated guesses… but educated guesses are, in many cases, the best we can do, and that alone isn’t a reason to discard them. I make educated guesses about how long to cook my dinner, for instance, just as I make educated guesses about the weather for the day, the reliability of bridges, and the likelihood of you having an ace in your hand. That information is invaluable to me, and I rely on it. I think Gavin puts it pretty well:

If policymakers don’t heed the models, “you’re throwing away information. And if you throw away information, then you know less about the future than we actually do,” said Gavin Schmidt, a climate scientist at NASA’s Goddard Institute for Space Studies.

“You can say, ‘You know what, I don’t trust the climate models, so I’m going to walk into the middle of the road with a blindfold on,’ ” Schmidt said. “But you know what, that’s not smart.”

More importantly, however, even though I rely on educated guesses, as well as all manner of scientific and non-scientific models, to help me make determinations about what I should do, I also make decisions about what to do independently of educated guesses and projected outcomes. In some cases, I make decisions about what to do with only a loose expectation or understanding of the impacts of my actions.

So, for instance, I can understand, more or less, that when an animal is raised on a factory farm, that it endures some substantial amount of discomfort, and may even endure some degree of suffering. Do I need to know the extent of this discomfort and suffering to make a determination about what to do? By my lights, not really. I just need to know that there is some morally significant discomfort and suffering, that a given threshold has been passed. This is enough to know that, arguably, I ought to change my behavior with regard to animals raised on factory farms. The models don’t actually matter so much.

What I’ve just given you is a considerably more consequentialist reason than one that I might normally give — I still need to know that there is suffering, for instance; and for the reason that there is this suffering, I therefore need to reevaluate my behavior — but it suffices to show that even reasoning along pretty strict consequentialist lines, hand-waving at the magnitude of discomfort and suffering is all that’s needed.

In the case of the climate, how much does it really matter if the climate goes up by one degree, up by ten degrees, or down by one degree? If human activity is having an effect on the climate, it seems reasonable to me that this matters, and that we ought to pay attention to this. The magnitude of the climate change — or what the models say — doesn’t affect the status of our requirement to do something about it.

Having said this, climate models do raise questions about the correct or effective anticipatory responses, but that’s a totally different question.



  1. Steve Easterbrook has a couple of published papers that sort of knock this into a cocked hat

    # Easterbrook, S. M. and Johns, T. C., Engineering the Software for Understanding Climate Change. Submitted for publication.
    # D. Matthews, G. V. Wilson and S. M. Easterbrook, Configuration Management for Large-Scale Scientific Computing at the UK Met Office. IEEE Computing in Science and Engineering .

    As well as any number of posts on the subject on his blog, like this one

  2. A point that even RealClimate finds unlikely to be persuasive (since they don’t blog on it) is the pretty clear picture that’s been developed from paleoclimate work in the last five years or so of what the equilibriuum climate will look like at various CO2 levels that we’ve already surpassed or will achieve soon. For example, at 350 ppm CO2 (last seen about 3.3 million years ago in the mid-Pliocene), global average temperatures were 2-3C higher, sea level was on the order of 25 meters higher, and massively increased numbers of tropical cyclones reached as far north as BC and Svalbard.

    The amount of time needed to reach such a state is the big question, and we may hope that the models tell us so. Of course our situation isn’t anywhere near so simple or benign since we’re already at 390 ppm and are unlikely to get things stabilized at less than 500 ppm. When we add to the unprecedentedly rapid CO2 transient the effect of fast carbon feedbacks like permafrost melt (and note that these are not a component of the equilibrium state), it becomes hard to exclude the possibility of some very unpleasant abrupt changes. Oh yeah, and ocean acidifcation, which is entirely related to the speed of the CO2 build-up.

    What is it with East African plains apes and Russian roulette?

    My favorite quote of the moment, from John Kenneth Galbraith: “Faced with the choice between changing one’s mind and proving that there is no need to do so, almost everyone gets busy on the proof.”

  3. Knock exactly what into a cocked hat, Eli?

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