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Climate Scientists Encounter Limits of Computer Models, Bedeviling Policy (wsj.com) 219

magzteel shares a report: For almost five years, an international consortium of scientists was chasing clouds, determined to solve a problem that bedeviled climate-change forecasts for a generation: How do these wisps of water vapor affect global warming? They reworked 2.1 million lines of supercomputer code used to explore the future of climate change, adding more-intricate equations for clouds and hundreds of other improvements. They tested the equations, debugged them and tested again. The scientists would find that even the best tools at hand can't model climates with the sureness the world needs as rising temperatures impact almost every region. When they ran the updated simulation in 2018, the conclusion jolted them: Earth's atmosphere was much more sensitive to greenhouse gases than decades of previous models had predicted, and future temperatures could be much higher than feared -- perhaps even beyond hope of practical remedy. "We thought this was really strange," said Gokhan Danabasoglu, chief scientist for the climate-model project at the Mesa Laboratory in Boulder at the National Center for Atmospheric Research, or NCAR. "If that number was correct, that was really bad news." At least 20 older, simpler global-climate models disagreed with the new one at NCAR, an open-source model called the Community Earth System Model 2, or CESM2, funded mainly by the U.S. National Science Foundation and arguably the world's most influential climate program. Then, one by one, a dozen climate-modeling groups around the world produced similar forecasts. "It was not just us," Dr. Danabasoglu said.

The scientists soon concluded their new calculations had been thrown off kilter by the physics of clouds in a warming world, which may amplify or damp climate change. "The old way is just wrong, we know that," said Andrew Gettelman, a physicist at NCAR who specializes in clouds and helped develop the CESM2 model. "I think our higher sensitivity is wrong too. It's probably a consequence of other things we did by making clouds better and more realistic. You solve one problem and create another." Since then the CESM2 scientists have been reworking their climate-change algorithms using a deluge of new information about the effects of rising temperatures to better understand the physics at work. They have abandoned their most extreme calculations of climate sensitivity, but their more recent projections of future global warming are still dire -- and still in flux. As world leaders consider how to limit greenhouse gases, they depend heavily on what computer climate models predict. But as algorithms and the computer they run on become more powerful -- able to crunch far more data and do better simulations -- that very complexity has left climate scientists grappling with mismatches among competing computer models.

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Climate Scientists Encounter Limits of Computer Models, Bedeviling Policy

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  • by hdyoung ( 5182939 ) on Monday February 07, 2022 @01:50PM (#62246793)
    The damage will be done and we'll be in mitigation/adaptation mode. I've said it before and I'll keep repeating it. Scientists and engineers should be thinking very hard about geoengineering strategies. Like it or not, we're almost certainly going to need them.
    • by Joce640k ( 829181 ) on Monday February 07, 2022 @02:02PM (#62246817) Homepage

      The damage will be done and we'll be in mitigation/adaptation mode. I've said it before and I'll keep repeating it. Scientists and engineers should be thinking very hard about geoengineering strategies. Like it or not, we're almost certainly going to need them.

      I've said it too, but not for the same reasons: Every politician out there has heard of geoengineering and is dumb enough to think that they don't have to do anything today (and risk their careers) because the clever climate scientists will fix it later.

      It's ironic that the climate scientists that the deniers are mocking today will be the same climate scientists they call upon to geoengineer that fix for them.

      • Same as covid-iots running to the hospital for help by the doctors who they mocked for years.

        Same as the fools and villains of most classic Sci-Fi... well, the villains sometimes die before they have a chance to ask for saving.

    • Re: (Score:2, Insightful)

      The models are already accurate. This is an argument about the precision of the models. It's like standing in the middle of the street and arguing about whether the bus that's about to hit you weighs 10,000 pounds or 10,050 pounds.
      • From what I understand, the discrepancies are bigger than that. But, yes, the general conclusion is the same.
    • The damage will be done and we'll be in mitigation/adaptation mode.

      Alternatively, we may find out we're systematically underestimating some feedback cycle or overestimating some other effect. I know, that's the optimistic view, and there's no guarantee it's right. That's the problem: we've heard for years "of course there's a problem" so most of us just implicitly believe it. But before we invest trillions addressing it, we should think about how possible it might be that we're getting it wrong.

    • Let's assume that the article is correct and we don't know how to model the climate accurately. Now you want to use this supposedly poor knowledge to do geoengeneering??? You realize that having good climate models are a must to even consider geoengineering, don't you?
  • This might be related to how current climate models don't predict the kinds of extreme weather events we're already experiencing.

    Rather than me paraphrasing I'll just point you at one of Sabine Hossenfelder's excellent videos: https://www.youtube.com/watch?... [youtube.com]

    No-one is being willfully wrong, this is a case of the science being continously developed. Don't be surprised by more stories about "we were wrong, now the best indications are that...".

    • This might be related to how current climate models don't predict the kinds of extreme weather events we're already experiencing.

      I wonder why that might be...

      • Watch the video. This isn't a "climate != weather" thing. It's not about trying to predict specific weather events. It's about the current models' predictions of the number of extreme weather events in a given period of years being nowhere near a correct appraisement.
    • I think it's more like chaotic equations don't necessarily have simple solutions. In some places there are attractors of various strengths, but not over most of the range.

      It's really unreasonable to expect that all problems will be stated precisely enough to determine what the answer should be. One doesn't expect to predict the results of rolling a die, even if one can predict (pretty well) the average result of rolling a hundred dice.

      What's significant here is that really small changes can have really large effects. And we can't predict which way things will twist when we get near the boundary conditions. Which is what we should have expected anyway.

  • Remember when working with models: always err on the side of caution. Assume that your estimates of breaking strength needed are the minimum breaking strength you need to target. If you have error bars in your results, assume that the actual numbers are towards the end that produces the least desirable outcome. Remember this, an optimist is usually disappointed when things go worse than expected while a pessimist is usually pleasantly surprised when things go better than predicted (which is also an easier p

  • Quite a Mouthful (Score:5, Insightful)

    by davide marney ( 231845 ) on Monday February 07, 2022 @02:41PM (#62246951) Journal

    What is really being said here? As near I can tell, it's: our models were wrong, we rewote them, they're still wrong, only now in a different way. Stay tuned.

    • What is really being said here? As near I can tell, it's: our models were wrong, we rewote them, they're still wrong, only now in a different way. Stay tuned.

      But *we are still right*.

    • What is really being said here? As near I can tell, it's: our models were wrong, we rewote them, they're still wrong, only now in a different way. Stay tuned.

      It depends on the quantity that you want to consider "wrong". No, the models are not off by 100% and so climate change isn't real. Much more likely, the models are off by a small amount.

      • by HiThere ( 15173 ) <[ten.knilhtrae] [ta] [nsxihselrahc]> on Monday February 07, 2022 @05:33PM (#62247489)

        Not precisely. The refined models are predicting really horrible results, but we don't think the actual results will be really that bad, so we're looking for how to fine tune them so they aren't so catastrophic.

        This isn't really implausible, but it's certainly not very comforting. Perhaps the clouds will reflect more UV than the model predicts, so things won't warm up quite as much. (That's a correction made to a model around a decade ago, and they decided that the correction was actually correct.) I don't know the details of this one, but the summary indicates that it has something to do with the behavior of cloud wisps.

        It's really a mistake to believe in these models as "this is what will happen". One should think of them as "This is an alarm bell. DANGER. Don't get too close.". They're modeling a chaotic system, and when you approach various boundaries to that kind of system you get behavior that depends on excruciatingly fine details. "The wings of a butterfly" is the traditional way to talk about the kind of detail that you need to know as you approach the boundary, so the real answer is "Don't get near that boundary!!!!"

    • Precipitation is like a conveyor belt that throws heat into space. There is no way to model this.
    • No what's being said is, we didn't like the outcome of our modelling, which was surprisingly bad, and now we're trying tone them down. The new, more advanced generation of models might be correct.
    • Right!

      But we've had 20+ years of
      1) it's settled science, we know what we're doing
      2) we must take extreme action right now or the world will end in 2012, then 2016, then 2020, then...

      And then they realize It's Complicated (R). Will the IPCC still recommend extreme action right now?

      • You are an idiot.
        2) we must take extreme action right now or the world will end in 2012, then 2016, then 2020, then...
        That is a lie. No scientist ever "predicted" anything like that.

  • My dad always said assumptions make an ass out of you and me, ass-u-me.

  • I'd love to see an article where the modelers fed all the available historical data to the their model, less the last ten or twenty years, and then show how well their model corresponded to what was measured in those years.

    If anybody knows of such an article, please let me know where to find it.
  • Every time I want a new computer I complain that mine can't do the job, and I usually get a new one. I don't see much of a difference between me and the climate scientists.

  • One of the most infuriating things about climate policy debates is how lazy, bad-faith "master debaters" seize on uncertainties in data even when the most pertinent fact is beyond dispute: Dumping vast quantities of both greenhouse gases and waste heat into a planetary atmosphere is destabilizing climate and killing people.

    The yearly average death toll from changes that have already occurred now runs in the thousands, with heat waves, floods, fires, and associated disasters occurring on levels found to b

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