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Why Are We Sure We're Right? #2

Posted on 4 May 2012 by Rob Honeycutt

This is a second installment in this series exploring why we are sure we're right on climate change issues.  In part 1 we heard from Skeptical Science authors Dikran Marsupial, Glenn Tamblyn and Ari Jokimäki.  This time I'm going to take my own stab at the question, and post the thoughts of Dana Nuccitelli and Andy S.

Rob Honeycutt...

What always strikes me as I read both pro-AGW and "skeptic" articles and science on the subject of AGW is this: Absolutism vs relative uncertainties.

On the "skeptic" side I continually read how this is a big hoax, scientists are altering data, "hiding the decline," they are in it for the money, they are perpetrating a fraud, we can't possibly know what the cause of warming is, or nothing we humans could do could possibly alter the climate. These positions range from the extreme with Lubos Motl keeping a list of scientists "who will be jailed," to the mainstream skeptics like Lindzen and Spencer who also attempt to lay out a case for fraud. This entire range of opinions on the skeptic side is absolute in the position that CO2 could not possibly have the effect climate scientists say. Across the gambit of arguments I see very little in the way of consistency. Any argument against AGW is okay and doesn't need to be internally consistent with any other argument against AGW.

On the side of science I read relative uncertainties rather than absolutes. There is a consistent, yet complex, message presented by a large body of published research. Atmospheric CO2 has radiative properties. We are dramatically increasing CO2 levels. Warming is occuring. Ice is melting. Glaciers are melting. Paleo data suggests there are feedbacks. There are uncertainties in the climate response but those uncertainties are constrained via multiple lines of evidence. The puzzle explaining AGW is well filled in, though not all the pieces are in place. It is unlikely adding the final pieces of the puzzle will change our understanding of the final picture.

To flip my own question around, I find the side that is "sure" about their position tends to be the "skeptic's" side. The more compelling argument, for me, is the relative and constrained uncertainties. Given this, there are decisions to be made. How do we take what is an overwhelming amount of evidence suggesting AGW is going to be a problem and balance that against the cost of action within the relative uncertainties?

Is there a chance that climate scientists have gotten this all wrong? Certainly. But the evidence is so overwhelming that the science is correct that it would be morally reprehensible to not take action to curb our greenhouse gas emissions.

Dana Nuccitelli...

We're not sure we're right - science is not about certainty, but rather about probabilities. Many different lines of evidence support the human-caused global warming theory, and that the Earth's surface will warm on average approximately 3°C in response to doubled atmospheric CO2. There is a chance the climate sensitivity to CO2 may be lower, but the odds of low sensitivity are slim, and it would be poor risk management if we were to ignore the high probability that our current path poses substantial risk for future generations.

Ultimately, as described so well by Greg Craven, our response does boil down to risk management. The scientific evidence clearly supports the human-caused global warming theory, and very harmful consequences are a possible (and probable) result if we continue with business-as-usual. The consequences if we choose to address that risk (by reducing greenhouse gas emissions) and the theory is wrong amount to a very small economic impact.

In short, we think we're right because the scientific evidence overwhelmingly supports our position, and reducing greenhouse gas emissions is clearly the correct risk management approach even if we're somehow wrong.

Andy S...

For most of my career, I have worked as an industrial scientist, either as an employee or consultant. It has been my responsibility to offer advice to employers and clients on when to go ahead, when to wait to get more data or when to drop a project. In practice, the data are usually inconclusive, often there is a real risk that the underlying technical model is wrong, and even successful outcomes have a large range of uncertainty. How do I know I’m right? I don’t. All I can do is honestly lay out all the pros and cons and use my best judgement in my recommendation.

Philosophically speaking, we can never claim perfect knowledge or certainty, especially about how events will unfold in the natural world. The best that we can do is to avoid bias, use multiple lines of evidence and to refine our ideas through discussion, criticism, testing and logic. From all my reading and attending conferences over the past few years, I am sure that climate science meets the highest standards of enquiry. It is clear beyond any reasonable doubt that our greenhouse gas emissions, mainly from fossil fuel use, are changing the atmosphere and that this will change the climate. It is going to get hotter and weirder, even if nobody knows precisely how hot, how weird or how fast the change will be.

No successful businessman can wait to make an investment decision until he has proof that all uncertainties and risks have been reduced to zero. Any delay, in the real world, means that the opportunity will go away or that someone else will seize it. Some climate skeptics claim that important decisions cannot be made until all the risks and uncertainties have been eliminated. These people obviously have never worked in a successful business.

We can’t ever know we are right. All we can do is rely on the best information we can get. Luckily, the knowledge provided by modern climate science is solid and consilient. But reliable information is only valuable if we act on it.

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Comments 51 to 57 out of 57:

  1. Jose - where do you get the idea that MODTRANS does? Look again the RTEs.
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  2. scaddenp @51
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  3. Then you appear to have misunderstood it. The equations are integrated over the height of atmosphere. How else could temperature be used? Again, do you understand why GHG effect depends on a temperature?
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  4. Tarcisio José D @45, there is no point saying the model "... cannot explain the behaviour ... presented by the atmosphere". Clearly the model explains the radiative behaviour of the atmosphere very well:

    Note that this agreement between a 1987 model using an approximation of atmospheric conditions prevailing at the time of observation, and predicting the resulting TOA radiative imbalance very well.

    This is the prediction compared to observation of an earlier (1979) model using more precise atmospheric conditions as determined by a radiosonde:

    This image is from Conrath 1979, a detail of which is reproduced in my post.

    If your theory of the radiative behaviour of the atmosphere predicts a substantially different result to that predicted by these models, as it must if you claim they "cannot explain the behaviour" of the atmosphere, then your theory is falsified by the observational evidence. It is that simple.

    So in scientific terms, there is no argument here. There is simply the choice of following you in believing a favoured theory in preference to the observations, or accepting the observations and the theory that predicts them.
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  5. Dear Dr. Tom Curtis.

    I am not saying that the "model" can not predict the Toa radiative imbalance. What I am saying is that "Models" can not be used to calculate the effect of possible changes in CO2 concentration or variations of cloud cover.
    Let's see.
    Tyndall found for the nitrogen gas, an "absorption" of 0.33% on a pipe 48 'or 1.22 m.
    This result indicates a tramitância of 0.9967 / m.
    If we calculate the attenuation of IR radiation from the ground to the center of mass of the atmosphere 5000 meters meet -58.83 dB. This tells me that the atmosphere is opaque to IR radiation or, in other words, it retains all the heat. What is measured in the TOA is radiation own radiation to the atmosphere and not the ground. Note that this is a simplified calculation for the real would have to still apply the cosine-integral point to point because we are working within the so-called near field.
    So we have two systems.
    The first, which transfers heat between the ground and the atmosphere (and vice versa), between 0 and 5000 meters, the second trasfere that heat from the atmosphere to the space (and vice versa) of 5000 meters upwards. Each with its temperature and its composição.This explains the effect diode like.
    Now if we consider a transparent atmosphere and apply the theory of isotropic radiator, by calculating the attenuation from 1m to 5.000m we meet 20log(5,000)=-73.9dB result that belies the "absorption" of gases that are not part of the GHG coctel.

    If you left any doubt consult a physicist.
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  6. Tarciso
    are you relying on 150 years old measurements, performed only at surface pressure and (unspecified) room temperature and not spectroscopic and still claiming that more recent radiative transfer codes with updated data are wrong? I don't think there's any need to comment any further on this.
    Also, radiative transfer calculation are indeed perfomend using the cosine integrals, though your point on near field is wrong.
    Finally, emission by small volumes of air with a random distribution of emitting particles is isotropic as well as the overall atmospheric emission (hint, emission is incoherent).

    You are clearly talking about one thing you didn't study deeply enough. It's not a problem per se, but I'd suggest that before coming to any conclusion, let alone claiming that decades of radiative transfer studies are wrong, you take more time studying it.
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  7. "If you left any doubt consult a physicist" - that's a funny comment to leave on this forum!

    As Riccardo says, your statements here clearly show that you are criticizing something you havent understood. The responses have been trying to find out where you have gone wrong (eg do you understand why lapse rate is important?) and to encourage further study. It would be far more constructive if you took some time to study what the theory actually says instead of what you think it says. You can get plenty of help here on that.
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  8. Hi Rob, don't want to go too much offtopic here, but I think you're wrong about one thing. In commenting on an Amazon review of Mann's "The Hockey Stick and the Climate Wars" you said that "'Mike's Nature trick' was merely adding on the modern temperature record to the proxy reconstruction. Mann just happened to be the first researcher to do that. The results were published in the journal Nature."

    As discussed on pages 39-40 of the book, in 1993 Raymond S. Bradley and Phil Jones published a Northern Hemisphere reconstruction, using a "composite-plus-scale" method to combine the proxies and relate them to the modern instrumental record, and this featured in the IPCC SAR.

    It's worth looking at the SAR, the graph shows this decadal summer temperature reconstruction together with a separate curve plotting instrumental thermometer data from the 1850s onwards.

    As far as I can tell, Mike's "Nature Trick" was different in that he used a different methodology to relate the proxies to the instrumental record. Unfortunate phrasing by Jones, and this specific point doesn't seem to be covered by explanations as far as I can recall.
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