- #106
Coldcall
- 256
- 0
Vanesch,
I'm not going to get into a slanging match about the defintion of chaos, but this wiki defintion should suffice:
"Chaos theory is an area of inquiry in mathematics, physics, and philosophy which studies the behavior of certain dynamical systems that are highly sensitive to initial conditions. This sensitivity is popularly referred to as the butterfly effect. Small differences in initial conditions (such as those due to rounding errors in numerical computation) yield widely diverging outcomes for chaotic systems, rendering long-term prediction impossible in general"
"So for this chaotic "weather" I could calculate rather well-defined "climate", and I could also calculate the influence of a changing boundary condition (sigma) on "climate" - even though the underlying "weather" is totally chaotic.
(again, I need to emphasise that this is a toy example for illustrative purposes only, and has nothing to do with a real climate system)."
Exactly, so what is your point? All you've shown is what we know already about chaotic systems. On the one had you say that using your simple example tells us we can make average projections/predictions which within a margin of error are correct-ish. We've always known that.
Then you go on to admit that your example is nothing like the climate system. Correct.
"Don't confuse issues please, so-called self-organisation has nothing to do with the definition of a chaotic system as we take it here."
Theres no confusion, but the climate is indeed self-organising. And it is relevant because we are discussing the stability factor which you brought into the discussion with the attractor, and the self organisation of the climate with negative and positive feedbacks is what helps it stay stable. Its the positive and negative feedbacks which applies self-organisation to such a system as the climate otherwise it would not have stayed so stable.
Do you not agree with that above statement? If not, why not?
"Absolutely not. You should maybe try to understand what the scientific AGW claim is. It is not about "rendering the climate chaotic", or "rendering the climate instable" or something of the kind. It is about changing the climate under the influence of human activities. And changing the climate means "changing average weather"."
Ahh but it should be about rendering the true physics of the (chaotic) climate into the climate models because otherwise they are not describing anything we know of in the physical world.
And yes it does appear to be rendering the climate as "unstable" if we add more human Co2 emissions to the mix. They talk of tipping points and run-away warming which would be events causing instability to the once stable climate. This is what we are supposed to be getting so worried about.
"So for the near-term projections (next century or so), any "chaotic behaviour" of the climate system itself doesn't really matter - and these are the only projections that matter on the level of political and societal decision making."
It seems to me you are saying that we can just add a huge caveat re margin of error and that will insulate from any major errors in policy making based on those projections. That depends on measures taken in view of such a projection.
How large is that margin of error? Look i could say that the temperature will not fall or increase within a + or - 2 degree spread in the next 50 years. I will likely be 100% correct, but from a scientific point of view its a worthless statement. I don't need any science to make that projection, just common sense.
"There can be an academic question of whether on the very long run, the 30-year weather average itself (climate) has a chaotic dynamics - in other words, whether the chaotic behavior of the underlying weather dynamics has very slow components that exhibit themselves a chaotic dynamics. I guess that's an open question, but it has nothing to do with the social implications of AGW."
Its not just an academic question. As I said earlier if they are building climate models which are supposed to (with some degree of accuracy) describe the physical climate then it is important to factor in the chaotic nature of the beast - so to speak.
It seems to me you are saying that we can ignore the physics of chaos and build an accurate climate model which does not take it into account.
And reading on how you treat "chaos" it seems to imply that you think the only chaotic factors which would be relevant would be dramatic ones which cause the system to spin out of control or become unstable.
For instance the butterfly effect shows how a small almost negligible disturbance can cause a much greater effect in another part of the system. That's chaos and it needs no dramatic tipping point to be classed as an important property of complex non-linear systems - such as the climate system.
What you appear to say above is that there is no such effect with the climate, or if there is we can account for it and its not important for projections. Since we don't even know what the causal sensitivity is in the climate i find it really diffiult to be satisifed with your hand waving away of the chaotic effects in climate systems.
So let's put it to the test, as science should be done. But so far the GCMs have failed every test and i have referenced on this htread the many independent papers which politely mock the models ability to project or predict anything significant.
PS: Just to add i sense a serious contradiction in your argument (if you are supporting the run-away warming). On the one hand you want to minimise the amplitude of chaotic effect, but that contradicts the idea that Co2 is going to cause the system to tip into some new dangerous configuration. Can you not see the contradiction?
I'm not going to get into a slanging match about the defintion of chaos, but this wiki defintion should suffice:
"Chaos theory is an area of inquiry in mathematics, physics, and philosophy which studies the behavior of certain dynamical systems that are highly sensitive to initial conditions. This sensitivity is popularly referred to as the butterfly effect. Small differences in initial conditions (such as those due to rounding errors in numerical computation) yield widely diverging outcomes for chaotic systems, rendering long-term prediction impossible in general"
"So for this chaotic "weather" I could calculate rather well-defined "climate", and I could also calculate the influence of a changing boundary condition (sigma) on "climate" - even though the underlying "weather" is totally chaotic.
(again, I need to emphasise that this is a toy example for illustrative purposes only, and has nothing to do with a real climate system)."
Exactly, so what is your point? All you've shown is what we know already about chaotic systems. On the one had you say that using your simple example tells us we can make average projections/predictions which within a margin of error are correct-ish. We've always known that.
Then you go on to admit that your example is nothing like the climate system. Correct.
"Don't confuse issues please, so-called self-organisation has nothing to do with the definition of a chaotic system as we take it here."
Theres no confusion, but the climate is indeed self-organising. And it is relevant because we are discussing the stability factor which you brought into the discussion with the attractor, and the self organisation of the climate with negative and positive feedbacks is what helps it stay stable. Its the positive and negative feedbacks which applies self-organisation to such a system as the climate otherwise it would not have stayed so stable.
Do you not agree with that above statement? If not, why not?
"Absolutely not. You should maybe try to understand what the scientific AGW claim is. It is not about "rendering the climate chaotic", or "rendering the climate instable" or something of the kind. It is about changing the climate under the influence of human activities. And changing the climate means "changing average weather"."
Ahh but it should be about rendering the true physics of the (chaotic) climate into the climate models because otherwise they are not describing anything we know of in the physical world.
And yes it does appear to be rendering the climate as "unstable" if we add more human Co2 emissions to the mix. They talk of tipping points and run-away warming which would be events causing instability to the once stable climate. This is what we are supposed to be getting so worried about.
"So for the near-term projections (next century or so), any "chaotic behaviour" of the climate system itself doesn't really matter - and these are the only projections that matter on the level of political and societal decision making."
It seems to me you are saying that we can just add a huge caveat re margin of error and that will insulate from any major errors in policy making based on those projections. That depends on measures taken in view of such a projection.
How large is that margin of error? Look i could say that the temperature will not fall or increase within a + or - 2 degree spread in the next 50 years. I will likely be 100% correct, but from a scientific point of view its a worthless statement. I don't need any science to make that projection, just common sense.
"There can be an academic question of whether on the very long run, the 30-year weather average itself (climate) has a chaotic dynamics - in other words, whether the chaotic behavior of the underlying weather dynamics has very slow components that exhibit themselves a chaotic dynamics. I guess that's an open question, but it has nothing to do with the social implications of AGW."
Its not just an academic question. As I said earlier if they are building climate models which are supposed to (with some degree of accuracy) describe the physical climate then it is important to factor in the chaotic nature of the beast - so to speak.
It seems to me you are saying that we can ignore the physics of chaos and build an accurate climate model which does not take it into account.
And reading on how you treat "chaos" it seems to imply that you think the only chaotic factors which would be relevant would be dramatic ones which cause the system to spin out of control or become unstable.
For instance the butterfly effect shows how a small almost negligible disturbance can cause a much greater effect in another part of the system. That's chaos and it needs no dramatic tipping point to be classed as an important property of complex non-linear systems - such as the climate system.
What you appear to say above is that there is no such effect with the climate, or if there is we can account for it and its not important for projections. Since we don't even know what the causal sensitivity is in the climate i find it really diffiult to be satisifed with your hand waving away of the chaotic effects in climate systems.
So let's put it to the test, as science should be done. But so far the GCMs have failed every test and i have referenced on this htread the many independent papers which politely mock the models ability to project or predict anything significant.
PS: Just to add i sense a serious contradiction in your argument (if you are supporting the run-away warming). On the one hand you want to minimise the amplitude of chaotic effect, but that contradicts the idea that Co2 is going to cause the system to tip into some new dangerous configuration. Can you not see the contradiction?
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