Sheesh. You’re the one who said the following:
Lol. That’s not exactly a strong argument either. Anyway, show me a cite that contradicts the basic claim (and not some strawman) and I will consider it.
Ok, but does that mean yes or no?
Here was my question:
Keep in mind that according to your explanation, the Milankovitch cycle causes the Earth to start cooling despite relatively high levels of CO2.
You made the claim that “the rule” is to assume negative feedbacks in modeling. That’s not a commonly held rule in modeling - it’s uncommon enough that two people who work with with models (I use unstable fluid flow simulations, and I believe jshore has mentioned his modeling experience in the past) haven’t heard of it before. You’re welcome to introduce new ideas that go against the general scientific consensus, but the onus is on you to provide evidence for those ideas. You haven’t provided that.
So every 100,000 to 125,000 years? Do you know off the top of your head the periods of the two eccentricity cycles of the Earth’s orbit?
As far as what drives the temperature-CO2 correlations… we’re back to the feedback loops that you’re so eager to dismiss. Nobody is claiming that CO2 is the only driver of climate change. Nobody’s even claiming that CO2 is always the major driver of climate change. The AGW claim is that the changes in CO2 over the last 150 years are the major driver of the climate change that we’re seeing today. But in same way CO2 changes can drive other factors that influence climate, other factors have the potential to drive CO2 concentration given different initial conditions.
You seem to be have trouble with any relationship that’s not immediate and linear. The Earth’s climate is far too complex to approach with that mindset.
The rule is to assume that a stable system is dominated by negative feedbacks as opposed to positive ones. And I admit that the only things I have to back it up are common sense and the one cite I provided earlier, which is to the website of a climate skeptic who claims some undergrad experience in control of systems.
I agree that for the time being, I haven’t provided enough evidence on this point to establish it.
I have no idea. But the point is that it would seem that according to Jshore, changes in the way that sunlight hits the earth can have a huge impact on climate - even to the point of dominating the hypothesized CO2 feedback loop and turning it on its head.
Initially this strikes me as a stunning admission, but I would need to give it some more thought.
That’s not true . . . I’m not sure how you got that impression.
Surely you’re not suggesting that the Earth’s climate is a stable system.
The Earth’s eccentricity (how “round” the orbit path is) runs on three cycles: one with a period of 95,000 years, one at 125,000 years, and one at 400,000 years. Among other cycles (obliquity, precession) these periods are components of the Milankovitch cycles that jshore referred to.
In another time, solar cycles were the main driver of global climate change. Millions of years ago, the climate was significantly altered by changes in ocean heat transport in response to tectonic shifts that opened new pathways for ocean circulation. Right now, it’s being forced mainly by rapid increases in atmospheric CO2 concentration. A million years from now, it will likely be controlled by some other factor. But climate change is never a singular response to a single factor, and the conditions of the Earth play a large part in determining the response times and feedback loops and responses to a change in any part of the system.
Yes I am. The hasn’t stayed exactly the same for the last million years, but it hasn’t run away into a Venus or Mars-like state either. To use the analogy of the web site I linked to, it has behaved more like a ball rolling around the bottom of a bowl than a ball rolling around the top of an upside down bowl.
I’m not sure what your point is. Do you dispute that the changes of 125000 years ago took place in the face of significantly changing CO2 concentrations? Are you saying that CO2 was unimportant back then?
I fail to see what the problem is with that. Do the models predict that it should run off into a Venus or Mars-like state given estimates of the natural forcings in those time periods? If they did, that would be a problem. However, they don’t. In fact, according to this paper, if anything, there seems to be the opposite problem: i.e., that it is hard to get the models to fully encompass the range of past climates that we have had, implying that they may err on the side of underestimating climate sensitivity. (Note: That is a paper in a prestigious peer-reviewed journal, not the website of some small businessman who apparently worked as an engineer at some point in the past and took undergraduate course in control theory.)
We are saying that one can estimate the importance of various factors such as CO2 and albedo changes and that the resulting behavior seen is consistent with those assumptions.
I have no idea. But that’s not the point. The point is that the Earth’s climate has been relatively stable for some time now. According to the web site I linked to, this supports an inference that the system is probably dominated by negative feedbacks as opposed to positive feedbacks. I realize you disagree with this conclusion, but there it is.
Ok, so again my question:
Interesting, so you believe that the effects of a change in sunlight distrubution was enough to dominate the CO2/warming loop that has been hypthesized?
Putting the word “relatively” in there changes “stable” from a word with specific scientific connotations to a meaningless qualifier with no concrete definition. The fact that the Earth hasn’t swung back and forth between two extremes says nothing at all about the stability of the system.
As both jshore and I have both already said, the answer is “sometimes.”
Whatever, it’s just a matter of semantics. Call it what you will, my point stands.
And was 125,000 years ago such a time?
Simple yes or no question.
Rather than just getting us to answer silly questions that aren’t even sensical, why don’t you actually contribute at the level of the scientific discussion. For example, why don’t you explain what your hypothesis is that can explain the ice age – interglacial oscillations with a low climate sensitivity so that the rise in temperatures due to the known radiative forcing of a certain percentage increase in CO2 is small?
Your point doesn’t stand, and it’s more than just semantics. Words have specific meanings, and the words used to describe scientific concepts have even more specific meanings in that context. When you use the wrong word in a scientific discussion, people are either going to misunderstand what you’re saying or think that you don’t know what you’re talking about.
Your insistence on reducing an entire field of science down to simple yes or no questions is why you’re out of your depth in a discussion like this.
Lol. It’s not a silly question and it’s not nonsensical. I’m simply testing the logical conclusion of your claims, which is that the Milankovitch cycle you posit must have overwhelmed the CO2 feedback that has been hypothesized.
Here’s the question I asked you before:
And here was your answer:
Why should I? Isn’t it possible to raise serious questions about CO2 as a driver of climate change without fully understanding the interplay of other potential factors? Without knowing anything about Milankovitch cycles, one can look at the data and conclude that there is something that turned the alleged CO2 feedback on its head.
Ok, then please explain what the word “stable” means to you in this context.
What about your insistence on dodging an extremely simple question? What should I conclude from that? Maybe you are the one who is out of his or her depth.
More likely, one can just fool oneself into believing that one knows more than people who understand things way more than one does.
What does it mean to “overwhelm” a feedback?
I already answered your question once:
A parameter with a value that isn’t changing doesn’t have a feedback loop. Feedback is a response to changes; positive feedback magnifies the change and negative feedback mitigates it. In a system in which the solar radiation is changing and the CO2 concentration isn’t, there is no CO2 feedback loop to overwhelm.
Perhaps, but in my experience it’s more often the people who claim to understand everything who are fooling themselves – as opposed to the people who admit ignorance.
To push and move a system in the opposite direction of the feedback.
Sorry, but that’s not an answer to my question. As I pointed out earlier, the examples I gave apparently took place in the face of significant changes in CO2 concentration.
Look at the graph I linked to. CO2 levels were changing.
You’re not admitting your ignorance. You are admitting other people’s ignorance. I.e., you are saying that you think that you know better than the scientists themselves (and the National Academy of Sciences, etc., etc.) what they understand and how well they understand it. That is not admitting your ignorance…in fact, it is the exact opposite of that.
You’re going to have to be more specific. I don’t see where you are talking about where CO2 changes significantly in one direction and temperature in the other.