The anonymous BBC “reporter” who wrote an article “No let up in greenhouse gas rise” either does not understand the subject or is dishonest.
The article claims that carbon dioxide is “the major contributor to climate change”. It is a lie not claimed by any scientist, but of course most people think this.
That is because they have been told that human generation of CO2 is causing a catastrophic rise in temperatures. What they have not been told is that this claim is based on an assumption of positive feedback, not only that but feedback that must have greater influence than the CO2. Heat trapping by CO2 just isn’t enough to support the claims of the warmists, and they randomly add large positive feedback to models. So even according to climate hysterics the carbon dioxide itself is not the major contributor, the putative feedback mechanism is.
This is not a trivial falsehood. How many times have we read that this is “basic physics”, and that “carbon dioxide is a greenhouse gas” so must be causing the rise in average temperatures? How rarely do the people who tell us this admit that without positive feedback CO2 cannot explain most of the warming since the 1970s? How many state that all the nightmare scenarios claimed in the press require a lot of feedback?
Feedback is very important to a lot of what I have studied and taught. It comes into a lot of physics, into geology and in aviation theory in the principles of flight (stability of an aircraft is determined entirely by feedback). What I can say is that positive feedback is that it is rare in natural systems and essentially unheard of in a stable system [correction: essentially unheard of in a non-linear system which shows long-term stability]. Positive feedback is the cause of instability.
Which thought brings us to an interesting place. Either the temperature has positive feedback, and is likely to be unstable, or else temperature is stable and shows little or negative feedback. The whole climate panic is based on the assumption that the temperature is stable (and so the recent fluctuations are unusual) but that temperature response to carbon dioxide shows positive feedback …
Update: thanks to an anonymous commenter for a useful correction. The comments now contain a brief discussion on stability.
6 comments:
"either does not understand the subject or is dishonest"
Both apply to you in spades.
ianam
In what way have I been dishonest? Where is the evidence that I do not understand the subject?
You are making an assertion, but you have made no argument to back it up. Two possibilities spring to mind. That you do not know enough to back up your statements (you are ignorant) or that you know know I am neither dishonest nor ignorant, and are just making wild swings (you are dishonest).
The only other possibility is that you are unaware of the idea that other people have different thoughts to you, so that you don't know that your assertions need to be backed by argument to have any possibility of relevance. At which point we are back to ignorance.
Notice I have not constructed an argument, but then I have made no assertion.
I do not intend this to encourage the silly alarmists, only to correct a mistaken assertion.
Positive feedback produces instability only it is part of a feedback loop whose gain exceeds +1. See http://en.wikipedia.org/wiki/Nyquist_stability_criterion if you doubt this or wish to learn the truth of it.
Good point, but Nyquist only applies to linear systems. Non-linear systems have much more complicated idea of stability, and climate is a non-linear system if ever there was one!
It does mean I should have expressed this differently. In a positive feedback situation one year's temperature would be influenced by not only the previous year's temperature, but also by the previous year's change in temperature. This is what I have called, inaccurately as you point out, instability.
The climate alarmists assume in their statistical calculations that one year's temperature is independent of the previous year's, and of existing trend. This is what I have called stability.
Now the first case is less stable than the second, so I have some justification, but my wording was misleading. My terminology is inadequate, and I don't know how these relationships should properly be described.
Thanks for the contribution!
Just to clarify, the above is still a gross oversimplification. If you try to look at the reality of feedback in a non-linear system your head is likely to explode.
It is really complicated, which is probably why the climate "scientists" have not even attempted to analyse it, they just assume it accounts for all 20th-century warming beyond the roughly 1 degree from carbon dioxide. Which is of course why their models then attribute all 20th century warming to carbon dioxide and feedback. Lovely circular reasoning - their models tell them that because that is what they told their models.
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