tracer,
While there are certainly some uncertainties in the understanding of the global CO2 budget, I think the answer to your question, at least as I understand it, is quite well-understood. See, for example, the IPCC Working Group 1 technical summary, pages 38-41 (available at the IPCC website). Here is a quote from there:
jshore: How does an isotopic analysis distingush between CO[sub]2[/sub] released by fossil fuel combustion, CO[sub]2[/sub] released by deforestation (i.e. burning trees), and CO[sub]2[/sub] released by other sources? The technical summary article you discussed (at http://www.ipcc.ch/pub/wg1TARtechsum.pdf) doesn’t say.
I thought I read a few years back that flux in global temberatures related precisely to cooling/collapsing and heating/expanding cycled in our sun, and that neutrinos or the evidence of times of lesser neutrino output was used as an indicator in this.
I think Bob Forward said it in a lecture I attended or ina magazine article, or excerpt from a book. Something about how the earth had always experienced heating and cooling cycles and likely always would. The term for a cooling cycle was a “something begginning with -m-'s minute”, referring to the relative time these cycles took compared to the total age of the planet, or Sol. I can’t remember precisely.
My understanding of how to distinguish between the different types of CO[sub]2[/sub] in the atmosphere is in the analysis of the percentage of CO[sub]2[/sub] that has C[sub]14[/sub] as compared to the CO[sub]2[/sub] that has C[sub]12[/sub]. Brief summary: C[sub]14[/sub] is a radioactive compound that has a half life of only ~6,000 years. It is constantly being produced in the upper atmosphere as the C[sub]12[/sub] is exposed to the elevated radiation there.
Thus, living organisms currently on the planet (or those that are only recently dead–less than a few thousand years) all contain a certain percentage of C[sub]14[/sub] (no, I don’t know what that percentage is) that is basically equivalent. Organic matter that has been buried under the earth for millions of years, however, effectively has 0% C[sub]14[/sub]. Thus, if you measure the percentage of CO[sub]2[/sub] in the atmosphere that is composed of C[sub]14[/sub], it has been steadily decreasing. This is evidence that the CO[sub]2[/sub] concentration in the atmosphere produced by fossil fuel consumption is rising (though, CO[sub]2[/sub] produced by a volcanic eruption would also decrease the C[sub]14[/sub] percentage in the atmosphere). CO[sub]2[/sub] produced by deforestation, or by animals exhaling would not decrease this concentration.
Welcome to the SDMB, purple_padre, and thanks for filling us in! My basic understanding was similar except I knew a lot less of the details!
zen101: It is certainly believed that variations in solar output are an important component influencing global temperatures and the best agreement to the temperature record of the last 100 years or so is obtained by including this factor in the climate models. [See Fig. 15 on p. 58 of the IPCC Working Group I technical summary (TS)…This figure used to be available on the IPCC website with an HTML link but seems to no longer be, so you gotta download the PDF file.] However, I am not exactly sure of the status of the specific idea that you discuss of neutrino output being used as an indicator of this.
That’s what I thought the technical summary might be talking about at first, but then I noted that:[LIST=A][li]the only other mention of carbon isotopes in the technical summary discusses the measurement of [sup]13[/sup]CO[sub]2[/sub] in seawater, not [sup]14[/sup]CO[sub]2[/sub], and[/li]the technical summary claims that the isotopic analysis (and the measurement of declining O[sub]2[/sub] levels) “demonstrates that the observed increase in CO[sub]2[/sub] is predominately due to the oxidation of organic carbon by fossil-fuel combustion and deforestation.”[/LIST]
jshore:
I think the neutrino traces are used to corroborate the variations in solar output. I think it was stated that a cooler sun puts out fewer neutrinos than a hotter sun.
As a side note, I thin Dr.Forward said that neutrinos pass through pretty much everything and so measurinf neutrinos on one side of the planet could/should be virtually identical to neutrino levels on the opposite side of the planet. But I may have misunderstood. I was mainly there because of his connection to Science fiction writing (he collaberates with Larry Niven, or advises him on a lot og his work.)