First of all C13 is an entirely separate issue. You are confusing two different things in every way. C13 and C14 are completely distinct in this matter.
C14 is a uniquely ideal isotope for identifying atmospheric CO2 for reasons already shown. So why exactly are you suggesting subtracting values of C13 from C14? Taking values of chalk away from cheese is a very strange, not to say weird, form of argument..
It is also nothing to do with the topic you raised when essentially stating human emissions in the atmosphere could not be identified and measured well enough to be sure it was due to anthropic emission. That is plain wrong, for it can and is measured at least by C14 quite precisely.
Isotope analysis produces highly accurate and precise results that correspond to the most basic and fundamental laws of physics. Suggesting the analysis can produce only rough estimates is frankly absurd.
There is no C14 in CO2 produced from fossil fuel. So to put it technically, burning shit loads of it causes the atmosphere to be diluted of C14 concentrations which otherwise occurs naturally.
The only way the current levels of dilution can be accounted for is from burned fossil fuel. Nothing else explains it. The only source of burned fossil fuel which can and in fact does account for the dilution, is anthropic CO2. There is nothing else.
Thank you, stu, for responding to my question and my post. I wasn't referring to subtraction between two isotopes concentrations. My remarks were meant to point out the difficulty of obtaining any arithmetic result from experiment data by subtraction when you are either subtracting two nearly equal numbers ,or subtracting two numbers that differ markedly in magnitude, and neither number is known with much precision or accuracy. I don't question the C-14 content measurements by scintillation counting, I question their interpretation.
The reason I believe that C-13 and C-14 are liable to encounter the same problems with regard to interpretation is that I assumed they were both being used in essentially the same way as markers, i.e., the concentration of both were being monitored. If both C-13 and C-14 are being used in this same way, then I would think that the problems that have plagued interpretation of the C-13 data would carry over to C-14 as well.
But am I wrong about how C-14 is being used?
Do you know
how C-14 is being used as a marker for anthro carbon in the atmosphere? That's really what I'd like to know. I guess I'll have to spend more time with Google!
Incidently, fossil fuels, at least coal, are not zero in C-14. The C-14 content of fossil fuels should be zero, but this is never found in practice so far as I know. Coal for example, when it is burned in large quantities, contributes a measureable amount of C-14 to the atmosphere. C-14 in coal corresponds to a carbon dating of about 30000-40000 years, so obviously that's too young (or is it?, I thought coal was millions of years old!). I don't know where the C-14 in fossil fuels comes from, but a small amount is still there. Uranium is often concentrated in coal, and there is a path to C14 via U decay, so possibly that is one contributor, who knows?
Another thing one would have to correct for is decay of the C-14 spike from the atmospheric bomb tests in the 1950's. If you just looked at C-14 in the air today you are going to see a steady decline in beta emission just due to the decay of all that extra C-14 that popped up in the mid-1950's. I know the competent scientists will be correcting for these things, but there is some pretty shoddy work out there when it comes to climate research. For example the early ice core measurements were apparently misinterpreted because correction for diffusion over the very long times involved was not done properly.
I realize you have more confidence than i do in the early work. As far as I'm concerned we are just now seeing really good work being published. It seems to me that in the 1980s and 1990s everyone was just jumping to conclusions without giving proper thought to their results. It is easy to get caught up in the feeding frenzy once an issue has been popularized and politicized.
The only scientific papers I have read and studied in some detail with regard to AGW were Lindzens, years ago now. It was obvious to me, though he stopped short of coming right out and saying it, that Lindzen had a very low opinion of Hansen's science. I then lost interest in the subject until you guys got me interested again.
