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"There's no way in hell that we even REMOTELY know all the sources and sinks for CO2. To assume so is the height of arrogance."

Sinks. perhaps not. Recent sources, yes: CO2 from fossil fuels has a different distribution of carbon 13/14 than CO2 from other proposed sources, the he observed isotopic trends are very good fit to CO2 from fossil fuel.

Sinks. perhaps not. Recent sources, yes: CO2 from fossil fuels has a different distribution of carbon 13/14 than CO2 from other proposed sources, the he observed isotopic trends are very good fit to CO2 from fossil fuel.

I thought that it was the ratio of C13 to C12. And the discussions that I have read make me wonder about the accuracy of the methodology. The source that I read described that the most common Carbon isotope is C12, but C13 is increased in the atmosphere when fossil fuels are burned. So the ratio of C13/C12 in today's atmosphere is compared against air captured from ice cores and other sources from the past for the ratios during those periods. Increases in the C13/C12 ratios indicate more fossil-fuel-derived Carbon. The problem I have with that is the levels of C13 are about 1% of the levels of C12, so you are talking about a very small ratio, and therefore the potential for error in comparing is high.

Sinks. perhaps not. Recent sources, yes: CO2 from fossil fuels has a different distribution of carbon 13/14 than CO2 from other proposed sources, the he observed isotopic trends are very good fit to CO2 from fossil fuel.

My understanding is that C-12 in the atmosphere tends to get turned into C-14 as a result of solar radiation; Carbon-14 dating is predicated upon the assumption that while something is alive, the percentage of C-14 within it will be roughly equal to that of the atmosphere; after it dies, the percentage of C-14 will constantly decay.

Fossil fuels would have a lower percentage of C-14 in them than the atmosphere as a whole, but so would any other natural sources of "old" carbon.