Saturday, March 7th 2009, 10:46 AM EST
By Research physicist Dr. Tom Quirk, a former University lecturer, fellow of three Oxford Colleges, and a board member of the Australian based Institute of Public Affairs.
The variation in the ratio of carbon-12 and carbon-13 isotopes is a sensitive measure of changes in atmospheric CO2. These measurements are expressed in units of ï¤13C and the values can be divided into two classes of CO2, that from biogenic or fossil fuel sources with ï¤13C = -26 to -28 and from oceanic sources with ï¤13C = +2 to -7. Over time the atmosphere exchanges CO2 with these sources and so has a ï¤13C determined by the magnitude of these exchanges.
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