Human fingerprint on atmospheric CO2

George Morrison points out the argument Human CO2 is a tiny % of CO2 emissions says nothing about carbon isotopes and how we know rising CO2 levels are due to human activity. The carbon atom has several different isotopes (eg - different number of neutrons). Carbon 12 has 6 neutrons, carbon 13 has 7 neutrons. Plants have a lower C13/C12 ratio than in the atmosphere. If rising atmospheric CO2 comes fossil fuels, the C13/C12 should be falling. Indeed this is what is occuring (Ghosh 2003) and the trend correlates with the trend in global emissions.

Many thanks to George for pointing out the oversight - I've updated the Human CO2 page.

Posted by John Cook on Thursday, 23 August, 2007

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