Consumption by plants is mostly carbon neutral, since they release it again later. It looks like individual CO2 molecules survive in the atmosphere only about

Consumption by plants is mostly carbon neutral, since they release it again later. It looks like individual CO2 molecules survive in the atmosphere only about 5 years. But still if you put a pulse of CO2 into the atmosphere, the half life is 30 years and (since it isn't a simple exponential decay) even 100 years from now still 36% of it will be in the atmosphere. In contrast, it looks like methane is gone in 12 years. There's much more detail in the 2007 IPCC report: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10...