Thursday, August 22, 2013

Does anyone else have a problem with being told that individual CO2 molecules reside in the atmosphere only 3-4 years, but also "more than 20 percent of carbon dioxide released into the atmosphere will remain there over 20,000 years after emissions stop"?

Leaked [IPCC] climate report: Ten nuggets worth noting
The recent rate of increase in carbon dioxide, methane and nitrous oxide in the atmosphere is unprecedented in the last 22,000 years.
...
It is very likely that more than 20 percent of carbon dioxide released into the atmosphere will remain there over 20,000 years after emissions stop.
Skeptical Science:  CO2 has a short residence time
A little quick counting shows that about 200 Gt C leaves and enters the atmosphere each year. As a first approximation then, given the reservoir size of 750 Gt, we can work out that the residence time of a given molecule of CO2 is 750 Gt C / 200 Gt C y-1 = about 3-4 years.

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