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.
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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.