Your link pretty much says "on average the CO2 stays in the atmosphere for 3-4 years, but if we change the definition, then it's up to 1000 years".
Do you understand the difference between average and 15-40%? How about the difference between average and median, non-normal distributions, etc.?
There's no changing of definitions from anyone except yourself in your misleading "quote".
Here's a more accessible article: http://www.nature.com/climate/2008/0812/full/climate.2008.12...