Originally Posted by onon

No, but for at least 1000 years prior to 300 years ago co2 trends were pretty flat at around 280ppm throughout.

http://www.ecoinfo.org/env_ind/regio...lobalco2_e.gif

So for that time period the earth was absorbing as much co2 as it was emitting. Only with the addition of human co2 emissions did emissions start outweighing absorption, and co2 levels in the atmosphere started to rise, following the exponential curve of co2 emissions.