1850. The beginning of the Industrial Revolution and just before the Civil War kicked off. Today's CO2 levels haven't changed since then IN THE ATMOSPHERE! Where does it go? The oceans absorb it, of course.
Alarmist scientists aren't going to like that this little tidbit got out there in a scientific journal.
ScienceDaily (Dec. 31, 2009) — Most of the carbon dioxide emitted by human activity does not remain in the atmosphere, but is instead absorbed by the oceans and terrestrial ecosystems. In fact, only about 45 percent of emitted carbon dioxide stays in the atmosphere.