mankind dominant cause of co2 says ippc, page-18

Beretta
"I suggest you discuss with Janti how very very very very small concentrations of stuff somehow have effects on people.

So from that point of view, why also couldnt it occur in the atmosphere?"
At a bit of a loss here tinnitus assume you are talking about Co2?
not quite sure what effects you are referring too but only too happy to carry on the discussion as mankinds emissions of Co2 are tiny compared to natures.
In itself Co2 is not a catalyst but a result.