yes Co2 is necessary for life. impossible to remove entirely - and this is what worries me with efforts to absorb Co2 from the atmosphere and geo-engineering.
the natural cycles have maintained Co2 and other GHGs at moderate levels for centuries. sure you can use Co2 to increase the plant growth rate. sure that works, even though there are identified problems with nutritional development through reduced mineral uptake.
what is recommended is not removal but stopping putting increasing amounts of GHG into the atmosphere. gradually GHG levels will fall back to natural levels.
one other point - deforestation has removed much of the planets ability to remove Co2 from the atmosphere, therefore reforestation is also necessary to restore the natural balance.
