Yes I'm a plant! provided I have adequate water, sunlight and minerals, I'd grow faster in the carbon dioxide rich atmosphere, produce oxygen at a greater rate, reduce the CO2 and increase the oxygen just as in the carboniferous period when the carbon dioxide levels were much much higher. I'd trap carbon in my leaves, stem, fruits and seeds, which if not eaten would eventually build up as sediment called soil, or peat, or if I'm particularly woody, as coal.