CO2 before the industrial revolution 200 ppm (0.02%)

CO2 after industrial revolution 400 ppm (0.04%)

CO2 levels used in greenhouses by farmers 1,000 - 2,000 ppm (0.1 - 0.2%)

CO2 530 million years ago at the start of life on this planet 20,000 ppm (2%)

CO2 plant extinction event 150 ppm (0.015%)