Carbon Dioxide in the atmosphere is essential to life on earth and is directly responsible for the food we eat and the oxygen we breathe. As of March 2009, carbon dioxide in the Earth's atmosphere was at a concentration of 387 ppm by volume.
The images below demonstrate how added CO2 affects plant growth:
(Numbers are parts per million OVER THE AMBIENT LEVEL of 387ppm)
For more information see: http://tinyurl.com/mpo4rl
Our food supply depends on plant growth.
Maybe we should not be so cavalier about assigning a level that is less than optimum.
Some say 350ppm has some significance. Why not 700ppm or 1000ppm?