“the temperature effect of atmospheric carbon dioxide is logarithmic (that means there is a diminishing response as you keep adding more). If we consider the warming effect of the pre-Industrial Revolution atmospheric carbon dioxide (about 280 parts per million by volume or ppmv) as 1, then the first half of that heating was delivered by about 20ppmv (0.002% of atmosphere) while the second half required an additional 260ppmv (0.026%).

To double the pre-Industrial Revolution warming from CO2 alone would require about 90,000ppmv (9%) but we’d never see it – CO2 becomes toxic at around 6,000ppmv (0.6%, although humans have absolutely no prospect of achieving such concentrations).”

See http://www.junkscience.com/Greenhouse/ for some more information on CO2 and how it relates to the greenhouse effect. As always, take what you read on a heated topic like this with a grain of salt. The possiblity of us destroying the earth is a very emotional topic.

But Greenhouse effect or not, We should all do out part to reduce our enviromental footprint.