The 'Greenhouse Effect' discovered in 1824 by Joseph Fourier is what keeps the earth from being a frozen ball in space. Without greenhouse gases (GHG's) the temperature of earth would be below freezing and incapable of supporting life as we know it. It is precisely because GHG's other than water are such a tiny fraction of the atmosphere that adding a little more can have a large effect on the climate system of earth. Reviewed by Ralph Keeling (http://scripps.ucsd.edu/); written & narrated by John P. Reisman