Global Warming: A Close Look at the Numbers

"Just how much of the 'Greenhouse Effect' is caused by human activity? It is about 0.28%, if water vapor is taken into account--about 5.53%, if not. This point is so crucial to the debate over global warming that how water vapor is or isn't factored into an analysis of Earth's greenhouse gases makes the difference between describing a significant human contribution to the greenhouse effect, or a negligible one."