e greater because it will double the warming from carbon dioxide alone. Experiments in the upper atmosphere by NASA show that the heating may not be as much as predicted.
Human Contribution to Greenhouse Effects
Human activity actually contributes very little to the greenhouse effect (Hieb). It only amounts to about 0.28 percent if water vapor is taken into account, and 5.53 percent if it is not. Water vapor is Earth's most significant greenhouse gas, accounting for roughly 95 percent of it. However, this fact is usually ignored in discussions of global warming. Natural origin accounts for 99.9 percent of water vapor, and the other greenhouse gases, carbon dioxide, methane, and nitrous oxide are also mostly of natural origin. Miscellaneous other gases are anthropogenic. Human activities such as farming, manufacturing, power generation and transportation contribute slightly to greenhouse gas concentrations, but these contributions are totally dwarfed by the contributions from natural emissions that efforts to reduce them would pro
...