What impact, if any, do man-made CO2 emissions have on global warming?

In the April 3 issue of the Wall Street Journal, deputy editor George Melloan noted that, according to “serious scientists,” “the greenhouse gases are a fundamental part of the biosphere, necessary to all life, and … industrial activity generates less than 5% of them, if that.” Furthermore, the theory that CO2 is the prime culprit in so-called global warming may also be flawed. In the compendium Earth Report 2000, Dr. Roy Spencer, senior scientist for climate studies at NASA’s Marshall Space Flight Center, noted: “It is estimated that water vapor accounts for about 95 percent of the earth’s natural greenhouse effect, whereas carbon dioxide contributes most of the remaining 5 percent. Global warming projections assume that water vapor will increase along with any warming resulting from the increases in carbon dioxide concentrations.” Dr. Spencer points out that such assumptions are unproven, noting that “there remain substantial uncertainties in our understanding of how the climate ...  more