Because CFCs are both greenhouse gases and destroyers of ozone, CFCs produce a cooling effect by means of ozone depletion. Therefore, the net contribution of CFCs to the greenhouse effect is uncertain. In fact, the cooling effect of ozone loss may be large enough to have offset a significant part of the heating from increases in all greenhouse gases over the past decade. If the warming effect of CFCs is offset by the newly discovered cooling effect, then the phasing out of CFC use will not decrease global warming. The primary sources of greenhouse gases in Missouri are carbon dioxide from the use of fossil fuels and methane from agricultural activities and solid waste landfills.
Methane emissions are inherently difficult to control.
Carbon dioxide is not only the most important greenhouse gas but it is the easiest to control. The most important sources of CO 2 in Missouri are transportation, industrial, residential and commercial activities. Energy consumption in the transportation and commercial sectors has grown steadily since 1960. In contrast, energy use in Missouri's industrial sector peaked in the 1970s, and residential use has shown no clear growth pattern. In 1992, the transportation accounted for 33 percent of energy use in Missouri.