There recently was a thread including discussion on global climate change. I though it worthwhile to give accurate information on the subject.
Greenhouse gases in the atmosphere have an important influence on the climate of our planet. Simply stated, greenhouse gases impede the outward flow of infrared radiation more effectively than they impede incoming solar radiation. Because of this asymmetry, the earth, its atmosphere, and its oceans are warmer than they would be in the absence of such gases.
The major greenhouse gases are water vapor, carbon dioxide (CO2), methane (CH4), chlorofluorocarbons (CFCs) and hydrogenated chlorofluorocarbons (HCFCs), ozone (O3), and nitrous oxide (N2O). Without the naturally occurring greenhouse gases (principally water vapor and CO2), the earth's average temperature would be about 33°C (59°F) colder than it is, and the planet would be much less suitable for human habitation.
Human activity has contributed to increased atmospheric concentrations of CO2, and CH4, and CFCs. The increased atmospheric concentrations of greenhouse gases may increase average global temperatures. The possible warming due to increased concentrations of these gases is called ''greenhouse warming." The atmospheric concentration of CO2 in 1990 was 353 parts per million by volume (ppmv), about 25 percent greater than it was before the Industrial Revolution (about 280 ± 10 ppmv prior to 1750). Atmospheric CO2 is increasing at about 0.5 percent per year. The concentration of CH4 was 1.72 ppmv in 1990, or slightly more than twice that before 1750. It is rising at a rate of 0.9 percent per year. CFCs do not occur naturally and were not found in the atmosphere until production began a few decades ago. Continued increases in atmospheric concentrations of greenhouse gases would affect the earth's radiative balance and might cause a significant amount of additional greenhouse warming.