About half of the current greenhouse warming is due to a group of at least 15 different gases. Although the individual concentrations of most of the gases is very small - they are measured in parts per billion (1 in 10^9) and parts per trillion (1 in 10^12) these gases have great potential to absorb infrared energy. On a molecule per molecule basis they have a greater greenhouse effect because they block IR radiation in the 8.5 to 12.5 micron region where CO2 and water vapor do not effectively absorb energy.
A most disturbing fact about these gases is their rapid build-up - much faster than the CO2 buildup. If steps are not taken to control the release of these other gases, they soon will collectively contribute more to the global warming problem than carbon dioxide.
These gases are produced from a variety of man's activities. The CFC gases are newly created industrial gases, used for refrigeration, solvents, and plastic foam. Methane is produced from both the production and transportation of coal and natural gas, as well as from agricultural production such a rice growing and cattle ranching. Tropospheric ozone results mainly from chemical reactions arising from automobile exhausts. N2O, nitrous oxide is produced when forests are burned to clear new land. ***
