Greenhouse Gases-3: N2O, CFCs, Water vapor, O3

Nitrous Oxide (N2O)

N2O

Enters the atmosphere primarily from fossil fuels and nitrogen based fertilizers.

Nitrous oxide (N2O) is a greenhouse gas for which one molecule is 200 more efficient than a CO2 molecule as an infrared absorber. The atmospheric lifetime for N2O is 114 years. (http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html#table-2-14)

Chlorofluorocarbons (CFCs)

CFCs

Are entirely the result of human activities. CFCs were widely used as refrigerant gases in refrigerators and air conditioners, as cleaning solvents, as propellants in aerosol containers, and as expanders in foam products.

Molecules of CFC-11 and CFC-12 in the atmosphere are about 12,400 and 15,800 times more effective, respectively, at affecting climate than an additional molecule of CO2 (IPCC, 1990). CFCs additionally destroys Ozone in the stratosphere.

The suggested replacements for the CFCs are generally halogenated hydrocarbons (HCFCs, HFCs) While the replacement compounds are also greenhouse gases, their potential for affecting climate is smaller than that of CFCs. They have shorter atmospheric lifetimes (<20years) and destroy ozone <10%. The atmospheric lifetimes are 45 years for CFC-11 and 100 years for CFC-12. (http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html#table-2-14)

Water vapor Water vapor is the most abundant and important greenhouse gases in our atmosphere. Its main source is evaporation from the oceans and it is primarily removed from the atmosphere when water forms raindrops and these fall to the surface.

Ozone (O3) Its abundance can reach 10 ppm in the stratosphere. It absorbs high energy ultraviolet radiation emitted by the sun before it reaches the earth’s surface. Ozone is also one of the primary components of photochemical smog and breathing it can lead to health problems in humans and animals; ground level ozone can also damage plants.

Ozone (O3) Ozone high up in the stratosphere is considered good ozone, whereas ozone near the ground (troposphere) is considered bad ozone.