Greenhouse Gases
The Sun's energy is trapped in the troposphere, causing the greenhouse
effect.
![[ Path of radiation incident on Earth's surface ]](images/heatbalance.gif)
A similar example would be when the Sun's energy is trapped in a car with the
windows rolled up. As the energy passes through the windshield it is trapped,
reflecting off the interior and refracting off the windshield back into the car.
The heat energy builds inside causing it to be much warmer on the inside of the
car than on the outside.
If the Earth were the car, global warming would occur. Without this
process Earth would be a very cold place. As with everything the key is
always balance. Too much greenhouse effect causes melting of polar
icecaps, changes in sea levels and possibly drought in some areas of the
globe. Scientists believe too little greenhouse effect could send us into
another ice age.
Carbon dioxide (CO2):
CO2 is produced
naturally by living organisms and by the burning of fossil fuels. Carbon
accounts for the largest share of US greenhouse gas emissions. In 1990,
the CO2 emissions were approximately 85% of the total, although the carbon
sinks in forested lands offset CO2 emissions by about 8%. Worldwide carbon
emissions have grown by about 27% since the industrial revolution.
Nitrous Oxide (N2O):
Naturally occurring,
N2O is produced by fuel burning and in fertilizer manufacturing. In 1990,
N2O accounted for about 2.5% of US emissions. Global Warming Potential
(GWP): 310 times greater than CO2.
Methane (CH4): Methane comes from coal formations
and from landfills, livestock digestive processes, decomposing waste, and
wetland rice cultivation. In 1990, methane accounted for almost 12% of
the US total emissions. Global warming potential: About 21 times higher
than that of CO2.
Hydrofluorocarbon gases (HFC): These
gases were developed largely as an alternative to ozone-damaging chlorofluorocarbons
(CFC) banned under the 1987 Montreal Protocol. HFCs do not damage the ozone
layer, but they do contribute to global warming. They are used largely
in refrigeration and as in semi-conductor manufacturing. Global warming
potential: 140 to 11,700 times that of CO2.
Perfluorocarbons (PFC): Result as
a by-product aluminum smelting, and uranium enriching. Also are manufactured
to replace CFCs in making semi-conductors. Global warming potential: 7,400
times CO2.
Sulphur Hexafluoride (SF6): Largely
used in heavy industry to insulate high-voltage equipment and to assist
the manufacturing of cable cooling systems. Global warming potential: 23,900
times that of CO2.
