3 Greenhouse Gases, Greenhouse Effect, Global Warming,
Global Warming Potential
A greenhouse gas (GHG) is any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include water vapor, carbon dioxide (CO 2 ), methane
(CH 4 ), nitrous oxide (N 2 O), halogenated fluorocarbons (HCFCs), ozone (O 3 ),
perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs), water vapor and
sulfur hexafluoride. Gases absorb heat in the atmosphere near the earth’s surface,
preventing it from escaping into space. If the atmospheric concentrations of these
gases rise, the average temperature of the lower atmosphere will gradually increase,
a phenomenon known as the greenhouse effect.
Specifically greenhouse effect is produced as greenhouse gases allow incoming
solar radiation to pass through the earth’s atmosphere, but prevent most of the
outgoing infrared radiation from the surface and lower atmosphere from escaping
into outer space. This process occurs naturally and has kept the earth’s temperature
about 60 degrees Fahrenheit warmer than it would otherwise be. Current life on earth
could not be sustained without the natural greenhouse effect. The greenhouse effect
trap and buildup heat in the atmosphere (troposphere) near the earth’s surface. Some
of the heat flowing back toward space from the earth’s surface is absorbed by water
vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then
reradiated back toward the earth’s surface. If the atmospheric concentrations of these
greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.
Global warming is known due to the recent and ongoing global average increase
in temperature near the earth’s surface. It is the observed increase in average
temperature near the earth’s surface and in the lowest layer of the atmosphere. In
common usage, “global warming” often refers to the warming that has occurred as a
result of increased emissions of greenhouse gases from human activities. Global
warming is a type of climate change; it can also lead to other changes in climate
conditions, such as changes in precipitation patterns.
Global warming potential (GWP) is a measure of the total energy that a gas
absorbs over a particular period of time (usually 100 years), compared to carbon
dioxide. GWP is a number that refers to the amount of global warming caused by a
substance. The GWP is also the ratio of the warming caused by a substance to the
warming caused by a similar mass of carbon dioxide (CO 2 ). Thus, the GWP of CO 2
is 1.0. Chlorofluorocarbon (CFC)-12 has a GWP of 8500; CFC-11 has a GWP of
5000; hydrochlorofluorocarbons and hydrofluorocarbons have GWPs ranging from
93 to 12,100; and water has a GWP of 0.
3.1 Main Contributors to Greenhouse Gases
It has been known that any gas that absorbs infrared radiation in the atmosphere is
GHG, which may include water vapor, carbon dioxide (CO 2 ), methane (CH 4 ),
4
L. K. Wang et al.
Global Warming Potential
A greenhouse gas (GHG) is any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include water vapor, carbon dioxide (CO 2 ), methane
(CH 4 ), nitrous oxide (N 2 O), halogenated fluorocarbons (HCFCs), ozone (O 3 ),
perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs), water vapor and
sulfur hexafluoride. Gases absorb heat in the atmosphere near the earth’s surface,
preventing it from escaping into space. If the atmospheric concentrations of these
gases rise, the average temperature of the lower atmosphere will gradually increase,
a phenomenon known as the greenhouse effect.
Specifically greenhouse effect is produced as greenhouse gases allow incoming
solar radiation to pass through the earth’s atmosphere, but prevent most of the
outgoing infrared radiation from the surface and lower atmosphere from escaping
into outer space. This process occurs naturally and has kept the earth’s temperature
about 60 degrees Fahrenheit warmer than it would otherwise be. Current life on earth
could not be sustained without the natural greenhouse effect. The greenhouse effect
trap and buildup heat in the atmosphere (troposphere) near the earth’s surface. Some
of the heat flowing back toward space from the earth’s surface is absorbed by water
vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then
reradiated back toward the earth’s surface. If the atmospheric concentrations of these
greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.
Global warming is known due to the recent and ongoing global average increase
in temperature near the earth’s surface. It is the observed increase in average
temperature near the earth’s surface and in the lowest layer of the atmosphere. In
common usage, “global warming” often refers to the warming that has occurred as a
result of increased emissions of greenhouse gases from human activities. Global
warming is a type of climate change; it can also lead to other changes in climate
conditions, such as changes in precipitation patterns.
Global warming potential (GWP) is a measure of the total energy that a gas
absorbs over a particular period of time (usually 100 years), compared to carbon
dioxide. GWP is a number that refers to the amount of global warming caused by a
substance. The GWP is also the ratio of the warming caused by a substance to the
warming caused by a similar mass of carbon dioxide (CO 2 ). Thus, the GWP of CO 2
is 1.0. Chlorofluorocarbon (CFC)-12 has a GWP of 8500; CFC-11 has a GWP of
5000; hydrochlorofluorocarbons and hydrofluorocarbons have GWPs ranging from
93 to 12,100; and water has a GWP of 0.
3.1 Main Contributors to Greenhouse Gases
It has been known that any gas that absorbs infrared radiation in the atmosphere is
GHG, which may include water vapor, carbon dioxide (CO 2 ), methane (CH 4 ),
4
L. K. Wang et al.