Greenhouse Effect

Greenhouse Effect

The greenhouse effect is an increase in the atmospheric temperature caused by
increasing amounts of greenhouse gases. These gases act as a heat blanket
insulating the Earth's surface absorbing and trapping heat radiation which
normally escapes from the earth. They include carbon dioxide, water vapor,
methane, nitrous oxide, CFC's, and other halocarbons. The earth's atmosphere
goes through two processes constantly. Global cooling is the first process. This
process uses the clouds which cover 60% of the earth's surface to reflect 30% of
the solar radiation. It also uses a sulfate haze, which is formed by sulfur
dioxide from industrial sources that enter the atmosphere and react with
compounds to form a high-level aerosol. These cool the atmosphere by blocking us
from direct contact with the sun. The reflection of the sunlight is referred to
as planetary albedo and contributes to the overall cooling. The second is the
warming process. This is when light energy comes through the atmosphere and is
absorbed by Earth and transformed to heat energy at the planet's surface. The
infrared heat energy then radiates upward into space. There the greenhouse gases
found naturally in the troposphere absorb some of the infrared radiation. The
gases insulate the Earth, but do eventually allow the heat to escape. Without
these greenhouse gases the earth would be would 33 C colder. Global temperature
is a balance of the effects of the factors leading to global cooling, and
warming. Unfortunately, increased emissions of greenhouse gases increase the
warming process. For example, every kilogram of fossil fuels burned equals 3
kilograms of carbon dioxide ( the mass triples because each carbon atom in fuel
bond to two oxygen atoms, in the course of burning, and forms C02. ) 6 billion
tons of fossil fuel carbon are burned each year adding 18 billion tons of C02 to
the atmosphere. This has increase the carbon dioxide concentrations by 25% and
has cause temperatures to increase more than 0.7 C over the last hundred years.

We hope that the forests will act as a sink for carbon dioxide but instead they
are a net source. This is because the forests are being cut and burned adding 1
to 2 billion tons annually to the 6 billion tons of carbon already from
industrial processes. Fortunately, the top 300 meters of oceans absorb most of
the carbon dioxide emitted by burning fossil fuels. Other factors are known to
increase the greenhouse effect. These factor are water vapor, methane, nitrous
oxide, CFC's and other halocarbons. Water vapor is also a major factor in what
has been called the "supergreenhouse effect" in the tropical Pacific
ocean. Water vapor traps energy that has been radiated back to the atmosphere.

The high concentration of H2O vapor contributes significantly to the heating of
the ocean surface and lower atmosphere in the tropical Pacific. Methane (CH4) is
a product of microbial fermentative reactions and is also emitted from coal
mines, gas pipelines, and oil wells. Methane is gradually destroyed, but it is
added to the atmosphere faster than it can be broken down. Nitrous oxide (N2O)
can be found in biomass burning, chemical fertilizers, and fossil fuel burning.

Nitrous oxide is more dangerous than some of the others because of its long
residence time of 170 years. CFC's and other halocarbons are found in
refrigerants, solvents, and fire retardants. Halocarbons have a greater
capacity, 10 000 times, for absorbing infrared radiation, which is about 60%
more, than CO2. Although there is increase in the application of some of these
gases, they will decrease in importance in the future leaving carbon dioxide as
the primary dilemma. In 1981, James Hansen of NASA invented a model with an
ability to track known temperature changes and link them to past and future
carbon dioxide levels as well as global temperature changes. The model suggested
the combination of CO2 and volcanic emissions was responsible for most of the
observed changes in temperature during the 1980's. A trend of warming of more
than 0.7 C coincides with an increase of 25% in carbon dioxide. Two major
impacts of greenhouse effect are regional climatic changes and a rise in sea
levels. A climactic change will lead to variations in temperature. Scientists
expect more precipitation which may prove to be disastrous for North America by
flooding rivers and lakes. A rise in the sea levels is anticipated because of an
increase in thermal expansion and the melting of ice caps and ice fields. Like
extensive rainfalls, a rise in the ocean will flood lakes and rivers covering
land and may someday bury continents. In order to control the effects of global
warming we must first admit that it's occurring, then take steps to end it. We
must stop burning the trees and not replacing them. Most importantly, we must
stop polluting the air.

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