Over the last one hundred years global temperature
             has increased between 0.6 and 1.1 degrees Fahrenheit,
             glaciers over the world have decreased in size and
             worldwide sea level has risen 10 to 20 centimeters.
             (Global Warming Opposing Viewpoints) Are these changes
             due to human behavior or natural causes? Is global
             warming a threat to the world environment? Global
             warming is a complex issue where scientists on both
             sides of the subject have a valid point of view.
             The green house effect is causing the earth to get
             warmer. But why is the earth getting warmer, what is
             causing global warming? What can we do to fight global
             warming or why don't we need to worry about it? These
             are some of the questions many people are asking.
             The earths atmosphere acts like a green house keeping
             the world at a very livable temperature, of about 60°F
             but to many green house gasses such as carbon dioxide,
             methane, and nitrous oxide are building up in the
             atmosphere, holding to much of that extra heat and
             causing global temperature to rise. The solar energy
             passes through our clear atmosphere where most of the
             energy is absorbed by the earth, keeping it warm but
             the energy that the earth does not absorb is reflected
             back up toward the atmosphere where it is absorbed by
             the greenhouse gas molecules and re-admitted in every
             direction instead of going back out to space.
             From the time when the industrial revolution started
             the atmosphere concentration of carbon dioxide have
             increased by almost 30% the methane concentration has
             doubled and nitrous oxide concentrations have raised
             by 15%. These changes in the earth's atmosphere have
             increased the earth ability to trap heat. Scientists
             believe the increase of carbon dioxide is due to the
             combustion of fossil fuels and other human activities.
             (www.epa.gov/globalwarming) Yet many scientists and
             researchers agree that methane may play a...