For about the last 10,000 years, the average temperature
the Earth has been about 15°Celsius (59°Farenheit).
During this time, the Earth's average
temperature has not changed by more than 1°C (1.8°F).
Scientists can now document that the average temperature
of the Earth has risen about 0.5°C (0.8°F)
since 1850. Additionally, the 1990's was the warmest decade
ever recorded. Scientists predict that the Earth will warm
1.0° to 3.5°C (1.8°
to 6.3°F) in the next 100 years. This appears
to be the more rapid and greater warming of Earth's temperature
than has ever occurred.
What is
causing Global Warming?
Many factors contribute to the Earth's
temperature, including the shape of the Earth's revolution
around the Sun, the Earth's tilt on its axis, the way the
Earth wobbles on its axis, solar activity such as sun spots,
and the chemical composition of Earth's atmosphere. Scientists
believe that human activities are affecting the chemcial
composition of Earth's atmosphere.
How are
human activities affecting Global Warming?
Earth's atmosphere is 78 percent nitrogen
and 21 percent oxygen. Less than one percent of the atmosphere
is carbon dioxide, water vapor, methane, nitrogen oxides,
and ozone, which are known as greenhouse gases. Greenhouse
gases act like the panes of glass in a greenhouse. They
keep some of Earth's heat from escaping to space. Until
about 100 years ago, the concentration of greenhouse gases
in Earth's atmosphere was stable. Scientists believe that
human activities are changing the concentration of greenhouse
gasses in Earth's atmosphere. Specifically, they are concerned
about how much carbon dioxide, methane, and nitrogen oxides
are being added to the atmosphere as a result of human activities.
Just like adding an extra blanket to your bed will keep
you warmer, more greenhouse gases will keep the planet warmer.
What might
be the consequences of Global Warming?
Minor changes in Earth's temperature
have resulted in dramatic changes for life on Earth. As
little as a 3° to 5° C (5.5°
to 9.0° F) decrease in Earth's temperature
have resulted in Ice Ages. Scientists are concerned because
they do not know what a similar change in the opposite direction
might cause. They do feel confident that a warmer planet
may not necessarily mean a more comfortable planet. Some
changes that may occur include: a rise in sea level, stronger
storms and where they occur, a change in where foods can
be produced, and stress on plants that will not have had
enough time to adapt.
How can
we reduce the impact of Global Warming?
The most important thing people can
do to reduce the impact of global warming is to reduce the
amount of greenhouse gases they add to the atmosphere. This
means we must reduce our use of fossil fuels. This means
driving less and using the most energy efficient appliances
available. We must also wisely choose what land will be
developed for houses and other construction. Land that is
developed reduces the amount of vegetation present. Vegetation
takes carbon dioxide out of the air, so less vegetation
means more carbon dioxide will remain in the atmosphere.
Where can
I learn more about Global Warming?
Look up the following web sites:
http://www.ucsusa.org
(Union for Concerned Scientists)
http://www.unep.ch (United
Nations Environment Programme)
http://www.epa.gov (United
States Environmental Protection Agency
