The Greenhouse Effect
Key
to understanding global warming, is understanding what scientists have
dubbed the “greenhouse effect.” As you may suspect, it got
its name from being similar to what happens in a greenhouse, but since
most of us have not spent a lot of time in greenhouses, it is not often
a helpful analogy. A better analogy is your car on a hot summer day. If
you do not crack the windows, you will return to find it much hotter
inside of your car than outside. This is because the windows allow the
sun’s energy to pass through to the interior. While some of the
energy leaves through the windows, much of it gets “stuck”
in the car, causing it heat to up. 
The
same principal operates in our atmosphere. Our atmosphere is
composed of a number of gasses that function like the windows of your
car, letting the sun’s energy pass through them to the Earth.
Under normal conditions, some of the sun’s energy would be
absorbed by the surface and some of it would bounce off and return
through the atmosphere into space. The trouble is that
“greenhouse gasses,” such as carbon dioxide, methane, and
nitrous oxide, have accumulated in our atmosphere and are preventing
more and more of the sun’s energy from leaving the Earth. The
result has been higher average surface temperatures and dramatic
changes in climate across the globe. Since 1990, we have had the 10
hottest years on record. To skip to our information on the Effects of
Global Warming, click here.