The opposing viewspoints on global warming are: 

ONE VIEW –  The earth’s climate is warming as a result of human actions; an extreme change in the earth’s climate is going to occur, caused by greenhouse gas emitted by the world’s use of fossile fuels (coal, oil, gas).  This temperature change will result in catastrophic problems in the environment. Humans must drastically reduce the consumption of fossile fuels immediately.  To prevent this man-made climate change, countries need to restrict energy use (reduce use of gas and oil).
Liberals generally hold this view.  Check out two liberal organizations which defend this viewpoint:
Natural Resources Defense Council and Greenpeace.

ANOTHER VIEW – Human activity does not affect the earth’s temperature.  Burning fossile fuels (gas, coal and oil) does not cause climate change.  The earth’s climate changes naturally, but not so much that it will cause a change of catastrophic proportions.  An extreme change in the earth’s climate won’t happen.  There are natural warming and cooling trends over time.  In the 1970’s a coming ice age was predicted, but now it this scare has been replaced with the current global warming scare.
Conservatives generally hold this view.  Two conservative organizations which support this view are: and Junk Science.