If you've got an hour to spend, these articles are the best introduction to global warming I've ever read. It was a three part series in the New Yorker by Elizabeth Kolbert. After reading these closely, you will be better educated on this issue than 95% of the American public. That's kind of scary. Please read these, even if you think you already know everything you need to. They are extremely well written.

http://www.newyorker.com/printables/fact/050425fa_fact3

http://www.newyorker.com/printables/fact/050502fa_fact3

http://www.newyorker.com/printables/fact/050509fa_fact3