You will find many video clips and teacher lesson plans on a variety of environmental topics like global warming. You must register, but it is a free and simple process.

Activity: You will find a lesson plan to get your students started examining the issues surrounding global warming. There is a carbon cycle diagram, a carbon counter for how much carbon each person produces in a day, and a couple of Quick Time videos. (sign in—go to Life Science—then to Ecology—then to Human Influences on Ecology)

Link.