When Oprah turns on the television, she says she sees a lot more "green" products being advertised. "Green is what 'no carbs' were five years ago," she says.

Though this is a sign of real progress, Gore warns consumers to be wary of something environmentalists call "greenwashing."

"There are some advertisements and promotions that make it seem as if there's progress when actually, underneath, the substance is not changing that much," he says.

Oprah credits Gore with making many people more aware of the world and how to help conserve its limited resources. "Thank you for walking the walk," she says.

See how Gore renovated his home to make it energy-efficient.