About the time they announced this year's topic, I was subbing in an environmental science class at the continuation high school. Coincidentally, the chapter they were studying was about climate change. (I already mentioned this day here.)
One girl raised her hand. The question had to do with the effects of climate change on the planet. She asked me if polar bears not finding ice was an effect of climate change. I said that it was, and I moved on, surprised that she knew of this.
Then later in the day, a boy was answering a question about what individuals can do to stop climate change. It really didn't take a lot of prompting from me for him to come up with three. Recycling was the first thing he thought of. He also came up with conserving water (especially since we're in a drought here). I had to prompt him to have him come up with driving less.
Sometimes what they know surprises me. Teens do pay attention. It may not seem like it sometimes, but they do actually care.