What do people around the world think about the threat of climate change and the promise of a new clean economy? Are they informed about the international negotiations in Copenhagen? If clean energy doesn't become a kitchen table issue, will the negotiations succeed? Some of the world's biggest advertising companies are putting aside their rivalries to collaborate on a new global campaign—Hopenhagen—about the hope of a green and prosperous future. Will they have any impact? How can they reach people outside the "environmental elite?" Experts discuss what's at stake.