South Korean students wearing polar bear outfits hold banners in front of a huge hour glass which placed to mark the opening of the Seoul Climate Change Expo, in Seoul, South Korea, Friday, May 15, 2009. Eighty cities around the world will meet in Seoul on May 18 to discuss climate concerns under the theme of 'Cities' Achievements and Challenges in the Fight against Climate Change. The banner read " Protect Global Warming."