In 2007, CNN took viewers around the world in "Planet in Peril," a four-hour documentary that examined our changing planet. This year, the worldwide investigation continues weekly on CNN International, culminating in a new special program in the fall, "Planet in Peril: Battle Lines," hosted by CNN's Anderson Cooper, chief medical correspondent Dr. Sanjay Gupta and National Geographic host and "The Oprah Winfrey Show" correspondent Lisa Ling.