50 years ago humpback whales were considered an endangered species after decades of commercial whaling decimated the population. around that same time scientists learned something extraordinary. whales were communicating with each other, sometimes by song over long distances. in part because of that discovery scientists and conservationists rallied to enact laws to protect the whales, and it worked. the humpback whale population has made a remarkable comeback. but now they face a host of new threats. global warming is killing off their food source, and human activity is causing thousands of whale deaths a year. from the stress of underwater construction noise to fishing entanglements and ship collisions. in the next hour cnn s bill weir takes us to antarctica, a place very few people get to visit, to study these remarkable creatures and show us why saving the whales may also be saving the planet. because they are one of our best partners in battling climate change. reporter