Air travel results in a lot of planet-warming emissions, but it's also sometimes necessary. That's a quandary for people who may be concerned about their personal contribution to the problem of climate change. Some travelers may turn to carbon offsets, which allow you to essentially pay for something — like planting a tree — that in theory will make up for your share of a flight's emissions. But are carbon offsets working? (AP Video: Aya Diab)