It started with An Inconvenient Truth. After watching Al Gore’s documentary, we used a carbon calculator to figure out our emissions footprint. We answered some basic questions about our lifestyle, hit “calculate,” and were shocked to find that our emissions were much higher than the US average. Why was the software making us look so bad? After all, we don’t own a car, we eat mostly vegetarian, and compost religiously. A deeper look revealed the culprit: Air travel.