Not a terrible idea. Four seems low, and I have no idea how they arrived at that exact number, but in principle plane travel is one of the most inexpensive and

Not a terrible idea. Four seems low, and I have no idea how they arrived at that exact number, but in principle plane travel is one of the most inexpensive and time-efficient ways an average person can release tons of carbon dioxide into the atmosphere. I mean, we ban drinking straws and fret about the environmental cost of electric cars, but really the biggest impact on the environment an average person could have would be to fly less.