Last year, John Kerry logged a lot of travel in his position as Secretary of State. By November of this year, he's certain to log many, many, many more.
As these trips necessarily involve going over large bodies of water, and as we have yet to invent a reliable method of transportation that replaces private air travel, such as a Star Trek transporter that allows John Kerry to hop from capitol to capitol in a sparkly haze of atoms, John Kerry is still forced to rely on fossil fuels. And even if he's not traveling for work, his home, cars and yacht don't run on puppy farts and rays of sunshine.
But being that he's John Kerry, it matters not how much of a carbon footprint he leaves behind. You see, he is very busy and important, saving the world from the greatest threat to humanity, carbon emissions. As such, his movement and egregious consumption of dead dinosaur juice is not only justified, it is warranted and necessary in the service of something much greater than the sum of John Kerry.