Site seeing: offsetting carbon footprints

As a traveler, I’m aware of the greenhouse gases I contribute, so with that, there’s an extra trip to make:

Go Zero, where

* $10 offsets an average trip including air travel, a one-night hotel stay, and rental car for one person.

* $25 negates air travel, four-night hotel stay, and rental car for two people.

* $40 equalizes the effects of air travel, four-night hotel stay, and rental car for four people.