Mr. Green is the Sierra Club's answer guy. He has a column about all things green that he updates weekly. In honor of Bike to Work Day, he's put out this discussion of the carbon emissions of biking vs. driving. He puts to rest the myth that fueling a bike (by feeding a person food that has been grown with fossil fuel inputs and traveled to them) is worse for the environment than fueling a car.
Isn't it true that cycling improves your fitness and your health and thus your life expectancy? Those additional years of life will increase your lifetime carbon footprint vs. a sedentary person who dies young. This is the real reason that Republicans are pro-car and anti-bicycle.