Transportation, it appears to be the biggest contribution to CO2 foot print, so we need to take less trips and use efficient or "green" cars.

I agree that transportation is a huge contribution to our carbon footprint. Society is starting to understand that a little, and that is why energy efficient cars are becoming more popular. As these new electric cars are slowly making it's way to popularity, we can do other things ourself to reduce the footprint left from cars. Many adults and teens have their own car, and they take it for granted sometimes. People drive their cars alone, when they could be doing things differently to save energy. Bart and bus are recourses that can be really useful for teens. People need to learn the system and know their way around so they can become part of a bigger picture, and a smaller CO2 contribution.

You are right, many people don't realize the damage they can do to the environment when they aren't paying any attention. Teens with cars tend to overuse the fact that they can now go anywhere on their own with their new car and they don't see the larger picture. However this is not just teens. There are many adults who travel to and from work alone. This just creates traffic and also more carbon in our atmosphere. Looking at the data it can also be surprising that even though this happens, the USA is near the lower end of the carbon producers from transportation. The leaders in this carbon method of production are Venezuela, Saudi Arabia, and Ghana.