This short video is a simple explanation of how humans have caused carbon emissions over the last 260 years.
Unless we begin sharp reductions in carbon emissions immediately, we will commit the world to more than 2 degrees C of warming.[youtube https://www.youtube.com/watch?feature=player_embedded&v=urewQRnA9iM]
It can be a little dangerous to think that we still have carbon to spend. In terms of ocean acidification and feedback risks, we have already emitted too much.