Coal is the most polluting fossil fuel, emitting around twice as much carbon dioxide as gas when used to generate power. (dotearth.blogs.nytimes.com)
Of relevance to the present subject is the question of how much carbon dioxide we are responsible for releasing into the atmosphere and how it affects other people. (ramblingsdc.net)
The world used to have five times as much carbon dioxide as it does now. (desmogblog.com)