Coal, oil and natural gas geologically transformed from ancient beds of plant matter into burnable hydrocarbons. All told, these industries put 800 tons of carbon dioxide into the air every second: a sobering number given that oxygen-breathing life on Earth depends on carbon remaining locked in the ground. Although none of these fuels carries much, if anything, left from the dinosaurs, these now-extinct saurons have come to symbolize them with an eerie persistence.