Artist Alfio Bonanno and architect Christophe Cornubert created a demonstration of the volume of a metric tonne of CO2 (1.1 short tons), the amount an average person produces in a month. It was made up of a giant four-sided video projector and was floating on the lake in front of Copenhagen's Tycho Brahe Planetarium during the Convention on Climate Change. Thanks to Treehugger.