Once upon a time, not so long ago, world leaders gathered to make an agreement to fight climate change. They met in Japan and agreed to the famous Kyoto Protocol. A principal feature of the Protocol turned out to be carbon trading: a magical solution to curb CO2 emissions. It was presented as a flexible market mechanism able to tackle climate change in a cost effective way. The magical elements were carbon credits, who reached the status of superheroes once their full potential was discovered.