As recognised on a scientific basis, carbon dioxide emissions to air (and the emissions of other GHG's) are almost exclusively associated with the conversion of energy carriers like natural gas, crude oil, etc. The carbon content released during the energy conversion process reaches the atmosphere and is deemed to be responsible for the global warming process (i.e. climate change).

The Kyoto Protocol defines legally binding targets and timetables for cutting the greenhouse-gas emissions of industrialised countries that ratified the Kyoto Protocol. Accordingly, from an economic or market perspective, one has to distinguish between a mandatory market and a voluntary market. Typical for both markets is the trade with emission certificates:

• Certified Emission Reduction (CER)
• Emission Reduction Unit (ERU)
• Verified Emission Reduction (VER).

To reach the goals defined in the Kyoto Protocol with least economical costs the following flexible mechanisms were introduced for the mandatory market:

• Emissions trading
• Clean Development (CDM)
• Joint Implementation (JI)