Setting a market price for carbon
For trading purposes, one allowance is considered equivalent to one metric tonne of CO2 emissions. These allowances can be sold privately or in the international market at the prevailing market price. These trade and settle internationally and hence allow allowances to be transferred between countries. Each transfer of ownership within Europe is validated by the EU ETS. Each international transfer is validated by the UNFCCC.
Climate exchanges have been established to provide a spot market in allowances, as well as futures and options market to help discover a market price and maintain liquidity. Carbon prices are normally quoted in Euros per tonne of carbon dioxide or its equivalent (CO2e). Other greenhouse gasses can also be traded, but are quoted as standard multiples of carbon dioxide with respect to their global warming potential. These features reduce the quota's financial impact on business, while ensuring that the quotas are met at a national and international level.
Currently there are at least four exchanges trading in carbon allowances: the Chicago Climate Exchange, European Climate Exchange, Nord Pool, and PowerNext. Recently, NordPool listed a contract to trade offsets generated by a CDM carbon project called Certified Emission Reductions (CERs). Many companies now engage in emissions abatement, offsetting, and sequestration programs to generate credits that can be sold on.
An individual allowance, such as a Kyoto Allocation Allowance Unit (AAU) or its equivalent European Union (EUA), may have a different market value to an offset such as a CER. This is due to the lack of a developed secondary market for CERs, a lack of homegeneity between projects which causes difficulty in pricing, as well as questions due to the principle of supplementarity and its lifetime. Additionally, offsets generated by a carbon project under the Clean Development Mechanism is potentially limited in value by the fact that regulated entities in the EU ETS are restricted as to what percentage of its quota can be accomplished via these flexible mechanisms.
