Certified emission reduction. A Kyoto Protocol emissions unit equal to 1 metric tonne of CO2 equivalent (CO2e). CERs are issued for emission reductions or removals from CDM project activities conducted in developing countries (see CDM). Such projects can earn saleable carbon credits that can be used by developed countries (Annex I Parties) to meet their emission reduction targets under the Kyoto Protocol. CERs can be bought by companies and governments in developed countries, to reduce emissions in developing countries where the cost of abatement is lower, instead of reducing emissions at home. (see also Emissions trading)