A market-based implementation mechanism defined in Article 6 of the Kyoto Protocol, allowing Annex I countries or companies from these countries to implement projects jointly that limit or reduce emissions or enhance sinks, and to share the Emissions Reduction Units. JI activity is also permitted in Article 4.2(a) of the United Nations Framework Convention on Climate Change (UNFCCC). See also Kyoto Mechanisms; Activities Implemented Jointly.(IPCC)
Joint implementation (JI) is one of three flexibility mechanisms set out in the Kyoto Protocol to help countries with binding greenhouse gas emissions targets (the Annex I countries) meet their obligations. JI is described in Article 6 of the Kyoto Protocol. Under Article 6, any Annex I country can invest in an emission reduction project (referred to as a "Joint Implementation Project") in any other Annex I country as an alternative to reducing emissions domestically. In this way countries can lower the costs of complying with their Kyoto targets by investing in projects that reduce greenhouse gas emissions in an Annex I country where reducing emissions may be cheaper, and then using the resulting Emission Reduction Units (ERUs) towards their commitment goal. A JI project might involve, for example, replacing a coal-fired power plant with a more efficient combined heat and power plant. Most JI projects are expected to take place in the economies in transition (the EIT Parties) noted in Annex B of the Kyoto Protocol. Currently Russia and Ukraine are slated to host the greatest number of JI projects. Unlike the case of the Clean Development Mechanism, the JI has caused less concern of spurious emission reductions, as the JI project, in contrast to the CDM project, takes place in a country which has a commitment to reduce emissions under the Kyoto Protocol. The process of receiving credit for JI projects is somewhat complex. Emission reduction projects are awarded credits called Emission Reduction Units (ERUs), which represents an emission reduction equivalent to one tonne of CO2 equivalent. The ERUs come from the host country's pool of assigned emissions credits, known as Assigned Amount Units, or AAUs. Each Annex I party has a predetermined amount of AAUs, calculated on the basis of its 1990 greenhouse gas emission levels. By requiring JI credits to come from a host country's pool of AAUs, the Kyoto Protocol ensures that the total amount of emissions credits among Annex I parties does not change for the duration of the Kyoto Protocol's first commitment period.
Source: Wikipedia - Joint Implementation