The UK Government's Quality Assurance Scheme for Carbon Offsetting

Glossary 

Certified Emissions Reductions (CERs) – These are tradable units generated by projects in developing countries (non-Annex 1 Parties) under the Clean Development Mechanism (CDM). They may be counted by Annex 1 Parties towards compliance with their UN and EU emissions target and are equal to one tonne of carbon dioxide equivalent gases. To deal with the issue of non permanence associated with afforestation temporary CERs (tCERs), which expire five years after their issue and long-term CERs (lCERs), which expire at the end of the crediting period of the project activity are used. Both should be replaced after their expiry date.

Emission Reduction Units (ERUs) – These are tradable units generated by projects in developed countries (Annex 1 Parties) (Joint Implementation). Emissions Reduction Units are converted from AAUs and Annex 1 Parties may count them towards compliance with their UN and EU emissions target. Each ERU is equal to one tonne of carbon dioxide equivalent gases.

EU Allowance (EUA) – These units are specific to the EU Emission Trading Scheme, (EU ETS) which started in 2005, and are equal to one tonne of carbon dioxide equivalent gases. They are valid for use within the Community scheme and wherever there is an agreement to link the EUETS with another greenhouse gas emissions trading scheme in accordance with Article 25 of the Emissions Trading Directive).

European Union Emission Trading Scheme (EU ETS) – A trading scheme across Europe to reduce emissions of carbon dioxide and combat the serious threat of climate change. Phase I of the Scheme began on 1 January 2005 and finished on 31 December 2007. Phase II began on 1 January 2008 and will finish on 31 December 2012 to coincide with the first Kyoto Protocol commitment period.

http://www.defra.gov.uk/environment/climatechange/trading/eu/index.htm

Radiative Forcing (RF) - There is currently considerable uncertainty on the relative impacts of non-CO₂ climate change effects of aviation through a process called radiative forcing (RF). Given the current uncertainty it seems reasonable for offsetting companies to make their own decision whether to include a factor for RF. However, for clarity and consistency there should be a requirement that if a factor to account for RF is included this is clearly and visibly stated and that a single consistent factor is used across all approved scheme for this purpose. The most recent research suggests a value of 1.9, which is deemed the most appropriate at this time. This position will be monitored and updated as necessary as the science becomes more certain in this area.