Credits issued in return for a reduction of atmospheric carbon emissions through projects such as the provision of renewable energy to replace fossil fuel energy, or reforesting cleared land to create a carbon sink. By paying for such emission reducing activities, individuals and organizations can use the resulting credits to offset their own emissions, either voluntarily or under the rules of most emissions trading schemes. One offset credit is equivalent to an emission reduction of one metric ton of CO2e.
Carbon Positive. "Glossary", 20 September 2010 http://www.carbonpositive.net/viewarticle.aspx?articleID=44#T
Carbon offsetting is the process of reducing greenhouse gas emissions by purchasing credits from others through emissions reductions projects, or carbon trading schemes. The term often refers to voluntary acts, arranged by a commercial carbon offset provider.
(Code1&2) FAO Language Resources Project, 2008