Carbon offset

A carbon offset is a credit representing a claimed reduction or removal of greenhouse-gas emissions, used to compensate for emissions elsewhere. Its climate value depends on whether the claimed benefit is real, additional, durable, and accurately measured.

Carbon credit: A tradable unit representing a quantified amount of greenhouse-gas emissions reduced, avoided, or removed. An offset is commonly issued and traded as a carbon credit.
Greenhouse gas: A gas that absorbs and emits infrared radiation, contributing to the greenhouse effect. Offsets address emissions of these heat-trapping gases.
Carbon insetting: A climate intervention within a company’s own value chain, rather than outside it. Insetting targets emissions connected to operations or suppliers instead of compensating elsewhere.
Voluntary carbon market: A market where organizations and individuals buy carbon credits outside mandatory emissions limits. Many offset purchases occur voluntarily rather than under legal obligations.
Carbon leakage: An increase in emissions outside a regulated or targeted area caused by measures that reduce emissions within it. Project benefits can be overstated when emissions shift elsewhere.
Additionality: The condition that an emissions benefit would not have occurred without the intervention or its financing. Without additionality, crediting rewards reductions that would have happened anyway.
Carbon dioxide equivalent: A common unit expressing the climate impact of different greenhouse gases relative to carbon dioxide. Credits aggregate unlike gases using a shared climate-impact measure.
Carbon avoidance: The prevention of greenhouse-gas emissions that would otherwise occur. Avoidance claims differ from removing carbon already present in the atmosphere.
Compliance carbon market: A regulated system in which covered entities must meet emissions limits using allowances or eligible credits. Some jurisdictions permit credits in systems created to enforce emissions rules.
Permanence (carbon offsetting): The durability of a credited greenhouse-gas reduction or removal over the period relevant to climate impact. Reversals, such as later forest fires, can undo benefits represented by credits.

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