A carbon offset is a mechanism for compensating greenhouse gas emissions. An activity, like protecting a threatened forest, that has avoided, reduced or removed a quantity of emissions (i.e. one tonne of C02 equivalent) is used to compensate for an equivalent amount of emissions.  For this to be credible, carbon offsets must be science-based, measurable, transparent and third-party verified. Meanwhile, using carbon offsets must be part of a broader strategy for lowering total emissions and also be science-based, measurable and transparent.