Systematic review of the achieved emissions reductions of carbon offset projects across all major sectors

Many net-zero emission targets by governments and fi¬rms rely on offsetting emissions. Several studies have raised concerns about the environmental integrity of individual offset projects, though systematic evidence is missing. We synthesised existing rigorous empirical studies evaluating 2,353 offset projects across all major offset sectors. Our analysis shows that offset projects achieved considerably lower emissions reductions than officially claimed. We estimate that only 12 % of the total volume of existing credits across four major sectors constitute real emissions reductions, with 0 % for wind power, 0 % for improved forest management, 9.6 % for cookstoves, 22.1 % for REDD+ and 59.6 % for chemical processes. Our results thus indicate that 88% of the total credit volume across these four sectors in the voluntary carbon market does not constitute real emissions reductions. This offset achievement gap corresponds to almost twice the annual German CO2 emissions. Our results do not apply to novel and permanent carbon removal methods that are currently emerging.