Systematic over-crediting of forest offsets
Carbon offsets are widely used by individuals, corporations, and governments to mitigate their greenhouse gas emissions. Because offsets effectively allow pollution to continue, however, they must reflect real climate benefits.
To better understand whether these climate claims hold up in practice, we performed a comprehensive evaluation of California's forest carbon offsets program — the largest such program in existence, worth more than $2 billion. Our analysis of crediting errors demonstrates that a large fraction of the credits in the program do not reflect real climate benefits. The scale of the problem is enormous: 29% of the offsets we analyzed are over-credited, totaling 30 million tCO₂e worth approximately $410 million.
This article provides an overview of how we identified crediting errors in California's offsets program. For a deeper dive on our methods and analysis, you can read our preprint. To better understand its implications, you can read a story by Lisa Song (ProPublica) and James Temple (MIT Technology Review) that covers and contextualizes our findings. Finally, you can browse an interactive online map of the projects we analyzed, or download the open source data and code that underlies our analysis.
Carbon offset programs issue credits to projects that purport to avoid greenhouse gas emissions or remove carbon dioxide from the atmosphere. For example, an oil refinery that is subject to an emissions limit might purchase an offset credit issued to a forest owner who agrees to reduce or delay a timber harvest. The refinery can then pollute more, claiming the avoided forest emissions as compensation.
