Effective forest-based climate change mitigation requires our best science.

California's Cap-and-Trade Program sets a limit on the major sources of greenhouse gas emissions and allows a portion of excess emissions to be offset through purchase of credits for climate benefits accrued elsewhere. Badgley et al. (2021, Global Change Biology, https://doi.org/10.1111/gcb.15943) describe how the use of mean forest carbon stocks from ecological supersections can create perverse incentives for project developers, potentially leading to over-crediting and nonadditional offsets. Carbon markets remain a valuable tool in combating climate change, but ensuring projects' additionality is of critical importance to effective carbon mitigation. Badgley's article should serve as a call to action to redouble efforts at integrating the latest carbon science into effective and timely policy solutions.