Carbon storage portfolios for the transition to net zero

Net-zero targets are widely adopted by companies and countries worldwide. To achieve these goals, more companies are investing in diverse carbon removal portfolios. This study develops a new risk management framework that combines forestry, biochar, and geological storage offsets into portfolios that could stabilize global temperatures over multi-century time periods. We find that if a carbon storage portfolio reaches an equilibrium state of CO₂ stored, it can be leveraged to stabilize global temperatures by increasing the size of the portfolio relative to the amount of removal claimed. For moderate-risk primarily forestry portfolios retaining 0.75–0.55 tCO₂ of the 1 tCO₂ stored, an additional 0.30–0.80 tCO₂ removal is needed to offset re-releases over 1,000 years. High-risk portfolios retaining only 0.10 tCO₂ require over 9 tCO₂ additional removal. Portfolios that are predicted to re-release almost all CO₂ cannot be leveraged and are ineffective at meeting temperature stabilization goals. These findings have implications for policy and corporate climate action.