Risks of relying on uncertain carbon dioxide removal in climate policy.

Scenarios for reaching net-zero and other climate policy goals are increasingly featuring widespread adoption of novel carbon dioxide removal (CDR) technologies. However, these technologies currently represent only a small fraction of total CDR and may face various barriers to large-scale deployment. What are the consequences of planning for levels of CDR today that may differ from those realized in the future? Here, we combine decision analysis and a global integrated assessment model (GCAM) to quantify the climate, technology, economic, and equity outcomes of planning for high or low CDR adoption under uncertainty. We find that planning for high CDR under a 2 °C target leads to minimal fossil fuel phase-out before mid-century. If large-scale CDR is not feasible, the rapid transition required after mid-century increases global stranded assets by 38%. A robust policy strategy that plans for low CDR opens up the possibility to limit end-of-century temperature change to 1.5 °C.