Temporary carbon dioxide removal to offset short-lived climate forcers.

Abstract

Carbon dioxide removal (CDR) is considered for achieving the long-term temperature objectives of the Paris Agreement and national net-zero emission targets^1-5. The durability of these CDR methods varies widely, ranging from decades to theoretically permanent⁶. Temporary CDR dominates present deployment, whereas permanent solutions face further feasibility and cost challenges at scale¹. However, efforts to integrate temporary CDR into climate policies have relied on equivalency assumptions between temporary and permanent CDR that contradict physical climate science: temporary CDR cannot fully offset CO₂ emissions as permanent CDR can^6,7. Here we show that temporary CDR can serve as compensation for non-CO₂ climate forcers, particularly for short-lived species whose compensation ratios are fairly insensitive to the choice of time horizon. For instance, offsetting 1 kg CH₄ requires 498 kg CO₂ with 20-year temporary storage (such as bioplastics) or 101 kg CO₂ with 100-year storage (such as durable wood products). We suggest a critical lifetime threshold separating short-lived and long-lived species for temporary CDR applications, with implementation requiring differentiated reporting of these categories. This framework can provide a physical basis for crediting temporary CDR activities in sectors such as agriculture, in which non-CO₂ emissions dominate and direct emission reductions remain challenging.