GoKawiilThe large-scale deployment of CDR is seen as essential to achieving net-zero greenhouse gas (GHG) emissions and remains a key part of most mitigation strategies1,33,34. However, the role of temporary CDR, which cannot store carbon permanently, remains unclear in present policy frameworks. At present, most of carbon removal—nearly 2 Gt CO 2 per year—is achieved through conventional land-based CDR1, which is arguably temporary CDR. Although new methods of durable CDR (achieving millennial-scale storage, referred to as permanent in theoretical frameworks) have been proposed, their present availability remains minimal, with most deployment slated for the future34,35. Previous attempts to include temporary CDR into existing GHG accounting have proved problematic (also demonstrated in this paper), as temporary CDR cannot offset the long-term warming effect of CO 2 emissions. Alternative policy instruments such as temporary crediting under the Kyoto Protocol address the reversal risk of non-permanent storage through periodic verification and credit renewal36 but do not quantify the climate benefit that temporary storage actually delivers. Therefore, it is important to evaluate and credit temporary CDR properly.
Here we demonstrate that temporary CDR, with its transient climate effect, can robustly compensate for short-lived non-CO 2 species but cannot fully offset long-lived CO 2 emissions6,7. On the basis of this principle, we have developed a physics-based accounting framework that quantifies required compensation ratios (α) for temporary CDR with different storage timescales (τ), enabling practical implementation of like-for-like compensation strategies. Because this compensation achieves cumulative rather than annual temperature neutrality, some residual annual temperature oscillation remains even at the optimal compensation ratio (Fig. 4). Policymakers assigning priority to temperature stabilization during critical periods may therefore choose to overcompensate by deploying higher α values than the minimum required or by estimating α so that even the peak warming of species x is compensated (that is, AGTP x (t) + α × AGTP tCDR (t, τ) ≤ 0, for each year t).
A key feature of our methodology is its strategic alignment with the analytical framework underpinning the GWPs already in use under the UNFCCC. Although GWP has well-documented limitations in representing short-lived climate forcers30,37, and alternative metrics such as GWP* have been proposed to address these issues38, these alternatives have not yet been officially adopted; we therefore align our framework with the present policy structure to facilitate practical implementation. The compensation metric α can be calculated using either temperature change (iAGTP, as we presented) or radiative forcing (AGWP, shown in Supplementary Table 8 and Extended Data Fig. 2). In the latter case, 1/α is mathematically equivalent to a GWP for temporary CDR, although we have refrained from presenting it in such a way for two reasons. First, it has long been argued by the climate science community that temperature-related metrics better describe climate impacts than those derived from radiative forcing39. Second, and more importantly, because temporary CDR cannot fully offset long-lived GHGs and notably CO 2 , assuming a GWP for temporary CDR in the present UNFCCC accounting framework is tantamount to assuming full fungibility with other climate forcers. This approach is not only physically incorrect but it could lead to strong distortions and disincentives if applied in a market or credit context. Therefore, implementing temporary CDR in climate policies and carbon markets requires at least a ‘two-basket’ approach to emissions accounting, segregating long-lived and short-lived climate forcers to reflect their differing fundamental behaviour40. This approach avoids the inaccuracies that arise when lumping all forcers together, offering a more precise and physically correct metric aligned with existing reporting frameworks20,41, and now enabling appropriate inclusion of temporary CDR. For instance, carbon already tracked in harvested wood product pools under national GHG inventories constitutes a form of temporary CDR whose potential to compensate for short-lived climate forcers can be directly quantified by applying the corresponding α values to carbon inputs, assuming their associated storage timescales but without requiring detailed tracking of product-pool decay dynamics. With this word of caution about the applicability of standard metrics, we provide a table for GWPs, GTPs and iGTPs of temporary CDR in Extended Data Table 2.
This framework has immediate relevance for agricultural sectors, in which emissions are dominated by short-lived species such as CH 4 . For countries with substantial hard-to-abate pastoral sectors, such as Brazil and New Zealand, our framework provides quantitative guidance for using temporary CDR to compensate livestock emissions. This sector-specific approach complements recent proposals for differentiated mitigation strategies, which emphasize that fossil CO 2 requires permanent geological storage42. That said, direct emission reductions of air pollutants such as CH 4 and black carbon (BC) provide substantial health co-benefits through improved air quality that CDR cannot replicate43. Temporary CDR should therefore be reserved for genuinely hard-to-abate sources rather than substituting for achievable pollution control. Conversely, our framework identifies a valuable application in which temporary CDR can support public health objectives: compensating for the unmasked warming from cleaning up short-lived cooling agents such as sulfate aerosols44, thereby enabling air quality improvements without compromising climate goals.
Although these applications demonstrate the potential of the framework, successful implementation requires careful attention to several operational and institutional considerations. First, for continuous emissions such as agricultural methane, maintaining climate benefits requires continuous deployment of temporary CDR through new or rotating projects, matching the temporal pattern of emissions (Supplementary Fig. 7). Second, although our framework provides scientifically consistent accounting, it does not eliminate reversal risks or moral hazard. Whether implemented through governmental regulations or voluntary corporate schemes, successful deployment requires strict adherence to the physics-based quantification identified here, transparent verification systems to ensure the integrity of temporary storage and prevent reversal risks, and complementary governance mechanisms to address moral hazard and prevent misuse. These considerations suggest that temporary CDR has strategic importance as a bridging mechanism but also clear limitations as an offsetting tool, and that appropriate safeguards in accounting rules would be needed to ensure its proper use45.
Beyond these implementation considerations, we emphasize that the metrics used at present under the UNFCCC rely only on physical science, thereby avoiding complications and arbitrary choices related to economics (such as the discounting rate used in tonne-year accounting methods), and possibly increasing the transparency of assessments46,47 and acceptability within the policymaking community. However, the integration of economic factors into this framework remains a possible extension, especially as previous work in that direction has failed to properly capture the physical climate dynamic18,48,49. If the costs associated with temporary CDR technologies are quantified, it becomes feasible to compare the physical effectiveness of temporary CDR strategies at reducing climate impacts against their financial implications within a more holistic analysis50,51. However, we note that limitations are substantial, both for costs of future climate impacts as well as reliability of the temporary carbon storage. Future work could seek to bridge this gap by integrating this compensation metric and financial costs in integrated assessment models to estimate a scientifically guided pricing of different temporary CDR strategies, while accounting for the implementation limitations discussed above.