Fair carbon removal obligations under climate response uncertainty
Cutting residual emissions can reduce the carbon removal needed to hedge against climate response uncertainty
Read the published paper ↗doi.org/10.1080/14693062.2025.2481138
We estimate that 323–787 GtCO2 (interquartile range) of additional 'preventive' carbon dioxide removal (CDR) may be needed after net-zero CO2 in 1.5 °C pathways. This is removal held in reserve in case the Earth system responds more strongly to emissions than the median expectation. CDR is considered unavoidable for global climate goals, yet current assessments tend to overlook this uncertainty. We use the IPCC's '1.5 °C with no or limited overshoot' pathways, which already deploy 418–763 GtCO2 (interquartile range) of removal after net-zero. The preventive amount comes on top, for a very likely (≥90%) chance of reaching 1.5 °C in 2100.
We cannot know now whether a net-zero society will need that preventive capacity, but the option must be available to it. We find that reducing residual emissions from long-lived climate forcers (such as CO2 and N2O) and short-lived ones (such as CH4) can significantly reduce the preventive removal required. This matters because large-scale CDR raises serious feasibility and sustainability concerns.
We also explore an illustrative equitable allocation of this responsibility. North America is allocated a preventive removal responsibility of 13 tCO2 per capita per year over 2020–2100 in a pathway with limited cuts to residual emissions. In a pathway with deeper residual cuts, this falls to 5.3 tCO2 per capita per year. Limiting so-called 'hard-to-abate' emissions, alongside rapid near-term cuts, is thus a preventive measure against over-reliance on removal.
@article{ganti_fair_2025,
title = {Fair carbon removal obligations under climate response uncertainty},
copyright = {All rights reserved},
issn = {1469-3062, 1752-7457},
url = {https://www.tandfonline.com/doi/full/10.1080/14693062.2025.2481138},
doi = {10.1080/14693062.2025.2481138},
abstract = {Deploying carbon dioxide removal (CDR) is considered unavoidable to meet global climate goals. However, current assessments of the potential role of CDR tend to overlook uncertainty in the Earth System response to our emissions. Here, we assess the level of ‘preventive’ CDR needed to draw warming down to 1.5°C in case of a stronger-than-median Earth System response. Using the ‘1.5°C with no or limited overshoot’ ensemble of pathways assessed by the Intergovernmental Panel on Climate Change (IPCC), we estimate that around 323–787 Gt CO2 (interquartile range) of additional CDR (beyond the 418–763 Gt CO2 (interquartile range) already deployed in these pathways) may be required after net zero CO2 for a very likely ({\textgreater} = 90\%) chance of reaching 1.5°C in 2100. We cannot know now whether a net zero society will need to utilize the preventive capacity, but the option must be available to them. Feasibility and sustainability concerns associated with large-scale CDR deployment raise fundamental questions over reducing potential future CDR reliance in light of Earth System uncertainty. Our analysis shows that reducing residual emissions from long-lived (e.g. CO2 and N2O) and short-lived climate forcers (e.g. CH4) can significantly reduce the scale of preventive CDR required. We also explore an illustrative approach to equitably allocate global preventive CDR needs. North America is allocated a per-capita removal responsibility of 13 t CO2/ capita annually between 2020 and 2100 in a pathway with limited residual emission cuts, which is more than halved in another with deeper residual emission cuts. Our results underscore the importance of limiting so-called ‘hard-to-abate’ emissions in addition to rapid near-term cuts in emissions as preventive measures to avoid over-reliance on unsustainable levels of preventive CDR.},
language = {en},
urldate = {2026-01-13},
journal = {Climate Policy},
author = {Ganti, Gaurav and Pelz, Setu and Klönne, Uta and Gidden, Matthew J. and Schleussner, Carl-Friedrich and Nicholls, Zebedee},
month = mar,
year = {2025},
pages = {1--13},
}