Abstract
Most climate policies are designed under a deterministic Earth system and their climate implications evaluated ex-post. Approaches that incorporate uncertainty ex-ante to anticipate Earth system risks remain underexplored. Here, we derive global climate strategies with an ex-ante approach, employing an integrated assessment framework that embeds estimates of physical uncertainty obtained through Bayesian fusion of Earth system models’ and observations’ data. These ex-ante strategies mitigate risks in the Earth system through precautionary measures unseen with the ex-post approach, in cost-benefit analysis and cost-effective implementations of various Earth system targets. Net-zero CO2 emissions must typically be reached a decade earlier, which can require up to a doubling of the near-term carbon price. Importantly, sustained and possibly century-long net-negative emissions must be planned for, albeit not to overshoot targets as in traditional scenarios but to mitigate long-term Earth system risks. This heightens the challenge faced by humanity to build a safe future within Earth system boundaries.
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Data availability
The data generated in this study is available for download at https://zenodo.org/records/1846148191.
Code availability
Original code of DICE-2016R2 unavailable publicly; code of a subsequent version available at https://www.openicpsr.org/openicpsr/project/114711/version/V1/view. Code of a stand-alone version of Pathfinder (in Python), along with all input data used for calibration, available at https://zenodo.org/records/719416192. GAMS code of our simulations is available at https://zenodo.org/records/1849152992.
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Acknowledgements
TG, AR, CC, AB, and MO were supported by the Austrian Science Fund (FWF) under grant agreement P31796-N29 (ERM project, DOI:10.55776/P31796). TG also acknowledges support by the European Union’s Horizon 2020 research and innovation programme under grant agreements #773421 (Nunataryuk project), #820829 (CONSTRAIN project) and #101003536 (ESM2025 project).
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T.G., A.R., C.C., A.B., and M.O. designed the study and experiments. T.G. designed the original Pathfinder model. A.B. and A.R. implemented two successive versions of the optimisation setup; C.C. adjusted and ran the final version and additional sensitivity tests. T.G. led the writing of the manuscript.
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Gasser, T., Rezai, A., Cheritel, C. et al. Negative emissions to mitigate Earth system risks. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69896-x
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DOI: https://doi.org/10.1038/s41467-026-69896-x
