Abstract
Climate boundaries are planetary boundaries for the climate system: limits within which humanity can sustainably prosper. Here we introduce a modelling framework to analyse global warming, ocean acidification, sea-level rise and Arctic sea-ice melt. Using a reduced-form model, we map out anthropogenic CO2 emissions, carbon dioxide removal and solar radiation management pathways compatible with these boundaries. We define safety levels as the probability to stay within one or several boundaries considering physical uncertainty. If CO2 emissions peak in 2030, net-zero CO2 is reached in 2050, and carbon dioxide removal capacity is 10 PgC yr−1, without solar radiation management, remaining within the global warming boundary of 2 °C exhibits a safety level of 80%. When all fou…
Abstract
Climate boundaries are planetary boundaries for the climate system: limits within which humanity can sustainably prosper. Here we introduce a modelling framework to analyse global warming, ocean acidification, sea-level rise and Arctic sea-ice melt. Using a reduced-form model, we map out anthropogenic CO2 emissions, carbon dioxide removal and solar radiation management pathways compatible with these boundaries. We define safety levels as the probability to stay within one or several boundaries considering physical uncertainty. If CO2 emissions peak in 2030, net-zero CO2 is reached in 2050, and carbon dioxide removal capacity is 10 PgC yr−1, without solar radiation management, remaining within the global warming boundary of 2 °C exhibits a safety level of 80%. When all four boundaries are considered together, the safety level drops to 35%. Our results highlight key trade-offs in mitigation options and suggest a need to assess climate boundaries holistically to develop sustainable future strategies.
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Data availability
No raw data are provided with this article because of the total size (>500 GB). However, we provide a code to generate this data.
Code availability
The source code of Pathfinder is openly available at https://github.com/tgasser/Pathfinder (last accessed 16 October 2023). A frozen version of the code as developed in the paper is available via Zenodo at https://doi.org/10.5281/zenodo.7003848 (ref. [71](https://www.nature.com/articles/s41558-025-02460-5#ref-CR71 “Gasser, T. Pathfinder: v1.0.1. Zenodo https://doi.org/10.5281/zenodo.7003848
(2022).“)). Additional code and data are available via Zenodo at https://doi.org/10.5281/zenodo.15235819 (ref. [72](https://www.nature.com/articles/s41558-025-02460-5#ref-CR72 “Bossy, T. & Gasser, T. Code for ‘Spaces of anthropogenic CO2 emissions compatible with climate boundaries’. Zenodo https://doi.org/10.5281/zenodo.15235819
(2025).“)). This contains the code to reproduce the input trajectories of Pathfinder as well as some examples of post-processing.
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Author information
Authors and Affiliations
Laboratoire des sciences du climat et de l’environnement (LSCE), IPSL, CEA/CNRS/UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France
Thomas Bossy, Philippe Ciais, Katsumasa Tanaka, Philippe Bousquet & Thomas Gasser 1.
International Institute for Applied System Analysis (IIASA), Laxenburg, Austria
Thomas Bossy & Thomas Gasser 1.
Earth System Division, National Institute for Environmental Studies (NIES), Tsukuba, Japan
Katsumasa Tanaka 1.
Centre International de Recherche sur l’Environnement et le Développement (CIRED), CNRS, EHESS, AgroParisTech, PontsParisTech, CIRAD, Nogent-sur-Marne, France
Franck Lecocq
Authors
- Thomas Bossy
- Philippe Ciais
- Katsumasa Tanaka
- Franck Lecocq
- Philippe Bousquet
- Thomas Gasser
Contributions
T.G. designed the research following a discussion with F.L. T.B. performed the research and wrote the original draft. T.B., P.C., K.T., F.L., P.B. and T.G. discussed the research and edited the paper.
Corresponding author
Correspondence to Thomas Gasser.
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Extended data
Extended Data Fig. 1 Trade-offs between year of emissions peak and CDR characteristics.
Panel a) shows the trade-offs between the date of emissions peak and the total amount of CDR needed before 2100, for a 67% safety level. Panels b) shows the trade-offs interaction between the year when CDR is deployed at large scale (more than 0.5 PgC.yr−1) and the year of peak emission for a 67% safety level. Shaded areas represent the spaces compatible with climate boundaries. Plain lines give the frontier of the compatible space. Black is for the GW boundary, green for the OA boundary, red for the RSLR boundary, blue for the ASI boundary, and purple for the combination all boundaries.
Extended Data Fig. 2 Trade-offs between SRM and CDR characteristics.
Trade-offs between available CDR and allowed SRM in the case of a peak of CO2 emission in 2030 for a 67% safety level. Shaded areas represent the spaces compatible with climate boundaries. Plain lines give the frontier of the compatible space. Black is for the GW boundary, green for the OA boundary, red for the RSLR boundary, blue for the ASI boundary, and purple for the combination all boundaries.
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Bossy, T., Ciais, P., Tanaka, K. et al. Spaces of anthropogenic CO2 emissions compatible with climate boundaries. Nat. Clim. Chang. (2025). https://doi.org/10.1038/s41558-025-02460-5
Received: 01 March 2024
Accepted: 17 September 2025
Published: 04 November 2025
Version of record: 04 November 2025
DOI: https://doi.org/10.1038/s41558-025-02460-5