Spaces of anthropogenic CO2 emissions compatible with climate boundaries

[Geoengineering News]

https://www.nature.com/articles/s41558-025-02460-5

Authors: Thomas Bossy, Philippe Ciais, Katsumasa Tanaka, Franck Lecocq, Philippe Bousquet & Thomas Gasser 

04 November 2025

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.

Source: Nature Climate Change