Uncertainty in non-CO2 greenhouse gas mitigation contributes to ambiguity in global climate policy feasibility

Harmsen, M., Tabak, C., Höglund-Isaksson, L. ORCID: https://orcid.org/0000-0001-7514-3135, Humpenöder, F., Purohit, P. ORCID: https://orcid.org/0000-0002-7265-6960, & van Vuuren, D. (2023). Uncertainty in non-CO2 greenhouse gas mitigation contributes to ambiguity in global climate policy feasibility. Nature Communications 14 (1) e2949. 10.1038/s41467-023-38577-4.

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Abstract

Despite its projected crucial role in stringent, future global climate policy, non-CO2 greenhouse gas (NCGG) mitigation remains a large uncertain factor in climate research. A revision of the estimated mitigation potential has implications for the feasibility of global climate policy to reach the Paris Agreement climate goals. Here, we provide a systematic bottom-up estimate of the total uncertainty in NCGG mitigation, by developing 'optimistic', 'default' and 'pessimistic' long-term NCGG marginal abatement cost (MAC) curves, based on a comprehensive literature review of mitigation options. The global 1.5-degree climate target is found to be out of reach under pessimistic MAC assumptions, as is the 2-degree target under high emission assumptions. In a 2-degree scenario, MAC uncertainty translates into a large projected range in relative NCGG reduction (40-58%), carbon budget (±120 Gt CO2) and policy costs (±16%). Partly, the MAC uncertainty signifies a gap that could be bridged by human efforts, but largely it indicates uncertainty in technical limitations.

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