Regional variation in the effectiveness of methane-based and land-based climate mitigation options

• Published in: Earth System Dynamics
• Main Authors: G. D. Hayman, E. Comyn-Platt, C. Huntingford, A. B. Harper, T. Powell, P. M. Cox, W. Collins, C. Webber, J. Lowe, S. Sitch, J. I. House, J. C. Doelman, D. P. van Vuuren, S. E. Chadburn, E. Burke, N. Gedney
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: Science; Q; Geology; QE1-996.5; Dynamic and structural geology; QE500-639.5; Jules; permafrost
• Online Access: https://doi.org/10.5194/esd-12-513-2021; https://doaj.org/article/4a448660d18d40979523384ad7b35134

Scenarios avoiding global warming greater than 1.5 or 2 ∘ C, as stipulated in the Paris Agreement, may require the combined mitigation of anthropogenic greenhouse gas emissions alongside enhancing negative emissions through approaches such as afforestation–reforestation (AR) and biomass energy with carbon capture and storage (BECCS). We use the JULES land surface model coupled to an inverted form of the IMOGEN climate emulator to investigate mitigation scenarios that achieve the 1.5 or 2 ∘ C warming targets of the Paris Agreement. Specifically, within this IMOGEN-JULES framework, we focus on and characterise the global and regional effectiveness of land-based (BECCS and/or AR) and anthropogenic methane ( CH 4 ) emission mitigation, separately and in combination, on the anthropogenic fossil fuel carbon dioxide ( CO 2 ) emission budgets (AFFEBs) to 2100. We use consistent data and socio-economic assumptions from the IMAGE integrated assessment model for the second Shared Socioeconomic Pathway (SSP2). The analysis includes the effects of the methane and carbon–climate feedbacks from wetlands and permafrost thaw, which we have shown previously to be significant constraints on the AFFEBs. Globally, mitigation of anthropogenic CH 4 emissions has large impacts on the anthropogenic fossil fuel emission budgets, potentially offsetting (i.e. allowing extra) carbon dioxide emissions of 188–212 Gt C. This is because of (a) the reduction in the direct and indirect radiative forcing of methane in response to the lower emissions and hence atmospheric concentration of methane and (b) carbon-cycle changes leading to increased uptake by the land and ocean by CO 2 -based fertilisation. Methane mitigation is beneficial everywhere, particularly for the major CH 4 -emitting regions of India, the USA, and China. Land-based mitigation has the potential to offset 51–100 Gt C globally, the large range reflecting assumptions and uncertainties associated with BECCS. The ranges for CH 4 reduction and BECCS implementation are valid for both ...