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

• Published in: Earth System Dynamics
• Main Authors: Hayman, Garry D., Comyn-Platt, Edward, Huntingford, Chris, Harper, Anna B., Powell, Tom, Cox, Peter M., Collins, William J., Webber, Chris, Lowe, Jason Anthony, Sitch, Stephen, House, Joanna I., Doelmann, Jonathan C., van Vuuren, Detlef P., Chadburn, Sarah E., Burke, Eleanor J., Gedney, Nicola
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union 2021
• Subjects: permafrost
• Online Access: https://centaur.reading.ac.uk/96959/; https://centaur.reading.ac.uk/96959/9/esd-12-513-2021%20%281%29.pdf; https://centaur.reading.ac.uk/96959/1/esd-2020-24-manuscript-version4.pdf

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 (CH4) emission mitigation, separately and in combination, on the anthropogenic fossil fuel carbon dioxide (CO2) 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 CH4 emissions has large impacts on the anthropogenic fossil fuel emission budgets, potentially offsetting (i.e. allowing extra) carbon dioxide emissions of 188-212 GtC. 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 CO2-based fertilisation. Methane mitigation is beneficial everywhere, particularly for the major CH4-emitting regions of India, USA and China. Land-based mitigation has the potential to offset 51-100 GtC globally, the large range reflecting assumptions and uncertainties associated with BECCS. The ranges for CH4 reduction and BECCs implementation are valid for both the 1.5° and 2°C ...