17:15 〜 19:15
[ACG55-P03] Projecting long-term pathways of greenhouse gas emissions and carbon dioxide removal with an Integrated Assessment Model emulator
キーワード：IAM emulator, Extended scenario, Carbon dioxide removal
Integrated Assessment Models (IAMs) combine economy, energy, and sometimes land-use modeling approaches and are commonly used to evaluate climate policies under least-cost scenarios. The marginal abatement cost (MAC) curve approach has been commonly used in climate policy analyses to show the carbon price level for a given abatement level, which has also been applied as a way to parameterize the complex behavior of IAMs. Here, we propose a new methodological framework to i) emulate the IAM’s emission reductions in response to carbon price pathways through MAC curves (i.e., IAM emulator) and then ii) extend IAM’s emission pathways (usually given until 2100) to 2300 with the emulator.
As part of the Horizon Europe RESCUE and OptimESM projects, our approach is used to extend the greenhouse gas (GHG) emission pathways from different sources and carbon dioxide removal (CDR) pathways generated by the REMIND-MAgPIE model. A key feature of the approach is that we individually capture the emission reductions associated with CDRs (i.e., afforestation, bioenergy and carbon capture and storage (BECCS), direct air capture with carbon storage (DACCS), industrial CCS, and ocean alkalinity enhancement (OAE)) through MAC curves. Our approach relies on the following simplifying assumptions: i) MAC curves are assumed time-independent over periods, ii) abatement levels across different sectors for each gas (CO2, CH4, and N2O) are partially linked through a uniform carbon price, as are those for different CDR technologies. iii) abatement levels across different GHGs can be partially linked using the fixed price ratios based on the Global Warming Potential over a 100-year time horizon (GWP100) metric.
We approximated the dynamics of REMIND-MAgPIE with MAC curves, using equation log(f(x)+1)=a*xb+c*xd for sectoral gases and equation f(x)=a*xb+c*xd for CDR options, respectively. f(x) represents the corresponding carbon price level at x, while the variable x represents the abatement level relative to the assumed baseline level, expressed as a percentage for sectoral emissions or the absolute amount of CO2 removed for CDR options. a, b, c, and d are the parameters that are optimized for each case. Additionally, we derived the maximum abatement levels of REMIND-MAgPIE from its simulation results under all carbon budgets, which reflect the limit of, for example, CCS capacity and sectoral mitigation potential. We also calculated for each gas, sector, and CDR option the maximum first and second derivatives of temporal changes in abatement levels to capture the limits of the technological change rate and the socio-economic inertia.
We combined the IAM emulator (emIAM) with a reduced-complexity climate model ACC2 to generate extended scenarios to 2300. Before 2100, a set of harmonized scenarios (e.g., cumulative carbon budget of 500 GtCO2 using the end-of-century approach) were prescribed as input into the coupled model ACC2-emIAM. With these harmonized scenarios prescribed up to 2100, we further generated extended emission pathways to 2300 using the least-cost approach for temperature trajectories (1 °C, 1.5 °C, and 2 °C), allowing for overshoots of up to 2 °C. Our generated emission pathways illustrate various CDR use cases over the coming centuries. Fig.1 presented an overview of these extended scenarios, while Fig. 2 indicated a specific example with details of emissions by gas, sector, and CDRs.
Our extended scenarios, generated on the basis of long-term climate-economy interactions, can serve as input to Earth System Models investigating the long-term consequences of climate change mitigation strategies, particularly the implications of CDR deployment and associated Earth system dynamics over centennial timescales.
References
Xiong, W, K Tanaka, P Ciais, D Johansson, M Lehtveer (2025) emIAM v1.0: an emulator for Integrated Assessment Models using marginal abatement cost curves. Accepted to Geoscientific Model Development on 2 January 2025. doi:10.5194/egusphere-2022-1508
Tanaka, K, W Xiong, L Merfort, N Bauer (submitted) Emulating an Integrated Assessment Model to Project Long-Term Emissions and Carbon Dioxide Removal Pathways to 2300. Submitted to the 2025 ESIF - Economics+Climate Science (ESIFCLIM), March 27 - 28, 2025, Barcelona, Spain.
As part of the Horizon Europe RESCUE and OptimESM projects, our approach is used to extend the greenhouse gas (GHG) emission pathways from different sources and carbon dioxide removal (CDR) pathways generated by the REMIND-MAgPIE model. A key feature of the approach is that we individually capture the emission reductions associated with CDRs (i.e., afforestation, bioenergy and carbon capture and storage (BECCS), direct air capture with carbon storage (DACCS), industrial CCS, and ocean alkalinity enhancement (OAE)) through MAC curves. Our approach relies on the following simplifying assumptions: i) MAC curves are assumed time-independent over periods, ii) abatement levels across different sectors for each gas (CO2, CH4, and N2O) are partially linked through a uniform carbon price, as are those for different CDR technologies. iii) abatement levels across different GHGs can be partially linked using the fixed price ratios based on the Global Warming Potential over a 100-year time horizon (GWP100) metric.
We approximated the dynamics of REMIND-MAgPIE with MAC curves, using equation log(f(x)+1)=a*xb+c*xd for sectoral gases and equation f(x)=a*xb+c*xd for CDR options, respectively. f(x) represents the corresponding carbon price level at x, while the variable x represents the abatement level relative to the assumed baseline level, expressed as a percentage for sectoral emissions or the absolute amount of CO2 removed for CDR options. a, b, c, and d are the parameters that are optimized for each case. Additionally, we derived the maximum abatement levels of REMIND-MAgPIE from its simulation results under all carbon budgets, which reflect the limit of, for example, CCS capacity and sectoral mitigation potential. We also calculated for each gas, sector, and CDR option the maximum first and second derivatives of temporal changes in abatement levels to capture the limits of the technological change rate and the socio-economic inertia.
We combined the IAM emulator (emIAM) with a reduced-complexity climate model ACC2 to generate extended scenarios to 2300. Before 2100, a set of harmonized scenarios (e.g., cumulative carbon budget of 500 GtCO2 using the end-of-century approach) were prescribed as input into the coupled model ACC2-emIAM. With these harmonized scenarios prescribed up to 2100, we further generated extended emission pathways to 2300 using the least-cost approach for temperature trajectories (1 °C, 1.5 °C, and 2 °C), allowing for overshoots of up to 2 °C. Our generated emission pathways illustrate various CDR use cases over the coming centuries. Fig.1 presented an overview of these extended scenarios, while Fig. 2 indicated a specific example with details of emissions by gas, sector, and CDRs.
Our extended scenarios, generated on the basis of long-term climate-economy interactions, can serve as input to Earth System Models investigating the long-term consequences of climate change mitigation strategies, particularly the implications of CDR deployment and associated Earth system dynamics over centennial timescales.
References
Xiong, W, K Tanaka, P Ciais, D Johansson, M Lehtveer (2025) emIAM v1.0: an emulator for Integrated Assessment Models using marginal abatement cost curves. Accepted to Geoscientific Model Development on 2 January 2025. doi:10.5194/egusphere-2022-1508
Tanaka, K, W Xiong, L Merfort, N Bauer (submitted) Emulating an Integrated Assessment Model to Project Long-Term Emissions and Carbon Dioxide Removal Pathways to 2300. Submitted to the 2025 ESIF - Economics+Climate Science (ESIFCLIM), March 27 - 28, 2025, Barcelona, Spain.