emIAM v1.0: an emulator for integrated assessment models using marginal abatement cost curves

Journal article, 2025

We developed an emulator for integrated assessment models (emIAM) based on a marginal abatement cost (MAC) curve approach. Drawing on the output of IAMs in the Exploring National and Global Actions to reduce Greenhouse gas Emissions (ENGAGE) Scenario Explorer and the GET model, we derived an extensive array of MAC curves, encompassing 10 IAMs, at the global and regional levels for 10 regions; three gases (CO2, CH4, and N2O); eight portfolios of available mitigation technologies; and two emission sources. We tested the performance of emIAM by coupling it with the simple climate model ACC2 (ACC2-emIAM). Our analysis showed that the optimizing climate-economy model ACC2-emIAM adequately reproduced a majority of the original IAM emission outcomes under similar conditions. This can facilitate systematic exploration of IAMs with small computational resources. emIAM holds the potential to enhance the capabilities of simple climate models as a tool for calculating cost-effective pathways directly aligned with temperature targets.