A multi-model analysis of long-term emissions and warming implications of current mitigation efforts

Mitigation pathways tend to focus on an end temperature target and calculate how to keep within these bounds. This work uses seven integrated assessment models to consider current mitigation efforts and project likely temperature trajectories. Most of the integrated assessment modelling literature focuses on cost-effective pathways towards given temperature goals. Conversely, using seven diverse integrated assessment models, we project global energy CO2 emissions trajectories on the basis of near-term mitigation efforts and two assumptions on how these efforts continue post-2030. Despite finding a wide range of emissions by 2050, nearly all the scenarios have median warming of less than 3 degrees C in 2100. However, the most optimistic scenario is still insufficient to limit global warming to 2 degrees C. We furthermore highlight key modelling choices inherent to projecting where emissions are headed. First, emissions are more sensitive to the choice of integrated assessment model than to the assumed mitigation effort, highlighting the importance of heterogeneous model intercomparisons. Differences across models reflect diversity in baseline assumptions and impacts of near-term mitigation efforts. Second, the common practice of using economy-wide carbon prices to represent policy exaggerates carbon capture and storage use compared with explicitly modelling policies.

Automated summary

Using seven integrated assessment models, this study projects global energy CO2 emissions trajectories based on near-term mitigation efforts and assumptions on post-2030 efforts. Although a wide range of emissions scenarios is found for 2050, most of them result in median warming of less than 3 degrees C by 2100. However, even the most optimistic scenario is insufficient to limit global warming to 2 degrees C. The study also highlights the importance of diverse model intercomparisons and the exaggeration of carbon capture and storage use in representing policy with economy-wide carbon prices.