Why the shared socioeconomic pathway framework has not been useful for improving climate change mitigation policy analysis

Abstract

Numerous ways to improve the usefulness of climate change mitigation scenarios that rely on the Shared Socioeconomic Pathway (SSP) framework that was developed over the last 10 years have been suggested. The problem with these proposals is that the diagnosis of what has led to the inability of integrated assessment modelers to properly analyze mitigation policies is wrong. The first main problem with the past use of the SSP-based mitigation scenarios is that few input variables for what is supposed to be the same SSP are given the same numerical values by different modeling teams. The more significant problem with the way in SSP-based mitigation scenarios have been used to analyze mitigation policies is that the different integrated assessment models (IAMs) have very different structures and functions. Thus, even if all the input variables comprising a single SSP had the same numerical values, the scenario results from running such a SSP through different IAMs would be quite different, leading to different understandings of the usefulness of different mitigation policies. This situation can be avoided by developing just two or three more detailed and improved IAMs focused on the critical next 10–20 years for mitigating climate change.