The role of direct air capture and negative emissions technologies in the shared socioeconomic pathways towards +1.5 °C and +2 °C futures

The development of the Shared Socioeconomic Pathways (SSPs) and associated integrated assessment modeling (IAM) exercises did not include direct air capture with carbon storage (DACCS) in their scenarios. However, recent more optimistic cost estimates and commercial or pilot-scale DACCS plants have led to increased attention to this technology in both IAM literature and in real-world policy discussions. DACCS is an energy-consuming negative emissions technology that has far lower land intensity than energy-producing BECCS, and afforestation. The requirement for different forms of DACCS, as well as their potential cost and energy efficiency improvements in the future will therefore pose unique interactions with socioeconomic and policy factors that have not yet been assessed. Here, we use the Global Change Analysis Model (GCAM) to for the first time model DACCS deployment across all 5 SSPs for below 2°C and below 1.5°C end-of-century warming goal. We assess its deployment relative to other geologic carbon storage methods, and its side effects for global energy, water, land systems. We find that subject to its ability to scale, DACCS can play a tens of Gt-CO2 yr-1 role in many of these scenarios, particularly those with delayed climate policy and or higher challenges to emissions mitigation. However, our “sustainable development” scenarios have far smaller deployments of DACCS and other negative emissions owing to immediate climate policy onset, greater ease of “conventional mitigation” and explicit consideration to limit future negative emissions reliance in our scenario design.