Integrated Assessment Modeling of Direct Air Capture for Negative CO₂ Emissions

Integrated assessment modeling (IAM) scenarios of the global energy, land-use, and climate systems have become increasingly reliant on future negative emissions in finding paths to limit global warming to below 2˚ C. The projected requirements for so-called negative emissions technologies (NETs) are often similar in magnitude to present-day positive emissions. This dissertation explores the implications for global and country-scale food, water, and energy systems of large-scale NET deployments, and how future policy and socioeconomic developments could influence the timing and required magnitude of these deployments in meeting ambitious climate change mitigation goals. First, a critical review was conducted to explore how IAMs could improve their treatment of NETs broadly, as well as how different NETs could interact with Sustainable Development Goals set out by the United Nations. Subsequently, a framework to model direct air capture with carbon storage (DACCS) was incorporated into the Global Change Assessment Model (GCAM), and the potential role and food-energy-water side effects of DACCS in meeting a 1.5˚ C temperature goal in 2100 were assessed. A case study was then conducted using this framework to understand the potential contribution of DACCS in meeting China’s recently announced goal of carbon neutrality by 2060. Finally, additional model development incorporated the ability to model multiple DACCS processes across 5 Shared Socioeconomic Pathway scenarios. Together, these studies reveal that DACCS could begin making large contributions to climate mitigation in the near-future and soften but not eliminate the negative side-effects of land-intensive NETs such as bioenergy with carbon capture and storage and afforestation. However, the prospect of future DACCS or other large-scale negative emissions should not serve as justification to continue delaying ambitious mitigation efforts using both conventional abatement and negative emissions technologies.