Deployment expectations of multi-gigaton scale of carbon dioxide removal could have adverse impacts on global climate system

Abstract

The window for limiting global warming to 1.5°C is rapidly closing, necessitating immediate climate action which some have proposed includes deploying carbon dioxide removal (CDR) at scale. However, CDR is characterized by varying trade-offs and spill-over effects, and an excessive reliance on them to reach climate milestones could affect global Earth system negatively. This study quantitatively investigates the impacts associated with different levels of reliance on negative emissions for Asia’s net zero ambitions. We employ a technology-rich integrated assessment model, i.e., GCAM-TJU, a modified version of the Global Change Assessment Model (GCAM) with the capability of deploying six different CDR approaches. Different levels of CDR reliance are modeled by varying CDR deployment times, availability, and removal capacities. Key findings are that deploying tens of gigaton scale of negative emissions by mid-century will perpetuate fossil fuel reliance, slow energy transitions and push back net zero timelines. High reliance on CDR also reduces building efficiency improvements and transport electrification rates significantly. Furthermore, timing of net zero for multiple Asian countries is advanced under lower availability of CDR, resulting in lower residual emissions with significant health co-benefits. Regarding land and food, high reliance on CDR leads to significant changes in land use with a severe reduction in cropland. There are potential concerns related to water demands and fertilizer needs under excessive reliance on CDR. Overall, our results show that tens of gigaton scale of negative emissions by mid-century could seriously impede climate goals. Prioritizing non-CDR mitigation strategies through rapid electrification, carbon-neutral/negative fuels (e.g., hydrogen), and efficiency mainstreaming could accelerate decarbonization. We must strive to pursue emission cuts maximally before utilizing negative emissions. While CDR is necessary for delivering the "net" in "net-zero emissions", it is worth exploring strategies that reduce the need for excessive reliance on CDR, while also capitalizing on its advantages when it is most viable.