Investigating the Dependence of the Effectiveness of Carbon Dioxide Removal on the Amount and Rate of Removal

Abstract:

To stay within the carbon budget consistent with the 1.5°C-2°C warming limits set by the Paris Agreement, strong mitigation of our CO₂ emissions must take place. In most future climate scenarios consistent with these limits, the use of negative emissions, or carbon dioxide removal (CDR) is used to offset positive CO₂ emissions or recover a carbon budget after overshoot. The degree by which CDR can reduce the atmospheric fraction of CO₂, and surface air temperatures varies depending on the initial CO₂ concentration and state of the climate system prior to the deployment of CDR. The effectiveness of CDR at drawing down atmospheric CO₂ and temperature based on the amount and rate at which atmospheric CO₂ is removed is not well quantified. Using an Earth System Model of Intermediate Complexity, a systematic investigation of the Earth system response to CDR is performed, and the dependence of the effectiveness of CDR based on the amount and rate of atmospheric CO₂ removal is quantified. Three different amounts and five different rates of removal within the range of these amounts are investigated in this research. We show that the effectiveness of CDR decreases as the magnitude of CO₂ removed increases, and that the effectiveness of CDR at reducing surface air temperature does not depend on the level or rate of removal on century timescales. This research provides a systematic understanding of CDR as it pertains to different magnitudes and rates of removal. The quantification of the effectiveness of CDR at reducing the carbon burden and temperature in the atmosphere will allow insights into the optimal timing of implementing CDR to ensure the maximum effectiveness of carbon sequestration.