Summary/Abstract
This paper assesses the ultimate physical limits on the amount of energy and land required for air capture and describes two systems that might achieve air capture at prices under 200 and 500 $/tC. The paper argues that air capture has important structural advantages over more conventional mitigation technologies which suggest that, in the long-run, air capture may play a significant role in mitigating CO2 emissions. In an optimal sequential decision framework with uncertainty, existence of air capture decreases the need for near-term precautionary abatement. The long-term effect is the opposite; assuming that marginal costs of mitigation decrease with time while marginal climate change damages increase, then air capture increases long-run abatement. Air capture produces an environmental Kuznets curve, in which concentrations are returned to preindustrial levels. In the second half of the paper, the authors examine the implications of air capture for the long-run policy and economics of climate change using a global integrated assessment model.