Abstract
This paper discusses the technology of direct capture of carbon dioxide from the atmosphere called air capture. It develops a simple arithmetic description of the magnitude of the challenge of stabilizing atmospheric concentrations of carbon dioxide as a cumulative allocation over the 21st century. This approach, consistent with and based on the work of the Intergovernmental Panel on Climate Change (IPCC), sets the stage for an analysis of the average costs of air capture over the 21st century under the assumption that technologies available today are used to fully offset net human emissions of carbon dioxide. The simple assessment finds that even at a relatively high cost per ton of carbon, the costs of air capture are directly comparable to the costs of stabilization using other means as presented by recent reports of the IPCC and the Stern Review Report.