After a brief overview of technology options for scrubbing carbon dioxide directly from the atmosphere and a discussion of the technical and economic hurdles that need to be overcome,  Dr. Lackner will consider the policy implications of air capture in the current climate change debate. Capture of carbon dioxide from ambient air renders emissions from any source reversible and it defines the cost of unauthorized emissions.  Rather than dwelling on the possibility that air capture could motivate a delay in action, the presentation will focus on the ability of air capture to create negative emissions, which the recent IPCC report considers necessary.  Finally, Dr. Lackner will outline different pathways for development and implementation of air capture technologies.