Carbon dioxide capture from ambient air could compensate for all carbon dioxide emissions to the atmosphere. Such capture would, for example, make it possible to use liquid, carbon-based fuels in cars or airplanes without negatively impacting the climate. We present a specific approach based on a solid sorbent in the form of an anionic exchange resin, that absorbs carbon dioxide when dry and releases it when exposed to moisture. We outline a particular implementation of such a moisture swing and discuss the scale of the collectors, the energy consumption, and the indirect carbon dioxide emissions related to the operation of carbon dioxide capture devices.