Carbon Offsets Daily

reports that a group of US scientists, led by a physicist at Columbia University in New York, is working towards creating a device that will "suck" or extract carbon-dioxide from the air. They say that a prototype of the machine should be ready in two years time. Previous attempts at creating such machines (or scrubbers) were in vain due to their high energy requirements. However, Lackner and his team claim that they will use changes in humidity to tackle this problem:

... The team says it can trap the CO2 from air on absorbent plastic sheets called ion exchange membranes, commonly used to purify water. Crucially, it has discovered that humid air can then make the membranes "exhale" their trapped CO2.

They still need to work out how exactly the carbon-dioxide captured by the device will be disposed off. Tentative solutions include using the CO2 in greenhouses for plant growth or to grow algae which could be used for food, fertilizer or fuel.

Lackner admits that their invention will not serve as a panacea for the problem of global warming. However, 

... the team says the technology may be the best way to avert dangerous temperature rises, as fossil fuel use is predicted to increase sharply in coming decades despite international efforts.