The most prominent geoengineering proposal is to spray minute reflective particles into the atmosphere. These are designed to act as a “global shadecloth” by blocking a small percentage of sunlight from warming the Earth.
Scientists in the US and UK are developing this technology, and it looks feasible. For just a few billion dollars it may be possible to inject these particles into the sky in an attempt to cool the planet.
Newcastle Herald, 4 Dec 2013