After twenty years of largely unproductive talks at the United Nations Framework Convention on Climate Change, delegates and politicians may be hoping that Geo Engineering can save us from global warming.
However, this is wishful thinking. Some proposals, such as launching solar reflectors into orbit, have more to do with science fiction than reality. Seeding clouds to reflect solar energy (one proposal involves ships that pump droplets of seawater into the atmosphere) is theoretically possible and would be easier and cheaper. However, neither would reduce the concentration of CO2 in the atmosphere and would not therefore address the root problem. The environmental consequences of such strategies are also very difficult to predict - and potentially very serious.
Devices that remove CO2 from the atmosphere would tackle the core issue, but cost and energy efficiency present problems. Either way, they are no more than long-term possibilities, not urgent solutions.
A 2009 report by the Royal Society in the UK http://royalsociety.org/policy/publications/2009/geoengineering-climate/ recommended that Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM) should only be considered as part of a wider package of options. However, it said CDR was preferable to SRM because its consequences were more predictable and less potentially dangerous.
For an overview, http://en.wikipedia.org/wiki/Geoengineering