Geoengineering: the deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change.
This can be done two ways. If the level of carbon dioxide in the atmosphere is reduced, heat in the form of infra-red radiation can escape the earth's surface more easily. The other way is not to let the solar radiation be absorbed in the first place, by increasing the reflectivity of the Earth. Now, what would it look like if we painted all the horizontal surfaces (roofs, for example, and parking lots) white? If you find this intriguing, or if you find you have insomnia, here is a report to browse http://royalsociety.org/displaypagedoc.asp?id=35094. The Summary is not so long-winded or obtuse for casual reading.