"Climate change policies at both the national and international levels have traditionally focused on measures to mitigate greenhouse gas (GHG) emissions and to adapt to the actual or anticipated impacts of changes in the climate. As a participant in several international agreements on climate change, the United States has joined with other nations to express concern about climate change. Some recent technological advances and hypotheses, generally referred to as 'geoengineering' technologies, have created alternatives to traditional approaches to mitigating climate change. If deployed, these new technologies could modify the Earth's climate on a large scale. Moreover, these new technologies may become available to foreign governments and entities in the private sector to use unilaterally--without authorization from the United States government or an international treaty--as was done in the summer of 2012 when an American citizen conducted an ocean fertilization experiment off the coast of Canada. The term 'geoengineering' describes an array of technologies that aim, through large-scale and deliberate modifications of the Earth's energy balance, to reduce temperatures and counteract anthropogenic climate change. Most of these technologies are at the conceptual and research stages, and their effectiveness at reducing global temperatures has yet to be proven. Moreover, very few studies have been published that document the cost, environmental effects, sociopolitical impacts, and legal implications of geoengineering. If geoengineering technologies were to be deployed, they are expected to have the potential to cause significant transboundary effects."
CRS Report for Congress, R41371