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Unformatted text preview: www.sciencemag.org SCIENCE VOL 327 29 JANUARY 2010 527 POLICY FORUM The Politics of Geoengineering CLIMATE CHANGE Jason J. Blackstock 1,2 * and Jane C. S. Long 3 Nations commencing geoengineering research must commit to full international collaboration and transparency. D espite mounting evidence that severe climate change could emerge rap- idly, the global reduction of carbon emissions remains alarmingly elusive ( 1 , 2 ). As a result, concerned scientists are now ask- ing whether geoengineeringthe intentional, large-scale alteration of the climate system might be able to limit climate change impacts. Recent prominent reviews have emphasized that such schemes are fraught with uncertain- ties and potential negative effects and, thus, cannot be a substitute for comprehensive miti- gation ( 3 , 4 ). But as unabated climate change could itself prove extremely risky, these reviews also recommend expanding geoengi- neering research. As such research is consid- ered ( 5 7 ), a process for ensuring global trans- parency and cooperation is needed. Geoengineering schemes can be divided into two very different categories: carbon dioxide removal (CDR) and solar radiation management (SRM) ( 4 ). CDR schemes such as direct air capture ( 8 ) or ocean fertilization ( 9 ) would remove the cause of climate change. However, technical challenges and large uncertainties surrounding large-scale CDR deployment, along with long delays in the cli- matic response to carbon forcing, mean that it would take decades to have notable effect ( 4 ). Conversely, SRM could substantially in u- ence the climate in months, but with much greater uncertainty about the net effects. SRM schemes such as stratospheric aerosols and cloud brightening aim to cool the planet by re ecting a fraction of the incoming sunlight away from Earth. Natural experiments caused by volcanoes have demonstrated the rapid impact potential of SRM, and such schemes should be technically simple to deploy at low cost, relative to mitigation ( 3 , 4 ). But SRM would at best unevenly ameliorate regional cli-...
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