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Scientists: artificial steps against global warming may be dangerous, necessary

Sept. 2, 2009
Courtesy Royal Society
and World Science staff

Hu­man­ity may be forced to take cost­ly, un­tested and pos­sibly dan­ger­ous ar­ti­fi­cial meas­ures to curb glob­al warm­ing, if ef­forts to do so the nat­u­ral way prove too fee­ble, a group of sci­en­tists says.

The “nat­u­ral” way would be by cut­ting car­bon di­ox­ide emis­sion­s—but most sci­en­tists and en­vi­ron­men­tal­ists say that such cuts have been too lit­tle and quite pos­sibly too late.

Some pro­posed meas­ures against glob­al warm­ing in­volve dis­pers­ing par­t­i­cles in the at­mos­phere that would de­flect some sun­light away from the plan­et. (Im­age cour­te­sy NA­SA)


A re­port pub­lished Sept. 1 by the Roy­al So­ci­e­ty, the U.K.’s na­tional acad­e­my of sci­ence, found that ar­ti­fi­cial meas­ures will need to go in­to gear un­less fu­ture ef­forts to re­duce car­bon and si­m­i­lar “green­house gas” emis­sions are much more suc­cess­ful than they have been so far.

The ar­ti­fi­cial op­tions are known as geo­engi­neer­ing tech­nolo­gies. The re­port con­cludes that these are probably tech­nic­ally pos­sible and could be use­ful to com­ple­ment emis­sions cuts ef­forts. But the re­port iden­ti­fied ma­jor un­cer­tain­ties re­gard­ing their ef­fec­tive­ness, costs and en­vi­ron­men­tal im­pacts.

“It is an un­pal­at­a­ble truth that un­less we can suc­ceed in greatly re­duc­ing [car­bon di­ox­ide] emis­sions we are head­ed for a very un­com­fort­a­ble and chal­leng­ing cli­mate fu­ture, and geo­engi­neer­ing will be the only op­tion left,” said John Shep­herd of the Na­tional Ocean­og­ra­phic Cen­tre in South­amp­ton, U.K., who chaired the stu­dy.

“Our re­search found that some geo­engi­neer­ing tech­niques could have se­ri­ous un­in­tend­ed and detrimen­tal ef­fects on many peo­ple and ecosys­tem­s—yet we are still fail­ing to take the only ac­tion that will pre­vent us from hav­ing to rely on them.”

The re­port as­sesses the two main kinds of geo­engi­neer­ing tech­niques: car­bon di­ox­ide re­mov­al and so­lar radia­t­ion man­age­ment. The first ad­dress the root of the prob­lem—ris­ing car­bon di­ox­ide—and so is thought to have few­er un­cer­tain­ties and risks. But none has yet been dem­on­strat­ed to be ef­fec­tive at an af­ford­a­ble cost, with ac­cept­a­ble en­vi­ron­men­tal im­pacts, and they only work to re­duce tem­per­a­tures over very long timescales.

So­lar radia­t­ion man­age­ment acts by re­flect­ing the sun’s en­er­gy away from Earth, mean­ing they low­er tem­per­a­tures rap­id­ly, but do not af­fect car­bon di­ox­ide lev­els. They there­fore fail to ad­dress the wid­er ef­fects of ris­ing car­bon di­ox­ide, such as ocean acidifica­t­ion, and would need to be de­ployed for a very long time, sci­ent­ists say. Al­though they are rel­a­tively cheap to de­ploy, there are con­si­der­able un­cer­tain­ties about their re­gion­al con­se­quenc­es, and they only re­duce some, but not all, of the ef­fects of cli­mate change, while pos­sibly cre­at­ing oth­er prob­lems, ac­cord­ing to re­search­ers.

“None of the geo­engi­neer­ing tech­nolo­gies so far sug­gested is a mag­ic bul­let,” said Shep­herd.


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Humanity may be forced to take costly, untested and possibly dangerous artificial measures to curb global warming, if efforts to do so the natural way prove insufficient, a group of scientists said. The “natural” way would be by cutting carbon dioxide emissions—but most scientists and environmentalists say that such cuts have been too little and quite possibly too late. The report published Sept. 1 by the Royal Society, the U.K.’s national academy of science, found that artificial measures will need to go into gear unless future efforts to reduce carbon and similar “greenhouse gas” emissions are much more successful than they have been so far. The artificial options are known as geoengineering technologies. The report concludes that these are probably technically possible and could be useful to complement emissions cuts efforts. But the report identified major uncertainties regarding their effectiveness, costs and environmental impacts. “It is an unpalatable truth that unless we can succeed in greatly reducing [carbon dioxide] emissions we are headed for a very uncomfortable and challenging climate future, and geoengineering will be the only option left,” said John Shepherd of the National Oceanography Centre in Southampton, U.K., who chaired the study. “Our research found that some geoengineering techniques could have serious unintended and detrimental effects on many people and ecosystems—yet we are still failing to take the only action that will prevent us from having to rely on them.” The report assesses the two main kinds of geoengineering techniques: carbon dioxide removal and solar radiation management. The first address the root of the problem—rising carbon dioxide—and so is thought to have fewer uncertainties and risks. But none has yet been demonstrated to be effective at an affordable cost, with acceptable environmental impacts, and they only work to reduce temperatures over very long timescales. Solar radiation management acts by reflecting the sun’s energy away from Earth, meaning they lower temperatures rapidly, but do not affect carbon dioxide levels. They therefore fail to address the wider effects of rising carbon dioxide, such as ocean acidification, and would need to be deployed for a very long time. Although they are relatively cheap to deploy, there are considerable uncertainties about their regional consequences, and they only reduce some, but not all, of the effects of climate change, while possibly creating other problems, according to researchers. “None of the geoengineering technologies so far suggested is a magic bullet,” said Shepherd.