ReducingtheEffectsofClimateChangeMarkRowereportsontheincreasinglyambitiousgeo-engineeringprojectsbeingexploredbyscientistsSuchisourdependenceonfossilfuels,andsuchisthevolumeofcarbondioxidealreadyreleasedintotheatmosphere,thatmanyexpertsagreethatsignificantglobalwarmingisnowinevitable.Theybelievethatthebestwecandoiskeepitatareasonablelevel,andatpresenttheonlyseriousoptionfordoingthisiscuttingbackonourcarbonemissions.Butwhileafewcountriesaremakingmajorstudiesinthisregard,themajorityarehavinggreatdifficultyevenstemmingtherateofincrease,letalonereversingit.Consequently,anincreasingnumberofscientistsarebeginningtoexplorethealternativeofgeo-engineering-atermwhichgenerallyreferstotheintentionallarge-scalemanipulationoftheenvironment.Accordingtoitsproponents,geo-engineeringistheequivalentofabackupgenerator:ifPlanA-reducingourdependencyonfossilfuels-fails,werequireaPlanB,employinggrandschemestoslowdownorreversetheprocessofglobalwarming.Geo-engineeringhasbeenshowntowork,atleastonasmalllocalisedscale.Fordecades,MayDayparadesinMoscowhavetakenplaceunderclearblueskies,aircrafthavingdepositeddryice,silveriodideandcementpowdertodisperseclouds.Manyoftheschemesnowsuggestedlooktodotheopposite,andreducetheamountofsunlightreachingtheplanet.Themosteye-catchingideaofallissuggestedbyProfessorRogerAngeloftheUniversityofArizona.Hisschemewouldemployupto16millionminutespacecraft,eachweighingaboutonegram,toformatransparent,sunlight-reactingsunshadeinanorbit1.5millionkmabovetheEarth.Thiscould,arguesAngel,reducetheamountoflightreachingtheEarthbytwopercent.Themajorityofgeo-engineeringprojectssofarcarriedout-whichincludeplantingforestsindesertsanddepositingironintheoceantostimulatethegrowthofalgae-havefocusedonachievingageneralcoolingoftheEarth.Butsomelookspecificallyatreversingthemeltingatthepoles,particularlytheArctic.Thereasoningisthatifyoureplenishtheicesheetsandfrozenwatersofthehighlatitudes,morelightwillbereflectedbackintospace,soreducingthewarmingoftheoceansandatmosphere.TheconceptofreleasingaerosolspraysintothestratosphereabovetheArctichasbeenproposedbyseveralscientists.Thiswouldinvolveusingsulphurorhydrogensulphideaerosolssothatsulphurdioxidewouldformclouds,whichwould,inturn,leadtoaglobaldimming.Theideaismodelledonhistoricvolcanicexplosions,suchasthatofMouncPinatubointhePhilippinesin1991,whichledtoashort-termcoolingofglobaltemperaturesby0.5°C.Scientistshavealsoscrutinisedwhetherit’spossibletopreservetheicesheetsofGreenlandwithreinforcedhigh-tensioncables,preventingicebergsfrommovingintothesea.MeanwhileintheRussianArctic,geo-engineeringplansincludetheplantingofmillionsofbirchtrees.Whereastheregionsnativeevergreenpinesshadethesnowandabsorbradiation,bircheswouldshedtheirleavesinwinter,thusenablingradiationtobereflectedbythesnow.Re-routingRussianriverstoincreasecoldwaterflowtoice-formingareascouldalsobeusedtoslowdownwarming,saysomeclimatescientists.Butwillsuchschemeseverbeimplemented?Generallyspeaking,thosewhoaremostcautiousaboutgeo-engineeringarethescientistsinvolvedintheresearch.Angelsaysthathisplanis'nosubstitutefordevelopingrenewableenergy:theonlypermanentsolution.AndDrPhilRaschoftheUS-basedPacificNorthwestNationalLaboratoryisequallyguardedabouttheroleofgeo-engineering:'Ithinkallofusagreethatifweweretoendgeo-engineeringonagivenday,thentheplanetwouldreturntoitspre-engineeredconditionveryrapid...