Originally published as:
Melamed, M. L., Monks, P. S., Goldstein, A. H., Lawrence, M. G., Jennings, J. (2015 online):
The international global atmospheric chemistry (IGAC) project: Facilitating atmospheric chemistry research for 25 years. - Anthropocene .
DOI: http://doi.org/10.1016/j.ancene.2015.10.001
The international global atmospheric chemistry (IGAC) project:
Facilitating atmospheric chemistry research for 25 years
Megan L. Melamed
a,*, Paul S. Monks
b, Allen H. Goldstein
c, Mark G. Lawrence
d, Jeff Jennings
aaIGACInternationalProjectOffice,CIRES,UniversityofColorado,Box216UCB,Boulder,CO,80309,USA
bDepartmentofChemistry,UniversityofLeicester,LeicesterLE17RH,UK
cDepartmentofCivilandEnvironmentalEngineeringandDepartmentofEnvironmentalScience,PolicyandManagementUniversityofCalifornia,137Mulford Hall,UniversityofCalifornia,Berkeley,CA94720-3114,USA
dInstituteforAdvancedSustainabilityStudies,BerlinerStrasse130,Potsdam14467Germany
ARTICLE INFO
Articlehistory:
Received19May2015
Receivedinrevisedform7October2015 Accepted11October2015
Availableonlinexxx
Keywords:
Atmosphericchemistry Airpollution Climatechange Earthsystem
Internationalcollaborations
ABSTRACT
This paper outlines the scientific achievements and insights gained from the International Global AtmosphericChemistry(IGAC)project,whichhasbeenjointlysponsoredbytheinternationalCommission onAtmosphericChemistryandGlobalPollution(iCACGP)andtheInternationalGeosphere-Biosphere Programme (IGBP) since1990. A shorthistoryof IGACis followedby representative keyscientific achievements.Over25years,IGAChasfacilitatedinternationalscientificcollaborationsthathavedeepened theunderstandingofhowatmosphericcompositionimpactsairquality,climatechange,andecosystems fromlocaltoglobalscales.ActivitiesfosteredbyIGACshowhowthefieldofatmosphericchemistryhas evolvedfromafocusontheatmosphereasasinglenaturalcompartmentoftheEarthsystemtoanemphasis onitsinteractionswithotherEarthcomponents,suchasoceans,thecryosphere,thebiosphere,andthe impactofhumansonatmosphericcomposition.Finally,oneofIGAC’ssignificantaccomplishmentshasbeen building scientificcapacityandcooperationinthefieldofatmosphericchemistryaround theglobe, especiallythroughitsbiennialscienceconferences.AspartofIGBP,IGAChascontributedtoimprovingthe currentstateofknowledgeoftheEarthsystemandprovidingthescientificbasistosuggestthatwehave entered the Anthropocene. IGACwill continue to play this role and expand its connections to thelarger global changeandsustainabilityresearchcommunities,capitalizingonthetransitiontoFutureEarth.
ã2015TheAuthors.PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Abbreviations:ACPC,aerosols,clouds,precipitationandclimate;AICI,air–icechemical interactions;ASGAMAGE,air–seagasexchange;ACE-Asia,Asianaerosol characterizationexperiment;ASTEX,Atlanticstratocumulustransitionexperiment;ACCMIP,atmosphericchemistryandclimatemodelintercomparisonproject;BIBEX, biomassburningexperiment:impactontheatmosphereandbiosphere;BATREX,biosphere–atmospheretracegasexchange;BATGE,biosphere–atmospheretracegas exchangeinthetropics:influenceoflandusechange;CARBICE,carbondioxideintercalibrationexperiment;CCMI,chemistry–climatemodelinitiative;CACR,Commissionon AtmosphericChemistryandRadiation;DEBITS,depositionofbiogeochemicallyimportanttracespecies;APARE,EastAsia–NorthPacificregionalexperiment;EXPRESSO, experimentforregionalsourcesandsinksofoxidants;FOS/DECAFE,fireofSavannas/dynamicsandatmosphericchemistryintheequatorialforest;ACE-1,firstaerosol characterizationexperiment;FAA,focusonatmosphericaerosols;GLOCHEM,globalatmosphericchemistrysurvey;GEIA,globalemissionsinitiative;GHOST,globalHO systematictests;GIM,globalintegrationandmodeling;GLOCARB,globaltroposphericcarbondioxidenetwork;GLONET,globaltroposphericozonenetwork;HESS,high- latitudeecosystemsassourcesandsinksoftracegases;IDAF,IGAC/DEBITS/Africa;ITCT-2k2,intercontinentaltransportandchemicaltransformations2002;IAPSO, InternationalAssociationforthePhysicalSciencesoftheOceans;IAMAS,InternationalAssociationofMeteorologyandAtmosphericSciences;iCACGP,international CommissiononAtmosphericChemistryandGlobalPollution;IGBP,InternationalGeosphere-BiosphereProgramme;IGAC,InternationalGlobalAtmosphericChemistry Project;ITOY,InternationalTroposphericOzoneYears;IUGG,InternationalUnionofGeodesyandGeophysics;JOSIE,Jülichozoneintercomparisonexperiment;MAGE,Marine aerosolandgasexchange;MLOPEX,MaunaLoaobservatoryphotochemistryexperiment;MOZAIC,measurementsofozoneinairbusin-serviceaircraft;MAC,multiphase atmosphericchemistry;NASA,NationalAeronauticsSpaceAdministration;NOAA,NationalOceanicandAtmosphericAdministration;ITCT2004,NewEnglandairquality study2004;NOMHICE,nonmethanehydrocarbonintercomparisonexperiment;ACE-2,NorthAtlanticregionalaerosolcharacterizationexperiment;NARE,NorthAtlantic regionalexperiment;PEACE,PacificexplorationofAsiancontinentalemissions;PEM-WestA,Pacificexploratorymission-westA;PEM-WestB,Pacificexploratorymission- westB;PASC,polaratmosphericandsnowchemistry;POLARCAT,polarstudyusingaircraft,remotesensing,surfacemeasurementsandmodelsofclimate,chemistry,aerosols andtransport;RCEI,reactivechlorineemissionsinventory;RICE,ricecultivationandtracegasexchange;TROPOZ-II,secondtroposphericozonecampaign;STARE,south tropicalAtlanticregionalexperiment;SAFARI,SouthernAfricanfire/atmosphericresearchinitiative;TRAGEX,tracegasexchange:mid-latitudeterrestrialecosystemsandthe atmosphere;TRACE-A,transport&atmosphericchemistryneartheequator-Atlantic;TARFOX,troposphericaerosolradiativeforcingobservationalexperiment;TRAGNET,U.
S.tracegasnetwork;NSF,USNationalScienceFoundation;WMO,WorldMeteorologicalOrganization.
* Correspondingauthor.Fax:+13034921149.
E-mailaddresses:megan@igacproject.org(M.L.Melamed),P.S.Monks@leicester.ac.uk(P.S.Monks),ahg@berkeley.edu(A.H.Goldstein),mark.lawrence@iass-potsdam.de (M.G.Lawrence).
http://dx.doi.org/10.1016/j.ancene.2015.10.001
2213-3054/ã2015TheAuthors.PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
xxx–xxx ContentslistsavailableatScienceDirect
Anthropocene
j o u r n a l h o m e p a g e : w w w . e l s ev i er . c o m / l o c a t e/ a n c en e
1.Introduction
Human emissions of pollutants into the atmosphere have causeddramatictransformationsoftheEarthsystem,alteringair quality, climate and nutrient flows in every ecosystem. These alterationssuggestthatwehaveenteredanewgeologicalepoch, theAnthropocene.Theeffectsofhumanemissionsaremanifold:
Airqualityhasamajorimpactonpublichealthandecosystems (UNEP/WMO,2011;OECD,2012;WHO,2014):
Changing atmospheric composition is driving climate change (IPCC,2013):
TheatmospherictransportanddepositionofSaharandusttothe Amazon determines the amount of phosphorus in this vital ecosystem(Artaxoetal.,1990;Korenetal.,2006;Ansmannetal., 2009;Bristowetal.,2010;Yuetal.,2015andreferencestherein).
The atmosphere is the integrator of the Earth system.
Understanding theglobal atmosphere requires an organization tocreate an international network of scientists to providethe intellectualleadershipinareasofatmosphericchemistrythatmust beaddressed,promoted, and thatwould benefitfrom research acrossdisciplinesandgeographicalboundaries.Acknowledgement of this need led to the formation of the International Global AtmosphericChemistry(IGAC)Project.
TheoriginsoftheInternationalGlobalAtmosphericChemistry (IGAC) projectdate back to the 1950s, when theInternational AssociationofMeteorologyandAtmosphericSciences(IAMAS)of the International Union of Geodesy and Geophysics (IUGG) initiatedtheCommissiononAtmosphericChemistryandRadiation (CACR),whichwaslaterrenamedtheinternationalCommissionon AtmosphericChemistryandGlobalPollution(iCACGP).Atthefifth iCACGPSymposiumin1983,acommitteewasappointedtoexplore the sponsorship of an international research program on atmospheric chemistry.A paralleleffortbegan in 1981 when a
numberofatmosphericchemistsandmeteorologistswrotealetter totheUSNationalScienceFoundation,urgingthegovernmentto support the development of a coordinated study on global tropospheric chemistry.Thiseffortresultedin a 1984reportof the U.S. NationalResearch Council, entitledGlobal Tropospheric Chemistry: A Plan for Action (National Research Council (NRC), 1984). The report recommended that, “The US undertake a cooperativeresearcheffortwithothercountriesininvestigating thechemistryoftheglobaltroposphere.”
Asaresultofthesetwosimultaneousefforts,ameetingwasheld in1988inDookie,Australia,ontheformationoftheInternational GlobalAtmosphericChemistry(IGAC)Project(Fig.1).Participants definedtheinitialsixfocithatwouldserveasthefoundationofthe firstphaseofIGAC. Thesixfociwere:(1)Naturalvariabilityand anthropogenicperturbationsofthemarineatmosphere;(2)Natural variationandanthropogenicperturbationoftropicalatmospheric chemistry;(3)Theroleofpolarregionsinthechangingatmospheric composition;(4)Theroleofborealregionsinchangingatmospheric composition;(5) Globaldistribution,transformations,trendsand modeling;and(6) Internationalsupportactivities.In1990,IGAC officiallybecame a core projectof theInternationalGeosphere- BiosphereProgramme(IGBP)andiCACGP(Galbally,1989),withits InternationalProjectOffice(IPO)locatedinandfundedbytheUS National ScienceFoundation (NSF),National Oceanicand Atmo- sphericAdministration(NOAA)andNationalAeronauticsandSpace Administration(NASA).
ThroughoutIGAC’srich25-yearhistory,thescientificfocihave evolvedinwaysthatreflecthowthefieldofatmosphericchemistry has matured. The first phase of IGAC, 1990–1999, focused on understanding the chemistry of thenatural atmosphere. In its secondphase,2000–2010,IGACfosteredscientificcollaborations thatbuiltuponourunderstandingofthenaturalatmosphereand began to examine how human emissions were impacting atmospheric chemistry and composition from local to global scales.Initsthirdandcurrentphase,IGAC’smissionisto“facilitate
Fig.1.Participantsofthe1988meetinginDookie,AustraliathatwastheformativeIGACmeeting.
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atmospheric chemistry research toward a sustainable world”, recognizingthefundamentalroleofhumanactivityindetermining atmospheric composition and how it relates to sustainability issues such as climate change, human health and ecosystems (Fig.2).ThisevolutionofIGACcoincideswiththetransitionofIGAC fromacoreprojectofIGBPtoaprojectofthenewFutureEarth initiative, a global research platform designed to provide the knowledge needed to supporttransformations toward sustain- ability.
Thispaperreportshow,overthecourseof25years,IGAChas facilitatedresearchinatmosphericchemistrytounderstandhow atmosphericcompositionimpactsairquality,climatechangeand nutrient flows in ecosystems. This understanding has been achievedthroughIGACfacilitatingactivitieson:
Synthesisandintegration
Internationalfieldmeasurementcampaigns
AtmosphericchemistryattheEarthsysteminterfaces Fundamentalscience
Capacitybuilding
Amongtheresults oftheseeffortsarefourbooks,32special issues and numerous peer reviewed journal articles. These documents show that IGAC has helped defined the goals, objectives, and priorities, and has acted as initiator, catalyst and coordinator for the international atmospheric chemistry community.
2.IGACScienceachievementsinadvancingEarthsystemscience 2.1.Synthesisandintegration
Gaininganintegratedviewofatmosphericchemistryhasbeen critical to developing the subject. The global nature of the troposphere has suggested a need to integrate multinational efforts.IGAChasplayedacentralroleinorganizing,coordinating, andpublishingseveralpublicationsthatsynthesizeinternational atmosphericchemistryresearch(seeTable1).Thesepublications underline the importance of IGAC in providing a platform for synthesis efforts without overly emphasizing one institute or nation.
GlobalAtmospheric-BiosphericChemistry(Prinn,1994b)greatly improved the understanding of the chemical and biological processesthatdeterminethecompositionofEarth’satmosphere.
AtmosphericChemistryinaChangingWorld(Brasseuretal.,2003)is consideredthefirstinternationalassessmentofglobaltropospher- icchemistry.Monksetal.(2009)broughttotheforefrontthepoint thatlong-rangetransportofairpollutantshasasignificantimpact onregionalairquality,demonstratingthatairpollutionisnota local,butaglobalissue.Asthepercentageoftheworldpopulation living in urban areas surpassed the 50% mark in 2008, IGAC releasedtheextensivereportWMO/IGACImpactsofMegacitieson AirPollutionandClimate(Zhuetal.,2012)thatsummarizedthe currentstateofknowledgeregardingairpollutionandclimatein megacitiesacrossAfrica,Asia,SouthAmerica,NorthAmericaand Europe.Inresponsetoacallfrompolicymakerstounderstandthe climateimpactsof blackcarbon,anIGAC-led effortpublisheda hallmark synthesis onBounding the Role of Black Carbon inthe Climate System: AScientific Assessment (Bond et al., 2013).This study showed that black carbon (BC) is not only a major air pollutant, but that previous studies underestimated the direct climateforcingduetoBCbyaboutafactoroftwo,makingBCthe secondmostimportantclimateforceraftercarbondioxide(CO2) (Fig.3).Thestudyalsohighlightedthevastcomplexityofvarious competing effects andthedifficultyof accountingand scenario development, especially due to co-emissions of other climate- forcingpollutantsinreachingthisestimate(Fig.4).TheIGAC-led synthesis publications indicatd how the field of atmospheric chemistry has evolved from understanding the natural atmo- sphere,tounderstandingtheimportanceofhumanemissionsand theirroleinairpollutionatthelocaltoglobalscale,toemphasizing thepressingneedtounderstandatmosphericchemistryatacity levelowingtotheimpactsofairpollutiononhumanhealth,to providingpolicyrelevantresearchtoaddresssustainabilityissues, suchasairpollutionandclimatechange.
2.2.Internationalfieldmasurementcampaigns
Exploringthetroposphereandgaininginsightintoitschanging tracegascompositionremainscriticalinanumberofareasfrom local air pollution to climate. IGAChas cultivatedinternational scientificcollaborationsthathaveledtothecoordinationoffield measurement campaigns on intercontinental transport and chemicaltransformations,aerosolcharacterization,biomassburn- ing and ozone chemistry (see Table 2), all of which included substantial international cooperation for in-situ observations, remotesensing,dataanalysisandmodelingefforts.Theabilityof IGAC to foster scientific collaborations that bring together
Fig.2. CurrentIGACvision.
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multinationalfieldmeasurementcampaignsintoanoverarching international research program allows scientists to have more collaboratorsandobservationstodrawfrom.Thus,fieldcampaign fosteredbyIGACresultsinasummuchgreaterthanitsparts.
Thefieldcampaignsthattookplaceintheearlytomid-1990s focusedmainlyongas-phasechemistry,whichatthetimewasnot well understood and was the dominant research area in atmospheric chemistry. One of the earliest campaigns was the East Asia-North Pacific Regional Experiment (APARE), which advanced understanding of the chemical processes and long- rangetransportoverthenorth-westernPacificOcean.Contempo- rary toAPARE, theNorth AtlanticRegional Experiment (NARE) investigated ozone, its precursors and its photochemical co- products in the near-continent region of North America and Europe. Both APARE and NARE showed that anthropogenic pollutionhasalargeimpactonozoneproductionovertheNorth Pacific and the North Atlantic. This finding highlighted the important need to understand how human emissions impact atmosphericcomposition.Inadditiontothesefieldcampaignsthat focusedonlong-rangetransportandchemicaltransformationof
atmospheric gases, IGAC coordinated a series of three field campaigns specifically on ozone chemistry in the early 1990s undertheGlobalAtmosphericChemistrySurvey(GLOCHEM).The GLOCHEMfieldcampaignsprovidedimportantobservationsand modeling studies toreduce the uncertainties in the budgetof troposphericozone.Thiseffortfocusedonmeasurementsofkey species that play roles in thephotochemical transformation of ozone,oddnitrogen,andoddhydrogenspeciesintheremotefree troposphere.It also showed thatlong-range transport of stable trace gases and mineral aerosol had a significant impact on controllingtheconcentrationofthesekeyspecies.
Asgas-phasechemistry becamebetterunderstood, attention turnedmoretowardaerosols,whichwereknowntoalsoplayan importantrole indeterminingatmosphericcomposition, witha significantanduncertaindirectandindirectclimateforcing.This workledtotheemergenceofchemicalandphysicalpropertiesof aerosolsasthenewhottopicinatmosphericchemistrybeginning in the late 1990s. At this time, IGAC fostered a series of four internationalfieldmeasurementcampaignsdesignedtoquantify thechemical, physicaland meteorological processescontrolling Table1
IGACledsynthesispublications.
Title Reference
GlobalAtmospheric-BiosphericChemistry Prinn,1994a,b
AtmosphericChemistryinaChangingWorld Brasseuretal.,2003
AtmosphericCompositionChange-GlobalandRegionalAirQuality Monksetal.,2009 WMO/IGACImpactsofMegacitiesonAirPollutionandClimate Zhuetal.,2012 BoundingtheRoleofBlackCarbonintheClimateSystem:AScientificAssessment Bondetal.,2013
Fig.3.GloballyaveragedclimateforcinginunitsofWm2fromblackcarbonemissionsintheyear2005comparedtothosein1750(pre-industrial).Theupperredbar indicatesabestestimateof0.71wm 2directradiativeforcingduetoblackcarbon,whichismorethan2greaterthanthebestpriorestimateof0.34Wm 2fromtheIPCC FourthAssessmentreport(IPCC,2007).FigurefromBondetal.,2013.
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theevolutionandpropertiesoftheatmosphericaerosolrelevantto radiativeforcing and climate(Fig.5).The southernhemisphere marineAerosolCharacterizationExperiment(ACE-1)wasthefirst intheseriesand took placein1995 overthesouthwestPacific Ocean, south of Australia. The second in the series was TroposphericAerosolRadiativeForcingObservationalExperiment (TARFOX),whichtookplaceofftheEastCoastoftheUS.In1997,the third experiment in the series,North Atlantic regionalAerosol Characterization Experiment (ACE-2), was carried out over the NorthAtlanticOceanbetweenPortugal,theAzoresandtheCanary Islands. The final experiment is the series, Asian Aerosol CharacterizationExperiment(ACEAsia),whichincludedbothan intensiveobservationperiodinthespringof2001andalonger- termnetworkofobservationstoassessseasonalandinterannual variability from 2000 to 2003. This series of experiments to characterizeaerosolsacrosstheglobesetthefoundationforthe next generation of laboratory, field and modeling studies on aerosolcharacterization(Fig.6).
Advancementsinaerosolcharacterizationbeginninginthelate 1990sresultedinfieldcampaignsofthe2000sfocusingonboth gas-phasechemistryandaerosolcharacterization.Nearlyadecade after the successful APARE and NARE campaigns in 2002, the IntercontinentalTransportand ChemicalTransformations(ITCT- 2k2) and Pacific Exploration of Asian Continental Emissions
(PEACE) experiments took place to further investigate the transportofAsian emissionsacrosstheNorthPacificandtothe westcoastofNorthAmerica,thistimeincludingmanyinstruments to studyaerosols. Two years later, as partof theInternational ConsortiumforAtmosphericResearchonTransportandTransfor- mation,theNew EnglandAir QualityStudy(NEAQS-ITCT 2004) investigatedthechemicalprocessandtransportofpollutantsfrom theMidwestoftheUS,acrosstheUSeastcoast,overtheNorth AtlanticandintoEurope.Thefinalfieldmeasurementcampaign takingplaceaspartoftheITCTstudieswasthePolarStudyusing Aircraft, RemoteSensing,Surface Measurementsand Models of Climate, Chemistry, Aerosols and Transport (POLARCAT), which investigatedthetransportofpollutantsproducedfromemissions at mid-latitudes to the Arctic. The ITCT campaigns provided scientific evidence to show that the long-range transport of anthropogenicandnatural emissionscouldinteract,inboththe gas-phaseandinaerosols,towardfarreachingimpactsacrossthe globe(Monksetal.,2009).
In addition to the long-range transport ITCT and ACE field campaigns,thestudyofbiomassburningwasalsobringingtothe forefront the need to investigate aerosol characterization in additiontogas-phasechemistrytotrulyunderstandtheimpacts ofbiomassburningontheatmosphereandbiosphere.TheBiomass BurningExperiment: Impacton theAtmosphereand Biosphere Fig.4.Schematicoverviewofthecomplexityofunderstandingtheroleofblackcarbonintheclimatesystem.FigurefromBondetal.,2013.
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(BIBEX) coordinated three different international efforts on biomass burning in 1992; South Tropical Atlantic Regional Experiment(STARE),TransportandAtmosphericChemistrynear theEquator-Atlantic(TRACE-A)andSouthernAfricanFire/Atmo- sphericResearchInitiative(SAFARI). Thefieldcampaignswithin BIBEXinvestigatedchemicallyimportantgasesandaerosolspecies resultingfrombiomassburning,theimpactofbiomassburningon regionaland global scales, the short- and long-term effects of biomassburningontheatmosphere,andimprovedunderstanding ofbiogeochemicalconsequencesduetoatmosphericdepositionof biomassburningproducts.
IGAC’s leadership in guiding the community to collaborate acrossgeographical boundariesonnewand emerging topicsin atmosphericchemistryisevidentintheevolutionofthefieldof atmosphericchemistry–fromgas-phasechemistrytoaerosolsto theinteractionsofthetwothroughoutthe1990sand2000s.
2.3.AtmosphericchemistryattheEarthsysteminterfaces
Astheunderstandingoftheatmosphereasasinglecompart- mentwithintheEarthsystemincreased,theneedtounderstand howtheatmosphereinteractedwithothercompartmentsofthe Table2
PublicationsfromIGACFosteredInternationalMeasurementFieldCampaigns.
IntercontinentalTransportAndChemicalTransformations IndicativeReference
EastAsia-NorthPacificRegionalExperiment(APARE) Akimoto,1992
PacificExploratoryMission-WestA(PEM-WestA) Hoelletal.,1996
PacificExploratoryMission-WestB(PEM-WestB) Hoelletal.,1997
NorthAtlanticRegionalExperiment(NARE) Fehsenfeld&Penkett,1992;Fehsenfeldetal.,1996;
Penkettetal.,1998
PacificExplorationofAsianContinentalEmissions(PEACE) Parish,2004
IntercontinentalTransportandChemicalTransformations(ITCT-2k2) Parish,2004
NewEnglandAirQualityStudy(NEAQS-ITCT2004) Parish,2006
PolarStudyusingAircraft,RemoteSensing,SurfaceMeasurementsandModelsofClimate,Chemistry,Aerosols andTransport(POLARCAT)
Stohletal.,2009;
Lawetal.,2014
AerosolCharacterization
FirstAerosolCharacterizationExperiment(ACE-1) Batesetal.,1998;Batesetal.,1999 TroposphericAerosolRadiativeForcingObservationalExperiment(TARFOX) Russell,1999;Hartleyetal.,2000 NorthAtlanticRegionalAerosolCharacterizationExperiment(ACE-2) Rodhe,2000
AsianAerosolCharacterizationExperiment(ACE-Asia) Huebertetal.,2004
BiomassBurning
BiomassBurningExperiment:ImpactontheAtmosphereandBiosphere(BIBEX) Brasseuretal.,2003
SouthTropicalAtlanticRegionalExperiment(STARE) Andreaeet al.,1996
Transport&AtmosphericChemistryneartheEquator-Atlantic(TRACE-A) Andreaeetal.,1996 SouthernAfricanFire/AtmosphericResearchInitiative(SAFARI) Lindesayetal.,1996 FireofSavannas/DynamicsandAtmosphericChemistryntheEquatorialForest(FOS/DECAFE) Lacaux,1995 ExperimentforRegionalSourcesandSinksofOxidants(EXPRESSO) Delmasetal.,1999
Ozone
GlobalAtmosphericChemistrySurvey(GLOCHEM)
MaunaLoaObservatoryPhotochemistryExperiment(MLOPEX) AtlasandRidley,1996
SecondTroposphericOzoneCampaign(TROPOZ-II) Jonquièresetal.,1998
MeasurementsofOzoneinAirbusin-serviceAircraft(MOZAIC) Marencoetal.,1998
Fig.5. Schematicoftheclimateeffectsofaerosolsonclimate(source:ACE-1ProjectDescription,https://www.eol.ucar.edu/field_projects/ace-1).
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Earth system evolved as an emerging area of research in atmosphericchemistry,withtheideathattheatmosphereisthe integratoroftheEarthsystem.IGAChasandcontinuestoplaya prominentroleindevelopinginterdisciplinarynetworksthatbring togetherscientiststoaddressatmosphericchemistryattheEarth systeminterfaces,includingatmosphere-biosphere,atmosphere- oceanandatmosphere–cryosphere(seeTable3)interactions.The interdisciplinary networks fostered by IGAC on atmospheric chemistry at the interfaces eventually led tothe formation of twomoreIGBPcoreprojects,theSurfaceOceanLandAtmosphere Study(SOLAS) and theIntegrated Land Ecosystem-Atmosphere ProcessesStudy (iLEAPS).IGAC continuesto collaborateclosely withSOLASandiLEAPSonatmosphericchemistryatthebiosphere, oceanandcryosphereinterfaces.
Atmosphericchemistryattheinterfacesrequiresunderstanding theemissionstotheatmospherefromthebiosphere,oceansand cryosphere, as well as the deposition of chemicals from the atmosphere to these interfaces, and how these are coupled to feedbacks in theEarth system.Much of the focusin this area, especiallyintheearly1990s,wasontracegasexchange.Intheearly 1990s,IGACfosteredmanyactivitiesontracegasexchangefrom thebiosphere,oceanandcryosphere.Specificactivitiesincludedthe TraceGasExchange:Mid-LatitudeTerrestrialEcosystemsandthe Atmosphere(TRAGEX)toMarineAerosolandGasExchange(MAGE) to Tropospheric Chemistry of the Antarctic Region. Important discoveriesatthistimeweretheimpactofnitrogenfertilizerson thefluxesofmethane(CH4),CO2,andnitrousoxide(N2O)tothe atmosphere(Smithetal.,1994)andcompoundsofmarineorigin, Fig.6. Theglobalbreadthofaseriesofaerosolcharacterizationexperimentsthatsetthefoundationforfuturelaboratory,fieldandmodelingstudiesonaerosol characterization.(FigurefromRaesetal.,2000).
Table3
PublicationsfromIGACFosteredActivitiesonAtmosphericChemistryattheInterfaces.
Atmosphere-biosphere References
High-LatitudeEcosystemsasSourcesandSinksofTraceGases(HESS) Reeburgh,1993
TheInteractiveAtmosphere:GlobalAtmospheric-BiosphereChemistry Prinn,1994a
TraceGasExchange:Mid-LatitudeTerrestrialEcosystemsandtheAtmosphere(TRAGEX) Smith&Robertson,1992
Biosphere-AtmosphereTraceGasExchange(BATREX) Brasseuretal.,2003
Biosphere-AtmosphereTraceGasExchangeintheTropics:InfluenceofLandUseChange(BATGE) Matson&Delmas,1992
RiceCultivationandTraceGasExchange(RICE) Sass&Neue,1992;Sass&Neue,1994
DepositionofBiogeochemicallyImportantTraceSpecies(DEBITS) Ayersetal.,1992;
Vetetal.,2014
U.S.TraceGasNetwork(TRAGNET) Ojimaetal.,2000
Atmosphere-ocean
MarineAerosolandGasExchange(MAGE) Huebert,1993;Huebert,1996
AtlanticStratocumulusTransitionExperiment(ASTEX) Albrechtetal.,1995
Air-SeaGasExchange(ASGAMAGE) Jacobsetal.,1999;Oost,2013
Atmosphere–cryosphere
PolarAtmosphericandSnowChemistry(PASC) Barrie&Delmas,1994
TroposphericChemistryoftheAntarcticRegion[SpecialIssues] Bodhaine&Barrie,1992
TroposphericChemistryoftheArcticRegion[SpecialIssue] Gruzden&Sitnov,1993
PolarsternExpedition Plattetal.,1992
PolarSunriseExperiment Barrieetal.,1994
Air-IceChemicalInteractions(AICI) Shepsonetal.,2007;McNeilletal.,2013
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suchasdimethylsulfide,affectclimate,theoxidativecapacityofthe atmosphereand thestratosphericozone layer (Bodhaine et al.,1992).
Tounderstandtheimpactofcloudsontheclimate,studyingthe interactionsbetweenaerosolsandcloudsiscritical.Inmanycases, thisstudyrequiresunderstandingtheemissionsofprecursorsand/
or aerosols from the biosphere, ocean, and cryosphere. Under MAGE,theAtlanticStratocumulusTransitionExperiment(ASTEX) wasorganizedtostudytherelationshipbetweenmarinechemis- try,aerosols,clouds,andair/seaexchange. AhighlightofASTEX was the discovery that non-sea-salt sulfate and nitrate have a substantialimpactoncloudcondensationnucleiovertheNorth AtlanticRegion(Harrisonetal.,1996).
Also important tounderstandingthe exchangebetweenthe atmosphere and other interfaces is establishing long-term monitoringnetworks.IGACfosteredthedevelopmentoftwosuch networks.TheTraceGasNetwork(TRAGNET)developedanopen databaseofmultiyeartracegasfluxandancillarydatafromawide rangeof ecosystems across North America, Europeand Central America.TRAGNETfocusedonthefluxesofCH4,NOX,andN2O.The datacollectedovermultipleyearswereusedinaprocess-oriented model,Intercomparison,tostudythecontrolsofecosystemand landusemanagementontracegasfluxes.TheIDAF(IGAC/DEBITS/
Africa)monitoringnetworkprovidedthefirstconsistentmeasure- mentofwetanddry depositioninAfrica(Fig.7).Althoughthe numberofmonitoringsitesinAfricacouldbeincreased,especially inEastAfrica,thecurrentsitesprovidelong-termdatasetspivotal inquantifyingthefutureimpactsofsulfuremissionsinAfrica,as thepopulationofmanyAfricancitiesincreasesenergydemandand hencesulfuremissions(Vetetal.,2014).
A hallmark of research at the Earth system interfaces is developing interdisciplinary knowledge.This work oftenbrings togetherscientists frombiology, oceanographyand cryospheric science with atmospheric scientists to better understand how processesinteractingattheseinterfacesimpactthecompositionof the atmosphere. By studying atmospheric chemistry at the interfaces, we can begin to fully understand the role of the atmosphere as the integrator of the Earth system, including theimpactofhumansonthesystem.
2.4.Fundamentalunderpinningscientificactivities
Recently,IGACpublishedapositionpaperonthefutureofthe fundamentalsofatmosphericchemistry(Abbattetal.,2014).The
article stressed the importance of maintaining a strong three- leggedstool approach of laboratory,ambient observations,and modelingstudiestoaddressthemostpressingissuesofourtime.
Eachlegofthestoolisonlyasstableasthefundamentalchemistry thatunderpinsit,i.e.withineachleg,theneedexiststounderstand theconnectionsbetweenthefundamentalpropertiesandreactiv- ityofmoleculesandobservableatmosphericphenomena(Fig.8).
Over the years, IGAC hasfostered, and will continue tofoster, activities that focus on research on fundamental atmospheric chemistry in order to keep the three-legged stool balanced (Table4).
Intheearlyyearsofresearchinatmosphericchemistry,muchof the laboratory work focused on measuring gas-phase rate constantsinordertounderstandtheproductionofphotochemical smog.Throughunderstandingchemicalreactionsandtheirrates, goingintothefieldwasnecessarytoapplytheknowledgegainedin the laboratory to investigate the reactions in the “real world”. ThesefieldcampaignsoftenrequiredmeasurementIntercompari- sonactivities,suchastheNonmethaneHydrocarbonIntercompar- isonExperiment(NOMHICE),fosteredbyIGAC,ortheJülichOzone IntercomparisonExperiment.Measurementintercomparisonac- tivities are often donein the laboratory after thefundamental developmentofinstruments,orinthefieldaftertheinstruments have been deployed in atmospheric conditions. NOMHICE, for example,wasalaboratory-basedintercomparisonexperimentin which participating groups sent around different samples of ambientlevelsofvariousatmosphericnon-methanehydrocarbons toidentifyexisting issues within each group’sanalysis, correct theseissuesandthereforeensurequalitycontrolofhydrocarbon measurementthroughouttheworld(Apeletal.,1994).
Similartomeasurement techniques,modelsare alsoimpor- tantinintercomparisonprojectstoreproduceobservationsand/
orevaluatehowtheyperformcomparedtoeachother.IGAChas organized modelintercomparison activities suchas theGlobal IntegrationandModeling(GIM)andtheAtmosphericChemistry andModelIntercomparison Project(ACCMIP). The Fourth IPCC assessment (IPCC, 2013) included model runs of ACCMIP, providing for the first time atmospheric chemistry in climate modeling. Through ACCMIP, it was shown that the aerosol effective radiative forcing (ERF) has masked a substantial percentageoflate20thandearly21stcenturyglobalgreenhouse forcing, indicating the importance of including atmospheric chemistrywhenstudyingclimate(Shindelletal.,2013).IGACis
Fig.7. Vegetationandlocationmapofthe10measurementstationsoftheIDAFmonitoringnetwork.FigurefromVetetal.,2014.
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fostering a new Chemistry-Climate Model Initiative (CCMI) to continueemphasizingatmosphericchemistryinclimatemodel- ing.Theinitiativeemphasizestheimportanceofmodeldevelop- mentand updatestoincludethemostuptodatefundamental sciencefromthelaboratoryandfield.
Understandingemissionsisa critical partofstudying atmo- sphericcompositionanditchanges.Since1990,IGAChasfostered theGlobalEmissionsInitiative(GEIA),whichaimstodevelopand distributescientificallysoundandpolicy-relevant inventoriesof gasesandaerosolsemittedintotheatmospherefromnaturaland anthropogenicsources(Scholesetal.,1994).Thedevelopmentand analysis of emission inventories requires measuring emission factorsinthelaboratory.Thesemeasurementsareimportantfor developing bottom-up emissions inventory, in-situ and remote sensing measurements for top-down verification. Atmospheric modelingisalsoimportanttocomparethetwodatasets.Inmany cases, emissions inventories are developed not for scientific researchbuttosupportpolicies,suchas theU.S. CleanAirAct.
In recognition of this point, GEIA has evolved to become a community effort that builds bridges between environmental scienceandpolicytocreateandmakeavailable,forbothscientific and policy applications, the highest quality information about emissions. GEIA is an excellent example of how the field of atmosphericchemistry hasevolved towardemphasizingpolicy- relevantissuesrootedinfundamentalscience.
2.5.Capacitybuilding
AprimaryroleofIGACistobuildscientificcapacityinthefieldof atmosphericchemistryaroundtheglobe.IGAChasastrongfocuson engagingthenextgenerationofearlycareeratmosphericscientists andscholarsfromdevelopingcountriesbyprovidingtravelgrantsto IGACco-sponsoredworkshops,meetings,andconferencesaswellas highlightingtheirworkintheIGACnewsletter.Early careerscientists joinaninternationalnetworkofatmosphericscientistsearlyintheir careerthatwillfurtherfacilitateatmosphericchemistryresearchat aninternationallevel.Forthedevelopingcountryscientists,IGAC fosters creating a strong cohesive community of atmospheric scientists in under-represented regions of the world. IGAC also connectsthescientiststothelargercommunityinordertofoster international collaborations. IGAC also works to communicate atmosphericchemistryresearchtotheinternationalatmospheric chemistry community, and to the wider global change and sustainabilitycommunities,includingstakeholders,policymakers andthepublic.
IGAC’sScienceConferenceisaprimarymechanismforIGACto buildcooperationanddisseminatescientificinformationacrossits internationalcommunity.ThefirstIGACScienceConferencewas heldin1993inEilat,Israel.Since,IGAChasheldfourteenscience conferences,consistentlybecomingabiennialconferencestarting in 2002 (see Table 5). The conference is jointly held with the iCACGP Symposiumeveryfouryears.ThebiennialIGACScience Conference is regarded as THE international conference on atmospheric chemistry and participation in the conference is typicallyintherangefrom350to650participants.Since 2004, IGAChasincludedanEarlyCareerScientistsProgramaspartofthe conferencetofosterthenext generationofscientists. TheIGAC conferencesandtheEarlyCareerProgramhaveshownthathelping young scientiststoformaninternational networkofcolleagues enhances future international collaborations in atmospheric chemistry.InadditiontoparticipatingintheEarlyCareerScience ProgramatthebiennialIGACScienceConferences,IGACencour- agesyoungscientiststojointheIGACcommunitybyparticipating in IGAC Activities and attending IGAC workshops and training schools, for which IGAC Early Career Travel Grants are often available (www.igacproject.org, clink on “Join IGAC” to receive announcementsonopportunitiesforearlycareerscientists).
Inadditiontocultivatingthenextgenerationofscientists,IGAC supports capacitybuildinginthedevelopingworld.Manygreat scientists work in many regions of the world, but often their researchisconductedindependentlyandtheirresultsoftendonot reach, orin turnbenefitfrom,theinternational community.As researchquestions in atmospheric chemistryand theirconnec- tions to societal issues become more global, engaging these scientists is important to incorporate their research and local knowledgeof theseregionsoftheworld.Therefore,since 2011, IGAC has fostered the formation of national/regional working groupsthataimtofacilitatescientificcollaborationsbothwithin the nation/region and between the nation/region and the internationalatmosphericchemistrycommunity.ThegoalofIGAC National/RegionalWorkingGroupsistwo-fold:tocreateastrong cohesivecommunityofatmosphericscientistsinaspecificnation/
regionthattogetherhaveasumgreaterthantheirparts;andto connect the National/Regional Working Groups to the larger multilateralIGACcommunitytofosterinternationalcollaboration.
TheIGACNational/RegionalWorkingGroupshavealreadyresulted in enhanced collaborations between the international IGAC communityandChina,LatinAmericaandSoutheastAsia.
3.Lookingforward
Aprescientneedremainsforresearchinglobalandregional atmosphericchemistrytoaddressthecoupledscientificchallenges ofairqualityandclimateintheAnthropocene.IGACisresponding to this challenge by facilitating atmospheric chemistry research toward a sustainable world. This challengeis achieved through IGAC’s three focal activities: fostering community, building capacity,andprovidingleadership.
Fosteringcommunity
IGACisaninternationalcommunityofatmosphericscientists actively collaboratingacrossgeographicalboundaries anddisci- plinesinordertocontributetoaddressingthemostpressingglobal changeandsustainabilityissuesthroughscientificresearch.
Buildingcapacity
IGAC is building scientific capacity through its national and regional working groups, itsearly career scientists program, its biennialconferencesandsupportofnumerousthematicworkshops.
Fig.8.Keepingthethree-leggedstoolapproachtoatmosphericchemistryresearch balancedrequireslaboratorystudies,fieldobservationsandmodelingthatmust eachberootedstronglyinfundamentalscience.
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Providingleadership
IGAC provides intellectual leadership by identifying and fosteringactivitiesoncurrentandfutureareaswithinatmospheric chemistrythatwouldbenefitfromresearchacrossgeographical boundariesand/ordisciplines.
The field of atmospheric chemistryis at its coreinterdisci- plinary.Sinceits inception,the fieldhasalso engaged societal partners.Atmospheric scientists are an amalgam of engineers, physicists, meteorologist, biologists, computer scientists, and chemist,all fields required tofully understand the roleof the atmosphereas theintegrator of theEarth system.IGAC works closelywithotherglobalenvironmentalchangeorganizationsto increaseunderstanding of theinteractions between the atmo- sphere-biosphere, atmosphere-ocean, atmosphere–cryosphere, and atmosphere-human interactions. The discipline of atmo- sphericchemistrybeganinthe1950stoaddresspressingissues related to air quality. Engagement with societal partners has included co-designing research and co-producing solutions in order to tackle air pollution, an issue that is still a major concern across the world. IGAC will continue to work with societal partners to facilitate co-design and co-production of knowledgewhereappropriateforaddressingglobalchangeand sustainabilityissues.
Therefore,thetransitionofIGACtoaresearchprojectofthenew internationalinitiativeFutureEarthin2015(FutureEarth,2013,
2014) is an appropriate and exciting opportunity for the internationalatmosphericchemistrycommunity.FutureEarthis a global researchplatform designed toprovide the knowledge neededtosupporttransformationstowardsustainability.Itworks with societal partners to co-develop knowledge around three research themes (Dynamic Planet, Global Sustainable Develop- ment, and Transformations toward Sustainability) to support decisionmakersandsocietalchange.IGACwillcontinuetoleadthe communitytoaddressFutureEarthResearchPrioritiesacrossthe threethemes,suchasunderstandinghowatmosphericemissions of pollutants are changing in different regions and sectors, understanding the lifecycle implications of different energy sources,andunderstandingtheopportunitiesandrisksthatmight arisefromnewtechnologies,e.g.geoengineering.
ThroughFutureEarth,IGACwillcontinuetofostercommunity, build capacity, and provide intellectual leadership. It will also extenditseffortstowardengagingsocietalpartnerstoco-design actions(research,policies,etc.)andsolutionsrequiredtorespond effectivelytothechallengesand opportunitiesofglobalchange and sustainability. IGAC aims to continue to represent the international atmospheric chemistry community by fostering activities that underpin fundamental scientific research on emissions,atmospheric processes,andatmosphericcomposition inwaysthatlinktoglobalchangeandsustainability.Itwillmakea centralcontributiontotheoverallmissionofFutureEarth.Asa projectofFutureEarth,IGACwillbepartofaglobalplatformfor Table4
PublicationsfromIGACFosteredActivitiesonFundamentalScience.
Emissions References
JointNorthAmerican-EuropeanWorkshoponMeasurementandModelingofMethaneFluxesfromLandfills Smith&Bogner1997
ReactiveChlorineEmissionsInventory(RCEI) GraedelandKeene,1999
GlobalEmissionsInitiative(GEIA) Graedel&Pacyna1992;
Frostetal.,2013
Aerosol
FocusonAtmosphericAerosols(FAA) HobbsandHuerbert,1995
Aerosols,Clouds,PrecipitationandClimate(ACPC) Andreaeetal.,2009
GasPhase
NonmethaneHydrocarbonIntercomparisonExperiment(NOMHICE) CalvertandFehsenfeld,1992
Apeletal.,1994;
Apeletal.,1999
GlobalTroposphericCarbonDioxideNetwork(GLOCARB) KeelingandTans,1993
CarbonDioxideIntercalibrationExperiment(CARBICE) Keeling&Cundari,1993
GlobalTroposphericOzoneNetwork(GLONET) Mohen,1996
InternationalTroposphericOzoneYears(ITOY) Mohen,1996
JülichOzoneIntercomparisonExperiment(JOSIE) SmitandKley,1996
GlobalHOSystematicTests(GHOST) Jöckeletal.,2003
Modeling
MultiphaseAtmosphericChemistry(MAC) Charlson,1992
GlobalIntegrationandModeling(GIM) Kanakidouetal.,1999
AtmosphericChemistryandClimateModelIntercomparisonProject(ACCMIP) Damerisetal.,2013
Table5
IGACScientificConferences.
Conference Location Conference Location
1993IGAC Eilat,Israel 2002IGAC/iCACGP Crete,Greece
1994IGAC/iCACGP Fuji-Yoshida,Japan 2004IGAC Cristchurch,NZ
1995IGAC Beijing,China 2006IGAC/IGACGP/WMO CapeTown,SA
1997IGAC/SPARC/WMO Toronto,Canada 2008IGAC Annecy,France
1997IGAC/iCACGP/IAPSO Melbourne,AUS 2010IGAC/iGACGP Halifax,Canada
1998IGAC/iCACGP Seattle,WA,USA 2012IGAC Beijing,China
1999IGAC Bologna,Italy 2014IGAC/iCACGP Natal,Brazil
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