Sustainable policy—key considerations for air quality and climate change

Institute for Advanced Sustainability Studies e.V.

Originally published as:

Benduhn, F., Schallock, J., Lawrence, M. G. (2016): Sustainable policy—key considerations for air quality and climate change.

- Current Opinion in Environmental Sustainability

23

DOI: http://doi.org/10.1016/j.cosust.2016.12.003

Under a Creative Commons license: http://creativecommons.org/licenses/by-nc-nd/4.0/

Sustainable policy—key considerations for air quality and climate change

Megan L Melamed

, Julia Schmale

and Erika von Schneidemesser

Airqualityandclimatechangeareinexorablylinkedfromtheir emissionsourcestotheirimpactsonclimate,humanhealth, andecosystems,includingagriculture.However,inglobal environmentalchangeandsustainabilitypoliciesthelink betweenairqualityandclimatechangeisoftenignored.To facilitateincludingthelinkbetweenairpollutionandclimate changeinthepolicyprocess,threekeyconsiderations(1)mix ofemissions,(2)lifetime,and(3)benefitsandtrade-offsshould betakenintoaccount.Thesethreekeyconsiderationswillhelp decisionmakersunderstandhowproposedpoliciesmay impacttheemissionsofairpollutantsandgreenhousegases andtheirresultingimpactsonclimate,humanhealth,and ecosystems,thusreducingunintendedconsequencesand likelyresultinginadditionaleconomicandenvironmental benefits.

Addresses

1IGACIPO,UniversityofColorado,CIRES,Box216UCB,Boulder, CO80309USA

2PaulScherrerInstitute,OFLB/008,5235Villigen—PSI,Switzerland

3InstituteforAdvancedSustainabilityStudies,BerlinerStrasse130, D-14467Potsdam,Germany

Correspondingauthor:Melamed,MeganL(megan@igacproject.org)

CurrentOpinioninEnvironmentalSustainability2017,23:85–91 ThisreviewcomesfromathemedissueonOpenissue,partI EditedbyEduardoSBrondizio,RikLeemansandWilliamDSolecki Received28June2016;Revised29November2016;

Accepted09December2016

http://dx.doi.org/10.1016/j.cosust.2016.12.003

1877-3435/ã2016TheAuthors.PublishedbyElsevierB.V.Thisisan openaccessarticleundertheCCBY-NC-NDlicense(http://creative- commons.org/licenses/by-nc-nd/4.0/).

Introduction

In2012,theOrganizationforEconomicCo-operationand Development(OECD)projectedthatby2050airpollu- tion will be the top environmental cause of mortality worldwide[1].However,theWorldHealthOrganization (WHO) reported shortly thereafter in 2012 that seven millionpeoplediedasaresultofexposuretoairpollution, making it the world’s largest single environmental risk [2]. In response, the United Nations Environment Assembly (UNEA) in 2014 made improving air quality a top priority for sustainable development,recognizing that clean air is critical to protect human health and simultaneouslybenefitclimateandecosystems,including

food security[3].Theseareas– climate, humanhealth, andecosystems–alsohavebroaderimplicationsforsocio- economic development which we consider associated impacts.

Furthermore,2015wasthewarmestyearonrecord,reach- ing 1C above the pre-industrial average (1850–1900 referenceperiod)[4].Including2015,15ofthe16warmest years on record have occurred in the 21st century [5].

Global carbon dioxide emissions from fossil fuels and industry in 2014 were 9.80.5GtC (billion tonnes of carbon), 60% above 1990emissions [6]. The continued increase in carbon dioxide emissions and the resulting warming of the planet are impacting extreme events, water resources, coastal erosion, ecosystems, wildfires, food production, human health, amongst many others.

In response, 195 nationsas part of the United Nations Framework Convention on Climate Change (UNFCC) adopted The ParisAgreement, which aims to limit the globaltemperatureincreasebelow2Cabovepre-indus- triallevels[7].

Increasingly, airquality andclimate changeare seenas two issues that are inexorably linked and should be addressedin acoordinatedmanner.Onone level,there isgrowingrecognitionofthisthroughthedevelopmentof international organizations, such as the Climate and Clean Air Coalition (CCAC) or the Global Alliance for CleanCookstovesthatareworkingtoreduceemissionsof airpollutantsthatbothwarmtheclimateandnegatively impacthumanhealthandecosystems[8,9].Nationaland regional governing bodies, out of recognition of the linkages, are also taking action to address air quality andclimatechangesimultaneously[10–12].

Onanotherlevel,formostdecisionmakersthereislittle guidanceonhowtobestaddressthelinkagesbetweenair quality andclimatechange withinthepolicyprocess to understandhowtheemissionsofairpollutantsandgreen- house gases(GHGs) will impact climate,human health andecosystems,includingagriculture.Guidanceonhow to incorporate air quality and climate change into the policy processcouldresultin morecomprehensivepoli- cies. For example, althoughtheair quality and climate change linkages are not explicitly stated as a United Nations Sustainable Development Goal (SDG), there is a great opportunity to contribute to meeting the SDGs by including the air quality and climate change linkagesindesigningpoliciestoaddressthem.Toaddress

this challenge, the International Geosphere-Biosphere Programme (IGBP) and the International Global Atmospheric Chemistry (IGAC) project launched the Air Pollution & Climate: A Science-Policy Dialogue initiativein 2010. Asafirst step, theinitiative released TimetoAct:TheOpportunitytoSimultaneouslyMitigateAir PollutionandClimateChangethatsummarizedthelinkages betweenair qualityand climatechange [13]and stated that“an integratedapproach to addressingair pollution andclimatechangeisessentialifsocietydesirestoslow therateofclimatechangeandtoprotecthumanhealth, food/watersecurityandecosystems.”

Here,as partof theAirPollution& Climate:AScience- Policyinitiative, we present threekey considerations to includeinanintegratedapproachtoaddressingairquality andclimate change as part of the policyprocess. These threekeyconsiderationscanbeusedforpoliciesnotonly specificallyaddressingairqualityand/orclimatechangebut for a broad range of policies from how a municipality designsawaste treatmentsystem tothe UnitedNations SustainableDevelopmentGoals,for example.Themain goal of the policies does not need to change, but by addressingthe following threekey considerationsin the developmentofglobalenvironmentalchangeandsustain- abilitypolicies,morecomprehensivepoliciescanresultthat maximizethebenefitsforairqualityandclimatechange.

Background

Bothinthescientificandpolicyworld,airpollutantsand greenhousegases(GHGs)areoftendefined,researched, andpoliticallyaddressedindependentlyof oneanother.

Therefore,theirimpacts onclimate,humanhealth,and ecosystems are also often considered independently.

However, the scientific evidence linking emissions of airpollutantsandGHGsandtheirassociatedimpactsis wellestablished[14,15,16,17].Increasingtheincentive for coordination, a number of studies have also shown clear economic benefits resulting from integrated air qualityandclimatechangepolicies[18–20].

Airpollutantsaremostoftendefined(fromahumanhealth perspective) as particulate matter (PM), ground-level ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2)[21].Inaddition,carbonmonoxide(CO)andvolatile organic compounds (VOCs) are also often considered whenaddressingairqualityastheyareprecursorsin the formation of ozone and particulate matter. Greenhouse gases are most often defined as carbon dioxide (CO2), nitrousoxide(N2O),methane(CH4)andfluorinatedgases (F-gases) [22]. Methane is also often considered when addressingairqualityasitisavolatileorganiccompound, andaprecursorto theformationofozone.

More recently, the focus for addressing air quality and climate change simultaneously has been through short-lived climate-forcing pollutants (SLCPs), which

are air pollutants that typically have a warming impact on the climate as well as negative impacts on human healthand ecosystems. SLCPsare generally defined as black carbon (BC, which is a component of particulate matter),methane,ozoneandhydrofluorocarbons(HFCs) [8]. Research indicates that by reducing emissions of SLCPssignificantbenefitsto humanhealthand toeco- systemswouldresultsuchasthepreventionofmillionsof prematuredeaths and anincrease of crop yields onthe orderoftensofmillionsoftonsannuallyonaglobalscale [14,15,16,17,23–25,26,27]. In addition, mitigation of SLCPs using existing measures has been projected to beabletoreduceglobalwarmingby0.5Cby2050iffull implementation of thesemeasures occursby 2030[15].

The 2C warming limit in the UNFCCC Paris Agree- mentreliesonextensivecarbondioxideemissionreduc- tionsaswellastechnologicalinnovationtoremovecarbon fromtheatmosphere(e.g.,carboncaptureandstorage)to achieve the limit. However, extensive carbon dioxide emissionreductions andsufficienttechnologicalinnova- tionareunlikelytohappentotheextentIPCCscenarios project[28].Therefore,reductionsof SLCPsareacom- plementarywaytoreducetherateofwarmingascarbon dioxideemissionreductionscomeonline[29].

However,thefocusononlythoseSLCPsthatcontribute towarmingfallsshortoftrulyunderstandingandaddres- singthelinksbetweenairpollutantandGHGemissions and their impacts. A more comprehensive view is required(Figure1and Section“KeyConsiderations”).

CommonGHGsarevery effectiveatabsorbing thermal and terrestrial radiation and thus warming the climate.

However,duetotherelativeinertnessofcommonGHGs suchas carbon dioxide, nitrousoxide, andchlorofluoro- carbons, and hydroflourocarbons, these gases have no direct impact on human health, with the exception of methane, which canreactto form ozone. Methane also reactsto formcarbondioxide whichcandirectly impact thephotosynthesisprocessfor plantgrowth.

Airpollutantscausehumanhealthandecosystemimpacts atthelocaltoregionalscale.Someoftheseairpollutants, suchasozone,arealsoeffectiveatabsorbingsolarradiation andwarmingtheclimate.Ontheotherhand,someofthese pollutants,forexamplesulfurdioxide,gothroughchemical andphysicalprocessestoformsulfateparticlesthatreflect sunlightandhaveanoverallcoolingimpactontheclimate.

Otherpollutants,forexamplevolatileorganiccompounds, areaprecursorforozoneandsecondaryorganicaerosoland thereforecanhaveeitherawarmingorcoolingimpact.

Whetheranairpollutantwarmsorcoolstheclimate,they alldirectlyimpacthumanhealthandecosystems onthe localtoregionalscale.Nitrogenoxidesandsulfurdioxide cause eutrophication and acidification of lakes and streams, damaging ecosystems. In addition, nitrogen

86 Openissue,partI

oxides and sulfur dioxide go through processes in the atmospheretoformparticles,contributingtotheparticu- late matter burden [30]. Particulate matter, especially under 2.5mm in diameter (50 times smaller than the diameter of a human hair) penetrates deeply into our lungs andcancause bothrespiratory and cardiovascular diseases [2,31]. Particulate matter can also directly interact withcloudformationprocessesandmayimpact both the amount and location of precipitation [32], for exampletheinteractionofhighconcentrationsofpartic- ulate matter in Asia and their influence on the Asian Monsoon[33].Breathinginozoneexacerbatesrespiratory illnesses such as asthma. The deposition of ozone on vegetation weakens plants and stunts their growth, including reduction of agricultural crop yields [34,35].

Methane,throughtheproductionof ozoneaswellas its warming impact, significantly reduces crop yields more than anyotherairpollutant orgreenhousegas[36].

Figure1summarizesthismorecomprehensiveviewofair pollutants, GHGs and their direct impacts on climate,

humanhealth,andecosystems.Indirectimpacts,suchas how awarming climateincreases thelikelihoodof heat waves that result in human health impacts, were not consideredas theyrely onfeedbackmechanismsin the systemthataredifficultto predict.Using thistableas a guide,policiescanbedesignedtomorecomprehensively account for the impacts emissions of air pollutants and GHGswillhavebytakingintoaccountseveralofthekey considerations.

Key considerations

An integrated approach to addressing air quality and climate change in order to understand the impacts on climate, humanhealthand ecosystems shouldtake into accountthreekeyconsiderations:(1)mixofemissions,(2) lifetime,and(3) benefitsandtrade-offs.

Mixofemissions

The particularmixof emissionsdetermines theiractual effectonairqualityandclimatechange.Whenyoudrive yourcardowntheroadorlightafireinyourfireplace,itis

Figure1

Air Pollutant / GHG Lifetime/Scale Climate Impact Health/Ecosystem Impacts

Carbon Dioxide (CO₂)

Flourinated Gases (F-gases)

Methane (CH₄)

Nitrogen Oxides (NO_x)

Nitrous Oxides (N₂O)

Particulate Matter (PM)

Sulfur Dioxide (SO₂)

Tropsopheric Ozone (O₃)

Volatile Organic Compounds (VOCs)/

Carbon Monoxide (CO)

Lifetime in Atmosphere = days/weeks

Impact Scale = local/regional

Lifetime in Atmosphere = years Imapct Scale = global

Cooling Warming

Human Health Impact

Ecosystem Impact

No direct impact on human health or ecosystems*

*No direct impact implies the substance in question either does not directly cause human health or ecosystem impacts or it does not go through a chemical process to create a substance that directly impact human health and ecosystems.

Current Opinion in Environmental Sustainability

Commonairpollutantsandgreenhousegasesandtheirimpactsonclimate,humanhealthandecosystems,includingagriculture.

notjustcarbondioxideorairpollutantsthatareemitted, but rather both. This is almost always the case; air pollutantsandGHGsareemittedfromthesamesources asamixture.Forexample,anysourceinvolvingcombus- tionwillemitnotonlycarbondioxide,butairpollutants suchasnitrogenoxides,carbonmonoxide,andparticulate matter.Therefore,itisnearlyimpossibletoreduceemis- sionsofonepollutantatasourcewithoutaffectingtheco- pollutantsalsoemittedbythesource.Forexample,theU.

S.CleanAirActfocusesonreducingtheconcentrationof sixcommonpollutants(ozone,particulatematter, sulfur dioxide, lead, carbon monoxide, and nitrogen dioxide), but the actions to decrease the concentration of these pollutantsalsoresultedinamodestassociateddecreasein carbondioxideemissions[10].Anotherexamplefromthe green energy sector shows the opposite. As combined heat and power plants as well as decentralized power generation werepromoted in theEuropean Union as a measuretoreducecarbondioxideemissions,thenumber ofsmallcombinedplantsinurbanareasincreased[37].As smallplantswithrelativelylowpowergenerationdonot fallunder thestrictair pollutantemission guidelinesof largerplants, urban airpollution increased [38].There- fore,in thepolicyprocess, themixtureof airpollutants andGHGemissionsatthesourceshouldbeconsideredto determine how the policy will impact climate, human healthandecosystems.

Lifetime

The atmospheric lifetime of GHGs and air pollutants determinesonwhichgeographicalscalestheimpactswill befelt. Carbon dioxide, along-livedgreenhouse gas,is essentiallychemicallynon-reactiveandthereforeremains in the atmosphere on the order of centuries or longer.

This long lifetime results in a large buildup of carbon dioxide in the atmosphere over time causing an incre- mentalincreaseinwarmingforeachkilogramemitted.In addition,thelonglifetimeofcarbondioxideintheairalso means that it becomes well mixed in the atmosphere, makingthelocationofthesourceoftheemissionsirrele- vant toits impactonwarmingthe climateglobally.For example, emissions of carbon dioxide from a coal fired powerplant in China andcarbon dioxide emittedfrom vehicletailpipesintheUSwillbecomewellmixedinthe atmosphereand have thesame impact on warmingthe climateglobally.Generally,GHGshavealifetimeinthe atmosphereontheorderofdecadestocenturiesresulting inaglobalscaleimpact.This,however,isnotthecasefor theairpollutants.

Airpollutantstypicallyhavelifetimesthatlastfromhours tomonthsresultinginlocalto regionalscaleimpacts.In thecaseoftheopenburningemissionsinsouthAsia,the associatedairpollutantemissions(nitrogenoxides,vola- tile organic compounds, particulate matter) contribute, for example, to the tremendously high levels of air pollution reported in Asia. Similarly, vehicle tailpipe

emissionsintheUSwillbemostnoticeableintheadverse air quality impacts they exert close to theirlocation of emission, for example smog in Los Angeles. This also holdsfortheclimatechangeimpactsofairpollutants.In Asia,thehighconcentrationofparticulatematter,which contains a significant amount of sulfate, has a cooling impactontheregion. Reducingparticulatemattercon- centrationsinAsia,whichislikely tooccur toimprove airquality,couldthereforeresultinwarmingtheregion by2Cbytheend ofthecentury[39].Inotherwords, the impact of air pollutants on air quality and climate changeiscloser(localtoregional)tothesourceoftheir emissions.

Benefitsandtrade-offs

Policy options aiming to address asingle issue, such as climatechange,mayhaveunintendedbenefitsandtrade- offsthatshouldbetakenintoconsideration.Forexample, as countries look at options for reducing their carbon dioxide emissions to mitigateclimatechange as part of theUNFCCCParisAgreement,theseoptionswillimpact airquality.Therefore,acoordinatedapproach consider- ing both climate change and air quality could lead to significant synergies and economic benefits. Another example,biofuelsareoftenconsidered acarbon neutral waytoproduce energy.Whiletheburningof fossilfuel blended with 5–85% ethanol, a biofuel from corn and sugarcanetypically usedincars,candecreasetheemis- sion of certain air pollutants such as carbon monoxide, totalhydrocarbonsandparticulatematter,itincreasesthe amountof acetaldehydeandotherunregulated toxicair pollutants[40].Emissionsofnitrogenoxidescomparedto normal gasoline or diesel vary, with studiesreporting a decrease[41]or increase[42]. Increasednitrogen oxide emissions from biofuels can lead to increased ozone levels, reducing air quality in urban areas as seen in Sao Paulo, Brazil [43]. Some mitigation options to improve air quality,such as diesel particulate filterson vehicles can result in slightly greater carbon dioxide emissions [38,44]. Burning biomass in our homes as a heatsourceis also oftenconsidereda‘green’ optionas thenetcarbondioxideemissionsarelowercomparedto fossilfuels.However,burningbiomasscanalsoresultin significantemissions ofair pollutants (nitrogen oxides, volatileorganiccompounds,particulatematter)andhave local/regional impacts on climate, human health and ecosystems [23]. This is especially true in regions of theworldthatusebiomassforcookingindoorswithopen fires.Considering thepossibleimplications forbenefits and trade-offs of such options can lead to improved policies.

To fully understand how a policy option will impact climate,humanhealthandecosystemsthemixofemis- sions,lifetime,andbenefitsandtrade-offsofairpollutants andGHGemissionsshouldbeconsidered.Thiscanoccur atvariouslevelsofdetaildependingonthespecificpolicy

88 Openissue,partI

context, ranging from a general mention in a strategy documentdowntotherequiredapplicationofintegrated assessment tools [45]or even incorporationof scientific support for detailed modelsimulations [46]. Following, weprovideoneexampleastohowthethreekeyconsid- erations canbeintegratedonagenerallevelin abroad sustainability global environmental change and policy approach.

Exampleofintegrating airquality and climate change intothe Water-Energy-FoodNexus Recently, the Water-Energy-Food Nexus has been a topic of much discussion both within the science and policy communities. This nexus is considered a useful

“conceptualapproach to better understandand system- atically analyze the interactions between the natural environment andhumanactivities, andtoworktowards a more coordinated management and use of natural resourcesacrosssectorsandscales”[47].Theimportance of providingfreshwater,energyand foodfor allshould not be understated. However, considering this nexus

solely in terms of water, energy, and food ignores the impact thisnexushasonmultipleotherpartsof natural andhumansystems,suchaslandandsoil,climatechange andairquality.

HerewediscusshowinthecontextoftheWater-Energy- FoodNexus,iftheemissionsofairpollutantsandGHGs as wellas their impacts are takeninto account, amore comprehensive policy design would result. Figure 2 shows how the domains of the nexus contribute to air pollutantandGHGemissions,andviceversahowwater, energy,andfooddomainscanbeaffectedbyairquality and climate change. For example, the production of energyfrombothbiofuelsandfossilfuelsemitsubstantial quantitiesof airpollutantsandGHGs.Food production and distribution also emit substantial quantities of air pollutants and GHGs. During drought conditions, air qualitycandecreasedueto increasedsoildust (particu- late matter) emissions [48]. In addition, it has been shown thatairpollutants,specificallyparticulatematter, impactalternativeenergyproductionoptionssuchassolar

Figure2

IMPACT:

EMISSIONS:

EMISSIONS:

IMPACT:

A warmer climate and deposition of black carbon on snow and ice can deplete water supply from glaciers

Droughts can increase dust (PM) emissions.

Food production and distribution emit air polluntants and GHGs.

Burning biofuels and fossil fuels emit air pollutants and GHGs.

PM can reduce the efficiency of solar energy production.

Ozone reduces crop yields and worker productivity in the fields.

EMISSIONS:

IMPACT:

ENERGY WATER

FOOD

Current Opinion in Environmental Sustainability

AirqualityandclimatechangeareintegraltotheWater-Energy-FoodNexus.Thefigureprovidessomeexamplesofhowthedomainsofthenexus cancauseairpollutantandgreenhousegasemissionsandinreturnhowwater,energyandfoodcanbeimpactedbyairpollutionandgreenhouse gases.

power[49]. Ozonereducescrop yields and workerpro- ductivity in the fields. Climate warming will lead to increasedmeltingof seasonalsnow packandglaciersin winterandspringresultinginadecreaseinthesummer andfallrun-off[50],whichmakeswatermanagementfor agriculturemorecomplex.Theseexamplesofemissions of air pollutants and GHGs and their impacts are an integral part of the Water-Energy-Food Nexus. There- fore,policiesinrelationtowater,energy,andfoodshould consider the three key aspects, the mix of emissions, lifetime, and benefits and trade-offs of air pollutants andGHGsthroughoutnexus.

Conclusions

Futureresearchagendasandprogramsshouldrecognize thebroaderconnectionsofenvironmentalissues,suchas was shown here for the links between air quality and climatechangewithinthewater-food-energynexus,and fosterresearchinvestigatingthewiderimplicationsofan issueratherthanlimitingresearchtoartificiallybounded issues.Thiswouldhelptobuildthescientificfoundation to support integrated policies. In addition, if there is politicalresistancetoaddressinganenvironmentalissue, recognizing the broader connections of environmental issue and implementing integrated policies could help toovercomethesepoliticalbarriers.InternationalNGO’s such as the Climate and Clean Air Coalition (CCAC) alreadymakeuseofthisstrategybyfocusingonimprov- ing public health through better air quality, which has resulted inconsensus-findingpolicies thatbenefitother environmental issues such as climate change and food security.

Thenumberofnational,regional,andglobalagreements and policies to address environmental change and sus- tainabilityissuesislikelytoincrease.Inmanycases,these agreementswillresultinchangingemissionsofairpollu- tantsandGHGsandtheirassociatedimpacts.Although improvingairqualityandmitigatingclimatechangemay not be the primary goal of some of these policies, by takingintoaccountthethreekeyconsiderations,(1)mix ofemissions,(2)lifetime,and(3)benefitsandtrade-offs, more comprehensive sustainable policies can bedevel- opedtomaximizethebenefitsforairqualityandclimate changemitigation.

Acknowledgements

TheauthorswouldliketothanktheInternationalGeosphere-Biosphere Programme(IGBP)andtheInternationalGlobalAtmosphericChemistry (IGAC)projectforlaunchingtheAirPollution&Climate:AScience-Policy DialogueInitiative.WealsothanktheparticipantsoftheNovember 2013workshopthattookplaceinBoulder,CO,USAhostedbythe CooperativeInstituteforResearchinEnvironmentalScience(CIRES)at theUniversityofColoradoentitled“DevelopingaStrategicFrameworkfor IntegratedProgramsonAirPollutionandClimateChange”forproviding ideasthatleadtotheformulationofthekeyconsiderationspresentedinthis manuscript.Inparticular,theauthorswouldliketothankFarrukhChishtie, ToddSanford,TimothyWallington,GaryKleiman,andJessicaSeddonfor theircomments.

Referencesand recommendedreading

Papersofparticularinterest,publishedwithintheperiodofreview, havebeenhighlightedas:

ofspecialinterest ofoutstandinginterest

1. OECD:OECDEnvironmentalOutlookto2050[Internet].

OrganisationforEconomicCo-operationandDevelopment;2012.

2.

WHO:BurdenofDiseasefromtheJointEffectsofHouseholdand AmbientAirPollutionfor2012.WHO;2014.

Thisreporthighlightedtheimminentneedtoimproveairqualityacrossthe world,stating7millionpeoplediedprematurelyin2012duetoexposure toairpollution.Thislargenumberofprematuredeathsmakesairpollution theworld’stopenvironmentalcauseofmortalityworldwide.

3. UNEA:ResolutionsandDecisionsAdoptedbytheUnitedNations EnvironmentalAssemblyoftheUnitedNationsEnvironment ProgrammeatitsFirstSessionon27June2014.UNEA;2014.

4. MoriceCP,KennedyJJ,RaynerNA,JonesPD:Quantifying uncertaintiesinglobalandregionaltemperaturechangeusing anensembleofobservationalestimates:theHadCRUT4data set.JGeophysResAtmos2012,117:D08101.

5. NOAANationalCentersforEnvironmentalInformation(NCEI):

StateoftheClimate:GlobalAnalysisforAnnual2015[Internet]

2016.

6. LeQue´re´ C,MoriartyR,AndrewRM,CanadellJG,SitchS, KorsbakkenJI,FriedlingsteinP,PetersGP,AndresRJ,BodenTA etal.:GlobalCarbonBudget2015.EarthSystSciData2015, 7:349-396.

7. UNFCC:AdoptionoftheParisAgreement[Internet].UNFCC;2015.

8. UNEP/CCAC:TimetoActtoReduceShort-LivedClimate Pollutants[Internet].UnitedNationsEnvironmentalProgramme;

2014.

9. GlobalAllianceforCleanCookstoves:AssessingtheClimateand HealthCo-BenefitsofCleanCooking—TechnicalWorkshop MeetingReport.UnitedNationsFoundationOffices;2015.

10. USEPA:OurNation’sAir—StatusandTrendsthrough

2010[Internet].U.S.EnvironmentalProtectionAgencyOfficeofAir QualityPlanningandStandards;2012.

11. EuropeanCommission:CleanAirPolicyPackage–Environment– EuropeanCommission[Internet].EuropeanCommission;2013.

12. MaioneM,FowlerD,MonksPS,ReisS,RudichY,WilliamsML, FuzziS:Airqualityandclimatechange:designingnewwin-win policiesforEurope[internet].EnvironSciPolicy2016,65:48-57 http://dx.doi.org/10.1016/j.envsci.2016.03.011.

13. IGBP/IGAC:TimetoAct:TheOpportunitytoSimultaneously MitigateAirPollutionandClimateChange.International Geosphere-BiospherePrgramme(IGBP)andInternationalGlobal AtmosphericChemistry(IGAC)Project;2012.

14. FioreAM,NaikV,SpracklenDV,SteinerA,UngerN,PratherM, BergmannD,Cameron-SmithPJ,CionniI,CollinsWJetal.:Global airqualityandclimate.ChemSocRev2012,41:6663-6683.

15. ShindellD,KuylenstiernaJCI,VignatiE,vanDingenenR, AmannM,KlimontZ,AnenbergSC,MullerN,Janssens- MaenhoutG,RaesFetal.:Simultaneouslymitigatingnear-term climatechangeandimprovinghumanhealthandfood security.Science2012,335:183-189.

16. SchmaleJ,ShindellD,vonSchneidemesserE,ChabayI, LawrenceM:Airpollution:cleanupourskies.Nature2014, 515:335-337.

Priorto the 20th United Nations Framework Convention on Climate Change(UNFCCC) Conference oftheparties inLima, Peru in2014, theauthorsurgedcountriestotakeintoaccountairqualityandclimate changeintheirnegotiationsbyconsideringmeasurestoreduceshort livedclimatepollutants(SLCPs.

17. vonSchneidemesserE,MonksPS,AllanJD,BruhwilerL, ForsterP,FowlerD,LauerA,MorganWT,PaasonenP,RighiM etal.:Chemistryandthelinkagesbetweenairqualityand climatechange.ChemRev2015,115:3856-3897.

90 Openissue,partI

Thispaperprovidesanexcellentoverviewofthelinkagesbetweenair qualityandclimatechange.Itnotesthatairpollutionandclimatechange arelinkedby(1)emissions(2)atmosphericproperties,processes,and(3) mitigationoptions.

18. NemetGF,HollowayT,MeierP:Implicationsofincorporating air-qualityco-benefitsintoclimatechangepolicymaking.

EnvironResLett2010,5:014007.

19. FowlieM,GoulderL,KotchenM,BorensteinS,BushnellJ,DavisL, GreenstoneM,KolstadC,KnittelC,StavinsRetal.:Aneconomic perspectiveontheEPA’sCleanPowerPlan.Science2014, 346:815-816.

20. ThompsonTM,RauschS,SaariRK,SelinNE:Asystems approachtoevaluatingtheairqualityco-benefitsofUS carbonpolicies.NatClimChange2014,4:917-923.

21. WHO:WHOAirQualityQuidelinesforparticulatematter,ozone, nitrogendioxideandsulfurdioxide:GlobalUpdate2005[Internet].

WHORegionalOfficeforEurope,2006.

22. IPCC:Climatechange2013.Thephysicalsciencebasis.

ContributionofWorkingGroupItotheFifthAssessmentReportof theIntergovernmentalPanelonClimateChange.Cambridge UniversityPress;2013.

23. UNEP/WMO:IntegratedAssessmentofBlackCarbonand TroposphericOzone:SummaryforDecisionMakers[Internet].

UNON/PublishingServicesSection;2011.

24. AnenbergSC,SchwartzJ,ShindellD,AmannM,FaluvegiG, KlimontZ,Janssens-MaenhoutG,PozzoliL,VanDingenenR, VignatiEetal.:Globalairqualityandhealthco-benefitsof mitigatingnear-termclimatechangethroughmethaneand blackcarbonemissioncontrols.EnvironHealthPerspect2012, 120:831-839.

25. BondTC,DohertySJ,FaheyDW,ForsterPM,BerntsenT, DeAngeloBJ,FlannerMG,GhanS,Ka¨rcherB,KochDetal.:

Boundingtheroleofblackcarbonintheclimatesystem:a scientificassessment.JGeophysResAtmos2013,118:5380- 5552.

26. ShindellDT:Thesocialcostofatmosphericrelease.Clim Change2015,130:313-326.

Using a new multi-impact economic valuation framework called the Social Cost ofAtmospheric Release (SCAR), the greatesteconomic benefitsofmitigatingcarbondioxideemissionswasfromsourcesthat co-emitairpollutants,suchascoal-firedownerlands.

27. ScovronickN,DoraC,FletcherE,HainesA,ShindellD:Reduce short-livedclimatepollutantsformultiplebenefits.Lancet 2015,386:e28-e31.

28. LeungDYC,CaramannaG,Maroto-ValerMM:Anoverviewof currentstatusofcarbondioxidecaptureandstorage technologies.RenewSustainEnergyRev2014,39:426-443.

29. CCAC:FrameworkfortheCCAC5-yearStrategicPlan(2015–

2020).CCAC;2015:.[novolume].

30. USEPA:ProgramProgress—CleanAirInterstateRule,AcidRain Program,andFormerNOxBudgetTradingProgram[Internet].US EPA;2013.

31. LimSS,VosT,FlaxmanAD,DanaeiG,ShibuyaK,Adair-RohaniH, AlMazroaMA,AmannM,AndersonHR,AndrewsKGetal.:A comparativeriskassessmentofburdenofdiseaseandinjury attributableto67riskfactorsandriskfactorclustersin 21regions,1990–2010:asystematicanalysisfortheGlobal BurdenofDiseaseStudy2010.Lancet2012,380:2224-2260.

32. BoucherO,RandallD,ArtaxoP,BrethertonC,FeingoldG, ForsterP,KerminenV-M,KondoY,LiaoH,LohmannUetal.:

Cloudsandaerosols.ClimateChange:ThePhysicalScience Basis.ContributionofWorkingGroupItotheFifthAssessment ReportoftheIntergovernmentalPanelonClimateChange [Internet].CambridgeUniversityPress;2013::2013.

33. KimMJ,YehS-W,ParkRJ:Effectsofsulfateaerosolforcingon EastAsiansummermonsoonfor1985–2010:aerosolforcing oneastAsianmonsoon.GeophysResLett2016,43:1364-1372.

34. GhudeSD,JenaC,ChateDM,BeigG,PfisterGG,KumarR, RamanathanV:ReductionsinIndia’scropyieldduetoozone.

GeophysResLett2014,412014GL060930.

35. TaiAPK,MartinMV,HealdCL:Threattofutureglobalfood securityfromclimatechangeandozoneairpollution.

NatClimChange2014,4:817-821.

36. ShindellDT:Cropyieldchangesinducedbyemissionsof individualclimate-alteringpollutants.Earth’sFuture2016,4 2016EF000377.

37. WHO:ReviewofEvidenceonHealthAspectsofAirPollution—

REVIHAAPProject:TechnicalReport.WHORegionalOfficefor Europe;2013.

38. WilliamsM:Tacklingclimatechange:whatistheimpactonair pollution.CarbonManage2012,3:511-519.

39. WesterveltDM,HorowitzLW,NaikV,GolazJ-C,MauzerallDL:

Radiativeforcingandclimateresponsetoprojected21st centuryaerosoldecreases.AtmosChemPhys2015,15:12681- 12703.

40. DunmoreRE,WhalleyLK,SherwenT,EvansMJ,HeardDE, HopkinsJR,LeeJD,LewisAC,LidsterRT,RickardARetal.:

AtmosphericethanolinLondonandthepotentialimpactsof futurefuelformulations[Internet].FaradayDiscuss2016.[no volume].

41. YoonSH,LeeCS:Leancombustionandemission

characteristicsofbioethanolanditsblendsinasparkignition (SI)engine.EnergyFuels2011,25:3484-3492.

42. GiakoumisEG,RakopoulosCD,RakopoulosDC:Assessmentof NOxemissionsduringtransientdieselengineoperationwith biodieselblends.JEnergyEng2014,140:A4014004.

43. SalvoA,GeigerFM:Reductioninlocalozonelevelsinurban SaoPauloduetoashiftfromethanoltogasolineuse.

NatGeosci2014,7:450-458.

44. MinjaresR,BlumbergK,PosadaSanchezF:Alignmentof policiestomaximizetheclimatebenefitsofdieselvehicles throughcontrolofparticulatematterandblackcarbon emissions.EnergyPolicy2013,54:54-61.

45. SchmaleJ,vanAardenneJ,vonSchneidemesserE:New directions:supportforintegrateddecision-makinginairand climatepolicies—developmentofametrics-based

informationportal.AtmosEnviron2014,90:146-148.

46. BollenJ,HersS,vanderZwaanB:Anintegratedassessmentof climatechange,airpollution,andenergysecuritypolicy.

EnergyPolicy2010,38:4021-4030.

47. FAO:TheWater-Energy-FoodNexus:ANewApproachinSupport ofFoodSecurityandSustainableAgriculture.FoodandAgriculture OrganizationoftheUnitedNations;2014.

48.

HealdCL,SpracklenDV:Landusechangeimpactsonair qualityandclimate.ChemRev2015,115:4476-4496.

Landusechange(LUC)hasforalongtimebeenontheglobalenviron- mentalchangeagendaforavarietyofreason.Thisarticleclearlydemon- stratestheimactnaturalandanthroogenicLUCcanhaveonairquality andclimate.

49. YassaaN:Airpollutionmayaltereffortstomitigateclimate change.AtmosEnviron2016,127:221-222.

50. FarinottiD,PistocchiA,HussM:Fromdwindlingiceto headwaterlakes:coulddamsreplaceglaciersintheEuropean Alps? EnvironResLett2016,11:054022.