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(Click for frequent words.) 77 CO2 74 co2 71 CO ² 67 carbon dioxide 66 co2 emissions 65 CO2 emmissions 65 Carbon Dioxide 65 CO2 emissions 64 emmissions 63 Carbon Dioxide CO2 63 carbon dioxide CO2 63 CO2 emitted 62 CO -2 62 Co2 emissions 62 emmisions 62 C# emissions 61 carbon emissions 60 greenhouse gasses 60 polution 60 CO2 emission 60 Greenhouse gasses 60 N2O 59 CO ² emissions 59 Carbon dioxide CO2 59 carbon dioxide emissions 59 greenhouse gases 59 GHGs 59 gaseous emissions 58 CO -2 emissions 58 CO2e 58 CO ₂ 58 potent greenhouse gas 58 carbon emitted 58 carbon emmissions 57 nitrous oxide N2O 57 anthropogenic emissions 57 Global Warming Potential GWP 57 carbon dioxide emission 57 greenhouse gases GHGs 57 carbon emission 56 emit #g/km 56 greenhouse gases GHG 56 NOX emissions 56 atmospheric CO2 56 sulphate aerosols 56 emissions 56 ghg emissions 56 greenhouse gas 56 greenhouse emissions 55 emmission 55 CO2 eq 55 NOx 55 ozone O3 55 anthropogenic CO2 55 Particulate Matter PM 55 water vapor 55 gaseous pollutants 55 nitrogen oxide NOX 54 CO2 concentrations 54 carbondioxide 54 SOx emissions 54 atmospheric CO 54 #g/km CO2 [002] 54 nitrous oxide emissions 54 Sulfur Dioxide 54 N2O emissions 54 particulate emissions 54 smog forming pollutants 54 carbon dioxides 54 emission 54 anthropogenic carbon dioxide 54 greenhouse gas emissions 54 sulfate aerosols 53 Co2 emission 53 CO2 CH4 53 carbon 53 CO2emissions 53 GHG 53 nitrous oxides 53 CO2e emissions 53 SO3 53 ozone depleting gases 53 atmospheric carbon dioxide 53 Carbon dioxide 53 SO2 emissions 53 gases emitted 53 harmful particulates 53 emissons 53 NO2 53 absorbs carbon dioxide 53 greenhouse gasses emitted 53 greenhouse gas nitrous oxide 53 nitrogen oxide NOx emissions 53 carbon dioxide CO ² 53 CO2 equivalents 53 GhG emissions 53 carbon dioxide emitted 53 nitrogen oxides NO 53 harmful gasses 52 sequestering CO2 52 CH4 52 carbon dioxide CO2 emission 52 carbon dioxide CO2 emissions 52 gases 52 methane CH4 52 nitrogen oxides NOx emissions 52 cow burps 52 CO2 Emissions 52 Nitrogen dioxide 52 greenhouses gases 52 Anthropogenic 52 NOx nitrogen oxide 52 #g CO2/km [001] 52 Nitrogen Oxides 52 hydrofluorocarbons HFCs perfluorocarbons PFCs 52 Nitrogen Oxide 52 Atmospheric CO2 52 unburned hydrocarbons 52 oxidized mercury 52 fluorocarbons 52 Emissions 52 CO2/km 52 gasses 52 carbon sequestered 52 ppmv 51 GHG emitted 51 carbon dioxide CO2 emitted 51 SO2 51 NOx emissions 51 sequesters carbon dioxide 51 emitting #g/km 51 reactive nitrogen 51 pollutant emissions 51 terrestrial biosphere 51 Ozone Depleting 51 Carbon Monoxide CO 51 sulphate particles 51 Gas Emissions 51 hydrocarbons HC 51 emit CO2 51 harmful tailpipe emissions 51 emit sulfur dioxide 51 GHG emissions 51 House Gases GHGs 51 dioxide emissions 50 cow farts 50 emits #g/km [001] 50 hydrogen H2 50 HFC# 50 methyl chloroform 50 carbons 50 Carbon Emissions 50 Nitrogen Oxide NOx 50 methane 50 radiative forcing 50 emits #g 50 Greenhouse Gases 50 SOx NOx 50 renewably 50 Nitrous Oxide 50 sulfur dioxide SO2 50 reducing CO2 emissions 50 heat trapping carbon dioxide 50 Nitrogen Dioxide 50 Carbon Emission 50 pollutants emitted 50 CO2 SO2 50 GtC 50 anthropogenic greenhouse gases 49 Sulphur dioxide 49 CO 49 aerosol particles 49 global warming gases emitted 49 GHG reductions 49 C0 49 harmful byproducts 49 GHG emission 49 carbondioxide emissions 49 manmade CO2 emissions 49 reducing carbon emissions 49 Carbon Footprints 49 nitrogen oxides emitted 49 pollution 49 CARBON DIOXIDE 49 CO2 emission reductions 49 tailpipe pollutants 49 greenhouse gas GHG emissions 49 cow flatulence 49 soot particulates 49 hydrocarbons carbon monoxide 49 GHG concentrations 49 Sulphur Dioxide 49 Sulfur Dioxide SO2 49 emitting CO2 49 fossile fuels 49 methane emitted 49 Nitrogen oxides 49 methane burps 49 sulfur oxide SOx 49 nitrous oxide emission 49 anthropogenic CO 49 emits #g/km [002] 49 exhaust emissions 49 Greenhouse Gasses 48 Kharecha 48 nitrogen monoxide 48 CO ₂ emissions 48 polluting gases 48 reduce carbon emissions 48 mercury emitted 48 particulate matter emissions 48 global warming gasses 48 biosequestration 48 Greenhouse gases 48 refrigerant leakage 48 stomatal conductance 48 greenhouse gas emmissions 48 atmospheric CO2 levels 48 absorbs CO2 48 absorbing carbon dioxide 48 CARBON FOOTPRINT 48 unburnt hydrocarbons 48 sulfur hexafluoride SF6 48 Nitrogen oxide emissions 48 Particulate Matter 48 Carbon dioxide emissions 48 carbon dioxide concentrations 48 R#a 48 CARBON 48 Halons 48 ppm CO2 48 hydrofluorocarbon HFC 48 nitrogen oxides NOx 48 bovine flatulence 48 hydrofluorocarbons HFCs 48 nitrous oxide NOx 48 gigaton 48 sulfur dioxide SO2 emissions 48 tailpipe CO2 emissions 48 Particulates 48 Nitrogen oxide 48 greenhouse gas concentrations 48 monoxide 48 particulate matter emitted 48 Emilie Moorhouse 48 diesel particulate 48 pollutant 48 Ozone depletion 48 NF3 48 produced Friedlingstein 48 greenhouse emission 48 dinitrogen 48 sequestering carbon dioxide 48 #ppm CO2 48 Carbon Dioxide CO 47 H#O# 47 isoprene 47 emit GHGs 47 carbon emitting 47 particulate matter nitrogen oxides 47 nitrous oxide NOx emissions 47 Emitted 47 BIO TECHNOLOGY GROUP 47 tailpipe gases 47 Refrigerants 47 greenhouse gases emitted 47 longwave radiation 47 sulfur dioxide SO 47 sulfur dioxides 47 Methane CH4 47 Nitrogen 47 gigatonne 47 CaCO 3 47 #g/km CO2 [001] 47 emitting fossil fuels 47 GHG abatement 47 ozone depleting refrigerant 47 dioxide 47 tropospheric ozone 47 emits greenhouse gases 47 nitrogen 47 cyanogen 47 diesel particulates 47 nitrogen trifluoride 47 Volatile Organic Compounds VOC 47 emitting greenhouse gases 47 SO2 emission 47 NOx emission 47 chlorofluorocarbons CFC 47 Volatile Organic Compounds 47 harmful gases emitted 47 particulate matter sulfur dioxide 47 NOx SOx 47 di oxide 47 HCFC 47 R #a refrigerant 47 deplete ozone 47 refrigerant gases 47 emit carbon dioxide 47 sulfate particles 47 carbon emission reductions 46 GHGs emitted 46 ozone depleting compounds 46 sulfate aerosol 46 Carbon Dioxide CO2 emissions 46 ozone layer depletion 46 particulate matter soot 46 sulfur oxide 46 Particulate emissions 46 carbon sinks 46 biomass combustion 46 megajoules 46 ammonia NH3 46 Ozone depleting 46 unburnt fuel 46 BZE 46 decarbonising 46 Heart Laser RenalGuard 46 emis sions 46 harmful gases 46 Laser Skin Resurfacing 46 ozone depletion 46 particulate soot 46 SF6 46 fossil fuel 46 carbon dioxide nitrous oxide 46 carbon dioxide equivalent CO2e 46 ozone depleting substance 46 fluorinated gases 46 carbon footprint 46 exhaust gasses 46 emitting carbon dioxide 46 terawatts 46 evaporative emissions 46 heat trapping pollutants 46 particulate matter PM 46 EMISSIONS 46 Emitting 46 reduce NOx emissions 46 Hydrazine 46 anthropogenic CO2 emissions 46 atmospheric pollutants 46 halogenated gases 46 flue gases 46 CFC refrigerants 46 CFCs chlorofluorocarbons 46 selective catalytic 46 noxious gasses 46 vaporising 46 ionised 46 sulfur dioxide 45 Biomethane 45 anthropogenic greenhouse gas 45 forcings 45 harmful pollutants 45 ionize 45 Global Warming 45 #yf 45 sulfur dioxide SO2 nitrogen 45 ii Helium 45 noxious pollutants 45 tailpipe exhaust 45 Mtoe 45 Acid Rain Program 45 Carbon Dioxide Emissions 45 cyclohexane 45 nitrogen oxides carbon monoxide 45 emitted 45 Carbon Offset 45 METHANE 45 hydrochlorofluorocarbon 45 EROEI 45 ionizing 45 respirable particulate matter 45 feebates 45 Ozone O3 45 nitrogen oxide 45 Evaporation 45 Amazonian forests 45 exothermic reaction 45 Emission 45 oC 45 Greenhouse Gas 45 sulfur dioxide particulate matter 45 GLOBAL WARMING 45 radiative 45 Chlorofluorocarbons CFCs 45 farting cows 45 burning fossil fuels 45 dimethyl sulphide 45 atmospheric methane 45 fluorinated greenhouse gases 45 ZPE 45 cosmic ray flux 45 respired 45 CFCs 45 megatonne 45 inert nitrogen 45 greenhouse gas HFC 45 pollutants 45 CO2 emission reduction 45 Emitters 45 combustion gases 45 #MPG [002] 45 hydroxyl radicals 45 Sulfur compounds 45 tailpipes smokestacks 45 perfluorocarbons PFCs 45 HFC refrigerants 45 hydroxyl radical 45 CFCs HCFCs 45 aqueous urea solution 45 fossil fuels 45 carbon monoxide particulate matter 45 sulfur oxides 44 sulfur dioxide pollution 44 nitrogen NOx emissions 44 nox 44 Ecological Footprint 44 marketable byproducts 44 Nuclear fission 44 photolysis 44 VOCs 44 nitrogen oxide emission 44 Gaseous 44 combustion 44 Volatile Organic Compound 44 sequester CO2 44 aerosols 44 smog forming gases 44 emit carbon monoxide 44 sequester carbon dioxide 44 NOX 44 dissolved salts 44 atmospheric CO2 concentration 44 ozone depleting 44 g bhp hr 44 kT 44 harmful radiations 44 polluting 44 greenhouse gas emission 44 smog forming 44 smog forming emissions 44 global warming 44 oil equivalent Mtoe 44 decarbonizing 44 anthropogenic 44 corona discharge 44 combustion byproducts 44 anerobic 44 hydrogen sulphide H2S 44 microbial decomposition 44 Electrostatic precipitators 44 tonnes CO2e 44 methane CH4 nitrous oxide 44 atmospheric aerosol 44 Terawatt 44 Global Warming Pollution 44 hoofed critters 44 limonene oxide 44 sulfur oxides SOx 44 Burning fossil fuels 44 nitrification 44 nitrous oxides NOx 44 Carbonfund 44 smog forming pollution 44 Anaerobic Digestion 44 hydrogen 44 House Gases GHG 44 Pollution Reduction 44 particulate pollutants 44 NOx nitrogen oxides 44 Cow burps 44 flatulent cows 44 2oC 44 greenhouse gas GHG emission 44 Sauven 44 exothermic 44 Fossil Fuel 44 Aerosols 44 greenhouse gas GHG 44 climate forcings 44 shredder residue 44 enthalpy 44 gasifying coal 44 ppbv 44 hydrofluorocarbon 44 chlorine peroxide 43 Powernext Carbon 43 demineralized water 43 tCO2e 43 Aerators 43 absorb carbon dioxide 43 Biogenic 43 NH3 43 superoxides 43 Gasses 43 emitting 43 particles emitted 43 Geologic Storage 43 carbon dioxide emission reductions 43 earths 43 GHG emission reductions 43 ozone depleting chlorofluorocarbons 43 Nitrogen Oxides NOx 43 acidifies 43 carbonic 43 #.#mpg [001] 43 nitrogen dioxides 43 stabilizing atmospheric concentrations 43 volcanic aerosols 43 Nd Yag 43 sulfur dioxide SOx 43 WtE 43 Acetaldehyde 43 decarbonisation 43 gas milage 43 smog forming compounds 43 Volatile Organic Compounds VOCs 43 glacial interglacial cycles 43 W/m2 43 suns rays 43 carbon dioxide nitrogen oxide 43 sequester carbon 43 UV photons 43 heat trapping carbon emissions 43 renewably generated 43 Greenhouse Gas GHG emissions 43 sulfur dioxide nitrous oxide 43 megatonnes 43 depleting substances 43 C#H# 43 chlorofluorocarbon 43 oxyhydrogen 43 sodium chloride salt 43 ozone 43 Carbon dioxide emission 43 nitrogen oxides 43 biogenic emissions 43 ammonia borane 43 greenhouse gas emission reductions 43 arable soils 43 liquefied ammonia 43 perfluorocarbons 43 carbonic acid 43 Biowaste 43 Earth biosphere 43 Carbon Credits 43 Emission Reduction 43 heat trapping gases emitted 43 atmospheric moisture 43 harmless nitrogen 43 Carbon 43 stratospheric ozone depletion 43 sulfuric acid mist 43 decarbonise 43 GOSAT 43 Greenhouse Effect 43 Electromagnetic radiation 43 carbon monoxide nitrogen oxides 43 Gigatonnes 43 H#SO# 43 toxic pollutant 43 emission reductions 43 Biochar 43 Methane 43 digestors 43 Methane Emissions 43 Nitrogen NOx 43 C# [001] 43 Ionized 43 chlorofluorocarbon CFC 43 sulfurous gases 43 Ozone Depleting Substances ODS 43 Mass Extinctions 43 boiling kettle 43 sequester carbon emissions 43 respirable suspended 43 SOx 42 atmospheric CO2 concentrations 42 teragrams 42 excrete methane 42 VOC emission 42 C#F# [002] 42 DPFs 42 liquification 42 Fluorinated 42 CO2 emitting 42 #ML [001] 42 Particulate 42 NaCN 42 Verified Emission Reductions 42 Volcanic gases 42 nitrogen oxide emissions 42 trillionth tonne 42 oxidation catalyst 42 Granular Activated Carbon 42 R#a refrigerant 42 HFC #a 42 Gt 42 sulfur gases 42 ultra violet radiation 42 nitrogenous compounds 42 Lengai 42 Reduce CO2 Emissions 42 exajoules 42 finite fossil fuels 42 halon 42 R#A [001] 42 sulphates 42 Chlorine bleach 42 PM# particles 42 geo sequestration 42 Pyrolysis 42 albedo 42 invisible odorless tasteless 42 pollen particles 42 pollutions 42 Degradation REDD 42 exhaust gases 42 Isobutanol 42 ILUC 42 singlet oxygen 42 Volatile organic compounds 42 helium nuclei 42 acidity pH 42 Hydrogen Sulphide 42 GENUINE PARTS 42 airborne pollutants 42 Greenhouse Gas Emissions 42 earths surface 42 methyl chloride 42 kWhr 42 osmotic pressure 42 Exhaled 42 2C #.#F 42 Ly alpha 42 gaseous methane 42 #.#kWh 42 particulates 42 CO2 Emission 42 emit 42 gigatons 42 oxidizing agent 42 nitrogen oxides NOX 42 exhale carbon dioxide 42 halogenated hydrocarbons 42 Reactive oxygen species 42 anaerobic decomposition 42 gigatonnes 42 dangerous anthropogenic interference 42 quadrillion BTUs 42 Hydrogen Sulfide 42 Xylene 42 terawatt 42 peroxynitrite 42 NT Plasmatron 42 offgas 42 diesel particulate filter DPF 42 sulfuric gases 42 VOC emissions 42 LIMITED CHINA 42 HumiFilters 42 ozone particulate matter 42 emission reduction 42 heat trapping gases 42 Polybrominated 42 2ppm 42 W/cm2 42 NH4 + 42 de carbonise 42 Greenhouse Gas Emission 42 Selective Catalytic Reduction 42 efficiency condensing boiler 42 Jan Kowalzig 42 anthracene 42 Albedo 42 reduces NOx emissions 42 VOCs volatile 42 seawater pH 42 smog forming nitrogen oxide 42 oxidation catalysts 42 Methyl Bromide 42 refrigerant 42 Joint Implementation JI 42 Fossil Fuels 42 upper troposphere 42 rainforest deforestation 42 Certified Emission Reductions CER 42 RenDiesel fuel 42 carbon offsetting 42 emit fumes 42 #ppm [001] 42 GHG Emissions 42 CarbonSMART ™ enterprise 42 SCR catalytic converter 42 hydrogen peroxide H#O# 42 nitrogen oxide pollution 42 microscopic airborne particles 42 carbonate minerals 42 photoionization 42 butyl acetate 42 sulfuryl fluoride 42 1ppm 42 Methane Gas 42 electromagnetic radiations 42 halons 42 nitrogen NOx 42 heat trapping greenhouse 42 atmospheric CO2 enrichment 42 decarbonised 42 carcinogens benzene 42 GHG emission reduction 42 warmists 41 vaporise 41 electrochemical oxidation 41 atmospheric 41 Stephan Singer 41 Ozone Depletion 41 hydroxide ions 41 preindustrial levels 41 #MWh 41 Disposable nappies 41 oxidiser 41 atmospheric nitrogen 41 warming gases 41 ethanol butanol 41 emit greenhouse gases 41 sulfer 41 Polluting 41 particulate emission 41 nonrenewable fossil fuels 41 Deuterium 41 polyaromatic hydrocarbons 41 Sulfur dioxide pollution 41 tropical deforestation 41 Hydrogen Sulfide H2S 41 NO3 41 methane oxidation 41 carbon monoxide nitrogen oxide 41 Refrigerant 41 HFCs perfluorocarbons PFCs 41 ₂ 41 ethane propane butane 41 GSHP systems 41 air pollution 41 mercury sulfur dioxide 41 carbon dioxide methane 41 boreal ecosystems 41 hydrazine hazardous 41 harmonic currents 41 Emissions Reduction 41 pollutant emission 41 biogenic 41 HCCI mode 41 gasses emitted 41 HCFC #b 41 Supercritical 41 mol 41 nitric oxides 41 Carbon Pollution 41 tailpipe emissions 41 Ford Econetic 41 rumen bacteria 41 toxic gasses 41 OXIDE 41 interfacial tension 41 #g CO2/km [002] 41 oxygens 41 EITE industries 41 tpy CO2e 41 Bio SNG 41 petrodiesel 41 chemically reactive 41 sulfur dioxide emission 41 sequestering carbon 41 Osmotic 41 Sulfate 41 electrolyzed 41 amine scrubbing 41 Volatile Organic Compound VOC 41 degassed 41 Elevated CO2 41 climate change 41 fluxes 41 atmospheric aerosols 41 carcinogenic toxins 41 H2O 41 Megawatt Hours 41 carbon footprints 41 nightglow 41 carbon sequestering 41 Acid Rain 41 SO2 sulfur dioxide 41 saline aquifer 41 hydrochlorofluorocarbons 41 flue gasses 41 sectoral crediting 41 EarthTalk 41 ozone depleting chemicals 41 sulphate 41 hydrogen ions 41 Carbon Emissions Trading 41 Clogged filters 41 Monbiot 41 allergenic pollen 41 smog soot 41 cyanogen poisonous gas 41 #.#kW [002] 41 particulate matter 41 biodegradability 41 sulfur trioxide 41 biosphere 41 Ecofys 41 Ocean Acidification 41 granulated activated 41 Microgeneration 41 nitrogen N2 41 trillion Btu 41 Sulfur dioxide 41 yr -1 41 endothermic 41 RockTron 41 SCR selective catalytic 41 electromagnetic flux 41 methane clathrates 41 climatic variability 41 CAS #-#-# Market [003] 41 #mpg [001] 41 Nano Tubes 41 greenhouse warming 41 stoichiometry 41 CPRS Carbon Pollution 41 VOCs Volatile Organic Compounds 41 -# º C [002] 41 carbon monoxide CO 41 methane nitrous oxide 41 Le Quéré 41 Incinerators 41 GHG emitters 41 #MPH [002] 41 mercury emissions 41 nitrogen oxides sulfur oxides 41 sulfur dioxide emissions 41 ionise 41 ozone pollutant 41 Motor Vehicle Emission 41 NOX SOX 41 Carbon Footprint 41 Incandescent bulbs 41 Your Carbon Footprint 41 volatilization 41 environmentally harmful 40 containing soot dioxins 40 leach toxic chemicals 40 tradeable permits 40 VOC Volatile Organic Compounds 40 gravitational radiation 40 vibrationally excited 40 biogases 40 martian atmosphere 40 Nuclear Fission 40 sulphite 40 infra red radiation 40 Ozone Depleting Substances 40 smokestack pollutants 40 methylamine 40 Carbon sequestration 40 Alkaline 40 ozone depleting substances 40 NaOH 40 uncharged particles 40 exhaled carbon dioxide 40 ionizer 40 Sceptical Environmentalist 40 anthropogenic warming 40 thermal decomposition 40 carboxylic acids 40 phosphorous 40 nitrate nitrite 40 CFL lightbulbs 40 sulpher 40 Hydrofluorocarbons 40 sooty particles 40 Stuart Haszeldine 40 Low Emission 40 Oxides 40 chlorinated compounds 40 Coal Combustion 40 Potassium hydroxide 40 hydrogen sulfide H2S 40 AdBlue 40 Ammonia borane 40 CLIMATE SPECTATOR 40 NOx SO2 40 Biobutanol 40 ATP hydrolysis 40 Adequate ventilation 40 Sulfuric Acid 40 thermal oxidizers 40 purchasing carbon offsets 40 particulate contaminants 40 emit pollutants 40 #kJ 40 emits 40 monoethanolamine 40 specular reflection 40 Fossil fuels 40 manmade greenhouse gas 40 Organic Compounds 40 EGR engines 40 superoxide anion 40 Nitric acid 40 GGAS 40 particulate matter PM# 40 Nitrous oxide 40 Offsetters 40 smokestack emissions 40 VHE gamma rays 40 Ultraviolet radiation 40 #,# bis 40 megajoule 40 evapotranspiration 40 sequestered CO2 40 millivolts 40 de carbonisation 40 peat soils 40 hydrocarbon vapor 40 Sequester 40 vaporisation 40 peat lands 40 Nitric Oxide 40 CO2 emission allowances 40 recyclable biodegradable 40 NOAA ESRL 40 outgas 40 nitrous oxide N2O hydrofluorocarbons 40 Ozone Depleting Substance 40 Greenhouse Emissions 40 Bryony Worthington 40 EROI 40 gobal warming 40 odorless colorless gas 40 Air Pollutants 40 Tropical deforestation 40 aldehydes 40 NADPH 40 sorption 40 demineralised water 40 Thawing permafrost 40 petcoke 40 unladen weight 40 smokestack scrubbers 40 decomposing manure 40 Gases 40 outgassing 40 heat trapping greenhouse gases 40 ceramic disc brakes 40 biochar 40 liquid oxygen LOX 40 Ozone Hole 40 methanogenic bacteria 40 Oxidative stress occurs 40 carbon monoxide nitrogen dioxide 40 furans 40 Acetylene 40 hydroxyl OH 40 Emission Reduction Units 40 Mt CO2e 40 synthetic nitrogen fertilizer 40 Cavitation 40 hydrocarbons nitrogen oxides 40 xenon propellant 40 compressive stress 40 oxidising 40 Ammonia NH3 40 unreacted 40 Recirculation 40 Flue Gas 40 Acidification 40 cow belches 40 Aggregates Levy 40 Diesel Particulate 40 chlorine atoms 40 emit greenhouse gasses 40 aerosol concentrations 40 unmineable coal seams 40 Emission Reductions 40 Fuel Consumption 40 Isoprene 40 Chlorofluorocarbons 40 Tarsands 40 Climate 40 conventional combustion engines 40 troposphere 40 hydrogens 40 absorbs sunlight 40 R#A refrigerant 40 condenser coil