1 May 14, 2014 Uncertainties in projections of ozone-depleting substances and alternatives - PowerPoint Presentation

1. 1May 14, 2014Uncertainties in projections of ozone-depleting substances and alternativesGuus VeldersThe Netherlands(RIVM)

2. Guus Velders2Focus on Ozone-Depleting SubstancesProjections of gases controlled by the Montreal ProtocolCFCs, halons, HCFCs, carbon tetrachloride, methyl chloroform, CH3BrProjections for WMO assessments: Made by 2D and 3D modelsPolicy options/scenarios often with box modelEquivalent Effective Stratospheric Chlorine (EESC)Index for stratospheric chlorine and bromine and their ability to destroy ozoneUncertainties mostly not taken into accountUncertainties are important for these projections

3. Guus Velders3Comprehensive uncertainty analysesEESC calculation using baseline production of ODSs from WMO(2011)Same box model as in WMO(2011) usedUncertainties applied to 1σ . Lifetimes of all ODSs from SPARC (2013): 12-33%Production (past from UNEP) and future: 5%Banks from TEAP: 10%, 20%Emission factors: 10%, 20%Fractional release values: 10%, 20%Alpha (efficiency of Br compared to Cl): 25%Age-of-air (vertical transport): 0.3 yrObserved mixing ratios (as constraint): 0.1 pptSurface factor: 3% Monte Carlo uncertainty analysis

4. Guus Velders4Range in future mixing ratiosLifetimes and uncertainties from SPARC (2013)Most likely and possible uncertainty ranges (1σ)CFC-11: 52 yr 11% or 22%CFC-12: 102 yr 8% or 15%HCFC-22: 12 yr 16%Halon-1211: 16 yr 33%Halon-1301: 72 yr 9% or 13%Data before 2010 constrained by observationsMixing ratio range (95% conf.) 2050±35 ppt for CFC-11±48 ppt for CFC-12

5. Guus Velders5Range in future EESC levelsUncertainties applied to lifetimes (of all ODSs) onlyEESC (mixing ratios) before 2010 constraint by observationsRange in EESC levelsMean: 1200 ppt in 2050Range 1050-1350 pptEESC return to 1980 levelsMid-latitudes: 2048Range 2040 to 2061Antarctic: 2075Range 2062 to 2101

6. Guus Velders6ODSs contributing most to EESC uncertaintyEESC return to pre-1980 levelsLargest contributions from CFC-11 and Halon-1211Correlations between uncertainties taken into account:CFCs, CCl4, Halon-1301:Species mainly removed by photolysis in stratosphereHCFCs, methyl chloroform, Halon-1211, CH3Cl, CH3Br:Species mainly removed by OH in troposphereCorrelations increase total uncertainty

7. Guus Velders7Range in future EESC levels: all uncertaintiesUncertainties applied to all parameters and all ODSsEESC return to 1980 levelsMid-latitudes: 2048Range 2039 to 2064Antarctic: 2075Range 2061 to 2105Ranges only slightly larger than with uncertainties in lifetimes onlyLower range: equal to zero emissions scenarioUpper range: 12 times total projected HCFC emissions (2014-2050)

8. Guus Velders8Parameters contributing most to EESC uncertaintyUncertainties applied to all parametersRanges in year of return to pre-1980 levelsLargest contributionsUncertainties in lifetimesOther contributions fromAge-of-airFractional release valuesBromine efficiency (alpha)Atmospheric burden much larger than current banksFactor of 4 for CFC-11Factor of 30 for CFC-12

9. Guus Velders9Uncertainties in ODP-weighted emissionsODPs also have uncertaintiesCFCs: 30-35%HCFCs: 55-70%Halons: 60-90%Large contributions again from uncertainties in lifetimesPeak emissionMean: 1.3 MtCFC-11-eq/yrRange 0.9 to 1.8 MtCFC-11-eq/yrTotal uncertainties (95% conf.) of 20% to more than 40%

10. Guus Velders10Other factors also affect future ozone layerNon-Montreal Protocol related changes also importantIncreases in other gases: CO2, CH4, N2O:Changes through chemical reactions: HOx, HCl, NOx, ClONO2Changes through temperature and dynamics of the atmosphereChanges in emissions of very short lives species (VSLS)Also potential effects from:RocketsAircraftVolcanoesGeoengineeringBiofuelsetc.Picture NOAA/ESRLMt Pinatubo

11. Guus Velders11Uncertainties in GWP-weighted emissions and RFUncertainties can also be translated to climate metrics: GWP and RFAdditional uncertainties from radiative efficiency and CO2 forcingUncertainties: 20-40% 10-30%

12. Guus Velders12Uncertainties in scenarios of ODS alternativesAlternatives used for ozone-depleting substancesHydrocarbons, CO2, NH3Alternative technologies: Mineral wool, etc.HFCs with long lifetimes: HFC-134a, HFC-125, HFC-143a, etc.HFCs with short lifetimes: HFC-1234yf, HFC-1234ze, etc.Uncertainties in HFCs lifetimes ~20%Scenario uncertainty more importantIf current HFC mix (lifetime 15 yr) were replaced by HFCs with lifetimes less 1 month  forcing in 2050 less than current HFC forcingVelders et al. Science (2012)

13. Guus Velders13Changes in types of applications: CFCs vs HFCsCFCs (1980s) used in very emissive applicationsSpray cans, chemical cleaningRelease within a yearHFCs used mostly in slow release applicationsRefrigeration, AC: release from 1 – 10 yrFoams: release > 10 yrVelders et al. (20124)

14. Guus Velders14Role of the banks increases for HFCsBanks: HFCs present in equipment: refrigerators, AC, foams, etc.Bank about 7 times annual emissionPhaseout in 2020 instead of 2050Avoided emission: 91-146 GtCO2-eqAvoided bank: 39- 64 GtCO2-eqBanks: climate change commitmentChoices:Bank collection, destruction: difficult/costlyAvoid the buildup of the bank: early phaseout

15. Guus Velders15Uncertainties in lifetimes most important for EESC projectionsScenario uncertainty more important for ODS alternativesGrowing importance of HFC banks for climate changeWork performed in close collaboration withJohn Daniel (NOAA, USA) Thank you for your attentionReferences: - Velders and Daniel, Atmos. Chem. Phys., 2014 - Velders, Solomon and Danel, Atmos. Chem. Phys., 2014Conclusions