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Uncertainties in projections of ozone-depleting substances and alternatives

( RIVM ). The Netherlands. Uncertainties in projections of ozone-depleting substances and alternatives. Guus Velders. Focus on Ozone-Depleting Substances. Projections of gases controlled by the Montreal Protocol CFCs, halons, HCFCs, carbon tetrachloride, methyl chloroform, CH 3 Br

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Uncertainties in projections of ozone-depleting substances and alternatives

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  1. (RIVM) The Netherlands Uncertainties in projections of ozone-depleting substances and alternatives Guus Velders

  2. Focus on Ozone-Depleting Substances • Projections of gases controlled by the Montreal Protocol • CFCs, halons, HCFCs, carbon tetrachloride, methyl chloroform, CH3Br • Projections for WMO assessments: • Made by 2D and 3D models • Policy options/scenarios often with box model • Equivalent Effective Stratospheric Chlorine (EESC) • Index for stratospheric chlorine and bromine and their ability to destroy ozone • Uncertainties mostly not taken into account • Uncertainties are important for these projections

  3. Comprehensive uncertainty analyses • EESC calculation using baseline production of ODSs from WMO(2011) • Same box model as in WMO(2011) used • Uncertainties 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 yr • Observed mixing ratios (as constraint): 0.1 ppt • Surface factor: 3% •  Monte Carlo uncertainty analysis

  4. Range in future mixing ratios • Lifetimes 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 observations • Mixing ratio range (95% conf.) 2050 • ±35 pptfor CFC-11 • ±48 pptfor CFC-12

  5. Range in future EESC levels • Uncertainties applied to lifetimes (of all ODSs) only • EESC (mixing ratios) before 2010 constraint by observations • Range in EESC levels • Mean: 1200 ppt in 2050 • Range 1050-1350 ppt • EESC return to 1980 levels • Mid-latitudes: 2048 • Range 2040 to 2061 • Antarctic: 2075 • Range 2062 to 2101

  6. ODSs contributing most to EESC uncertainty • EESC return to pre-1980 levels • Largest contributions from CFC-11 and Halon-1211 • Correlations between uncertainties taken into account: • CFCs, CCl4, Halon-1301: • Species mainly removed by photolysis in stratosphere • HCFCs, methyl chloroform, Halon-1211, CH3Cl, CH3Br: • Species mainly removed by OH in troposphere • Correlations increase total uncertainty

  7. Range in future EESC levels: all uncertainties • Uncertainties applied to all parameters and all ODSs • EESC return to 1980 levels • Mid-latitudes: 2048 • Range 2039 to 2064 • Antarctic: 2075 • Range 2061 to 2105 • Ranges only slightly larger than with uncertainties in lifetimes only • Lower range: equal to zero emissions scenario • Upper range: 12 times total projected HCFC emissions (2014-2050)

  8. Parameters contributing most to EESC uncertainty • Uncertainties applied to all parameters • Ranges in year of return to pre-1980 levels • Largest contributions • Uncertainties in lifetimes • Other contributions from • Age-of-air • Fractional release values • Bromine efficiency (alpha) • Atmospheric burden much larger than current banks • Factor of 4 for CFC-11 • Factor of 30 for CFC-12

  9. Uncertainties in ODP-weighted emissions • ODPs also have uncertainties • CFCs: 30-35% • HCFCs: 55-70% • Halons: 60-90% • Large contributions again from uncertainties in lifetimes • Peak emission • Mean: 1.3 MtCFC-11-eq/yr • Range 0.9 to 1.8 MtCFC-11-eq/yr • Total uncertainties (95% conf.) of 20% to more than 40%

  10. Other factors also affect future ozone layer • Non-Montreal Protocol related changes also important • Increases in other gases: CO2, CH4, N2O: • Changes through chemical reactions: HOx, HCl, NOx, ClONO2 • Changes through temperature and dynamics of the atmosphere • Changes in emissions of very short lives species (VSLS) • Also potential effects from: • Rockets • Aircraft • Volcanoes • Geoengineering • Biofuels • etc. Mt Pinatubo Picture NOAA/ESRL

  11. Uncertainties in GWP-weighted emissions and RF • Uncertainties can also be translated to climate metrics: GWP and RF • Additional uncertainties from radiative efficiency and CO2 forcing • Uncertainties: 20-40% 10-30%

  12. Uncertainties in scenarios of ODS alternatives • Alternatives used for ozone-depleting substances • Hydrocarbons, CO2, NH3 • Alternative 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 important • If current HFC mix (lifetime 15 yr) were replaced by HFCs with lifetimes less 1 month  forcing in 2050 less than current HFC forcing Velders et al. Science (2012)

  13. Changes in types of applications: CFCs vs HFCs • CFCs (1980s) used in very emissive applications • Spray cans, chemical cleaning • Release within a year • HFCs used mostly in slow release applications • Refrigeration, AC: release from 1 – 10 yr • Foams: release > 10 yr Velders et al. (20124)

  14. Role of the banks increases for HFCs • Banks: HFCs present in equipment: refrigerators, AC, foams, etc. • Bank about 7 times annual emission • Phaseout in 2020 instead of 2050 • Avoided emission: 91-146 GtCO2-eq • Avoided bank: 39- 64 GtCO2-eq • Banks: climate change commitment • Choices: • Bank collection, destruction: difficult/costly • Avoid the buildup of the bank: early phaseout

  15. Conclusions • Uncertainties in lifetimes most important for EESC projections • Scenario uncertainty more important for ODS alternatives • Growing importance of HFC banks for climate change Work performed in close collaboration with John Daniel (NOAA, USA) Thank you for your attention References:- Velders and Daniel, Atmos. Chem. Phys., 2014 - Velders, Solomon and Danel, Atmos. Chem. Phys., 2014

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