1. 1May 14, 2014 Uncertainties in projections of ozone- depleting substances and alternatives Guus Velders The Netherlands (RIVM)

2. Guus Velders 2 Focus on Ozone-Depleting Substances ●Projections of gases controlled by the Montreal Protocol –CFCs, halons, HCFCs, carbon tetrachloride, methyl chloroform, CH 3 Br ●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. Guus Velders 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. Guus Velders 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 ppt for CFC-11 –±48 ppt for CFC-12

5. Guus Velders 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. Guus Velders 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, CCl 4, Halon-1301: –Species mainly removed by photolysis in stratosphere HCFCs, methyl chloroform, Halon- 1211, CH 3 Cl, CH 3 Br: –Species mainly removed by OH in troposphere ●Correlations increase total uncertainty

7. Guus Velders 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. Guus Velders 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. Guus Velders 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. Guus Velders 10 Other factors also affect future ozone layer ●Non-Montreal Protocol related changes also important ●Increases in other gases: CO 2, CH 4, N 2 O: –Changes through chemical reactions: HO x, HCl, NO x, ClONO 2 –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. Picture NOAA/ESRL Mt Pinatubo

11. Guus Velders 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 CO 2 forcing ●Uncertainties: 20-40%10-30%

12. Guus Velders 12 Uncertainties in scenarios of ODS alternatives ●Alternatives used for ozone-depleting substances –Hydrocarbons, CO 2, NH 3 –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. Guus Velders 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. Guus Velders 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 GtCO 2 -eq –Avoided bank: 39- 64 GtCO 2 -eq  Banks: climate change commitment ●Choices: –Bank collection, destruction: difficult/costly –Avoid the buildup of the bank: early phaseout

15. Guus Velders 15 ●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 Conclusions