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(RIVM) The Netherlands Uncertainties in projections of ozonedepleting substances and alternatives Guus Velders 1 May 14, 2014 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 2 Guus Velders Comprehensive uncertainty analyses ● EESC calculation using baseline production of ODSs from WMO(2011) ● Same box model as in WMO(2011) used ● Uncertainties applied to – – – – – – – – – Lifetimes of all ODSs from SPARC (2013): Production (past from UNEP) and future: Banks from TEAP: Emission factors: Fractional release values: Alpha (efficiency of Br compared to Cl): Age-of-air (vertical transport): Observed mixing ratios (as constraint): Surface factor: 1σ . 12-33% 5% 10%, 20% 10%, 20% 10%, 20% 25% 0.3 yr 0.1 ppt 3% Monte Carlo uncertainty analysis 3 Guus Velders 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 4 Guus Velders 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 5 Guus Velders 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, Halon1211, CH3Cl, CH3Br: – Species mainly removed by OH in troposphere ● Correlations increase total uncertainty 6 Guus Velders 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) 7 Guus Velders 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 8 Guus Velders 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% 9 Guus Velders 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 10 Guus Velders 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% 11 10-30% Guus Velders 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) 12 Guus Velders 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) 13 Guus Velders 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 14 Guus Velders 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 15 Guus Velders