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Uncertainty in aerosol emissions. Joyce E. Penner University of Michigan Presented to UNFCC Expert meeting London September 24-26, 2002. Validation of climate attribution models.
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Uncertainty in aerosol emissions Joyce E. Penner University of Michigan Presented to UNFCC Expert meeting London September 24-26, 2002
Validation of climate attribution models • Use IPCC recommended methods for deriving direct and indirect forcing from fossil fuel emissions (These have been tested by comparison with present day surface measurements and total optical depth): • SO42- • BC • OC • Reconstruct historical emissions • Test with change in global or hemispheric surface temperature
Sources of uncertainty in past aerosol emissions • Reconstructed historical fuel use by sector • Assumed historical emission factors by technology development
Example: Coal use by sector for OECD (breakdown not available for non-OECD) • Hard coal • Energy sector • Transformation • Industry sector • Transport sector • Other sectors (residential) • Lignite • Brown coal coke • Coke-oven coke • Gas coke • Hard coal briquettes • Lignite briquettes • Charcoal
Total coal use reconstructed from: UN Data tapes and Formula based on production, etc. ES, ESAB, ESY, WES (consumption data)
Total lignite use reconstructed from: UN Data tapes ES, ESAB, ESY, WES
Coal residential Lignite residential 7 - 12 16 - 4.6 Example: Range of estimated emission factors for BC for developing world (g/kg): Cooke - Bond (quote in Bond)
Power generation Industry Res. Coal Residential other Transport diesel Transport other Total 0.12 - 1.54 0.29 - 1.19 0.9 - 0.64 0.18 - 0.50 0.51 - 2.83 0.19 - 0.11 2.19 - 6.81 Estimated emissions of BC (Tg/yr): Bond Cooke These new emissions underestimate BC when used in models
BC emissions from fossil fuels (using Cooke emissions factors)
Recommend that IPCC should conduct: • Comparison of fuel reconstruction by: • Ardenne, Liousse, Bond, Penner, LeFohn, Marland, Smith, Novakov - include regional emissions estimates (Reddy for India) • Comparison of emission factors • Derivation of recommended historical emissions and uncertainty range • Continued evaluation of aerosol forcing using models compared to observations • Open question: Evaluation of forcing by comparison with hemispheric temperature trends?
Open questions • Can we use comparison with hemispheric temperature trends to evaluate historical aerosol forcing? • How well do we need to know the aerosol forcing and ozone forcing to derive the climate sensitivity? • How do we treat historical biomass burning emissions?