1. Uncertainty in aerosol emissions Joyce E. Penner University of Michigan Presented to UNFCC Expert meeting London September 24-26, 2002

2. 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): –SO 4 2- –BC –OC Reconstruct historical emissions Test with change in global or hemispheric surface temperature

3. Sources of uncertainty in past aerosol emissions Reconstructed historical fuel use by sector Assumed historical emission factors by technology development

4. 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

5. Total coal use reconstructed from: ES, ESAB, ESY, WES (consumption data) UN Data tapes and Formula based on production, etc.

6. Total lignite use reconstructed from: ES, ESAB, ESY, WES UN Data tapes

7. Reconstructed sulfur emissions

8. Example: Range of estimated emission factors for BC for developing world (g/kg): Coal residential Lignite residential 7 - 12 16 - 4.6 Cooke - Bond (quote in Bond)

9. Estimated emissions of BC (Tg/yr): 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 BondCooke These new emissions underestimate BC when used in models

10. BC emissions from fossil fuels (using Cooke emissions factors)

11. 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?

12. 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?