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Mitigating BC. Kristin Rypdal and Terje Berntsen. Based on paper in prep. by Rypdal, Rive, Berntsen and Klimont All results preliminary. Current mitigation efforts. Targeting PM 10 , PM 2.5 or TSP with the objective of reducing health impacts Will indirectly reduce emissions of BC Europe
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Mitigating BC Kristin Rypdal and Terje Berntsen Based on paper in prep. by Rypdal, Rive, Berntsen and Klimont All results preliminary
Current mitigation efforts • Targeting PM10, PM2.5 or TSP with the objective of reducing health impacts • Will indirectly reduce emissions of BC • Europe • LRTAP Convention • EU NEC Directive • National policies and regional cooperation in most parts of the world
Questions • Is mitigation of PM from the perspective of health concerns sufficient to also address the concerns we may have for RF caused by BC? • What would be an efficient strategy to reduce radiative forcing caused by BC in terms of minimizing global costs?
Regional share of emissions (2030, CLE) Cofala et al. (2007)
CLE-MFR 2030 CLE = Current Legislation; MFR = Maximum Feasible Reduction, Cofala et al. (2007)
Strategy • Seek to maximize reductions in global RF from BC • 1. Undertake reductions first in regions where the benefits per tonne BC reduced are the largest • 2. As 1, but also minimizing global costs • 3. As 2, but also considering regional ability to pay for abatement • 4. Emphasize sources where PM exposure is large • 5, 10 and 20 % in global RF by BC in 2030 • MFR constitutes a ceiling to the amount abated
CLE Regional costs Increasing costs Higher RF reduction 10 % reduction in RF Regional forcing MFR
Open burning and OC • When BC is abated OC is abated as well • Counterweight the benefit in terms of reduced RF • Mitigating BC from biomass burning has no or little benefit in reducing net RF • Open burning very important in Latin America and Africa (more important than contained) • Cost estimates hard to define for open burning • For simplicity we ignore biomass burning in the analysis shown here
Regional radiative properties • Use GWP as an approximation • Arbitrary time-horizon • Direct effect of BC in air • Indirect effect of BC deposited on snow in the Arctic
Regional radiative forcing Source: Reddy and Boucher (2007)
Climate efficacies • Temperature response of one unit RF of BC deposited on snow is larger than for the direct component • Here we have multiplied the indirect GWP value by 3 (Flanner et al. JGR, 2007) Direct GWP; Total GWP; Efficacies
Abatement costs • Consider cost of end-of pipe abatement • Fuel switch is an important option for reducing BC emissions • Marginal abatement costs for Europe available from the IIASA RAINS model • Per source, fuel and technology • Consistent with the emission scenarios used
Abatement costs • Lack comparable data for other world regions • Use intervals of the Europe curve for other regions • Taking on board differences in source and fuel structure • Technology assumptions • North-America as EU-17 • Other regions as Former Soviet Union
Costs (direct GWP only) GWP only Min costs Ability to pay Health focus
Correction for income S2 = cost-effective; S3 = corrected for GDP
Health focus • Ignoring biomass burning increases costs of reducing PM10 emissions! • Giving higher weight to sources and regions where exposure is high • For fossil sources and processes emphasis on high-exposure sources does not substantially increase total abatement costs
Abating BC instead of CO2 • Complicated question! • 100 years time horizon • 5 % reduction in RF is inexpensive • 10 % reduction in RF is • Expensive considering the direct effect only • Within the higher range of expected ETS prices considering the total GWP (30-40 Euro per tonnes) • Efficacies: In the range of expected CO2 (20-30 Euro per tonnes)
Conclusions • Need better data on • regional abatement costs • Regional GWPs or other metric • OC metric? • May want: • Higher regional resolution! • Improved treatment of biomass burning (open and contained)
Conclusions • Seeking global cost-effectiveness important to get political acceptance for additional mitigation efforts • Primary focus on health concerns may not target sources where RF benefits are the largest • Focus on abatement in Asia • Most cost-effective in terms of reducing global RF • Highest co-benefits in terms of reduced PM10 emissions • Benefits for the Arctic?
Conclusions • Poorer countries may not be able to pay for the globally most cost-effective reductions • Need a mechanism (“CDM”, fund)? • Considering the indirect component of GWP from BC on snow and the climate efficacy should lead to higher abatement efforts in Europe • Does not increase overall cost as less tonnes BC need to be abated • Adds overall justification to abating BC rather than other forcing agents