1. SPAC meeting, NILU, 5-7 Nov '07 Arctic Ozone Possible Reduction Strategies What can be done given uncertanties in the (Arctic) O 3 budget and climate change? Kathy Law Service d’Aéronomie/IPSL-UPMC-CNRS

2. SPAC meeting, NILU, 5-7 Nov '07 Outline O 3 radiative forcing - IR altitude sensitivity O 3 radiative forcing - IR altitude sensitivity O 3 budget (Arctic & NH) - uncertainties - photochemical lifetime vs transport timescales O 3 budget (Arctic & NH) - uncertainties - photochemical lifetime vs transport timescales Which emissions? Which emissions? Regions Regions NOx, CO/VOCs or CH4? NOx, CO/VOCs or CH4? Response in a changing climate (O3, CH4) Response in a changing climate (O3, CH4)

3. SPAC meeting, NILU, 5-7 Nov '07 O 3 radiative forcing Max effect on Ts from IR heating between 4 - 22 km Surface ∆O3 less important From Forster & Shine, 1997

4. SPAC meeting, NILU, 5-7 Nov '07 Uncertainties in O 3 RF: Results from IPCC models - GHGs plus strat. O3 (Gauss et al., 2006) Results from IPCC models - GHGs plus strat. O3 (Gauss et al., 2006) Strat. vs trop. model differences (1850 to 2000) Strat. vs trop. model differences (1850 to 2000) T=trop, S=strat.

5. SPAC meeting, NILU, 5-7 Nov '07 Arctic Ozone Budget North PoleSTE UT Transport LT transport Dry Deposition Flux out Flux in Residence Time

6. SPAC meeting, NILU, 5-7 Nov '07 Arctic O 3 Budget (TOPSE) Emmons et al., 2003

7. SPAC meeting, NILU, 5-7 Nov '07 Transport Pathways to Arctic Winter: anthrop. Europe (LT), Asia? (UT) Summer: forest fires (Siberia, Alaska) anthrop. (Asia, N. America) AMAP, 2006

8. SPAC meeting, NILU, 5-7 Nov '07 Age of Arctic Air Stohl, 2006

9. SPAC meeting, NILU, 5-7 Nov '07 Ozone Photochemical Lifetime (days) Lifetime - April - Surface Lifetime - April - 500hPaLifetime - July - 500hPa Lifetime - July - Surface MOZART model results, courtesy Claire Granier (CNRS), NCAR

10. SPAC meeting, NILU, 5-7 Nov '07 Northern Hemisphere O 3 Budget North Pole Brewer-Dobson/STE Local heating from local O 3 30N Dry Deposition Transport of heat or mid-lat O 3 to Arctic 30N

11. SPAC meeting, NILU, 5-7 Nov '07 Key is UT O 3 Budget North Pole Brewer-Dobson/STE Local heating from local O 3 ? 30N Dry Deposition Transport of heat or mid-lat O 3 to Arctic 30N

12. SPAC meeting, NILU, 5-7 Nov '07 Tropospheric O 3 - where is the ∆O 3 ?

13. SPAC meeting, NILU, 5-7 Nov '07 Where is there a constant source of ∆O3? Mid-lat anthrop. plumes transported into UT Lagrangian study using NARE-ACSOE data (Real et al., 2007) Photochemical trajectory model initialised with obs upwind Determine O3 change due to chemistry, mixing etc.

14. SPAC meeting, NILU, 5-7 Nov '07 Intercontinental Transport Of Pollutants Lagrangian match analysis (Methven et al.,2006), FF analysis (Real et al., 2007) CO ↓ : 200 ppbv O3 ↑ : 20 ppbv DC8 – 18 July B146 – 20 July Falcon – 22/23 July Where is there a constant source of ∆O3? Boreal Forest Fire plumes (ICARTT summer 2004) IGAC Lagrangian 2K4 - ITOP campaign, July 2004

15. SPAC meeting, NILU, 5-7 Nov '07 Lagrangian photochemical model: chemistry + aerosols + dilution (Real et al., 2007) NPO 3 depends on altitude (PAN decomp. vs H 2 O) plus mixing & residence time of plumes in UT OHP Falcon Mozaic Jungfraujoch Chemistry only (inc. aerosols) Chemistry + mixing

16. SPAC meeting, NILU, 5-7 Nov '07 Forest Fire Plume - Trace Gas Correlation Evolution CO (ppbv) O3 (ppbv) DC8 - 18 July 2004BAe-146 - 20 July 2004 Falcon – 22 et 23 July 2004

17. SPAC meeting, NILU, 5-7 Nov '07 Forest Fire Plume Correlation Evolution - evaluation of global models - MOCAGE (Bousserez et al., 2007) and GEOSCHEM (courtesy Isabelle Bey) 140 0 50 350 100 0225 60 MOCAGE Observations GEOS-CHEM 75 45 100150 80 18030 90 MOCAGE O3 too high on 18 July GEOSCHEM CO (PAN) too low on 18 July O3 too low on 23 July 0600 200 CO (ppb) O3 (ppbv) DC8 18 July DF20 23 July DC8 18 July 45

18. SPAC meeting, NILU, 5-7 Nov '07 Forest Fire Plume Transport to Arctic (ICARTT 2004) Barrow Alert 80°N 90°N Stohl, 2006

19. SPAC meeting, NILU, 5-7 Nov '07 FF plume transport to the Arctic (Lacresson, Real, Law, 2007) Ny-Alesund Summit Ozone - Ny-Alesund (Rao et al, 2004 ) 8km 6km 2km Summit @ 3km 2004 Ny-Alesund surface: high O3 episode in July 2004 Ozone Data (Helmig et al, 2007 ) Broad summer Max in FT

20. SPAC meeting, NILU, 5-7 Nov '07 AMAP, 2006 So which regional emissions to reduce?

21. SPAC meeting, NILU, 5-7 Nov '07 Uncertainties in Regional Emissions Courtesy Claire Granier et al.

22. SPAC meeting, NILU, 5-7 Nov '07 Decadal emissions - up to date info is needed on 1990 to present Courtesy Claire Granier, Cathy Liousse et al.

23. SPAC meeting, NILU, 5-7 Nov '07 Regional O 3 changes from reduced emissions (1) Bernsten et al., 2006

24. SPAC meeting, NILU, 5-7 Nov '07 Regional O 3 changes from reduced emissions (2) Dentener et al., 2005

25. SPAC meeting, NILU, 5-7 Nov '07 O 3 RF from BAU (upper) & reduced emissions (lower) Dentener et al., 2005

26. SPAC meeting, NILU, 5-7 Nov '07 Stohl, 2006 - Anthrop BC particle sources 30 days previously Air spending at least 5 days in Arctic in winter (left) & summer (right) Do the same for O 3 precursors with some kind of RF clock related to residence time in the UT

27. SPAC meeting, NILU, 5-7 Nov '07 Stohl, 2006 - BC particle sources 30 days previously Air spending at least 5 days in Arctic in summer - forest fires (left) & anthrop (right)

28. SPAC meeting, NILU, 5-7 Nov '07 Which Emissions - CH4, NOx, VOC or CO? 20% emission reductions in CH4, NOx CO & VOCs (West, Fiore, et al 2007)

29. SPAC meeting, NILU, 5-7 Nov '07 CH 4 emission scenarios (Tg yr-1) - Dentener et al., 2005 Net difference BAU - MRF ∆CH4ems = 100 Tg (1990 to 2030)

30. SPAC meeting, NILU, 5-7 Nov '07 How to reduce CH4? Law & Nisbet, 1996 Reduction in Gas CH4 by 15 Tg over 3 years led to 4 ppbv yr-1 decrease @ 66N

31. SPAC meeting, NILU, 5-7 Nov '07 But is CH 4 already going down? … and CO 2 going up faster than predicted?? Hansen et al., 2007

32. SPAC meeting, NILU, 5-7 Nov '07 Stratospheric O 3 recovery Eyring et al., 2007

33. SPAC meeting, NILU, 5-7 Nov '07 Climate Change Possible Impacts on O 3 Budget

34. SPAC meeting, NILU, 5-7 Nov '07 Climate change effects on strat. & trop. O3 Gauss et al., 2006

35. SPAC meeting, NILU, 5-7 Nov '07 Sensitivity of PO 3 to Temperature (PAN decomposition) Real et al., 2007

36. SPAC meeting, NILU, 5-7 Nov '07 More local anthropogenic emissions? Gas/oil extraction - CH 4, VOCs (alkanes), BC? Gas/oil extraction - CH 4, VOCs (alkanes), BC? Smelters (copper) - SOx, NOx, aerosol Smelters (copper) - SOx, NOx, aerosol Ships - NOx, aerosols Ships - NOx, aerosols

37. SPAC meeting, NILU, 5-7 Nov '07 Loss of summer sea-ice  more O 3 (ships), less halogens (not clear), more DMS, etc 2040 Granier et al, 2006 Holland et al, 2006 Are the models right??!!

38. SPAC meeting, NILU, 5-7 Nov '07 Recommendations Reduce CH 4 (but need to understand current trends and climate sensitivity) - plus CO 2 also of course Reduce CH 4 (but need to understand current trends and climate sensitivity) - plus CO 2 also of course Take into account planned O 3 precursor emission reductions (CLRTAP) & post- Kyoto Take into account planned O 3 precursor emission reductions (CLRTAP) & post- Kyoto O 3 budget - important where O 3 is formed O 3 budget - important where O 3 is formed (smoking gun - boreal forest fires?)