Björn-Martin Sinnhuber Institute of Environmental Physics University of Bremen December 2006

1. The impact of short-lived source gaseson the ozone layer underthe influence of a changing climateA proposed contribution to G-SPARC Björn-Martin Sinnhuber Institute of Environmental Physics University of Bremen December 2006

2. Very Short-Lived Source gases: The paradigm from WMO (2003)

3. Open issues • What is the (current) contribution of very short-lived source (VSLS) gases to stratospheric ozone depletion? • How are VSLS transported through the tropical tropopause layer (TTL) into the stratosphere? • Rate of convective transport into the upper troposphere / lower stratosphere • Chemical degradation in the TTL • Wet removal of degradation products from the TTL • How will the contribution of VSLS change in a changing climate? • How will the (oceanic / biogenic) sources change? • How will the transport processes (incl. wet removal) change?

4. Future Considerations for Halogenated VSLS (WMO, 2007) • Possible future changes in anthropogenic VSLS. If anthropogenic emissions increased, or if presently unused halogenated VSL SGs were to come into widespread commercial use, then halogenated VSLS would become of increased importance in affecting the future behavior of stratospheric ozone. • Delivery of VSLS to the stratosphere may change in the future in response to circulation changes. The impact of natural halogenated VSLS might also be influenced by changes in the atmospheric circulation, which could, for example, increase the rate of delivery of VSL SGs and PGs into the stratosphere. • Natural VSLS emissions may respond to future changes in climate processes. Natural sources could respond to changes in, for example, CO2, land use, wind speed, and temperature.Our knowledge about these potential effects, and many other relevant feedbacks, is very limited at present.

5. Context How will the emissions, transport, and effects of VSLS change in a changing cimate ? • addresses New SPARC Initiative 1 - Chemistry Climate Interactions • is of direct relevance for the (next, 2010) WMO/UNEP Scientific Assessment of Ozone Depletion • expands on previous work of our group

6. Previous work / related activities • Investigation of SCIAMACHY BrO observations(Sinnhuber et al., GRL, 2005; Sheode et al., ACP(D), 2006;Alexei Rozanov: „BOOST“ BrO intercomparison / validation project) • Modelling studies on the impact of bromine from VSLS on past stratospheric ozone trends(Sinnhuber et al., ACP(D), 2006) • Idealized model studies on transport of VSLS through the TTL(Sinnhuber and Folkins, ACP, 2006) • Validation of convective transport in global models(SCOUT-O3 WP 6.2; Folkins et al., JGR, 2006) • Investigation of oceanic phytoplankton from SCIAMACHY observations(Astrid Bracher: DFG project „PASAT“; HGF Nachwuchsgruppe)

7. BrO „climatology“ from SCIAMACHY observations DJF MAM JJA SON from Sheode et al., ACP(D), 2006

8. SCIAMACHY BrO: Stratospheric bromine from VSLS SCIAMACHY BrO observations suggest present contribution of ~3ppt bromine from very short-lived source gases. from WMO (2007), based onSinnhuber et al., GRL (2005)

9. Impact of short-lived bromine on ozone trends Additional bromine from very short-lived source gases has significant impact on calculated ozone trends (in particular for periods with enhanced aerosol loading). from Sinnhuber et al., ACPD (2006)

10. Transport processes: Convective transport into the TTL How will this respond to climate change(e.g. changes in tropical SST and tropospheric temperature) ? from Sinnhuber and Folkins, ACP (2006)

11. Importance of wet removal in the TTL: Model calculations from WMO (2007), based on Sinnhuber and Folkins, ACP (2006)

12. Convective transport of VSLS: Model vs aircraft observations Observations of VSLS very limited at present. from Sinnhuber and Folkins, ACP (2006)

13. Validation of modelled tropical tracer transport Comparison of idealized tracers as part of European IP SCOUT-O3. Large differences in modelled short-lived tracers between different models.

14. Observation of oceanic source regions from SCIAMACHY A. Bracher, DFG project „PASAT“ Oceanic bromoform emissions related to phytoplankton (in particular diatoms, e.g. see Quack et al., GRL, 2004).

15. Suggested methodology Analysis of SCIAMACHY BrO (plus NO2, O3, ...) observations for VSLS (All going well there will be ~10 years of SCIAMACHY data by the end of the project) • Process oriented model studies to investigate transport of VSLS through the TTL • How will the transport processes (incl. wet removal) change for changes in tropical SST ? • Are the relevant processes adequately represented in current CCMs ? Investigate how oceanic VSLS emissions may change for changes in tropical SST (e.g., investigate changes in plankton distribution and calculated air-sea fluxes as a result of ENSO) Full model calculations on the effect of VSLS in a changing climate 15

16. Extra slides

17. Very Short-Lived Source gases: The paradigm from WMO (2007)(update from WMO, 2003)

18. Validation of modelled tropical tracer transport Bromoform - 20 day Methyl Iodine - 5 day Comparison of idealized tracers in different CTMs and CCMs as part of European IP SCOUT-O3.

19. Chlorophyl concentration from MERIS

20. Suggested methodology • Investigation of stratospheric BrO (and NO2, O3, ...) from SCIAMACHY observations • All going well there will be ~10 years of SCIAMACHY observations towards the end of the project • Investigate transport processes of VSLS and their sensitivity to climate change from a range of modelling tools • How will the transport processes (incl. wet removal) change for changes in tropical SST ? • Are the relevant processes adequately represented in current CCMs? • Can we learn anything about changes in oceanic biogenic production in a changing climate? • Analysis of SCIAMACHY observations (plus other data)