2. Effect of Stratospheric Water Vapor Change on Ozone Layer and Climate Wenshou Tian Martyn P. Chipperfield 1 Collage of the Atmospheric Science Lanzhou University, Lanzhou, Gansu, China 2 Institute for Atmospheric Science, School of the Earth and Environment, University of Leeds, UK Acknowledgments. Dr. Peter Braesicke from Cambridge University; Dr Alan Iwi and Dr J. Kettleborough from RAL, Dr Jeff Cole from University of Reading; Dr. Jason Lader at Leeds University 1,22

3. Climate is Changing ! ObservationsModelling Not believe or believe but no action. Believe and do something. The average global temperature is likely to rise 1.1 to 6.4 K by 2100. Correspondingly, the sea level may rise 16 to 120 cm (Joel Smith, 2001) Severe ozone loss begins to be observed in Arctic frequently (e.g. Rex et al, 2004 GRL). Arctic ozone hole may appear in the near future? ‘The Day after Tomorrow’

4. Ozone Layer: What Does It Mean to Us Effects of the reduction of ozone 1.The ultraviolet radiation reaching the ground increases about 2% for each 1% decrease in the atmospheric ozone. 2. The UV with wavelength equaling 0.26um attacks DNA or reproductive molecules in all living systems. 3. EPA estimated that a 1% drop in the global ozone could cause 20,000 additional skin cancers in the US annually.

5. Where are we?  The amendments to the Montreal protocal have resulted a decrease in stratospheric halogen loading. Consequently, ozone is expected to start to recover. Recover point?

6. Evolution of Ozone Hole From web page: http://www.theozonehole.com

7. Stratospheric Water Vapour Is Increasing Oltmans, S., et al (2000, GRL)

8. Increase H2O Decrease temperature Increase OH Slow down O3 depletionMore O3 loss Net effect : reduce ozone or increase ? More PSCs More O3 loss Role of H2O in Stratospheric ozone depletion Global warming will increase tropospheric H2O Sources leading to stratospheric H2O increase are still not well understood.

9. Issues to be Addressed  What is the role of the chemical and radiative effects of H 2 O on the stratospheric O 3 depletion and temperature change  How does the stratospheric O 3 look like by 2100 Science, 1998, by David Rind

10. The Chemistry Climate Model (CCM) CCM = Unified Model + SLIMCAT chemistry + STOCHEM UM version 4.5 with a resolution 2.5 o x 3.75 o. 64 Levels (surface – 0.01 hPa). Chemistry coupled to the UM radiation scheme through modelled O 3, H 2 O, CH 4 and N 2 O. Details in Tian and Chipperfild, 2005,QJRM,281-303

11. Age of Air and Importance of Coupling Chemistry and climate coupling is important! Maximum 0.5 year difference in the mean age of air in the stratosphere can be induced by chemistry coupling.

12. R2 A fully coupled run in which O3, N2O, CH4, and H2O from chemistry are coupled to the UM radiation scheme. R3 A fully coupled run in which stratosphere H2O used in radiation scheme is increased by 2ppm. R1 A run which is identical to Control Run R0 except that H2O field in the chemistry scheme is increased by 2ppm. R4 A run with 2050 conditions. GHG, and halocarbon scenarios are from IPCC (2001). Other configurations are the same as Control Run. Six Integrations R5 A run with 2100 conditions. R0 Control run with 2000 conditions

13. Chemistry Related Effects of H2O R1 – R0 (Time and zonal averaged fields) T CH4 Responses of the atmosphere to 2ppmv H2O increase in the chemistry. Note that CH4 decreases implying that transport of CH4 from troposphere to stratosphere is slowing down or more CH4 oxidation.

14. Radiation Related Effects of H2O R3 – R2 (Time and Zonal Averaged Fields) CH4 Overall increase in CH4 implying an increased stratospheric wave forcing The cooling of stratosphere is evident. T

15. Ozone Changes Radiative Effects on 2ppmv Water Vapor increase Chemical Effects on 2ppmv Water Vapor increase Temperarure Changes Note the offset effect on ozone. Significant Cooling! Radiative + Chemical Effects

16. Dynamic Response to Increasing H2O Chemistry-induced Response Radiation-induced Response Winter Summer Spring Autumn Winter Summer Spring Autumn R0 R1 R0 R1 R2 R3 R2 R3

17. Recovery of Ozone Layer Arctic in March A persistent recovery of polar ozone from 2000 to 2100 Antarctic in September

18. Summary and Conclusion 1 Increasing H2O in radiation gives rise to an overall increase in the total column ozone, particularly in the northern high latitudes. 2 Increasing H2O in chemistry leads to an increase in total column ozone in the northern high latitudes and more ozone depletion in the southern high latitudes. 3 From 2000 to 2100, a persistent ozone recovery can be noted in both the Artic and Antarctic stratosphere. The Arctic ozone by 2100 seems to be unlikely.