1. 1 First Stage of Recovery in the Stratospheric Ozone Layer Eun-Su Yang/Ga Tech Derek M. Cunnold/Ga Tech Ross J. Salawitch/JPL M. Patrick McCormick/Hampton U James Russell III/Hampton U Joseph M. Zawodny/LaRC Samuel Oltmans/CMDL Michael J. Newchurch/UAH AGU Spring Meeting 23-27 May 2005 New Orleans, LA

2. Equivalent Effective Stratospheric Chlorine EESC peak in ~1997. Timing adjusted for transport to the stratosphere in WMO [2003].

3. Fractional Ozone loss calculated in PC model. Peak loss during Pinatubo, as expected. Larger losses at higher latitudes. Consistent with loss expected from EESC record.

4. Residual ozone column from SAGE and HALOE above 18km 60S-60N [O3]t =  +  t + [Seasonal terms] + [QBO terms] + γ [F10.7]t + a 1 N t-1 +  t Cumulative sum of SAGE residual, ,, departures from projected trend line 1997-2005. 2-Sigma envelope (dotted). Constant level (green).

5. Residual total ozone column from Dobson/Brewer 30S-60N (top) and merged TOMS/SBUV 60S-60N (bottom).

6. Cumulative sum total ozone column Dobson/Brewer 30S-60N (top) and Merged TOMS/SBUV 60S-60N (bottom) residuals from projected trend line 1997-2005. Total columns recover more than 18 km-TOA due to gains between tropopause – 18 km.

7. SAGE/HALOE (black) stratospheric ozone column (TP+2km to TOA) 60S-70S Temperature effects removed, and saturation effect shown to be negligible north of 70S (not negligible at 90S). Also shows clear chlorine signature (red) ~1997 inflection and slight increasing afterward [Yang et al., accepted, GRL, 2005]

8. Middle stratospheric ozone data from SAGE (pre 91) and HALOE (post 93) in black. EESC regression onto ozone (blue). Ozone expected from observationally constrained PC model calculations (red). Consistent results. Time series (top) CUSUMs (bottom)

9. Middle stratospheric ozone data from ozonesondes 18-25 km agree with SAGE/HALOE and EESC regression. Time series (top) CUSUMs (bottom)

10. EESC influence on Lower Stratosphere: moderate EESC influence on Middle stratosphere: strong

11. PV influence on Lower Stratosphere: moderate Similar for Tropopause Height Tropopause – 18 km18-25 km PV influence on Middle Stratosphere: none Similar for Tropopause Height

12. CONCLUSIONS The decline in the global stratospheric ozone layer has stopped. 3 independent satellite sensors: SAGE, HALOE, merged TOMS/SBUV and 2 ground networks: Dobson/Brewer and ozonesondes, all show consistent results in ozone trends and recovery signatures. Most (81%) of the ozone loss occurred above 18 km. Half of the recovery occurred tropopause-18km. Chlorine signature expected from the Montreal Protocol and Amendments is clear in ozone improvement in the middle and upper stratosphere. Dynamics, not chlorine, controls ozone behavior in lower stratosphere. Climate change interactions and potential stratospheric aerosol injections will influence the ozone recovery signature.

13. http://nsstc.uah.edu/atmchem/ Acknowledgements WOUDC NASA/ESE NOAA/NGDC Swiss Met Service Steve Montzka/CMDL NASA/LaRC data center NASA/GSFC data center International ozonesonde programs This work is dedicated to the memory of Professor Greg Reinsel