1. Ozone Layer in the 21 st Century Swagath Navin Manohar

2. Framework for evaluating changes in ozone 1.Stages in evolution of the ozone layer 2.Ozone changes in the Near and Long term 3.Milestones in evolution of ozone layer 4.Significance of statistical tools Factors affecting the increase of ozone - Non ODS s 1.Atmospheric Chemical Composition 2.Stratospheric Temperature Statistical Methods 1.Change in Linear Trend 2.CUSUM Attribution of recent behavior of ozone 1.Upper Stratosphere 2.Lower Stratosphere 3.Polar Ozone

3. Stages in evolution Slowing of ozone decline (near term) Turnaround of ozone (near term) Full recovery (long term)

4. Milestones Milestones 1─Weakening of negative trend Milestones 2─Reversal of trend Milestones 3─EESC back to pre-1980s value Milestones 4─Parameter reaching pre 1980s value Statistical Analyses ─Principal tool ─Could be used to derive trends in changes in the ozone ─Defines the uncertainty ─More complex models are required to represent the atmospheric processes sufficiently

5. Factors Affecting the Detection, Attribution and Timing of Milestones 1.Stratospheric Halogen Loading 2.Atmospheric Chemical Composition 3.Stratospheric Temperature 4.Atmospheric Transport 5.Solar Cycle 6.Volcanic Eruptions Stratospheric Halogen Loading 1.Important factor impacting the ozone level 2.Estimation could lead to observing changes in the levels 3.Could mislead to wrong milestone time scales

6. Atmospheric Chemical Composition 1.Changes in levels of other gases and their effects 2.Compositional change of ozone depleting gas-Example Stratospheric Temperature 1.Changes in temperature could have large influence on ozone 2.Important factor in future predictions 3.Major source of uncertainty 4.Dependence on various factors 5.Greenhouse Effect Atmospheric Transport 1.Major factor contributing to stratospheric ozone variability 2.Detection of recovery milestones 3.Signal-noise ratio 4.Experimental discussion

7. Solar Cycle 1.Solar maximum 2.Variation with altitude and latitude Volcanic Eruptions 1.Large impact on stratospheric ozone 2.Future projections 3.Eruption of Mt. Pinatubo 4.High chlorine conditions 5.Low chlorine conditions

8. Statistical Methods for Detection of Milestones 1.Significance of statistics 2.Multiple linear regression Fits 3.Types of statistical method used Change in Trend CUSUM

9. Attribution of Recent Behavior of Ozone Deals with scientific assessment Difficulty Applications in different regions Upper Stratospheric ozone Lower and total column ozone Polar ozone

10. Lower Stratospheric Ozone 1.Slowing of ozone decline in lower stratospheric ozone and in total ozone column 2.Role of atmospheric transport 3.Region dominated by Dynamical and transport processes 4.Changes in transport makes a major contribution to ozone column

12. Polar Ozone 1.Severity of ozone depletion discontinued 2.Anomalous stratospheric temperature and reduced frequency of PSC 3.Polar EESC decreasing 0.6% per year 4.Could be linked with that of future recovery in the long term

13. Danke!!!!!!!