1. 1 Polar Ozone: Past, Present and Future Dr. Paul A. Newman http://code613-3.gsfc.nasa.gov/People/Newman/ NASA’s Goddard Space Flight Center Polar Gateways Conference January 25, 2008 Dr. Paul A. Newman http://code613-3.gsfc.nasa.gov/People/Newman/ NASA’s Goddard Space Flight Center Polar Gateways Conference January 25, 2008

2. 2 Outline Ozone hole theory Antarctic losses Arctic losses Future of ozone in the polar region Summary

3. 3 Large polar ozone losses result from chlorine and bromine compounds that are mainly human produced

4. 4 Atmospheric Chlorine Trends from NOAA/ERL - Climate Monitoring Division Updated Figure made by Dr. James Elkins from Trends of the Commonly Used Halons Below Published by Butler et al. [1998], All CFC-113 from Steve Montzka (flasks by GC/MS), and recent updates of all other gases from Geoff Dutton (in situ GC). 50 years 102 years 5 years 42 years 85 years CFC-11 CH 3 CCl 3 CCl 4 CFC-113 CFC-12 U. S. CFC production stopped by President George Bush in 1992 Montreal Protocol Signed (1987)

5. 5 Source Gases Cl is much more abundant than Br, but … Br is about 60 times more effective at O 3 destruction From Ozone FAQ - see http://www.unep.org/ozone/faq.shtml

6. 6 CFC-12 released in troposphere Carried into stratosphere in the tropics by slow rising circulation CFC-12 photolyzed in stratosphere by solar UV, releasing Cl Cl catalytically destroys O 3 Cl reacts with CH 4 or NO 2 to form non- reactive HCl or ClONO 2 Polar loss Chlorine Pathway

7. 7 Polar Stratospheric Clouds Central, Sweden January 14, 2003 - P. Newman

8. 8 Solomon et al. (1986), Wofsy and McElroy (1986), and Crutzen and Arnold (1986) suggest reactions on cloud particle surfaces as mechanism for activating Chlorine HCl ClONO 2 HNO 3 Cl 2 Cl 2 is easily photolyzed by UV & blue/green light HNO 3 is sequestered on PSC Antarctic ozone hole theory

9. 9 Polar Ozone Destruction 1. O 3 + Cl  ClO + O 2 Only visible light (blue/green) needed for photolyzing ClOOCl No oxygen atoms required Net: 2  O 3 + h  3  O 2 2 O 3 3 O 2 3. ClOOCl+h  2 Cl+O 2 2. 2 ClO + M  ClOOCl + M

10. 10 Digression: Dobson Units 3 mm = 300 Dobson Units Total Ozone is a measure of the total column amount above us. Measured in Dobson Units If we bring all of the ozone above us down to the Earth’s surface The thickness would be about 3 millimeters (~0.1 inches) = 300 Dobson Units (approximately the global average) 100 Dobson Units = 1 millimeter in thickness *The Dobson Unit is a convenient unit of measurement for total column ozone 2¢ 10¢

11. 11 October Antarctic Ozone pre-1985

12. 12 October Antarctic Ozone

13. 13 TOMS - August 31, 2003 Orange/Yellow indicates higher ozone levels. Blue colors indicate low ozone values Dark color over pole shows the extent of polar night, no ozone observations Antarctic ozone hole is defined as the region covered by low ozone values

14. 03/04/200214 Ozone Hole Area 3.9 7.7 11.6 N. America

15. 15 Arctic & Antarctic Trends

16. 16 March Average total ozone

17. 17 Ozone future Projected area of the ozone hole

18. 18 Summary Stratospheric ozone is a critical gas for screening solar UV radiation. Human produced ozone destroying substances (ODS) have caused large losses of polar ozone over both poles ODSs have been regulated under international agreements and are slowly decreasing. Ozone levels should recover within the next 50-70 years. Climate change remains a big unknown for ozone recovery

19. 19 END Jan. 10, 2003 - local noon, Kiruna, Sweden