# Presentation: 240231

## Polar Ozone: Past, Present and Future

**Dr. Paul A. Newman**
- _[http://code613-3.gsfc.nasa.gov/People/Newman/](mailto:Jeannette_Allen@ssaihq.com)_
**NASA’s Goddard Space Flight Center**
- Polar Gateways Conference
- January 25, 2008

**Notes:**
Clyde Dry - 610-327-0577
ER-2 in front of Arena Arctica in January 2000 - SOLVE

## Outline

**Ozone hole theory**
**Antarctic losses**
**Arctic losses**
**Future of ozone in the polar region**
**Summary**

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

## 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**

**Notes:**
CFC-12: GWP = 10340
CFC-11: GWP = 6330)
CH3CCl3 - Methyl Chloroform: GWP = 476
CCl4 - Carbon tetrachloride: GWP = 2540
CFC-113: GWP = 6150

## Source Gases

- Cl is much more abundant than Br, but ...
- Br is about 60 times more effective at O3 destruction

- From Ozone FAQ - see http://www.unep.org/ozone/faq.shtml

## Chlorine Pathway

**Chlorine Pathway**

## Polar Stratospheric Clouds

**Central, Sweden January 14, 2003 - P. Newman**

## Antarctic ozone hole theory

**Cl****2**** is easily photolyzed by UV & blue/green light**
**HNO****3**** is sequestered on PSC**

- Antarctic ozone hole theory

**Notes:**
Type I PSC forms at 195 K or -109F
Type II PSC forms at 188 or -121F
Temperature over Antarctica typically reaces about 180K or -136F in mid-winter
Cl2 is photolyzed from 270-420nm (Visible light is 400-700 nm)

## Polar Ozone Destruction

- 1. O3 + Cl  ClO + O2

**Only visible light (blue/green) needed for photolyzing ClOOCl**
**No oxygen atoms required**
**Net: 2********O****3**** + h******** ******** 3********O****2**

- 2 O3

- 3 O2

- 3. ClOOCl+h2 Cl+O2

- 2. 2 ClO + M  ClOOCl + M

**Notes:**
Cl2O2 is easily photolyzed by visible light
Molina & Molina (1987) catlytic reaction

## Digression: Dobson Units

**Digression: Dobson Units**

- ozone layer

**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¢**

## October Antarctic Ozone pre-1985

**Notes:**
BUV data from Nimbus-4
TOMS continuous coverage, except for 1995

## October Antarctic Ozone

**Notes:**
BUV data from Nimbus-4
TOMS continuous coverage, except for 1995

## TOMS - August 31, 2003

## Ozone Hole Area

- 3.9

- 7.7

- 11.6

- N. America

- 03/04/2002

## Arctic & Antarctic Trends

## March Average total ozone

**March Average total ozone**

**Notes:**
Continents
position of Halley Bay
data voids October-70, 71, 73
Ozone is naturally low over Antarctica
Last 4 years shows the extremely low values over Antarctica
Mid-latitudes (high collar) has also decreased

## Ozone future

- Projected area of the ozone hole

## 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

## END

**Jan. 10, 2003 - local noon, Kiruna, Sweden**