Presentation Slides for Atmospheric Pollution: History, Science, and Regulation Chapter 11: Global Stratospheric Ozone Reduction By Mark Z. Jacobson Cambridge University Press, 399 pp. (2002) Last update: March 28, 2005 The photographs shown here appear in the textbook and are provided to facilitate their display during course instruction. Permissions for publication of photographs must be requested from individual copyright holders. The source of each photograph is given below the figure and in the back of the textbook.

Column Abundance of Ozone Figure 11.1

Ozone Column Abundance in 2000 Versus Latitude and Month Figure 11.2 Latitude (degrees )

Variation with Latitude of Yearly- and Zonally-Averaged Ozone in ‘79, ‘99, ‘00 Figure 11.3 Ozone (Dobson units)

Vertical Profile of Ozone Figure 11.4 Altitude (km)

Downward Solar Radiation at Top of Atmosphere (TOA) and Ground Figure 11.5 Radiation intensity (W m -2  m -1 ) UV-AUV-CUV-B

Major Absorbers of UV Radiation at Different Altitudes Table 11.1 WavelengthsDominantLocation of Spectrum (  m)AbsorbersAbsorption Far-UV N 2 Thermosphere O 2 Thermosphere Near-UV UV-C O 3 Stratosphere UV-B O 3 Stratosphere Troposphere ParticlesPolluted troposphere UV-A NO 2 Polluted troposphere ParticlesPolluted troposphere

UV-B Trends A 1% reduction in ozone results in roughly a 2% increase in UV-B Observed UV-B changes % higher in NH midlatitudes during winter/spring 4% higher in NH midlatitudes during summer/autumn 6% higher in SH midlatitudes all year 130% higher in Antarctica during SH spring 22% higher in Arctic during NH spring

Sidney Chapman ( ) American Institute of Physics Emilio Segrè Visual Archives, Physics Today collection

Natural Ozone Production (11.1) - (11.4)

Natural Ozone Destruction (11.5) - (11.7)

Stratospheric NO x Production (11.9)

NO x Ozone Catalytic Destruction Cycle (11.10) - (11.12)

Stratospheric HO x Production (11.15)

HO x Ozone Catalytic Destruction Cycle (11.16) - (11.18)

(11.13) - (11.19) Removal of NO x and HO x From Catalytic Cycles

Changes in Monthly-Averaged Global Ozone From Figure 11.7 Percent difference in global ozone from 1979 monthly average

Mount Pinatubo, June 12, 1991 Dave Harlow, United States Geological Survey

March- and October-Averaged Ozone at High Latitudes Since 1979 Figure 11.9(a) Percent difference in ozone from 1979 monthly average

Variation with Latitude of October Zonally-Averaged Ozone in ‘79, ‘99, ‘00 Figure 11.9(b) Ozone (Dobson units)

Variation with Latitude of March Zonally-Averaged Ozone in ‘79, ‘99, ‘00 Figure Ozone (Dobson units)

Chlorofluorocarbons Are Derived From Methane CH 4 (Methane)CFCl 3 (CFC-11)CF 2 Cl 2 (CFC-12)

Chlorine Compounds Mixing ratio Chemical (pptv) Lifetime (yr) Chlorofluorocarbons CFCl 3 (CFC-11) (1932)27045 CF 2 Cl 2 (CFC-12)(1928) CFCl 2 CF 2 Cl (CFC-113) (1934) 7085 Hydrochlorofluorocarbons (HCFCs) CF 2 ClH (HCFC-22)(1943) Other chlorinated compounds CCl 4 (Carbon tetrachloride)10035 CH 3 CCl 3 (Methyl chloroform)904.8 CH 3 Cl (Methyl chloride) HCl (Hydrochloric acid) <1 Table 11.2

Bromine and Fluorine Compounds Mixing ratio Chemical Chemical (pptv) Lifetime (yr) Bromocarbons-Halons CF 3 Br (H-1301)265 CF 2 ClBr (H-1211)211 Other bromocarbons CH 3 Br (Methyl bromide)120.7 Fluorine compounds CH 2 FCF 3 (HFC-134a)413.6 C 2 F 6 (Perfluoroethane)410,000 SF 6 (Sulfur hexafluoride) Table 11.2

Reported Sales of CFC-11 and 12 in 1976 and 1998 Figure 11.11, AFEAS (2000) CFC sales (1000 metric tonnes/year)

Variations With Altitude of CFCs and Other Chlorinated Compounds Figure Altitude (km) CCl 4 (g)

Chlorine Emission to Stratosphere Table 11.3 Chemical Percent emission to stratosphere Anthropogenic sources CFC-12 (CF 2 Cl 2 )28 CFC-11 (CFCl 3 )23 Carbon tetrachloride (CCl 4 )12 Methyl chloroform(CH 3 CCl 3 )10 CFC-113 (CFCl 2 CF 2 Cl)6 HCFC-22 (CF 2 ClH)3 Natural sources Methyl chloride (CH3Cl)15 Hydrochloric acid (HCl)3 Total100

Cl x Ozone Catalytic Destruction Cycle (11.23) - (11.25)

(11.26) - (11.27) Removal of Cl x From Catalytic Cycles to Form Reservoirs Hydrochloric acid

Br x Ozone Catalytic Destruction Cycle (11.29) - (11.31)

(11.32) - (11.33) Removal of Br x From Catalytic Cycles to Form Reservoirs

Ozone Regeneration Figure Change in globally-averaged ozone column abundance during two global model simulations in which all ozone was initially removed and chlorine was present and absent, respectively. Average global ozone column (Dobson units)

Change in Size of Antarctic Ozone Hole Figure Ozone minimum (Dobson units) Ozone hole area (10 6 km 2 )

Ozone Column Abundance on October 1, 2000 Figure Latitude (degrees)

Summary of Ozone Hole Formation Southern-Hemisphere winter (June-Sept.) without sunlight over Antarctica --> cold Polar vortex (jet stream) encircles Antarctica, confining air, cooling it further When temperatures drop below 195 K in the stratosphere, polar stratospheric clouds (PSCs) form On the surface of these clouds, “inactive” chlorine reservoirs, HCl(g) and ClONO 2 (g), react to form Cl 2 (g), HOCl(g), ClNO 2 (g) When sun rises in spring, sunlight breaks down new molecules into “active” chlorine, which destroys ozone --> ozone hole As air warm, PSCs melt, vortex breaks down, outside air brought in. Ozone hole re-fills by November

Polar Stratospheric Clouds Type I Nitric acid trihydrate (NAT) HNO 3 -3H 2 O(s) Form below 195 K Comprise 90% of PSCs Typical diameter: 1  m Typical number concentration: 1 particle cm -3 Type II Water ice H 2 O(s) Form below 187 K Comprise 10% of PSCs Typical diameter: 20  m Typical number concentration: <0.1 particle cm -3

Polar Stratospheric Clouds in the Arctic (2000) National Aeronautics and Space Administration

(11.34) - (11.38) Heterogeneous Reactions

(11.39) - (11.41) Active Chlorine Formation in Spring

(11.42) - (11.46) Dimer Mechanism

(11.47) - (11.50) Bromine-Chlorine Mechanism

Conversion of Chlorine Reservoirs to Active Chlorine Figure 11.17

Melanin Dark pigment in skin for protection against UV radiation Developed originally in populations living under intense UV radiation in equatorial Africa Populations that migrated to higher latitudes became lighter due to natural selection since some UV is needed to produce vitamin D in the skin, and dark pigmentation blocks the little UV available at higher latitudes for vitamin D production. Vitamin D necessary to prevent bone fractures, bow legs, slow growth (rickets). As populations moved across Asia to North America and down toward equatorial South America, production of melanin again became an advantage Lighter skin color in equatorial South America than in equatorial Africa due to shorter presence of population in South America

UV Effects on the Skin Sunburn (erythema) Skin reddening, blisters Photoaging (accelerated aging of skin) Loss of skin elasticity, wrinkles, altered pigmentation, decrease in collagen

Skin Cancer Basal-cell carcinoma (BCC) (79%) Tumor develops in basal cells, deep in skin Grows through skin and scabs Doesn’t spread; removable by surgery, radiation, rarely fatal Squamous-cell carcinoma (SCC) (19%) Tumor develops in squamous cells, outside of skin Appears as red mark Spreads but removable by surgery, radiation, rarely fatal Cutaneous melanoma (CM) (2%) Dark-pigmented malignant tumor arising in melanocyte cell Spread quickly; fatal in 1/3 of cases CM as common as SCC in Northern Europe Skin cancer rates increase from Equator to poles Relatively high cancer rates in Australia/New Zealand Lifetime exposure to UV not necessary to obtain skin cancer

UV Effects on the Eye Snowblindness Inflammation or reddening of the eyeball Cataract Loss in transparency of the lens Blindness unless lens removed Ocular melanoma Cancer of iris and related tissues

Other UV Effects Immune system effects Reduces ability to fight disease and tumors Effects on microorganisms (e.g., phytoplankton), animals, plants Effects on global carbon and nitrogen cycles Damage to phytoplankton reduces CO 2 (g) uptake UV-B enhances photodegradation of plants, increasing CO 2 (g) UV-B affects rate of nitrogen fixation by cyanobacteria Effects on tropospheric ozone Enhanced UV-B increases tropospheric ozone Enhanced absorbing aerosols reduce UV-B, reducing ozone

Regulation of CFCs June 1974: Effects of CFCs on ozone hypothesized by Rowland & Molina Dec. 1974: Bill to study, regulate CFCs killed in U.S. Congress 1975: Congress sets up committee to study CFC effects 1976: U.S. National Academy of Sciences releases report suggesting long-term damage to ozone layer due to CFCs 1976: On basis of report, U.S Food and Drug Administration, Environmental Protection Agency, Consumer Product Safety Commission recommend phase out of spray cans in the U.S. Oct. 1978: Manufacture/sale of CFCs for spray cans banned in U.S.

Regulation of CFCs 1980: U.S. EPA proposes limiting emission of CFCs from refrigeration, but proposal rebuffed 1985: Vienna Convention.Initially 20 countries obligated to reduce CFCs 1987: Montreal Protocol. Initially 27 countries agreed to limit CFCs and Halons. 1990: London Amendments 1997: Copenhagen Amendments

Phaseout Schedule of CFCs Table 11.4 MontrealLondonU.S. CleanCopenhagenEur. Com. ProtocolAmend.Amend.Amend.Schedule Year (1987)(1990)(1990)(1992)(1994)

CFC Emission Since the 1930s Figure Release (1000 metric tonnes/yr)

CFC Mixing Ratios Over Time Figure Mixing ratio (pptv)

Chlorinated Gas Mixing Ratios Over Time Figure Mixing ratio (pptv)

HCFC and HFC Mixing Ratios Over Time Figure Mixing ratio (pptv)