Where is the ozone layer? Global ozone column abundance

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Gregory Webster
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1 Where is the ozone layer? Altitude (km) Thermosphere 20-30km Mesosphere Stratosphere Troposphere Temperature (K) Mesopause Stratopause Tropopause Global ozone column abundance WMO, 2002, 20 questions 1

2 UV protection by the ozone layer Ozone formation animation 2

Examples: Methane CFC11 CFC12 H Cl Cl H H C H Cl C Cl

3 What s the story about CFC s? Chlorofluorocarbons: organic molecules where the H atoms have been completely replaced by fluorine and chlorine (synthetic molecules- entirely artificial) Examples: Methane CFC11 CFC12 H Cl Cl H H C H Cl C Cl F F C Cl F wonder gas CFCs were invented in 1928 Use of CFCs increases rapidly 3

4 Sources of chlorine and bromine to the stratosphere WMO, 2002, 20 questions Destruction of ozone by the chlorine catalytic cycle Animation 4

5 CFC emissions Atmospheric residence time of CFC s: ~ 100 yrs Turco, Fig

decreasing each October Year 1980s column 50% lower compared to 1960s values!

6 What is the ozone hole? Ozone column abundance (DU) Farman et al. published 1985 this picture that shows that the total ozone column over Antarctica was decreasing each October Year 1980s column 50% lower compared to 1960s values! What is the ozone hole? Today ozone hole covers an area larger than the Antarctic continent 6

7 Difference between 1970s ozone column and 1990s column in October Largest ozone losses confined to the Antarctic region. What is the ozone hole? At certain altitudes ozone disappears completely in the ozone hole 7

8 Polar Stratospheric Clouds Clouds of ice/liquid particles at km altitude Animation of Antarctic Ozone Hole (Aug-Nov 2000) 8

9 Is there an ozone hole over the Arctic? Is there an ozone hole in the north? yes, but it is rather small ( ozone dent ) Hole is smaller because the polar vortex is weaker + warmer (because of the geography) 9

Globally, the ozone layer is thinner by 3% relative to 20 years ago.

10 Animation of Arctic ozone depletion (Feb-Apr 1997) How large is the depletion of the global ozone layer? Globally, the ozone layer is thinner by 3% relative to 20 years ago. Largest decreases at high latitude (Antarctic ozone hole + Arctic ozone dent). Also significant changes at mid-latitudes (5%) 10

11 Does depletion of the ozone layer increase ground level UV radiation? Yes, UV-B radiation (sunburning UV) at the surface increases as the amount of overhead ozone decreases. This increase is on the order of a few % per decade since

12 Effects of enhanced UV-B radiation Attack molecules in cells, particularly DNA cellular dysfunction / mutation / formation of toxic species Skin:!sunburn,!premature aging of skin,!skin cancer (basal cell carcinomas ; squanous cell carcinomas; melanoma (dark tumor-like growth) Eyes: Affects cornea (covers iris+lens)!snow blindness!cataract (loss of transparency of cornea) Immune system: UV-B kills cells which fight infections on skin Affects crops, plants (slower growth, photosynthesis), animals, and microrganisms. Regulations on the production of CFCs Vienna convention (1985): Convention for the Protection of the ozone layer signed by 20 nations (research, future protocols) Montreal Protocol (1987): Protocol on substances that deplete the ozone layer ratified in Legally binding controls freezing production to 1985 levels. London Amendment (1990): phaseout of production by 2000 for developed nations and by 2010 for developing nations. Copenhagen Agreement (1992): Phaseout for developed nations by HCFC production allowed as short-term substitutes for CFCs. HCFC production to be phased out by 2030 (developed nations), 2040 (developing nations). First environmental problem solved on an international basis! 12

13 Projected evolution of tropospheric chlorine Has the Montreal Protocol been successful in reducing ozone-depeting gases in the atmosphere? Yes! WMO, 2002, 20 questions 13

14 Estimated excess cases of skin cancer if no controls had been imposed on CFCs WMO, 2002, 20 questions 2050 no protocol: U.S. 33,000 excess skin cancer cases/year Europe 14,000 excess skin cancer cases/year 14

STRATOSPHERIC OZONE DEPLETION. Adapted from K. Sturges at MBHS

STRATOSPHERIC OZONE DEPLETION. Adapted from K. Sturges at MBHS STRATOSPHERIC OZONE DEPLETION Adapted from K. Sturges at MBHS Ozone Layer Ozone is Good up high Stratosphere Bad nearby Troposphere Solar Radiation - range of electromagnetic waves UV shortest we see if