“ Natural ” O 3 Destruction

1. “Natural” O3 Destruction Water: H2O + UV light  •H + •OH Free Radicals: Unpaired electrons Uncharged Very reactive Convert O3 to O2

2. NO 2 N2O + O2 4 NO (soil bacteria) NO + O3 NO2 + O2 energy +N2 + O2 2 NO Energy = lightning or jet engine

3. Chlorofluorocarbons (CFCs) • Natural means don’t account for O3 loss • Even with seasonal cycles • Main suspect: CFCs • Cl + F + C • Man-made, gases • Unreactive (non-toxic, non-flammable, cheap)

4. Uses: Coolants, propellants, styrofoam… Related: Halons (C and F or Br – no Cl)

5. Inert CFCs? Upper atmosphere = high energy UV  bonds break CFC (or halon) + UV  •Cl 2 •Cl + 2 O3 2 ClO• + O2 2 ClO•  ClOOCl ClOOCl + UV  ClOO• + •Cl ClOO•  Cl• + O2 Catalytic cycle

6. Fig.2.15

7. Why do we care about energy? Reactions require energy If light has enough E, the reaction occurs If not, the reaction will not occur, no matter how much light you put in! You won’t get a tan from standing in front of a radio - no matter how long!

8. In the Greenhouse (3.1) • Avg. Temp. - Compare Earth to Venus: Earth Venus Based on distance: 0°F 212°F Actual 59°F 840°F Why? Heat is held in longer by CO2 and H2O in the atmosphere

9. Fig.03.02 Fig. 3.2

10. Greenhouse Gases Absorb IR radiation - trap heat CO2 & H2O (also methane, CH4) - No change in water CO2 is on the rise More now than 150 years ago Earth temp. has changed

11. Greenhouse Effect Process where gases trap heat Heat stays and warms the planet Needed for life – planet would freeze otherwise Too much = bad “Enhanced greenhouse effect” Energy return of > 81%  avg. temp. increase

12. Produced Consumed History of Our Atmosphere • Early atmosphere: 1000X CO2 • Bacteria used CO2, made sugars 6 CO2 + 6 H2O  C6H12O6 + 6O2 (glucose)

13. How do we know? Core samples from the ocean Bacterial remains tell temp. Magnetic alignment tells when (relate to Earth’s magnetic core) “Heavy water” composition of ice More heavy water = higher temp. Trapped bubbles Tell conc. of CO2 when bubble formed

14. Fig.3.4

15. Theory: Global warming: Caused by high CO2 and CH4 levels Possible: High CO2 and CH4 levels are a result of warming, not a cause Fact: CO2 and CH4 trap heat and do contribute

16. Recent Evidence Atmospheric CO2 is increasing Global temps. are increasing Fig. 3.6 Fig. 3.5

18. Other Factors Orbital changes Temp maxima Major and minor ice ages Doesn’t entirely account for temp. changes Airborne dust – volcanic activity Cloud cover – weather patterns Greenhouse gases