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“ Natural ” O 3 Destruction. Water:. H 2 O + UV light  •H + •OH. Free Radicals: Unpaired electrons Uncharged Very reactive. Convert O 3 to O 2. NO. 2 N 2 O + O 2  4 NO (soil bacteria) NO + O 3  NO 2 + O 2. energy + N 2 + O 2  2 NO.

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natural o 3 destruction
“Natural” O3 Destruction

Water:

H2O + UV light  •H + •OH

Free Radicals:

Unpaired electrons

Uncharged

Very reactive

Convert O3 to O2

slide2
NO

2 N2O + O2 4 NO

(soil bacteria)

NO + O3 NO2 + O2

energy +N2 + O2 2 NO

Energy = lightning or jet engine

chlorofluorocarbons cfcs
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)
slide4

Uses: Coolants, propellants, styrofoam…

Related: Halons (C and F or Br – no Cl)

inert cfcs
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

slide7

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!

in the greenhouse 3 1
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

fig 03 02
Fig.03.02

Fig. 3.2

greenhouse gases
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

greenhouse effect
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

history of our atmosphere

Produced

Consumed

History of Our Atmosphere
  • Early atmosphere: 1000X CO2
  • Bacteria used CO2, made sugars

6 CO2 + 6 H2O  C6H12O6 + 6O2

(glucose)

how do we know
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

theory
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

recent evidence
Recent Evidence

Atmospheric CO2 is increasing

Global temps. are increasing

Fig. 3.6

Fig. 3.5

other factors
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