Global Warming

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Global Warming

• Fact or Fiction???

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Layers of the Atmosphere

• Troposphere-
• ground to 15km
• decreased T with altitude
• Wx occurs
• Stratosphere
• 15km to 50km
• T increase with altitude
• O3 layer, which raises the T of the
  stratosphere

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• Mesosphere
• 50km-85km
• T decrease with alt.
• meteors
• Thermosphere
• gt85km
• rapidly increasing T
• ionosphere part of this
• Exosphere from gt500km, transition from Earths
  atmosphere to space

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Layers of the Atmosphere
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Gases

• Troposphere
• 78 N
• 21O
• lt1 Ar, CO2, Ne, He, CH4,Kr, H, NO, Xe
• Lighter gases (H He) rise to the exosphere
• -dust, salts and ice

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Carbon and Nitrogen Cycles
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CO2 in the atmosphere

• Equilibrium
• Enters when plants and animals decompose
• Fossil fuel is burned and C?CO2
• Negative impact??

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C- 2nd most important greenhouse gas
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N Cycle

• Recycled
• Fixed
• Lightening
• N2(g) O2(g) ? 2NO(g)
• 2NO (g) O2(g)? 2NO2(g)
• 2NO2(g) H2O(l) ? HNO3(aq) HNO2(aq) ?NO3(aq)
• N-fixing bacteria
• N2 ?NH3 NH4 ? NO3

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Greenhouse Effect
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Greenhouse Gases

• CO2
• occurs naturally
• fossil fuels add
• rain forests
• ?CO2 increasing

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Effects?

• Increases the GH effect
• Positive Feedback loop
• Negative Feedback loop

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Negative Feedback loop

• When the action causes a reaction that then
  decreases the occurrence of the original action
• Sweat to maintain a lower body temp

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Positive Feedback Loop

• When an action causes a reaction that then
  prompts the original action to reoccur, resulting
  in a cycle between the two.
• Birth rates increase, pop increases continually

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Positive Feedback Loop
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Another example.

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History and Timeline of O3
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• 1839- Christian Schöbien- detected O3 by it odor
  while studying electrolysis of water
• 1850s- shown to be a natl atmospheric
  constituent
• 1880- Walter Hartley-identified atmospheric
  absorbance lines, O3 strongly absorbs UV
  radiation
• 1902- Léon Phillipe Teisserene de Bort-
  stratosphere defined as warming with increasing
  alt. due to O3
• 1913- Proof that most of atmospheres O3 is
  located in the stratosphere

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• 1920- Gordon Dobson- measures atmospheric O3, and
  it increased larger in the spring, lead to simple
  atmospheric circulations with Alan Brewer
• 1928- Thomas Midgley, Jr.- invented CFCs
• CFCs-
• Replaced SO2 and NH3
• Non-toxic, non-flammable, almost inert
• Dont break down until the ozone layer- UV-C ?
  Cl, where it does the most damage

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1930- Sidney Chapman- proposes production of O3
from atmospheric O2?Chapmans Cycle - Null
cycle
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• 1950-David Bates and Marcel Nicolet- H and OH
  destroys O3 in catalytic cycles, from now until
  the 70s CFC use rises rapidly
• 1965-John Hampson- H2O(v) in stratosphere can
  affect ozone chemistry

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• 1966- B.G. Hunt- proposes rate constants for
  these cycles which approach observed ozone
  missing ratios
• HOx
• H2O?OH H
• OH O3 ? HO2 O2
• O3 HO2 ? OH 2O2
• Net 2O3 ?3O2

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HOx Cycle

• Free oxygen atoms in excited state are produced
  by radiation with wavelength less than 300 nm.
• These excited oxygen atoms can than react with
  water vapor to produce OH radicals.
• The catalytic cycle leading to ozone destruction
  is indicated by the orange arrows.

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• 1970- Paul Crutzen- proposes that NOx from
  bacterial N2O formed in the stratosphere
• NO and OH
• 1971- James McDonald- SST (super sonic transport)
  with damage O3
• 1971- Harold Johnston- NOx chemistry mechanism
• NOx
• NO O3? NO2 O2
• O NO2? O2 NO
• Net O3 O ? 2O2

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• 1971- Paul Crutzen- publishes a paper est. SSTs
  1-4 O3 depletion
• N2O ? N2 O2
• ? NO NO
• 1970s- Michael McElroy and Steven Wofsy- Cl acts
  as a catalyst
• A single atom of Br or Cl are more significant
  threats to stratosphereic O3

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• ClOx
• Cl O3 ? ClO O2
• ClO O ? Cl O2
• Net O O3 ? 2O2
• Can deplete ozone via catalytic cycles, other
  source of Cl from volcanoes

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PSCs

• Polar Stratospheric Clouds
• Support chemical rxn that produce active Cl
• Catalyzes O3 destruction
• Remove HNO3, perturbing N and Cl cycles which
  increases O3 destruction
• Cl comes out of reservoirs
• Happens in the spring.WHY???

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