Global Warming… Fact or Fiction???

Layers of the Atmosphere Troposphere- ground to 15km ground to 15km decreased T with altitude decreased T with altitude Wx occurs Wx occursStratosphere 15km to 50km 15km to 50km T increase with altitude T increase with altitude O 3 layer, which raises the T of the stratosphere O 3 layer, which raises the T of the stratosphere

Mesosphere 50km-85km 50km-85km T decrease with alt. T decrease with alt. meteors meteorsThermosphere >85km >85km rapidly increasing T rapidly increasing T ionosphere part of this ionosphere part of this Exosphere from >500km, transition from Earth’s atmosphere to space

Layers of the Atmosphere

Gases Troposphere –7–7–7–78% N –2–2–2–21%O – <– <– <– <1% Ar, CO2, Ne, He, CH4,Kr, H, NO, Xe Lighter gases (H & He) rise to the exosphere -dust, salts and ice

Carbon and Nitrogen Cycles

CO 2 in the atmosphere Equilibrium Equilibrium Enters when plants and animals decompose Enters when plants and animals decompose Fossil fuel is burned and C → CO 2 Fossil fuel is burned and C → CO 2 Negative impact?? Negative impact??

C- 2 nd most important greenhouse gas

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) →NO3ˉ(aq) N-fixing bacteria N2 →NH3 + NH4+ → NO3ˉ

Greenhouse Effect Greenhouse Effect

Greenhouse Gases CO2 –o–o–o–occurs naturally –f–f–f–fossil fuels add –r–r–r–rain forests →CO2 increasing

Effects? Increases the GH effect Increases the GH effect Positive Feedback loop Positive Feedback loop Negative Feedback loop Negative Feedback loop

Negative Feedback loop When the action causes a reaction that then decreases the occurrence of the original action When the action causes a reaction that then decreases the occurrence of the original action –Sweat to maintain a lower body temp

Positive Feedback Loop When an action causes a reaction that then prompts the original action to reoccur, resulting in a cycle between the two. 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

Positive Feedback Loop Ice and snow decrease Decreases surface albedo Increase in Absorbed Solar radiation Earth warms

Another example…. Atmosphere warms Increase in amt. Of H2O(v) More Evaporation, More H2O(v) Higher Temps Earth warms

History and Timeline of O 3

1839- Christian Schöbien- detected O 3 by it odor while studying electrolysis of water Christian Schöbien- detected O 3 by it odor while studying electrolysis of water 1850’s- shown to be a nat’l atmospheric constituent 1850’s- shown to be a nat’l atmospheric constituent Walter Hartley-identified atmospheric absorbance lines, O 3 strongly absorbs UV radiation Walter Hartley-identified atmospheric absorbance lines, O 3 strongly absorbs UV radiation Léon Phillipe Teisserene de Bort- stratosphere defined as warming with increasing alt. due to O Léon Phillipe Teisserene de Bort- stratosphere defined as warming with increasing alt. due to O Proof that most of atmospheres O 3 is located in the stratosphere Proof that most of atmospheres O 3 is located in the stratosphere

1920- Gordon Dobson- measures atmospheric O 3, and it increased larger in the spring, lead to simple atmospheric circulations with Alan Brewer Gordon Dobson- measures atmospheric O 3, and it increased larger in the spring, lead to simple atmospheric circulations with Alan Brewer Thomas Midgley, Jr.- invented CFC’s Thomas Midgley, Jr.- invented CFC’s CFC’s- CFC’s- –Replaced SO 2 and NH 3 –Non-toxic, non-flammable, almost inert –Don’t break down until the ozone layer- UV-C → Cl, where it does the most damage

1930- Sidney Chapman- proposes production of O 3 from atmospheric O 2 → Chapman’s Cycle - Null cycle

1950-David Bates and Marcel Nicolet- H and OH destroys O 3 in catalytic cycles, from now until the 70’s CFC use rises rapidly 1950-David Bates and Marcel Nicolet- H and OH destroys O 3 in catalytic cycles, from now until the 70’s CFC use rises rapidly 1965-John Hampson- H 2 O (v) in stratosphere can affect ozone chemistry 1965-John Hampson- H 2 O (v) in stratosphere can affect ozone chemistry

1966- B.G. Hunt- proposes rate constants for these cycles which approach observed ozone missing ratios B.G. Hunt- proposes rate constants for these cycles which approach observed ozone missing ratios HO x H 2 O → OH + H H 2 O → OH + H OH + O 3 → HO 2 + O 2 OH + O 3 → HO 2 + O 2 O 3 + HO 2 → OH +2O 2 O 3 + HO 2 → OH +2O 2 Net: 2O 3 → 3O 2

HO x 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.

1970- Paul Crutzen- proposes that NO x from bacterial N 2 O formed in the stratosphere Paul Crutzen- proposes that NO x from bacterial N 2 O formed in the stratosphere –NO and OH James McDonald- SST (super sonic transport) with damage O James McDonald- SST (super sonic transport) with damage O Harold Johnston- NO x chemistry mechanism Harold Johnston- NO x chemistry mechanism NO x NO + O 3 → NO 2 + O 2 O + NO 2 → O 2 + NO Net: O 3 + O → 2O 2

1971- Paul Crutzen- publishes a paper est. SST’s 1-4% O 3 depletion Paul Crutzen- publishes a paper est. SST’s 1-4% O 3 depletion N 2 O → N 2 + O 2 → NO + NO → NO + NO 1970’s- Michael McElroy and Steven Wofsy- Cl acts as a catalyst 1970’s- Michael McElroy and Steven Wofsy- Cl acts as a catalyst –A single atom of Br or Cl are more significant threats to stratosphereic O 3

ClO x Cl + O 3 → ClO + O 2 ClO + O → Cl + O 2 Net: O + O 3 → 2O 2 Can deplete ozone via catalytic cycles, other source of Cl from volcanoes

PSC’s Polar Stratospheric Clouds Polar Stratospheric Clouds –Support chemical rxn that produce active Cl Catalyzes O 3 destruction Catalyzes O 3 destruction –Remove HNO 3, perturbing N and Cl cycles which increases O 3 destruction Cl comes out of reservoirs Cl comes out of reservoirs Happens in the spring….WHY??? Happens in the spring….WHY???