Global Warming…Global Warming…

Fact or Fiction???Fact or Fiction???

Layers of the AtmosphereLayers of the Atmosphere

Troposphere-Troposphere-• ground to 15kmground to 15km• decreased T with altitudedecreased T with altitude• Wx occursWx occurs

StratosphereStratosphere• 15km to 50km15km to 50km• T increase with altitudeT increase with altitude• OO33 layer, which raises the T of the layer, which raises the T of the

stratospherestratosphere

MesosphereMesosphere• 50km-85km50km-85km• T decrease with alt.T decrease with alt.• meteors meteors

ThermosphereThermosphere• >85km>85km• rapidly increasing Trapidly increasing T• ionosphere part of thisionosphere part of this

Exosphere from >500km, transition from Exosphere from >500km, transition from Earth’s atmosphere to spaceEarth’s atmosphere to space

Layers of the AtmosphereLayers of the Atmosphere

GasesGases

TroposphereTroposphere– 78% N78% N– 21%O21%O– <1% Ar, CO<1% Ar, CO22, Ne, He, CH, Ne, He, CH44,Kr, H, NO, Xe,Kr, H, NO, Xe

Lighter gases (H & He) rise to the Lighter gases (H & He) rise to the exosphereexosphere

-dust, salts and ice-dust, salts and ice

Carbon and Nitrogen Carbon and Nitrogen CyclesCycles

COCO22 in the atmosphere in the atmosphere

• EquilibriumEquilibrium

• Enters when plants and animals Enters when plants and animals decomposedecompose

• Fossil fuel is burned and CFossil fuel is burned and C→CO→CO22

• Negative impact??Negative impact??

C- 2C- 2ndnd most important greenhouse gas most important greenhouse gas

N CycleN Cycle

• RecycledRecycled

• FixedFixedLightening Lightening

NN2(g)2(g) + O + O2(g)2(g) → 2NO(g)→ 2NO(g) 2NO2NO (g) (g) + O + O2(g)2(g)→ 2NO→ 2NO2(g)2(g)

2NO2NO2(g)2(g) +H +H22OO(l)(l) → HNO → HNO3(aq)3(aq) + HNO + HNO2(aq) 2(aq) →NO→NO33ˉ̄(aq)(aq)

N-fixing bacteriaN-fixing bacteriaNN2 2 →NH→NH33 + NH + NH44+ → NO+ → NO33ˉ̄

Greenhouse EffectGreenhouse Effect

Greenhouse GasesGreenhouse Gases

• COCO22

– occurs naturallyoccurs naturally– fossil fuels add fossil fuels add – rain forestsrain forests

→→COCO22 increasing increasing

Effects?Effects?

• Increases the GH effectIncreases the GH effect

• Positive Feedback loopPositive Feedback loop

• Negative Feedback loopNegative Feedback loop

Negative Feedback loopNegative Feedback loop

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

Positive Feedback LoopPositive Feedback Loop

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

continuallycontinually

Positive Feedback LoopPositive Feedback Loop

Ice and snow decrease

Earth warms

Decreasessurfacealbedo

Increase in Absorbed

Solar radiation

Another example….Another example….

Atmosphere warms

Higher Temps

Earth warms

Increase in amt. Of H2O(v)

MoreEvaporation, More H2O(v)

History and Timeline of OHistory and Timeline of O33

• 1839-1839- Christian Sch Christian Schöbien- detected Oöbien- detected O33 by it by it odor while studying electrolysis of waterodor while studying electrolysis of water

• 1850’s1850’s- shown to be a nat’l atmospheric - shown to be a nat’l atmospheric constituentconstituent

• 18801880- Walter Hartley-identified atmospheric - Walter Hartley-identified atmospheric absorbance lines, Oabsorbance lines, O33 strongly absorbs UV strongly absorbs UV radiationradiation

• 19021902- Léon Phillipe Teisserene de Bort- - Léon Phillipe Teisserene de Bort- stratosphere defined as warming with stratosphere defined as warming with increasing alt. due to Oincreasing alt. due to O33

• 19131913- Proof that most of atmospheres O- Proof that most of atmospheres O33 is is located in the stratospherelocated in the stratosphere

• 1920-1920- Gordon Dobson- measures Gordon Dobson- measures atmospheric Oatmospheric O33, and it increased larger , and it increased larger in the spring, lead to simple atmospheric in the spring, lead to simple atmospheric circulations with Alan Brewercirculations with Alan Brewer

• 19281928- Thomas Midgley, Jr.- invented CFC’s- Thomas Midgley, Jr.- invented CFC’s

• CFC’s-CFC’s-– Replaced SOReplaced SO22 and NH and NH33

– Non-toxic, non-flammable, almost inertNon-toxic, non-flammable, almost inert– Don’t break down until the ozone layer- UV-C Don’t break down until the ozone layer- UV-C → →

Cl, where it does the most damageCl, where it does the most damage

19301930- Sidney Chapman- proposes production of O- Sidney Chapman- proposes production of O3 3

from atmospheric Ofrom atmospheric O22→Chapman’s Cycle→Chapman’s Cycle- Null cycle- Null cycle

• 1950-1950-David Bates and Marcel Nicolet- David Bates and Marcel Nicolet- H and OH destroys OH and OH destroys O33 in catalytic in catalytic cycles, from now until the 70’s CFC cycles, from now until the 70’s CFC use rises rapidlyuse rises rapidly

• 1965-1965-John Hampson- HJohn Hampson- H22OO(v)(v) in in stratosphere can affect ozone stratosphere can affect ozone chemistrychemistry

• 19661966- B.G. Hunt- proposes rate - B.G. Hunt- proposes rate constants for these cycles which constants for these cycles which approach observed ozone missing approach observed ozone missing ratiosratios

HOHOxx

HH22OO→OH + H→OH + H OH + OOH + O3 3 → HO→ HO22 + O + O22

OO33 + HO + HO2 2 → OH +2O→ OH +2O22

Net: 2ONet: 2O3 3 →3O→3O22

HOHOxx Cycle CycleFree oxygen atoms in Free oxygen atoms in excited state are excited state are produced by radiation produced by radiation with wavelength less with wavelength less than 300 nm. than 300 nm.

These excited oxygen These excited oxygen atoms can than react atoms can than react with water vapor to with water vapor to produce OH radicals.produce OH radicals.

The catalytic cycle The catalytic cycle leading to ozone leading to ozone destruction is destruction is indicated by the indicated by the orange arrows.orange arrows.

• 1970- Paul Crutzen- proposes that NO1970- Paul Crutzen- proposes that NOxx from bacterial Nfrom bacterial N22O formed in the O formed in the stratospherestratosphere– NO and OH NO and OH

• 19711971- James McDonald- SST (super sonic - James McDonald- SST (super sonic transport) with damage Otransport) with damage O33

• 19711971- Harold Johnston- NO- Harold Johnston- NOxx chemistry chemistry mechanismmechanism

NONOxx

NO + ONO + O33→ NO→ NO22 + O + O22

O + NOO + NO22→ O→ O22 + NO + NONet:Net: O O33 + O → 2O + O → 2O22

• 1971- Paul Crutzen- publishes a 1971- Paul Crutzen- publishes a paper est. SST’s 1-4% Opaper est. SST’s 1-4% O33 depletion depletion

NN22O O →→ N N22 + O + O22

→→ NO + NONO + NO

• 1970’s- Michael McElroy and Steven 1970’s- Michael McElroy and Steven Wofsy- Cl acts as a catalystWofsy- Cl acts as a catalyst

– A single atom of Br or Cl are more A single atom of Br or Cl are more significant threats to stratosphereic Osignificant threats to stratosphereic O33

ClOClOxx

Cl + OCl + O33 → ClO + O→ ClO + O22

ClO + O → Cl + OClO + O → Cl + O22

Net: Net: O + OO + O3 3 → 2O→ 2O22

Can deplete ozone via catalytic cycles, other source of Cl Can deplete ozone via catalytic cycles, other source of Cl from volcanoesfrom volcanoes

PSC’sPSC’s

• Polar Stratospheric CloudsPolar Stratospheric Clouds

– Support chemical rxn that produce active ClSupport chemical rxn that produce active Cl

• Catalyzes OCatalyzes O33 destruction destruction

– Remove HNORemove HNO33, perturbing N and Cl cycles which , perturbing N and Cl cycles which increases Oincreases O33 destruction destruction

• Cl comes out of reservoirsCl comes out of reservoirs

• Happens in the spring….WHY???Happens in the spring….WHY???