global warming… fact or fiction??? layers of the atmosphere troposphere- ground to 15km ground to...
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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
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
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??
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 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)
• 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???