Atmospheres & Global Warming Earth and the Other Terrestrial Worlds.

Atmospheres Atmospheres &&

Global WarmingGlobal WarmingEarth and the Other Terrestrial WorldsEarth and the Other Terrestrial Worlds

Weather and ClimateWeather and Climate

These are Earth’s These are Earth’s global wind global wind patterns patterns or circulationor circulation• local weather systems move along local weather systems move along

with themwith them

• weather moves from W to E at weather moves from W to E at mid-latitudes in N hemispheremid-latitudes in N hemisphere

Two factors cause these patternsTwo factors cause these patterns• atmospheric heatingatmospheric heating

• planetary rotationplanetary rotation

Weather – short-term changes in wind, clouds, temperature, and pressure in an atmosphere at a given location

Climate – long-term average of the weather at a given location

Global Wind PatternsGlobal Wind Patterns Air heated more at equatorAir heated more at equator

• Warm air rises at equator; Warm air rises at equator; Pressure pushes to polesPressure pushes to poles

• Cold air moves from poles to Cold air moves from poles to equator along the surfaceequator along the surface

Two circulation cells are Two circulation cells are created in each hemisphere created in each hemisphere

Cells of air do not go directly from pole Cells of air do not go directly from pole to equator; air circulation is diverted to equator; air circulation is diverted by…by…

Coriolis effectCoriolis effect• moving objects veer moving objects veer rightright on a surface on a surface

rotating rotating counterclockwisecounterclockwise• moving objects veer moving objects veer leftleft on a surface on a surface

rotating rotating clockwiseclockwise

Global Wind PatternsGlobal Wind Patterns On Earth, the Coriolis effect breaks each On Earth, the Coriolis effect breaks each

circulation cell into three separate cellscirculation cell into three separate cells• winds move either W to E or E to W winds move either W to E or E to W

• Coriolis effect not strong on Mars & Venus• Mars is too small

• Venus rotates too slowly

• In thick Venusian atmosphere, the pole-to-equator circulation cells distribute heat efficiently

• surface temperature is uniform all over the planet

Earth’s AtmosphereEarth’s Atmosphere

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Structure of Earth’s AtmosphereStructure of Earth’s Atmosphere Pressure & density of Pressure & density of decrease decrease with altitudewith altitude Temperature both increases and decreases with altitude Temperature both increases and decreases with altitude

• Temperature domains define the major atmospheric layers Temperature domains define the major atmospheric layers

exosphereexosphere

• low density; fades into spacelow density; fades into space

thermospherethermosphere

• temp begins to rise at the toptemp begins to rise at the top

stratospherestratosphere• rise and fall of temprise and fall of temp

tropospheretroposphere• layer closest to surfacelayer closest to surface• temp drops with altitudetemp drops with altitude

Ozone Layer (absorbs UV)

(mesosphere)

Troposphere

Stratosphere

Reasons for Atmospheric StructureReasons for Atmospheric Structure Absorption of sunlight energyAbsorption of sunlight energy causes layering structure. causes layering structure. TroposphereTroposphere

• Air absorbs IR photons from the surface Air absorbs IR photons from the surface

• Hot air rises and high gas density causes storms (Hot air rises and high gas density causes storms (convectionconvection))

• Temperature drops with altitudeTemperature drops with altitude

StratosphereStratosphere• Lies above the greenhouse gases (no IR absorption)Lies above the greenhouse gases (no IR absorption)

• Absorbs heat via Solar UV photons which dissociate ozone (OAbsorbs heat via Solar UV photons which dissociate ozone (O33))

• UV penetrates only top layer; hotter air is above colder airUV penetrates only top layer; hotter air is above colder air

ThermosphereThermosphere• Absorbs heat via Solar X-rays which ionizes all gasesAbsorbs heat via Solar X-rays which ionizes all gases

• Contains ionosphere, which reflects back human radio signals Contains ionosphere, which reflects back human radio signals

ExosphereExosphere• Hottest layer; gas extremely rarified; provides noticeable drag on satellitesHottest layer; gas extremely rarified; provides noticeable drag on satellites

Structure of Terrestrial Planet Structure of Terrestrial Planet AtmospheresAtmospheres

Mars, Venus, Earth allMars, Venus, Earth all• have warm tropospheres have warm tropospheres

(and greenhouse gases)(and greenhouse gases)• have warm thermospheres have warm thermospheres

which absorb Solar X rayswhich absorb Solar X rays Only Earth hasOnly Earth has

• a warm stratosphere a warm stratosphere • an UV-absorbing gas (Oan UV-absorbing gas (O33))

All three planets have All three planets have warmer surface temps due warmer surface temps due to greenhouse effectto greenhouse effect

Climate History of VenusClimate History of Venus Venus should have outgassed as much HVenus should have outgassed as much H22O as Earth.O as Earth.

• Early on, when the Sun was dimmer, Venus may have had oceans of Early on, when the Sun was dimmer, Venus may have had oceans of waterwater

Venus’ proximity to the Sun caused all HVenus’ proximity to the Sun caused all H22O to evaporate.O to evaporate.

• HH22O caused runaway greenhouse effect O caused runaway greenhouse effect

• surface heated to extreme temperaturesurface heated to extreme temperature

• COCO22 released from rocks: Adds to greenhouse effect released from rocks: Adds to greenhouse effect

• UV photons from Sun dissociate HUV photons from Sun dissociate H22O; HO; H22 escapes, O is stripped escapes, O is stripped

If Earth moved to Venus’ Orbit

Venusian Weather TodayVenusian Weather Today

• Venus has Venus has nono seasons to speak of. seasons to speak of.• rotation axis is nearly 90rotation axis is nearly 90º to the ecliptic planeº to the ecliptic plane

• Venus has little wind at its surfaceVenus has little wind at its surface• rotates very slowly, so there is no Coriolis effectrotates very slowly, so there is no Coriolis effect

• The surface temperature stays constant all over Venus.The surface temperature stays constant all over Venus.• thick atmosphere distributes heat via two large circulation cellsthick atmosphere distributes heat via two large circulation cells

There is no rain on the surface.There is no rain on the surface.• it is too hot and Venus has almost no Hit is too hot and Venus has almost no H22OO

Venusian clouds contain sulfuric acid!Venusian clouds contain sulfuric acid!• implies recent volcanic outgassing?implies recent volcanic outgassing?

Mars’ Thin AtmosphereMars’ Thin Atmosphere

Martian sunset Martian sunset illustrates just how illustrates just how thin the Martian thin the Martian atmosphere is.atmosphere is.



Martian Weather: N Polar Ice Cap & Martian Weather: N Polar Ice Cap & Dust StormDust Storm

Martian Weather TodayMartian Weather Today

• Seasons on Mars are more extreme than on EarthSeasons on Mars are more extreme than on Earth• Mars’ orbit is more ellipticalMars’ orbit is more elliptical

• COCO22 condenses & vaporizes at opposite poles condenses & vaporizes at opposite poles• changes in atmospheric pressure drive pole-to-pole windschanges in atmospheric pressure drive pole-to-pole winds• sometimes cause huge dust stormssometimes cause huge dust storms

The last decade of the The last decade of the 20th Century was the 20th Century was the warmest in the entire warmest in the entire global instrumental global instrumental temperature record, temperature record, starting in the mid-1800’s. starting in the mid-1800’s.

All 10 years rank among the All 10 years rank among the 15 warmest, and include the 15 warmest, and include the 6 warmest years on record. 6 warmest years on record.

Through the reconstruction Through the reconstruction of past climate we can of past climate we can evaluate the rarity and evaluate the rarity and magnitude of this warming.magnitude of this warming.



4.6 Billion Years Ago ...4.6 Billion Years Ago ...

(150 million km from Sun)

1 AU0.7 AU 1.5 AU

SUNSUNVenusVenus EarthEarth MarsMars

Temperature: Top of Atmosphere Temperature: Top of Atmosphere T

emp

erat

ure

(C

elsi

us)

500

300

100

0

-100-100

0

100

200

300

400

500

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

decreases with distance from Sun

1 AU

5500 oC

Earth-18oC (0oF)

Venus

0

-100Distance From Sun

0 AU

Mars

Clue: atm composition

-100

0

100

200

300

400

500

0.5 1 1.5 2

500

300

100

0

-100

Tem

per

atu

re (

Cel

siu

s)

EARTHEARTH:Surface 15oC (60oF)Top of Atm: -18oC (0oF)

All three phases of water

Surface warmer than top of atm Greenhouse Effect

Surface

No Greenhouse

Vibrational Modes for COVibrational Modes for CO22

C OO

CO O

O OC

symmetric

bending 15 m

asymmetric 4.3 m

Greenhouse effect: Radiation at specific wavelengths excite CO2 into higher energy states. Light energy is absorbed by the CO2 molecules

Other Greenhouse GasesOther Greenhouse Gases

O

O O

O

H H

water ozone

N NO C

H

H

H H

methanenitrous oxide

Absorption by different molecules Absorption by different molecules = 0-15 µm = 0-15 µm

Absorption

Transmission

Peak terrestrial emission at ~300K

COCO22

BendingBendingModeMode

How Greenhouse Gases How Greenhouse Gases Warm the TroposphereWarm the Troposphere



CO2

Energy BalanceEnergy Balance

Carbon Dioxide:Carbon Dioxide:in our atmosphere isin our atmosphere is

Increasing rapidlyIncreasing rapidly







Worldwide CO2 EmissionBy fuel type: 1970 - 2020

CO2 Causes Global Warming:Stay tuned . . .



Burning coalBurning coal

gasoline

Natural gas

Since 1850: Since 1850: Atmospheric CO2 has Atmospheric CO2 has increased by 30% increased by 30%

Increase in Temperature tracksIncrease in Greenhouse Gases

Year1850 2000

Temperture vs Time

CO2 in atmosphere, measured in thick arctic ice.

COCO22 Since the Year 1000 AD Since the Year 1000 AD

Heat ContentHeat Content::Increase in Atmosphere and Increase in Atmosphere and Ocean since 1945. Ocean since 1945.

Retreat of GlaciersRetreat of Glaciers



1948 2002

Trift Glacier, Gadmental, Berner, Oberland Switzerland

2006

Franz Josef Franz Josef Glacier In RetreatGlacier In Retreat











1951

1960

1964

19391939

1500 2000

Receding GlaciersReceding GlaciersGlacierLength (km)

South Cascade Glacier inWashington. The yellow line indicates the location of the terminus in 1958. The red line shows the position of the terminus in 1998.

Is the Sun to Blame ? Is the Sun to Blame ? No. No. Luminosity has been constant.Luminosity has been constant.

Sunlight hitting Earth:

• 11 year Sunspot cycle• Offsets among instruments• No trend



W /

m2

Year

Global WarmingGlobal Warming Made a political issue by certain people.Made a political issue by certain people.

Three Facts are Absolute:Three Facts are Absolute:

1.1. Earth has warmed by 0.5 C in past 50 years. Temperature rise greatest in Earth has warmed by 0.5 C in past 50 years. Temperature rise greatest in past 10 years.past 10 years.

2.2. Humans are increasing by 30-50% the COHumans are increasing by 30-50% the CO22 in the atmosphere. in the atmosphere.

3.3. Rising CORising CO22 will cause rising temperatures will cause rising temperatures

Only Question: Not Whether, but by how much are humans contributing to Global Warming ?

Feedback Proceses:Feedback Proceses:Positive and Negative Positive and Negative

Suppose Temp rises ==> Suppose Temp rises ==> Evaporation of ocean water.Evaporation of ocean water.

Feedback:Feedback: HH22O is a greenhouse gas ==>O is a greenhouse gas ==>

Earth gets even Warmer !Earth gets even Warmer !

But clouds may form, increasing albedo.But clouds may form, increasing albedo.==> Earth cools.==> Earth cools.

The Arctic:The Arctic:Positive Feedback ProcessPositive Feedback Process

Temp rise causes polar cap ice to melt.Temp rise causes polar cap ice to melt. Artic ground exposed: dirt absorbs more Artic ground exposed: dirt absorbs more

sunlight (lower albedo).sunlight (lower albedo). Ground warms up more: Earth gets hotter.Ground warms up more: Earth gets hotter. More polar cap ice melts. Earth gets even More polar cap ice melts. Earth gets even

hotter.hotter.

Consequences ofConsequences of

Global WarmingGlobal Warming1.1. More evaporation of oceans: More storms, More evaporation of oceans: More storms,

and more severe storms.and more severe storms.2.2. Water in oceans exand with rising Temp. Water in oceans exand with rising Temp.

Sea level has already risen 20 cm in past Sea level has already risen 20 cm in past 100 years. Coastal regions and islands 100 years. Coastal regions and islands flood.flood.

3.3. Polar caps and Glaciers melt: Causes rising Polar caps and Glaciers melt: Causes rising ocean levels.ocean levels.

4.4. Change in ocean current patterns. Change in ocean current patterns. Desserts may get rain; Farmland may get Desserts may get rain; Farmland may get none.none.

Predictions of temperatures Predictions of temperatures next 100 yearsnext 100 years

DEPENDS ON MAGNITUDE OF FEEDBACK AND RATE OF INCREASE OF GHG. IN 100 YEARS, FORCED CLIMATE CHANGE WILL MOST LIKELY EXCEED NATURAL VARIABILITY



The Kyoto AgreementThe Kyoto Agreement

The Kyoto Protocol, negotiated by more than 160 nations in 1997, will reduce emissions of certain greenhouse gases (primarily CO2). Each of the participating developed countries must decide how to meet its respective reduction goal.

Signed by every country in the Signed by every country in the European Union,European Union,by Japan, and by Russia.by Japan, and by Russia.

Kyoto Agreement:Kyoto Agreement:

The United States Won’t SignThe United States Won’t Sign In March 2001, President Bush announced that the United In March 2001, President Bush announced that the United

States would not sign the Kyoto Protocol on Global Climate States would not sign the Kyoto Protocol on Global Climate Change. Change.

The Protocol requires signatories to cut carbon dioxide The Protocol requires signatories to cut carbon dioxide emissions an average of 5 percent below 1990 levels between emissions an average of 5 percent below 1990 levels between 2008 and 2012. Developing nations are exempt from emission 2008 and 2012. Developing nations are exempt from emission reductions.reductions.

““President Bush strongly opposes any treaty or policy that would President Bush strongly opposes any treaty or policy that would cause the loss of a single American job, let alone the nearly 5 cause the loss of a single American job, let alone the nearly 5 million jobs Kyoto would have cost.” million jobs Kyoto would have cost.” - James Connaughton, chairman of - James Connaughton, chairman of the White House council on Environmental Quality.the White House council on Environmental Quality.

Show the movieShow the movie::An Inconvenient TruthAn Inconvenient Truth


are needed to see this picture. QuickTime™ and aTIFF (Uncompressed) decompressor


Three Perspectives onThree Perspectives onGlobal WarmingGlobal Warming

Kyoto Protocol:Kyoto Protocol:

unfccc.int/resource/convkp.htmlunfccc.int/resource/convkp.html

White House Council on Environmental White House Council on Environmental Quality: Quality: www.whitehouse.www.whitehouse.gov/ceqgov/ceq

Pew Center on Global Climate Change:Pew Center on Global Climate Change:

www.pewclimate.orgwww.pewclimate.org

http://www.whitehouse.gov/ceq


http://www.eia.doe.gov/oiaf/1605/vrrpt/summary/longform.html

United States Policy on COUnited States Policy on CO22

“Voluntary Reductions”“Voluntary Reductions”

Three Perspectives onThree Perspectives onGlobal WarmingGlobal Warming

Kyoto Protocol:Kyoto Protocol:

unfccc.int/resource/convkp.htmlunfccc.int/resource/convkp.html

White House Council on Environmental White House Council on Environmental Quality: Quality: www.whitehouse.gov/www.whitehouse.gov/ceqceq

Pew Center on Global Climate Change:Pew Center on Global Climate Change:

www.pewclimate.orgwww.pewclimate.org



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Atmospheres & Global Warming Earth and the Other Terrestrial Worlds.

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