atmospheres & global warming earth and the other terrestrial worlds
Post on 20-Dec-2015
221 views
TRANSCRIPT
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
CO2
Energy BalanceEnergy Balance
Carbon Dioxide:Carbon Dioxide:in our atmosphere isin our atmosphere is
Increasing rapidlyIncreasing rapidly
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Worldwide CO2 EmissionBy fuel type: 1970 - 2020
CO2 Causes Global Warming:Stay tuned . . .
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
1948 2002
Trift Glacier, Gadmental, Berner, Oberland Switzerland
2006
Franz Josef Franz Josef Glacier In RetreatGlacier In Retreat
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture. QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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.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